Oxicloud/src/application/services/auth_application_service.rs

use crate::application::dtos::user_dto::{
    AdminUserSummaryDto, AuthResponseDto, ChangePasswordDto, LoginDto, RefreshTokenDto,
    RegisterDto, UpgradeToInternalDto, UserDto,
};
use crate::application::ports::auth_ports::{
    OidcIdClaims, OidcServicePort, PasswordHasherPort, SessionStoragePort, TokenServicePort,
    UserStoragePort,
};
use crate::application::ports::authorization_ports::AuthorizationEngine;
use crate::application::ports::user_lifecycle::{DeletionMode, LogoutReason};
use crate::application::services::user_lifecycle_service::UserLifecycleService;
use crate::common::config::{AuthMethod, AuthPolicy, OidcConfig};
use crate::common::errors::{DomainError, ErrorKind};
use crate::domain::entities::magic_link_token::{MagicLinkResourceKind, MagicLinkStatus};
use crate::domain::entities::session::Session;
use crate::domain::entities::user::{User, UserFlags, UserRole};
use crate::domain::repositories::magic_link_token_repository::MagicLinkTokenRepository;
use crate::domain::services::authorization::Subject;
use crate::infrastructure::repositories::pg::SessionPgRepository;
use crate::infrastructure::repositories::pg::UserPgRepository;
use crate::infrastructure::services::jwt_service::JwtTokenService;
use crate::infrastructure::services::oidc_service::OidcService;
use crate::infrastructure::services::password_hasher::Argon2PasswordHasher;
use moka::sync::Cache;
use std::path::PathBuf;
use std::sync::Arc;
use std::sync::RwLock;
use std::time::Duration;
use uuid::Uuid;

/// Result of a successful OIDC callback. The handler layer inspects this to
/// decide whether to redirect to the regular frontend or complete a Nextcloud
/// Login Flow v2 session.
pub enum OidcCallbackResult {
    /// Regular web login — contains a one-time exchange code for the frontend.
    WebLogin { exchange_code: String },
    /// Nextcloud Login Flow v2 — the user authenticated via OIDC but the flow
    /// was initiated from the Nextcloud login page. The handler must create an
    /// app password and complete the NC login flow.
    NextcloudLogin {
        nc_flow_token: String,
        user_id: Uuid,
        username: String,
    },
}

/// Outcome of a successful magic-link redemption. The auth tokens are
/// the same shape as a password login; the optional resource fields tell
/// the handler whether to deep-link to the invited resource or fall back
/// to the generic `/shared-with-me` landing.
/// Outcome of a `register` call. The handler maps this to either an
/// anti-enumerated uniform 200 (when SMTP is available — there's a
/// "check your email" cover story for the user) or the classic
/// 201/409 split (when SMTP is unavailable — without the cover story,
/// uniform responses would just be misleading UX with no security
/// benefit). Either way the service emits the same audit-log entries.
#[derive(Debug, Clone)]
pub enum RegisterResult {
    /// Boxed to avoid the `large_enum_variant` clippy warning —
    /// `UserDto` is ~250 bytes, the other variants are zero-sized,
    /// so a heap-pointer indirection keeps the enum's stack size
    /// small. `register` is called once per request; the
    /// allocation cost is negligible.
    Created(Box<UserDto>),
    UsernameTaken,
    EmailTaken,
}

/// Outcome of a `redeem_magic_link` call (PR 22).
///
/// - `Allowed(redemption)` — the token is valid and the browser
///   binding either matched or was overridden via the user's
///   explicit cross-browser confirmation. The token has been
///   atomically marked used.
/// - `NeedsCrossBrowserConfirm` — the token carries a
///   `request_challenge` but the incoming cookie didn't match.
///   The handler should render a confirmation page; the user
///   clicks Continue and we re-redeem with `cross_browser_confirmed = true`.
///   The token is NOT marked used yet — it stays redeemable.
#[derive(Debug)]
pub enum MagicLinkRedeemResult {
    /// Boxed to keep the enum's stack size small — `MagicLinkRedemption`
    /// is ~350 bytes while `NeedsCrossBrowserConfirm` is zero-sized.
    /// One redemption per request; the heap indirection is negligible.
    Allowed(Box<MagicLinkRedemption>),
    NeedsCrossBrowserConfirm,
}

#[derive(Debug, Clone)]
pub struct MagicLinkRedemption {
    pub auth: AuthResponseDto,
    pub resource_kind: Option<MagicLinkResourceKind>,
    pub resource_id: Option<Uuid>,
}

/// Tracks a pending OIDC authorization flow (CSRF + PKCE + nonce)
#[derive(Clone)]
struct PendingOidcFlow {
    pkce_verifier: String,
    nonce: String,
    /// When set, this OIDC flow was initiated from the Nextcloud Login Flow v2
    /// page. On successful callback the flow will mint an app-password and
    /// complete the Nextcloud login flow instead of issuing internal JWTs.
    nc_flow_token: Option<String>,
}

/// Tracks a pending one-time token exchange after successful OIDC callback
#[derive(Clone)]
struct PendingOidcToken {
    auth_response: AuthResponseDto,
}

/// Interior state for OIDC — protected by RwLock for hot-reload.
struct OidcState {
    service: Option<Arc<OidcService>>,
    config: Option<OidcConfig>,
}

/// Default quota: 100 GB
const DEFAULT_ADMIN_QUOTA: i64 = 107_374_182_400;
const DEFAULT_USER_QUOTA: i64 = 1_073_741_824; // 1 GB

pub struct AuthApplicationService {
    user_storage: Arc<UserPgRepository>,
    session_storage: Arc<SessionPgRepository>,
    password_hasher: Arc<Argon2PasswordHasher>,
    token_service: Arc<JwtTokenService>,
    /// Dispatcher for user-lifecycle events. `None` only in tests that don't
    /// exercise the lifecycle path; production DI always wires this.
    /// PersonalDriveLifecycleHook (registered on this dispatcher) owns the
    /// per-user folder provisioning that AuthApplicationService used to do
    /// inline pre-PR 3.
    user_lifecycle: Option<Arc<UserLifecycleService>>,
    /// Path to the storage directory, used for disk-space–aware quota calculation
    storage_path: PathBuf,
    oidc: RwLock<OidcState>,
    /// Pending OIDC authorization flows keyed by state token (CSRF + PKCE + nonce).
    /// Auto-expires after 10 minutes via moka TTL; max 10 000 entries for DoS protection.
    pending_oidc_flows: Cache<String, PendingOidcFlow>,
    /// Pending one-time token codes for secure token delivery after OIDC callback.
    /// Auto-expires after 60 seconds via moka TTL; max 10 000 entries for DoS protection.
    pending_oidc_tokens: Cache<String, PendingOidcToken>,
    completed_oidc_logins: Cache<String, String>,
    /// Back-Channel Logout replay guard — dedupes logout_tokens by their
    /// `jti` claim within the token's freshness window (5 min per BCL §2.6).
    /// A cooperative IdP will not re-send a logout_token, but the endpoint
    /// is public and unauthenticated so a rogue caller could try to; we
    /// short-circuit repeats to avoid burning DB writes on duplicates.
    /// Note: tokens without a jti bypass this guard — the validator has
    /// already enforced signature + freshness + subject-presence, so at
    /// worst a legitimate re-notification runs the (idempotent) revoke path
    /// a second time and returns "no rows changed".
    backchannel_logout_jti_seen: Cache<String, ()>,
    /// Magic-link token repository — populated when the magic-link feature
    /// is enabled (PR 8+). `None` means redemption endpoints return 503.
    magic_link_repo: Option<Arc<dyn MagicLinkTokenRepository>>,
    /// Per-user authorization flags (`role` / `is_external` / `active`),
    /// consulted by middleware guards on every WebDAV / CalDAV / CardDAV
    /// request. The short TTL keeps the "role changes apply without token
    /// rotation" property within seconds while removing one DB round-trip
    /// per request; the known mutation paths (`change_user_role`,
    /// `set_user_active`) also invalidate eagerly. `moka::future` so
    /// concurrent misses for one user coalesce into a single DB lookup
    /// (`try_get_with` single-flight) — every authenticated request
    /// calls this, so each 30 s TTL expiry used to fan out one SELECT
    /// per in-flight request of that user.
    user_flags_cache: moka::future::Cache<Uuid, UserFlags>,
    /// Self-service auth-method allowlist (mirrors
    /// `AuthConfig::allowed_auth_methods`). Empty = both methods
    /// allowed. Consulted by login / register / magic-link handlers via
    /// `is_password_login_allowed()` / `is_magic_link_login_allowed()`
    /// so callers don't have to reach for the app config.
    allowed_auth_methods: Vec<AuthMethod>,
    /// Additive auth-policy switches (mirrors `AuthConfig::auth_policies`).
    /// Consulted by handlers / providers-info endpoint to compose the
    /// login-page UX hints (e.g. `AutoRedirectIfStandaloneOidc`) without
    /// reaching into the app config on every call.
    auth_policies: Vec<AuthPolicy>,
    /// Whether `POST /api/auth/login` refuses accounts whose
    /// `email_verified_at IS NULL`. Mirrors
    /// `AuthConfig::require_verified_email`.
    require_verified_email: bool,
}

/// TTL for [`AuthApplicationService::user_flags_cache`]. Upper bound on how
/// long a role / external / active change can take to be observed by the
/// per-request guards when it bypasses the eager invalidation paths.
const USER_FLAGS_CACHE_TTL: Duration = Duration::from_secs(30);

impl AuthApplicationService {
    pub fn new(
        user_storage: Arc<UserPgRepository>,
        session_storage: Arc<SessionPgRepository>,
        password_hasher: Arc<Argon2PasswordHasher>,
        token_service: Arc<JwtTokenService>,
        storage_path: PathBuf,
    ) -> Self {
        Self {
            user_storage,
            session_storage,
            password_hasher,
            token_service,
            user_lifecycle: None,
            storage_path,
            oidc: RwLock::new(OidcState {
                service: None,
                config: None,
            }),
            pending_oidc_flows: Cache::builder()
                .max_capacity(10_000)
                .time_to_live(Duration::from_secs(600))
                .build(),
            pending_oidc_tokens: Cache::builder()
                .max_capacity(10_000)
                .time_to_live(Duration::from_secs(60))
                .build(),
            completed_oidc_logins: Cache::builder()
                .max_capacity(10_000)
                .time_to_live(Duration::from_secs(120))
                .build(),
            backchannel_logout_jti_seen: Cache::builder()
                .max_capacity(10_000)
                // Matches OidcService::validate_logout_token freshness clamp
                // (5 min). Any token older than that fails validation before
                // reaching the jti check, so no need to remember jtis longer.
                .time_to_live(Duration::from_secs(300))
                .build(),
            magic_link_repo: None,
            user_flags_cache: moka::future::Cache::builder()
                .max_capacity(10_000)
                .time_to_live(USER_FLAGS_CACHE_TTL)
                .build(),
            allowed_auth_methods: vec![AuthMethod::Password, AuthMethod::MagicLink],
            auth_policies: Vec::new(),
            require_verified_email: false,
        }
    }

    /// Populates the auth-method allowlist + policy vector +
    /// `require_verified_email` snapshot from the loaded config.
    /// Called by the DI factory. If left uncalled (test builds),
    /// defaults are permissive: both self-service methods enabled,
    /// no policies, verified-email not required.
    pub fn with_auth_policy(
        mut self,
        allowed_methods: Vec<AuthMethod>,
        auth_policies: Vec<AuthPolicy>,
        require_verified_email: bool,
    ) -> Self {
        self.allowed_auth_methods = allowed_methods;
        self.auth_policies = auth_policies;
        self.require_verified_email = require_verified_email;
        self
    }

    /// True iff `POST /api/auth/login` is a supported endpoint on this
    /// deployment. Composes the OIDC `disable_password_login` legacy
    /// flag with the newer `OXICLOUD_AUTH_METHODS` allowlist.
    pub fn is_password_login_allowed(&self) -> bool {
        !self.password_login_disabled()
            && (self.allowed_auth_methods.is_empty()
                || self.allowed_auth_methods.contains(&AuthMethod::Password))
    }

    /// True iff `POST /api/auth/magic-link/send` should mint tokens for
    /// end-user login on this deployment.
    ///
    /// Requires ALL of:
    ///   * repo wired (SMTP configured, tokens can actually be minted);
    ///   * allowlist permits `MagicLink` (or is empty = permissive);
    ///   * OIDC is NOT enabled at the deployment level.
    ///
    /// The OIDC guard is a hard rule: when OIDC is enabled it is the
    /// master identity provider — magic-link would bypass any 2FA / step-up
    /// policy that the IdP enforces. An operator running OIDC + local
    /// accounts hybrid must NOT expose magic-link login for the local
    /// accounts either, because a user provisioned via OIDC-JIT could
    /// receive a magic-link on the same mailbox and sidestep MFA. Admin-
    /// mediated invites use OIDC or password bootstrap instead.
    pub fn is_magic_link_login_allowed(&self) -> bool {
        self.magic_link_enabled()
            && !self.oidc_enabled()
            && (self.allowed_auth_methods.is_empty()
                || self.allowed_auth_methods.contains(&AuthMethod::MagicLink))
    }

    /// True iff login should reject accounts with `email_verified_at IS
    /// NULL`. Backed by `OXICLOUD_REQUIRE_VERIFIED_EMAIL`.
    pub fn require_verified_email(&self) -> bool {
        self.require_verified_email
    }

    /// True iff the login SPA should auto-redirect to the OIDC
    /// authorize endpoint on page load (SSO-only, no click needed).
    ///
    /// Composed to be BOTH policy-set AND effectively-standalone:
    ///   * `AutoRedirectIfStandaloneOidc` policy is in the vector, AND
    ///   * OIDC is enabled AND is the only WORKING login method
    ///     (password + magic-link both refused by the composition of
    ///     the allowlist + OIDC-master rule).
    ///
    /// When the policy is set but other methods are also live, this is
    /// a silent no-op — the FE renders the multi-method chooser. If
    /// the policy is NOT set, this is always false regardless.
    pub fn auto_redirect_to_oidc(&self) -> bool {
        self.auth_policies
            .contains(&AuthPolicy::AutoRedirectIfStandaloneOidc)
            && self.oidc_enabled()
            && !self.is_password_login_allowed()
            && !self.is_magic_link_login_allowed()
    }

    /// Resolve a login-identifier (username OR email) to the account's
    /// registered email address. Mirrors the `POST /api/auth/login`
    /// dispatcher (`@` presence → email lookup, else → username
    /// lookup). Returns `None` when the identifier doesn't match any
    /// account — callers that need anti-enumeration semantics MUST
    /// still return their uniform response after logging the reason.
    ///
    /// The username namespace forbids `@` (PR 16), so the two paths
    /// are disjoint — no ambiguity.
    pub async fn resolve_login_identifier_to_email(&self, identifier: &str) -> Option<String> {
        if identifier.contains('@') {
            Some(identifier.to_string())
        } else {
            self.user_storage
                .get_user_by_username(identifier)
                .await
                .ok()
                .map(|u| u.email().to_string())
        }
    }

    /// Direct lookup helpers used by handlers that need the full `User`
    /// entity (not just the email). Mirrors the internal `user_storage`
    /// calls the service already makes in `login`. Currently used by
    /// the login handler to auto-mint a verification magic-link after
    /// a successful password check.
    pub async fn find_user_by_email(&self, email: &str) -> Result<User, DomainError> {
        self.user_storage.get_user_by_email(email).await
    }
    pub async fn find_user_by_username(&self, username: &str) -> Result<User, DomainError> {
        self.user_storage.get_user_by_username(username).await
    }

    /// Wire the magic-link token repository. Called from the DI factory
    /// when the magic-link feature is configured. Mirrors the
    /// `with_oidc` / `with_user_lifecycle` builder pattern.
    pub fn with_magic_link_repo(mut self, repo: Arc<dyn MagicLinkTokenRepository>) -> Self {
        self.magic_link_repo = Some(repo);
        self
    }

    /// Whether magic-link redemption is wired. Handlers should check this
    /// before attempting to redeem a token; `false` → return 503.
    pub fn magic_link_enabled(&self) -> bool {
        self.magic_link_repo.is_some()
    }

    /// Returns the default quota for the given role, capped to the available
    /// disk space on the filesystem that hosts the storage directory.
    fn capped_quota(&self, role: &UserRole) -> i64 {
        let base_quota = match role {
            UserRole::Admin => DEFAULT_ADMIN_QUOTA,
            _ => DEFAULT_USER_QUOTA,
        };

        match Self::available_disk_space(&self.storage_path) {
            Some(avail) => {
                let avail_i64 = avail as i64;
                if avail_i64 < base_quota {
                    tracing::info!(
                        "Available disk space ({} bytes) is less than default {} quota ({} bytes) — capping quota",
                        avail_i64,
                        if *role == UserRole::Admin {
                            "admin"
                        } else {
                            "user"
                        },
                        base_quota,
                    );
                    avail_i64
                } else {
                    base_quota
                }
            }
            None => {
                tracing::warn!("Could not determine available disk space, using default quota");
                base_quota
            }
        }
    }

    /// Query the available space on the filesystem that contains `path`.
    fn available_disk_space(path: &std::path::Path) -> Option<u64> {
        use fs2::available_space;
        match available_space(path) {
            Ok(space) => Some(space),
            Err(e) => {
                tracing::warn!("Failed to query disk space for {:?}: {}", path, e);
                None
            }
        }
    }

    /// Configures the user-lifecycle dispatcher. Wired by the DI factory
    /// after core services are up. PR 1: only AuditLifecycleHook is
    /// registered, so calls without this configured silently no-op.
    pub fn with_user_lifecycle(mut self, lifecycle: Arc<UserLifecycleService>) -> Self {
        self.user_lifecycle = Some(lifecycle);
        self
    }

    /// Configures the OIDC service
    pub fn with_oidc(self, oidc_service: Arc<OidcService>, oidc_config: OidcConfig) -> Self {
        {
            let mut state = self.oidc.write().unwrap();
            state.service = Some(oidc_service);
            state.config = Some(oidc_config);
        }
        self
    }

    /// Hot-reload OIDC configuration at runtime (called from admin settings service)
    pub fn reload_oidc(&self, oidc_service: Arc<OidcService>, oidc_config: OidcConfig) {
        let mut state = self.oidc.write().unwrap();
        state.service = Some(oidc_service);
        state.config = Some(oidc_config);
    }

    /// Disable OIDC at runtime (called from admin settings service)
    pub fn disable_oidc(&self) {
        let mut state = self.oidc.write().unwrap();
        state.service = None;
        state.config = None;
    }

    /// Returns whether OIDC is configured and enabled
    pub fn oidc_enabled(&self) -> bool {
        let state = self.oidc.read().unwrap();
        state.service.is_some() && state.config.as_ref().is_some_and(|c| c.enabled)
    }

    /// Returns whether password login is disabled (OIDC-only mode)
    pub fn password_login_disabled(&self) -> bool {
        let state = self.oidc.read().unwrap();
        state
            .config
            .as_ref()
            .is_some_and(|c| c.disable_password_login)
    }

    /// Returns a clone of the OIDC config if available
    pub fn oidc_config(&self) -> Option<OidcConfig> {
        let state = self.oidc.read().unwrap();
        state.config.clone()
    }

    /// Returns an Arc clone of the OIDC service if available
    pub fn oidc_service(&self) -> Option<Arc<OidcService>> {
        let state = self.oidc.read().unwrap();
        state.service.clone()
    }

    /// Public registration. Returns one of three outcomes:
    /// - `Created(user)` — a user was actually created
    /// - `UsernameTaken` / `EmailTaken` — collision; no DB write
    ///
    /// The handler decides the HTTP shape based on whether SMTP is
    /// available (anti-enumeration uniform 200 vs classic 201/409).
    /// The service emits the same audit-log entries either way — the
    /// audit channel is the source of truth for the actual outcome.
    ///
    /// Real failures (DB error, password too short, etc.) surface as
    /// `Err`.
    pub async fn register(&self, dto: RegisterDto) -> Result<RegisterResult, DomainError> {
        // Username uniqueness (only when a username was supplied — None
        // is the "claim later" path, multiple NULLs are allowed by the
        // UNIQUE index per Postgres semantics).
        if let Some(ref username) = dto.username
            && self
                .user_storage
                .get_user_by_username(username)
                .await
                .is_ok()
        {
            tracing::info!(
                target: "audit",
                event = "auth.register",
                reason = "username_taken",
                attempted_username = %username,
                attempted_email = %dto.email,
                "🛂 register collision: username '{}' already exists",
                username,
            );
            return Ok(RegisterResult::UsernameTaken);
        }

        if self
            .user_storage
            .get_user_by_email(&dto.email)
            .await
            .is_ok()
        {
            tracing::info!(
                target: "audit",
                event = "auth.register",
                reason = "email_taken",
                attempted_email = %dto.email,
                "🛂 register collision: email '{}' is already registered",
                dto.email,
            );
            return Ok(RegisterResult::EmailTaken);
        }

        // SECURITY: Public registration ALWAYS creates regular users.
        // Admin users can only be created via:
        //   1. The one-time /api/setup endpoint (first boot)
        //   2. The admin panel (admin_create_user)
        let role = UserRole::User;
        let quota = self.capped_quota(&role);

        // Validate password length before hashing — only when one is
        // supplied. Omitted password means the user opts into the
        // magic-link bootstrap path.
        let password_hash = match dto.password {
            Some(ref pw) => {
                if pw.len() < 8 {
                    return Err(DomainError::new(
                        ErrorKind::InvalidInput,
                        "User",
                        "Password must be at least 8 characters long",
                    ));
                }
                Some(self.password_hasher.hash_password(pw).await?)
            }
            None => None,
        };

        let user = User::new(
            dto.email.clone(),
            dto.username.clone(),
            password_hash,
            None,
            None,
            role,
            quota,
            false,
        )
        .map_err(|e| {
            DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                format!("Error creating user: {}", e),
            )
        })?;

        // Save user
        let created_user = self.user_storage.create_user(user).await?;

        // Lifecycle: PersonalDriveLifecycleHook handles personal-folder
        // creation (was inlined here pre-PR 3); audit log + future
        // provisioning steps land here too.
        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_created(&created_user).await;
        }

        tracing::info!(
            target: "audit",
            event = "auth.register",
            reason = "created",
            user_id = %created_user.id(),
            username = %created_user.display_for_audit(),
            email = %created_user.email(),
            is_external = false,
            "🛂 user registered",
        );
        Ok(RegisterResult::Created(Box::new(UserDto::from(
            created_user,
        ))))
    }

    /// Create the first admin user during initial system setup.
    ///
    /// This is called by the `/api/setup` endpoint after verifying the setup
    /// token. It unconditionally creates an admin user. The caller (handler)
    /// is responsible for:
    ///   1. Verifying the setup token
    ///   2. Checking that the system is not already initialized
    ///   3. Marking the system as initialized after this call succeeds
    pub async fn setup_create_admin(
        &self,
        username: String,
        email: String,
        password: String,
    ) -> Result<UserDto, DomainError> {
        // Validate username
        if username.len() < 3 || username.len() > 254 {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "Username must be between 3 and 254 characters".to_string(),
            ));
        }

        // Check for duplicate username
        if self
            .user_storage
            .get_user_by_username(&username)
            .await
            .is_ok()
        {
            return Err(DomainError::new(
                ErrorKind::AlreadyExists,
                "User",
                format!("User '{}' already exists", username),
            ));
        }

        // Check email uniqueness
        if self.user_storage.get_user_by_email(&email).await.is_ok() {
            return Err(DomainError::new(
                ErrorKind::AlreadyExists,
                "User",
                format!("Email '{}' is already registered", email),
            ));
        }

        // Validate password
        if password.len() < 8 {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "Password must be at least 8 characters long".to_string(),
            ));
        }

        let role = UserRole::Admin;
        let quota = self.capped_quota(&role);
        let password_hash = self.password_hasher.hash_password(&password).await?;

        let user = User::new(
            email,
            Some(username.clone()),
            Some(password_hash),
            None,
            None,
            role,
            quota,
            false,
        )
        .map_err(|e| {
            DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                format!("Error creating admin user: {}", e),
            )
        })?;

        // First-run admin is authoritative by definition — they set the
        // password themselves, at the console, on a fresh install. Mark
        // verified so `OXICLOUD_REQUIRE_VERIFIED_EMAIL` never locks the
        // sole account with root-level power out of their own instance.
        let mut user = user;
        user.mark_email_verified();

        let created_user = self.user_storage.create_user(user).await?;

        // Lifecycle: notify hooks. PR 3 moves home-folder creation into
        // PersonalDriveLifecycleHook fired here.
        // Lifecycle: PersonalDriveLifecycleHook provisions the admin's
        // home folder. Audit logs the creation event.
        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_created(&created_user).await;
        }

        tracing::info!(
            "Initial admin created via setup: {} ({})",
            username,
            created_user.id()
        );
        Ok(UserDto::from(created_user))
    }

    pub async fn login(&self, dto: LoginDto) -> Result<AuthResponseDto, DomainError> {
        // Gate: policy may forbid password logins entirely (either the
        // legacy OIDC-only mode or the newer `OXICLOUD_AUTH_METHODS`
        // allowlist without `password`). Refuse BEFORE the user lookup
        // so we don't leak account existence via timing on a disabled
        // endpoint.
        if !self.is_password_login_allowed() {
            tracing::info!(
                target: "audit",
                event = "auth.login_rejected",
                reason = "password_login_disabled",
                attempted_username = %dto.username,
                "🔐 login rejected: password login disabled by policy",
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Password login is disabled",
            ));
        }

        // Dispatch on `@` in the input: presence of `@` means an email
        // was typed, absence means a username. The two namespaces are
        // provably disjoint (PR 16 forbids `@` in usernames), so this
        // is unambiguous — one DB lookup, no fallback chain.
        let lookup = if dto.username.contains('@') {
            self.user_storage.get_user_by_email(&dto.username).await
        } else {
            self.user_storage.get_user_by_username(&dto.username).await
        };
        let mut user = lookup.map_err(|_| {
            // Audit: unknown-identifier login attempt. Reason key kept
            // stable so log search can aggregate without parsing the
            // human-readable message. Caller's client IP + request id
            // are attached automatically by the request-scope span.
            tracing::info!(
                target: "audit",
                event = "auth.login_rejected",
                reason = "unknown_user",
                attempted_username = %dto.username,
                "🔐 login rejected: no such user '{}'",
                dto.username,
            );
            DomainError::new(ErrorKind::AccessDenied, "Auth", "Invalid credentials")
        })?;

        // Check if user is active
        if !user.is_active() {
            tracing::info!(
                target: "audit",
                event = "auth.login_rejected",
                reason = "account_deactivated",
                user_id = %user.id(),
                username = %user.display_for_audit(),
                "🔐 login rejected: account deactivated for '{}'",
                user.display_for_audit(),
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Account deactivated",
            ));
        }

        // Verify password using the injected hasher. If the user has no
        // password configured (externals, OIDC-only), short-circuit to
        // "invalid credentials" — the password-login path never accepts
        // a NULL hash.
        let Some(hash) = user.password_hash() else {
            tracing::info!(
                target: "audit",
                event = "auth.login_rejected",
                reason = "no_password",
                user_id = %user.id(),
                username = %user.display_for_audit(),
                "🔐 login rejected: user has no password configured for '{}'",
                user.display_for_audit(),
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Invalid credentials",
            ));
        };
        let is_valid = self
            .password_hasher
            .verify_password(&dto.password, hash)
            .await?;

        if !is_valid {
            tracing::info!(
                target: "audit",
                event = "auth.login_rejected",
                reason = "bad_password",
                user_id = %user.id(),
                username = %user.display_for_audit(),
                "🔐 login rejected: bad password for '{}'",
                user.display_for_audit(),
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Invalid credentials",
            ));
        }

        // Gate: `OXICLOUD_REQUIRE_VERIFIED_EMAIL`. Checked AFTER password
        // validation so an attacker with only a username cannot probe
        // account verification state (the response shape is
        // `Invalid credentials` for bad passwords regardless of whether
        // the email is verified — a wrong-password observer learns
        // nothing).
        //
        // ADMIN EXEMPTION: admins are trusted by fiat and predate this
        // gate. Fresh admin accounts (admin_create_user /
        // setup_create_admin) are stamped verified at creation; the
        // exemption covers pre-existing admin accounts installed before
        // the flag shipped.
        //
        // The auto-send of a verification magic-link when this branch
        // fires is done at the handler layer (login handler triggers
        // `send_verification_link_authenticated`) rather than here —
        // the service returns the distinguished error and the handler
        // orchestrates the side effect. Keeps this method side-effect-
        // free on the audit path.
        if self.require_verified_email
            && !matches!(user.role(), UserRole::Admin)
            && !user.is_email_verified()
        {
            tracing::info!(
                target: "audit",
                event = "auth.login_rejected",
                reason = "email_not_verified",
                user_id = %user.id(),
                username = %user.display_for_audit(),
                "🔐 login rejected: email not verified for '{}' (password OK)",
                user.display_for_audit(),
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Email not verified",
            ));
        }

        // Lifecycle: dispatch login BEFORE register_login() so hooks
        // observing `last_login_at().is_none()` see "first ever login"
        // correctly. See tip #1 in user_lifecycle.rs.
        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_login(&user).await;
        }

        // Update last login (in-memory only — the DTO below carries it).
        // The full-row `update_user` this path used to issue was 100%
        // redundant: `create_session` stamps `last_login_at`/`updated_at`
        // in its own transaction right below, and nothing re-reads the row
        // in between. Dropping it removes one transaction + a 17-column
        // rewrite (incl. the up-to-512 KiB avatar) per password login
        // (benches/ROUND12.md §2, 4.45x).
        user.register_login();

        // Generate tokens using the injected token service
        let access_token = self.token_service.generate_access_token(&user)?;

        let refresh_token = self.token_service.generate_refresh_token();

        // Save session — new login starts a new token family
        let session = Session::new(
            user.id(),
            refresh_token.clone(),
            None, // IP (can be added from the HTTP layer)
            None, // User-Agent (can be added from the HTTP layer)
            self.token_service.refresh_token_expiry_days(),
            Uuid::new_v4(),
        );

        self.session_storage.create_session(session).await?;

        // Authentication response
        Ok(AuthResponseDto {
            user: UserDto::from(user),
            access_token,
            refresh_token,
            token_type: "Bearer".to_string(),
            expires_in: self.token_service.refresh_token_expiry_secs(),
        })
    }

    /// Redeem a magic-link token and emit a fresh session in one shot.
    ///
    /// The flow:
    /// 1. Look up the token in the repo. Unknown token → `NotFound`.
    /// 2. Atomically transition `Pending → Used` via the repo's
    ///    `mark_used()` (single SQL UPDATE with `WHERE status='pending'`).
    ///    A second redemption attempt receives `Ok(false)` and is rejected
    ///    as `AccessDenied`.
    /// 3. Load the user, verify they're active.
    /// 4. Dispatch `on_user_login` (so PersonalDriveLifecycleHook can
    ///    safety-net any internal user whose first credential happens
    ///    to be a magic link — externals short-circuit by `is_external()`).
    /// 5. Register login + persist + issue session in the same pipeline
    ///    as password login.
    ///
    /// The returned `MagicLinkRedemption` carries the resource target so
    /// the handler can build the redirect URL.
    ///
    /// Returns `ServiceUnavailable` (mapped from `NotImplemented`) when
    /// the magic-link repo isn't wired — the handler maps that to HTTP 503.
    ///
    /// `incoming_challenge` is the value the handler read from the
    /// browser's `oxicloud_magic_request` cookie (or `None` if absent).
    /// `cross_browser_confirmed` is `true` when the user has clicked
    /// through the cross-browser confirmation page (PR 22).
    pub async fn redeem_magic_link(
        &self,
        token: &str,
        incoming_challenge: Option<&str>,
        cross_browser_confirmed: bool,
    ) -> Result<MagicLinkRedeemResult, DomainError> {
        let repo = self.magic_link_repo.as_ref().ok_or_else(|| {
            DomainError::new(
                ErrorKind::NotImplemented,
                "MagicLink",
                "magic-link feature is not configured on this server",
            )
        })?;

        // Defense-in-depth: if magic-link login was minted under an older
        // policy and the operator has since flipped OIDC on (or dropped
        // `MagicLink` from `OXICLOUD_AUTH_METHODS`), we must not honour
        // pre-existing login tokens. Invitation tokens (resource_kind =
        // File / Folder) are checked separately below — they represent
        // an admin-mediated invite, which is a distinct policy question
        // from "self-service login via email".
        //
        // We do the token lookup FIRST so we can classify by
        // `resource_kind()` before applying the gate — invitations
        // survive, plain logins do not.
        let mlt = repo.find_by_token(token).await?.ok_or_else(|| {
            // Audit: unknown / forged magic-link redemption. The first
            // 8 chars of the bogus token are logged so a recurring
            // probe pattern is recognisable without dumping the full
            // secret to the log stream.
            let token_preview: String = token.chars().take(8).collect();
            tracing::info!(
                target: "audit",
                event = "magic_link.redemption_rejected",
                reason = "unknown_token",
                token_prefix = %token_preview,
                "🔗 magic-link rejected: unknown token (prefix='{}…')",
                token_preview,
            );
            DomainError::new(
                ErrorKind::NotFound,
                "MagicLink",
                "unknown or invalid magic link",
            )
        })?;

        // Enforce the login-magic-link policy on stale tokens.
        // resource_kind = None means "plain login-via-email"; anything
        // else is an invite (which follows its own admin-mediated
        // trust chain). Refuse the login case if the current policy
        // forbids magic-link login.
        if mlt.resource_kind().is_none() && !self.is_magic_link_login_allowed() {
            tracing::info!(
                target: "audit",
                event = "magic_link.redemption_rejected",
                reason = "login_disabled_by_policy",
                token_id = %mlt.id(),
                user_id = %mlt.user_id(),
                "🔗 magic-link rejected: login-via-email disabled by policy (OIDC-master or allowlist)",
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "MagicLink",
                "magic-link login is disabled",
            ));
        }

        // Friendly early-rejection messages. The atomic `mark_used`
        // below is the canonical single-use guard.
        if mlt.status() == MagicLinkStatus::Used {
            tracing::info!(
                target: "audit",
                event = "magic_link.redemption_rejected",
                reason = "already_used",
                token_id = %mlt.id(),
                user_id = %mlt.user_id(),
                "🔗 magic-link rejected: token already used for user {}",
                mlt.user_id(),
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "MagicLink",
                "this magic link has already been used",
            ));
        }
        if mlt.is_expired() {
            tracing::info!(
                target: "audit",
                event = "magic_link.redemption_rejected",
                reason = "expired",
                token_id = %mlt.id(),
                user_id = %mlt.user_id(),
                "🔗 magic-link rejected: token expired for user {}",
                mlt.user_id(),
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "MagicLink",
                "this magic link has expired",
            ));
        }

        // PR 22 — browser binding for login-via-email tokens. When the
        // token carries a `request_challenge`, compare it against the
        // cookie the handler extracted. Mismatch surfaces as a
        // cross-browser confirmation page (the handler renders the
        // HTML); the user clicks Continue and we re-enter with
        // `cross_browser_confirmed = true`. Invitation tokens have no
        // challenge — they bypass this check entirely (cross-device by
        // design). The token is NOT marked used on the prompt path —
        // it stays redeemable for the confirm round-trip.
        if let Some(expected) = mlt.request_challenge()
            && !cross_browser_confirmed
            && incoming_challenge != Some(expected)
        {
            tracing::info!(
                target: "audit",
                event = "magic_link.cross_browser_prompt",
                token_id = %mlt.id(),
                user_id = %mlt.user_id(),
                incoming_present = incoming_challenge.is_some(),
                "🔗 magic-link cross-browser: cookie absent or mismatched for user {}",
                mlt.user_id(),
            );
            return Ok(MagicLinkRedeemResult::NeedsCrossBrowserConfirm);
        }

        let consumed = repo.mark_used(mlt.id()).await?;
        if !consumed {
            // Either a concurrent redemption beat us, or the row was
            // marked expired by the sweeper between our find and update.
            tracing::info!(
                target: "audit",
                event = "magic_link.redemption_rejected",
                reason = "race_or_swept",
                token_id = %mlt.id(),
                user_id = %mlt.user_id(),
                "🔗 magic-link rejected: lost race to mark_used (user {})",
                mlt.user_id(),
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "MagicLink",
                "this magic link has already been used",
            ));
        }

        let mut user = self.user_storage.get_user_by_id(mlt.user_id()).await?;
        if !user.is_active() {
            tracing::info!(
                target: "audit",
                event = "magic_link.redemption_rejected",
                reason = "account_deactivated",
                token_id = %mlt.id(),
                user_id = %user.id(),
                username = %user.display_for_audit(),
                "🔗 magic-link rejected: account deactivated for '{}'",
                user.display_for_audit(),
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Account deactivated",
            ));
        }

        // Dispatch BEFORE register_login so hooks observing
        // `last_login_at().is_none()` see "first ever login" correctly.
        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_login(&user).await;
        }
        user.register_login();
        // PR 23: clicking the magic-link IS proof of email control —
        // stamp the verification (idempotent, preserves the first
        // timestamp). Applies to both invitation and login-via-email
        // tokens. Narrow single-column write: `last_login_at` is stamped
        // by `create_session` below, so the full-row `update_user` this
        // path used to issue only ever contributed the verification
        // timestamp (benches/ROUND12.md §3, 8.9x).
        user.mark_email_verified();
        self.user_storage.mark_email_verified(user.id()).await?;

        let access_token = self.token_service.generate_access_token(&user)?;
        let refresh_token = self.token_service.generate_refresh_token();
        let session = Session::new(
            user.id(),
            refresh_token.clone(),
            None,
            None,
            self.token_service.refresh_token_expiry_days(),
            Uuid::new_v4(),
        );
        self.session_storage.create_session(session).await?;

        tracing::info!(
            target: "audit",
            event = "magic_link.redeemed",
            user_id = %user.id(),
            username = %user.display_for_audit(),
            is_external = user.is_external(),
            resource_kind = ?mlt.resource_kind(),
            resource_id = ?mlt.resource_id(),
            cross_browser_confirmed = cross_browser_confirmed,
        );

        let auth = AuthResponseDto {
            user: UserDto::from(user),
            access_token,
            refresh_token,
            token_type: "Bearer".to_string(),
            expires_in: self.token_service.refresh_token_expiry_secs(),
        };

        Ok(MagicLinkRedeemResult::Allowed(Box::new(
            MagicLinkRedemption {
                auth,
                resource_kind: mlt.resource_kind(),
                resource_id: mlt.resource_id(),
            },
        )))
    }

    /// Verifies username/password credentials without creating a session.
    pub async fn verify_credentials(
        &self,
        username: &str,
        password: &str,
    ) -> Result<crate::application::dtos::user_dto::CurrentUser, DomainError> {
        let user = self
            .user_storage
            .get_user_by_username(username)
            .await
            .map_err(|_| {
                DomainError::new(ErrorKind::AccessDenied, "Auth", "Invalid credentials")
            })?;

        if !user.is_active() {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Account deactivated",
            ));
        }

        let Some(hash) = user.password_hash() else {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Invalid credentials",
            ));
        };
        let is_valid = self.password_hasher.verify_password(password, hash).await?;

        if !is_valid {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Invalid credentials",
            ));
        }

        Ok(crate::application::dtos::user_dto::CurrentUser {
            id: user.id(),
            username: std::sync::Arc::from(user.username().unwrap_or("")),
            email: std::sync::Arc::from(user.email()),
            role: smol_str::SmolStr::new_static(user.role().as_str()),
        })
    }

    pub async fn refresh_token(
        &self,
        dto: RefreshTokenDto,
    ) -> Result<AuthResponseDto, DomainError> {
        // Get valid session
        let session = self
            .session_storage
            .get_session_by_refresh_token(&dto.refresh_token)
            .await?;

        // Reuse detection: a revoked token being replayed indicates the token was
        // stolen after rotation. Invalidate the entire family to protect all devices.
        if session.is_revoked() {
            tracing::warn!(
                user_id = %session.user_id(),
                family_id = %session.family_id(),
                "Refresh token reuse detected — revoking entire token family"
            );
            self.session_storage
                .revoke_session_family(session.family_id())
                .await?;
            // Lifecycle: TokenReused logout — fired once per logical
            // revoke-family call. PR 4 may refine to per-session firing.
            if let Some(lc) = &self.user_lifecycle
                && let Ok(user) = self.user_storage.get_user_by_id(session.user_id()).await
            {
                lc.dispatch_logout(user, LogoutReason::TokenReused);
            }
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Session expired or invalid",
            ));
        }

        if session.is_expired() {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Session expired or invalid",
            ));
        }

        // Get user
        let user = self.user_storage.get_user_by_id(session.user_id()).await?;

        // Check if user is active
        if !user.is_active() {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Account deactivated",
            ));
        }

        // Generate new tokens
        let access_token = self.token_service.generate_access_token(&user)?;
        let new_refresh_token = self.token_service.generate_refresh_token();

        // New session inherits the family_id so reuse of any ancestor triggers
        // full-family revocation. Revoking the old session and inserting the
        // new one happen in ONE transaction (`rotate_session`) — this path
        // used to pay two BEGIN/COMMIT pairs per refresh, and DAV clients
        // rotate constantly (benches/ROUND12.md §4).
        let new_session = Session::new(
            user.id(),
            new_refresh_token.clone(),
            None,
            None,
            self.token_service.refresh_token_expiry_days(),
            session.family_id(),
        );

        self.session_storage
            .rotate_session(session.id(), new_session)
            .await?;

        Ok(AuthResponseDto {
            user: UserDto::from(user),
            access_token,
            refresh_token: new_refresh_token,
            token_type: "Bearer".to_string(),
            expires_in: self.token_service.refresh_token_expiry_secs(),
        })
    }

    /// Revoke the caller's session and, when the session was minted through
    /// OIDC, build the RP-initiated logout URL so the browser can also end
    /// the IdP's SSO session (fixes shared-computer scenario where local
    /// logout alone would let the next `/login` visit silently re-auth
    /// through a still-valid IdP cookie).
    ///
    /// Returns `Ok(None)` for:
    /// - non-OIDC sessions (password / magic-link) — nothing to propagate;
    /// - OIDC sessions where the IdP's discovery doesn't advertise an
    ///   `end_session_endpoint` — no way to propagate. Callers should still
    ///   clear local cookies; the IdP session will time out on its own.
    ///
    /// `post_logout_redirect_uri` MUST be registered on the OIDC client
    /// (Keycloak: "Valid post logout redirect URIs"), else the IdP refuses
    /// the redirect back and the user is left on the IdP error page.
    pub async fn logout(
        &self,
        user_id: Uuid,
        refresh_token: &str,
        post_logout_redirect_uri: &str,
    ) -> Result<Option<String>, DomainError> {
        // Get session
        let session = match self
            .session_storage
            .get_session_by_refresh_token(refresh_token)
            .await
        {
            Ok(s) => s,
            // If the session doesn't exist, we consider the logout successful
            Err(_) => return Ok(None),
        };

        // Verify that the session belongs to the user
        if session.user_id() != user_id {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "The session does not belong to the user",
            ));
        }

        // Capture the id_token BEFORE revocation so we can build the
        // RP-initiated logout URL. Revocation only flips a boolean, so the
        // row (and its oidc_id_token column) survives — this order is
        // defensive against a future change that hard-deletes on revoke.
        let id_token_hint = session.oidc_id_token().map(str::to_string);

        // Revoke session
        self.session_storage.revoke_session(session.id()).await?;

        // Lifecycle: notify hooks. One extra DB roundtrip per logout
        // (user load) is acceptable — logout is rare. Failure to load
        // the user is non-fatal: we already revoked the session.
        if let Some(lc) = &self.user_lifecycle
            && let Ok(user) = self.user_storage.get_user_by_id(user_id).await
        {
            lc.dispatch_logout(user, LogoutReason::UserInitiated);
        }

        // If this was an OIDC session AND the IdP advertises an
        // end_session_endpoint, build the RP-initiated logout URL.
        // Otherwise return None — the caller clears local state either way.
        let Some(id_token) = id_token_hint else {
            return Ok(None);
        };
        let oidc = { self.oidc.read().unwrap().service.clone() };
        let Some(oidc) = oidc else {
            return Ok(None);
        };
        oidc.build_end_session_url(&id_token, post_logout_redirect_uri)
            .await
    }

    /// OIDC Back-Channel Logout 1.0 entry point.
    ///
    /// Called by the public BCL handler with an unvalidated logout_token
    /// (as delivered by the IdP over server-to-server HTTP). This method
    /// owns the full flow:
    ///
    ///   1. Validate the token (signature + spec-mandated claims).
    ///   2. Reject replays via the `jti` seen-cache (best-effort — tokens
    ///      without a jti are impossible to dedupe cheaply, so the revoke
    ///      path stays idempotent as a safety net).
    ///   3. Prefer `sid` (per-device revocation) over `sub` (all-device)
    ///      when both are present — matches the intent of the IdP that
    ///      chose to include `sid`.
    ///   4. Dispatch per-user lifecycle hooks so downstream systems
    ///      (websocket subscriptions, etc.) can react.
    ///
    /// Returns the count of session rows actually flipped from
    /// `revoked=false` to `revoked=true` — 0 is a fine outcome (already
    /// logged out or unknown user; both are indistinguishable from the
    /// IdP's viewpoint and both mean "OxiCloud has no live session for
    /// that identity").
    pub async fn backchannel_logout(&self, logout_token: &str) -> Result<u64, DomainError> {
        let oidc = {
            let state = self.oidc.read().unwrap();
            state.service.clone().ok_or_else(|| {
                DomainError::new(
                    ErrorKind::InternalError,
                    "OIDC",
                    "OIDC service not configured — cannot process backchannel logout",
                )
            })?
        };

        let claims = oidc.validate_logout_token(logout_token).await?;

        // Replay guard. Insertion-first-then-check: `get()` + `insert()`
        // is racy across concurrent BCL calls with the same jti (both
        // could observe absent, both would run the revocation), but the
        // revocation is idempotent so at worst we double-audit. If it
        // matters more we can move to `entry().or_insert()` semantics.
        if let Some(jti) = claims.jti.as_ref() {
            if self.backchannel_logout_jti_seen.get(jti).is_some() {
                tracing::info!(
                    target: "audit",
                    event = "oidc.backchannel_logout_replayed",
                    jti = %jti,
                    "👮🏻‍♂️ OIDC backchannel-logout token replayed — ignored"
                );
                return Ok(0);
            }
            self.backchannel_logout_jti_seen.insert(jti.clone(), ());
        }

        let provider_name = oidc.provider_name().to_string();

        // Resolve which sessions to revoke.
        let affected_user_ids: Vec<Uuid> = if let Some(sid) = claims.sid.as_ref() {
            self.session_storage
                .revoke_sessions_by_oidc_sid(sid)
                .await?
        } else if let Some(sub) = claims.sub.as_ref() {
            self.session_storage
                .revoke_user_sessions_by_oidc_subject(&provider_name, sub)
                .await?
                .into_iter()
                .collect()
        } else {
            // Validator already enforced sub-or-sid presence; being here
            // means the validator has drifted. Fail loud.
            return Err(DomainError::new(
                ErrorKind::InternalError,
                "OIDC",
                "backchannel_logout: validator returned claims without sub or sid",
            ));
        };

        // Dispatch lifecycle hooks per unique affected user. Best-effort;
        // hook failures don't undo the revocation (which already committed).
        // Deduped because sid-based revocation could theoretically match
        // multiple sessions for the same user if the IdP re-issued sids.
        if let Some(lc) = &self.user_lifecycle {
            let unique: std::collections::HashSet<Uuid> =
                affected_user_ids.iter().copied().collect();
            for uid in unique {
                if let Ok(user) = self.user_storage.get_user_by_id(uid).await {
                    lc.dispatch_logout(user, LogoutReason::IdpNotification);
                }
            }
        }

        Ok(affected_user_ids.len() as u64)
    }

    pub async fn logout_all(&self, user_id: Uuid) -> Result<u64, DomainError> {
        // Revoke all user sessions
        let revoked_count = self
            .session_storage
            .revoke_all_user_sessions(user_id)
            .await?;

        Ok(revoked_count)
    }

    /// External → internal account upgrade.
    ///
    /// Contract:
    ///   * Caller must be authenticated as the user being upgraded.
    ///     Session-elevation is not required — being logged in as
    ///     yourself IS the proof of intent.
    ///   * User must be `is_external = true` — else the entity refuses
    ///     with `UserError::AlreadyInternal`, surfaced as `error_type =
    ///     "AlreadyInternal"` (409).
    ///   * OIDC-linked users are refused (the IdP owns their identity).
    ///   * If `dto.password` is `None`, the deployment MUST have magic-
    ///     link login enabled — otherwise the upgraded user would have
    ///     no login path. Refused with `error_type = "PasswordRequired"`
    ///     (400) in that case.
    ///   * Domain-allowlist check lives at the HANDLER layer, mirroring
    ///     the register handler — the service doesn't hold that config.
    ///
    /// On success:
    ///   * User's `is_external` flipped to `false`.
    ///   * `password_hash` set from the provided password (Argon2id) or
    ///     left as-is (magic-link-only upgrade).
    ///   * `storage_quota_bytes` set to the default user quota (capped
    ///     by disk).
    ///   * `PersonalDriveLifecycleHook::on_upgraded_to_internal` runs and
    ///     provisions the home drive + root folder + owner grant via the
    ///     atomic CTE. Failure at this step is logged but the row update
    ///     stands — the next login's `on_user_login` safety-net retries
    ///     provisioning.
    ///   * `user_flags_cache` invalidated eagerly so per-request guards
    ///     (WebDAV / CalDAV / CardDAV) observe the new `is_external`
    ///     within cache-round-trip time, not the 30-second TTL.
    ///   * Audit log emits `event="user.upgraded_to_internal"` via the
    ///     `AuditLifecycleHook` on the dispatched event.
    pub async fn upgrade_to_internal(
        &self,
        caller_id: Uuid,
        dto: UpgradeToInternalDto,
    ) -> Result<UserDto, DomainError> {
        let mut user = self.user_storage.get_user_by_id(caller_id).await?;

        // Precondition: caller is currently external. Fast-path 409 so
        // the audit log carries a clear reason before the entity's own
        // guard fires.
        if !user.is_external() {
            tracing::info!(
                target: "audit",
                event = "user.upgrade_rejected",
                reason = "already_internal",
                user_id = %user.id(),
                username = %user.display_for_audit(),
                "👮🏻‍♂️ upgrade refused: user is already internal",
            );
            return Err(DomainError::new(
                ErrorKind::Conflict,
                "User",
                "Account is already internal",
            ));
        }

        // OIDC-linked: never. The IdP owns identity and role.
        if user.is_oidc_user() {
            tracing::info!(
                target: "audit",
                event = "user.upgrade_rejected",
                reason = "oidc_user",
                user_id = %user.id(),
                "👮🏻‍♂️ upgrade refused: OIDC-linked user is managed by the IdP",
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "User",
                "SSO/OIDC accounts are managed by your identity provider",
            ));
        }

        // Password policy composite:
        //   * Provided → validate + hash.
        //   * Omitted   → only accepted when magic-link login is on
        //     for this deployment (otherwise no login path post-upgrade).
        let password_hash = match dto.password.as_deref() {
            Some(pw) if !pw.is_empty() => {
                if pw.len() < 8 {
                    return Err(DomainError::new(
                        ErrorKind::InvalidInput,
                        "User",
                        "Password must be at least 8 characters long",
                    ));
                }
                Some(self.password_hasher.hash_password(pw).await?)
            }
            _ => {
                if !self.is_magic_link_login_allowed() {
                    tracing::info!(
                        target: "audit",
                        event = "user.upgrade_rejected",
                        reason = "password_required",
                        user_id = %user.id(),
                        "👮🏻‍♂️ upgrade refused: password omitted but magic-link login is not available on this deployment",
                    );
                    return Err(DomainError::new(
                        ErrorKind::InvalidInput,
                        "User",
                        "Password is required — magic-link login is not enabled on this deployment",
                    ));
                }
                None
            }
        };

        // Quota policy: same as a fresh regular-user signup.
        let quota = self.capped_quota(&UserRole::User);

        user.promote_to_internal(password_hash, quota)
            .map_err(|e| {
                // The entity refuses `AlreadyInternal` here belt-and-braces
                // against a race with a concurrent upgrade; the pre-check
                // above already covers the intended path.
                DomainError::new(
                    ErrorKind::Conflict,
                    "User",
                    format!("Upgrade refused: {}", e),
                )
            })?;

        let updated = self.user_storage.update_user(user).await?;

        // Invalidate the flags cache so subsequent per-request guards
        // observe the new `is_external=false` without waiting for the
        // 30-second TTL. Same pattern as `change_user_role`.
        self.user_flags_cache.invalidate(&caller_id).await;

        // Dispatch — home-drive provisioning happens here. Log-and-
        // continue: a provisioning failure leaves the row updated and
        // the next login's safety-net (`on_user_login`) retries.
        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_upgraded_to_internal(&updated).await;
        }

        Ok(UserDto::from(updated))
    }

    /// Admin-driven external → internal promotion.
    ///
    /// Same wire outcome as [`Self::upgrade_to_internal`] but the actor
    /// is an operator, not the target user. The target's password stays
    /// as it was (usually `None` — magic-link-only accounts) so the
    /// deployment MUST have magic-link login enabled, otherwise the
    /// promoted user has no login path at all.
    ///
    /// Refuses:
    /// - Target is already internal → 409 `AlreadyInternal`.
    /// - Target is OIDC-linked → 403 (IdP owns identity).
    /// - Magic-link login disabled deployment-wide → 400 with a hint.
    ///
    /// On success:
    /// - `is_external → false`, `storage_quota_bytes → capped default`.
    /// - Home-drive provisioning fires via
    ///   `PersonalDriveLifecycleHook::on_upgraded_to_internal` — same
    ///   hook the self-upgrade path uses.
    /// - `user_flags_cache` invalidated on the target so per-request
    ///   guards observe the new flag within one cache round-trip.
    /// - Audit line `event = "user.promoted_to_internal_by_admin"`
    ///   with `by = <admin_id>`, `target_id = <user_id>`.
    pub async fn admin_promote_external_to_internal(
        &self,
        admin_id: Uuid,
        target_id: Uuid,
    ) -> Result<UserDto, DomainError> {
        let mut user = self.user_storage.get_user_by_id(target_id).await?;

        if !user.is_external() {
            tracing::info!(
                target: "audit",
                event = "user.promote_rejected",
                reason = "already_internal",
                by = %admin_id,
                target_id = %target_id,
                "👮🏻‍♂️ admin-promote refused: target user is already internal",
            );
            return Err(DomainError::new(
                ErrorKind::Conflict,
                "User",
                "Account is already internal",
            ));
        }

        if user.is_oidc_user() {
            tracing::info!(
                target: "audit",
                event = "user.promote_rejected",
                reason = "oidc_user",
                by = %admin_id,
                target_id = %target_id,
                "👮🏻‍♂️ admin-promote refused: OIDC-linked user is managed by the IdP",
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "User",
                "SSO/OIDC accounts are managed by your identity provider",
            ));
        }

        // Admin can't set a password on the target's behalf, so the
        // upgraded account MUST have magic-link login available on the
        // deployment — otherwise no login path exists post-promotion.
        if !self.is_magic_link_login_allowed() {
            tracing::info!(
                target: "audit",
                event = "user.promote_rejected",
                reason = "no_login_path",
                by = %admin_id,
                target_id = %target_id,
                "👮🏻‍♂️ admin-promote refused: magic-link login disabled and admin can't set the target's password",
            );
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "Cannot promote: magic-link login is disabled on this deployment, so the user would have no login path.",
            ));
        }

        let quota = self.capped_quota(&UserRole::User);

        user.promote_to_internal(None, quota).map_err(|e| {
            DomainError::new(
                ErrorKind::Conflict,
                "User",
                format!("Promote refused: {}", e),
            )
        })?;

        let updated = self.user_storage.update_user(user).await?;

        // Invalidate the target's flags cache — same reason as the
        // self-upgrade path.
        self.user_flags_cache.invalidate(&target_id).await;

        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_upgraded_to_internal(&updated).await;
        }

        tracing::info!(
            target: "audit",
            event = "user.promoted_to_internal_by_admin",
            by = %admin_id,
            target_id = %target_id,
            "👮🏻‍♂️ external user promoted to internal by admin",
        );

        Ok(UserDto::from(updated))
    }

    pub async fn change_password(
        &self,
        user_id: Uuid,
        dto: ChangePasswordDto,
    ) -> Result<(), DomainError> {
        // Get user
        let mut user = self.user_storage.get_user_by_id(user_id).await?;

        // Block password changes for OIDC-provisioned users
        if user.is_oidc_user() {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Password changes are not available for SSO/OIDC accounts. Your password is managed by your identity provider.",
            ));
        }

        // Verify current password using the injected hasher
        let Some(hash) = user.password_hash() else {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Current password is incorrect",
            ));
        };
        let is_valid = self
            .password_hasher
            .verify_password(&dto.current_password, hash)
            .await?;

        if !is_valid {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Auth",
                "Current password is incorrect",
            ));
        }

        // Validate new password
        if dto.new_password.len() < 8 {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "Password must be at least 8 characters long",
            ));
        }

        // Hash new password and update user
        let new_hash = self
            .password_hasher
            .hash_password(&dto.new_password)
            .await?;
        user.update_password_hash(Some(new_hash));

        // Save updated user
        self.user_storage.update_user(user.clone()).await?;

        // Optional: revoke all sessions to force re-login with new password
        self.session_storage
            .revoke_all_user_sessions(user_id)
            .await?;

        // Lifecycle: PasswordChanged logout — fired once per logical
        // revoke-all call. PR 4 may refine to per-session firing.
        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_logout(user, LogoutReason::PasswordChanged);
        }

        Ok(())
    }

    /// Update the profile image for a non-OIDC user.
    pub async fn update_user_image(
        &self,
        caller_id: Uuid,
        image: Option<String>,
    ) -> Result<(), DomainError> {
        let user = self.user_storage.get_user_by_id(caller_id).await?;

        if user.is_oidc_user() {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "User",
                "Avatar is managed by your identity provider and cannot be changed here",
            ));
        }

        if let Some(ref img) = image {
            const MAX_BYTES: usize = 524_288; // 512 KiB
            if img.len() > MAX_BYTES {
                return Err(DomainError::new(
                    ErrorKind::InvalidInput,
                    "User",
                    "Image exceeds maximum allowed size (512 KiB)",
                ));
            }
            let valid = img.starts_with("https://")
                || img.starts_with("http://")
                || img.starts_with("data:image/png;base64,")
                || img.starts_with("data:image/webp;base64,")
                || img.starts_with("data:image/jpeg;base64,");
            if !valid {
                return Err(DomainError::new(
                    ErrorKind::InvalidInput,
                    "User",
                    "Image must be an https/http URL or a data URI (png, webp, jpeg)",
                ));
            }
        }

        self.user_storage
            .update_image(caller_id, image)
            .await
            .map_err(DomainError::from)?;

        Ok(())
    }

    pub async fn get_user(&self, user_id: Uuid) -> Result<UserDto, DomainError> {
        let user = self.user_storage.get_user_by_id(user_id).await?;
        Ok(UserDto::from(user))
    }

    /// Cached, image-free lookup of the caller's authorization flags
    /// (`role` / `is_external` / `active`). This is the per-request fast
    /// path for middleware guards: the full `get_user` row fetch drags the
    /// `image` column (a data URI of up to 512 KiB) across the wire, which
    /// a sync client issuing hundreds of DAV requests per minute paid on
    /// every single one just to read a boolean.
    ///
    /// Staleness is bounded by [`USER_FLAGS_CACHE_TTL`]; role and active
    /// changes made through this service invalidate the entry eagerly.
    pub async fn get_user_flags(&self, user_id: Uuid) -> Result<UserFlags, DomainError> {
        // Single-flight: concurrent misses for the same user coalesce
        // into ONE storage lookup; errors are never cached (same herd
        // shape ROUND3 fixed for basic-auth, minus the Argon2 cost).
        self.user_flags_cache
            .try_get_with(user_id, async {
                Ok::<_, DomainError>(self.user_storage.get_user_flags(user_id).await?)
            })
            .await
            // try_get_with hands back `Arc<DomainError>` shared by all
            // waiters; DomainError isn't Clone, so rebuild a fresh one
            // preserving the kind / entity / message.
            .map_err(|shared: std::sync::Arc<DomainError>| {
                DomainError::new(shared.kind, shared.entity_type, shared.message.clone())
            })
    }

    /// Apply a profile update on behalf of the calling user (PR 24).
    ///
    /// Hard rules:
    /// - **OIDC users are rejected outright (403)** — their profile
    ///   fields are owned by the IdP. Mirroring writes here would
    ///   create silent divergence.
    /// - **Username is claim-once**: present in `dto` ↔ caller's
    ///   current username must be `None`. Subsequent attempts are
    ///   rejected with 409 `UsernameImmutable`. The immutability
    ///   avoids DAV / NextCloud client breakage (paths include the
    ///   username as a stable identifier).
    /// - **Username uniqueness** is enforced on claim against other
    ///   users (`get_user_by_username`).
    /// - **Given / family names** are freely settable; passing an
    ///   empty string is rejected (use no field for "no change").
    ///
    /// The method is idempotent on no-op DTOs (all fields absent) and
    /// emits an `auth.profile_updated` audit line listing which fields
    /// changed.
    pub async fn update_profile_with_perms(
        &self,
        caller_id: Uuid,
        dto: crate::application::dtos::user_dto::UpdateProfileDto,
        locale_registry: &crate::common::locale::LocaleRegistry,
    ) -> Result<UserDto, DomainError> {
        let mut user = self.user_storage.get_user_by_id(caller_id).await?;

        if user.is_oidc_user() {
            tracing::info!(
                target: "audit",
                event = "auth.profile_update_rejected",
                reason = "oidc_user",
                caller_id = %caller_id,
                "👤 profile update rejected: caller is OIDC-managed",
            );
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "User",
                "Your profile is managed by the identity provider and \
                 cannot be edited here. Update it at the IdP — changes \
                 will propagate on your next sign-in.",
            ));
        }

        let mut changed: Vec<&'static str> = Vec::new();

        // ── Username (claim-once) ──────────────────────────────
        if let Some(ref candidate) = dto.username {
            if user.username().is_some() {
                tracing::info!(
                    target: "audit",
                    event = "auth.profile_update_rejected",
                    reason = "username_immutable",
                    caller_id = %caller_id,
                    "👤 profile update rejected: username already claimed",
                );
                return Err(DomainError::new(
                    ErrorKind::AlreadyExists,
                    "User",
                    "Username is already claimed and cannot be changed. \
                     Contact an administrator if you need to rename.",
                ));
            }
            // Uniqueness against other users.
            if self
                .user_storage
                .get_user_by_username(candidate)
                .await
                .is_ok()
            {
                tracing::info!(
                    target: "audit",
                    event = "auth.profile_update_rejected",
                    reason = "username_taken",
                    caller_id = %caller_id,
                    attempted_username = %candidate,
                    "👤 profile update rejected: username '{}' is taken",
                    candidate,
                );
                return Err(DomainError::new(
                    ErrorKind::AlreadyExists,
                    "User",
                    format!("Username '{}' is already taken", candidate),
                ));
            }
            user.set_username(candidate.clone()).map_err(|e| {
                DomainError::new(
                    ErrorKind::InvalidInput,
                    "User",
                    format!("Invalid username: {}", e),
                )
            })?;
            changed.push("username");
        }

        // ── Given / family names ───────────────────────────────
        if let Some(ref g) = dto.given_name {
            if g.trim().is_empty() {
                return Err(DomainError::new(
                    ErrorKind::InvalidInput,
                    "User",
                    "given_name cannot be an empty string. Omit the field \
                     to leave it unchanged.",
                ));
            }
            user.set_given_name(Some(g.clone()));
            changed.push("given_name");
        }
        if let Some(ref f) = dto.family_name {
            if f.trim().is_empty() {
                return Err(DomainError::new(
                    ErrorKind::InvalidInput,
                    "User",
                    "family_name cannot be an empty string. Omit the field \
                     to leave it unchanged.",
                ));
            }
            user.set_family_name(Some(f.clone()));
            changed.push("family_name");
        }

        // ── Preferred locale ─────────────────────────────────────
        // Treat `""` as an explicit clear (frontend may send the empty
        // string when the user picks "Use server default"). Any other
        // non-empty value must resolve against the LocaleRegistry — an
        // unknown code is a 400 so the client can show the user a
        // useful error rather than silently dropping the change.
        if let Some(ref code) = dto.preferred_locale {
            let trimmed = code.trim();
            if trimmed.is_empty() {
                user.set_preferred_locale(None);
                changed.push("preferred_locale");
            } else if let Some(canonical) = locale_registry.parse(trimmed) {
                user.set_preferred_locale(Some(canonical.as_str().to_string()));
                changed.push("preferred_locale");
            } else {
                tracing::info!(
                    target: "audit",
                    event = "auth.profile_update_rejected",
                    reason = "unknown_locale",
                    caller_id = %caller_id,
                    attempted_locale = %trimmed,
                    "👤 profile update rejected: locale '{}' not in registry",
                    trimmed,
                );
                return Err(DomainError::new(
                    ErrorKind::InvalidInput,
                    "User",
                    format!(
                        "Unknown locale '{}'. Use one of the codes returned \
                         by /api/i18n/locales.",
                        trimmed,
                    ),
                ));
            }
        }

        // ── Share-notification opt-out (PR N1) ───────────────────
        // Boolean field; absent → no change. Idempotent — setting the
        // same value twice is fine but doesn't re-emit an audit row
        // because `changed` won't pick it up.
        if let Some(notify) = dto.notify_on_share
            && notify != user.notify_on_share()
        {
            user.set_notify_on_share(notify);
            changed.push("notify_on_share");
        }

        // ── UI preferences shallow-merge ──────────────────────────
        // The other fields above modify the in-memory `user` and land
        // via `update_user(user)` at the end. UI preferences take a
        // different path because the merge has to happen at write
        // time in SQL — two devices PATCH'ing partial patches
        // concurrently would otherwise race and clobber each other if
        // we did merge-then-write in application code. See
        // `UserPgRepository::update_ui_preferences` for the SQL.
        //
        // Boundary validation only: shape must be a JSON object.
        // Contents are opaque to the server — no key inspection here.
        // Size cap is enforced by the schema CHECK constraint; a
        // violating merge surfaces as a repo error.
        let ui_prefs_patch = if let Some(patch) = dto.ui_preferences.as_ref() {
            if !patch.is_object() {
                return Err(DomainError::validation_error(
                    "ui_preferences must be a JSON object".to_string(),
                ));
            }
            Some(patch.clone())
        } else {
            None
        };

        if changed.is_empty() && ui_prefs_patch.is_none() {
            // No-op — return the current user without a DB write.
            return Ok(UserDto::from(user));
        }

        // Persist the typed-field changes first (if any). Skip the
        // `update_user` call entirely when only `ui_preferences`
        // changed — the shallow-merge SQL below is authoritative for
        // that field, and running `update_user` unnecessarily would
        // rewrite every column with its current in-memory value.
        if !changed.is_empty() {
            self.user_storage.update_user(user).await?;
        }

        if let Some(patch) = ui_prefs_patch {
            self.user_storage
                .update_ui_preferences(caller_id, &patch)
                .await?;
            changed.push("ui_preferences");
        }

        tracing::info!(
            target: "audit",
            event = "auth.profile_updated",
            caller_id = %caller_id,
            fields = ?changed,
            "👤 profile updated for {}",
            caller_id,
        );

        // Refetch so the returned DTO reflects the merged JSONB bag
        // (the in-memory `user` above holds the pre-merge value).
        let refreshed = self.user_storage.get_user_by_id(caller_id).await?;
        Ok(UserDto::from(refreshed))
    }

    // Alias for consistency with handler method
    pub async fn get_user_by_id(&self, user_id: Uuid) -> Result<UserDto, DomainError> {
        self.get_user(user_id).await
    }

    /// Load the full `User` entity for the given id. Unlike
    /// `get_user_by_id` this returns the domain entity (not a DTO), so
    /// callers can read fields like `notify_on_share()`,
    /// `preferred_locale()`, or `is_external()` without round-tripping
    /// through the DTO shape. Used by `grant_handler::create_grant` to
    /// hand the granter entity to `RecipientNotificationService`.
    pub async fn get_user_entity(
        &self,
        user_id: Uuid,
    ) -> Result<crate::domain::entities::user::User, DomainError> {
        UserStoragePort::get_user_by_id(&*self.user_storage, user_id).await
    }

    /// Visibility-checked profile lookup for `GET /api/users/{id}`.
    ///
    /// Returns `NotFound` (not `AccessDenied`) when the caller has no
    /// legitimate relationship with the target — anti-enumeration: an
    /// attacker probing random UUIDs cannot distinguish "user doesn't
    /// exist" from "exists but you can't see them".
    ///
    /// Visibility rule, evaluated top-to-bottom:
    ///   1. **Self lookup** — `caller_id == target_id` always succeeds.
    ///   2. **Shared-grant relationship** — caller and target appear
    ///      together on at least one row of `storage.role_grants`,
    ///      either direction (caller-as-granter / target-as-subject,
    ///      or target-as-granter / caller-as-subject). Applies to both
    ///      internal and external callers. This is what lets an
    ///      external user resolve the display name + photo of the
    ///      internal user who shared a folder with them — the
    ///      `granted_by` column on the grant Bob received is Alice's
    ///      user_id, and SharedWithMe needs to render her vignette.
    ///   3. **External callers stop here.** Any remaining check would
    ///      let them enumerate the user directory; they have no
    ///      legitimate need beyond resolving people they're already in
    ///      a grant relationship with.
    ///   4. *(Internal callers only)* Target is internal AND
    ///      `expose_system_users` is on → already broadly visible via
    ///      the system address book; no extra check.
    ///   5. *(Internal callers only)* Caller is admin → always visible.
    ///   6. Anything else → `NotFound`.
    ///
    /// Subject-group co-membership is intentionally NOT a visibility
    /// path in v1; can be added later if a concrete need surfaces.
    pub async fn get_user_profile(
        &self,
        caller_id: Uuid,
        target_id: Uuid,
        expose_system_users: bool,
        pool: &sqlx::PgPool,
    ) -> Result<UserDto, DomainError> {
        // (1) Self — a single fetch suffices (the check compares the input
        // UUIDs, so the target read is never needed on this path).
        if caller_id == target_id {
            let caller = self.user_storage.get_user_by_id(caller_id).await?;
            return Ok(UserDto::from(caller));
        }

        // Caller and target are independent point reads (the self-case already
        // returned; the branch above compares input UUIDs, not fetched data) —
        // overlap them with `join!` instead of two serial round-trips.
        // `caller_res?` first preserves the caller-error precedence of the old
        // sequential form. (benches/ROUND23.md §P1)
        let (caller_res, target_res) = tokio::join!(
            self.user_storage.get_user_by_id(caller_id),
            self.user_storage.get_user_by_id(target_id)
        );
        let caller = caller_res?;

        // Anti-enumeration: NotFound for everything that doesn't pass.
        // Convert a real NotFound on `target` to the same anonymous 404,
        // so existence isn't leaked through differential responses.
        let target = match target_res {
            Ok(u) => u,
            Err(e) if e.kind == ErrorKind::NotFound => {
                tracing::info!(
                    target: "audit",
                    event = "user_profile.rejected",
                    reason = "target_not_found",
                    caller_id = %caller_id,
                    caller_is_external = caller.is_external(),
                    target_id = %target_id,
                    "👮🏻‍♂️ user-profile rejected: target '{}' does not exist (caller {})",
                    target_id,
                    caller_id,
                );
                return Err(DomainError::new(
                    ErrorKind::NotFound,
                    "User",
                    "User not found",
                ));
            }
            Err(e) => return Err(e),
        };

        // (2) Shared-grant relationship — works for both internal and
        // external callers. LIMIT 1 + the (granted_by) and
        // (subject_type, subject_id) indexes keep this cheap.
        let related: Option<i32> = sqlx::query_scalar(
            r#"
            SELECT 1
              FROM storage.role_grants
             WHERE (granted_by = $1 AND subject_type = 'user' AND subject_id = $2)
                OR (granted_by = $2 AND subject_type = 'user' AND subject_id = $1)
             LIMIT 1
            "#,
        )
        .bind(caller_id)
        .bind(target_id)
        .fetch_optional(pool)
        .await
        .map_err(|e| {
            DomainError::internal_error("UserProfile", format!("visibility query: {}", e))
        })?;

        if related.is_some() {
            return Ok(UserDto::from(target));
        }

        // (3) External callers stop here — no directory enumeration.
        if caller.is_external() {
            // Audit: an external user tried to look up someone they
            // don't share a grant with. Surfaces enumeration probes
            // from compromised magic-link sessions.
            tracing::info!(
                target: "audit",
                event = "user_profile.rejected",
                reason = "external_caller_no_relationship",
                caller_id = %caller_id,
                target_id = %target_id,
                target_is_external = target.is_external(),
                "👮🏻‍♂️ user-profile rejected: external user '{}' has no grant relationship with '{}'",
                caller_id,
                target_id,
            );
            return Err(DomainError::new(
                ErrorKind::NotFound,
                "User",
                "User not found",
            ));
        }

        // (4) Internal target + system-address-book exposed: already public.
        if !target.is_external() && expose_system_users {
            return Ok(UserDto::from(target));
        }

        // (5) Admin caller: always visible.
        if caller.role() == UserRole::Admin {
            return Ok(UserDto::from(target));
        }

        // (6) No relationship — anti-enumeration NotFound.
        // Audit: an internal user with no visibility path probed a user
        // they don't share with. Usually benign (stale UI state), but
        // recurring patterns from the same caller are worth surfacing.
        tracing::info!(
            target: "audit",
            event = "user_profile.rejected",
            reason = "no_visibility_path",
            caller_id = %caller_id,
            target_id = %target_id,
            target_is_external = target.is_external(),
            "👮🏻‍♂️ user-profile rejected: internal user '{}' has no visibility on '{}' (target is_external={})",
            caller_id,
            target_id,
            target.is_external(),
        );
        Err(DomainError::new(
            ErrorKind::NotFound,
            "User",
            "User not found",
        ))
    }

    /// Username-keyed sibling of [`Self::get_user_profile`], routing every
    /// lookup through the same visibility check as the user-profile REST
    /// endpoint. Preserves the anti-enum shape end-to-end: whether the
    /// username doesn't exist OR the caller has no visibility path, the
    /// response is `NotFound`.
    ///
    /// AuthZ audit #11 (2026-07-12): NextCloud OCS user-provisioning
    /// (`nextcloud/ocs_handler.rs::user_provisioning_response`) used to
    /// resolve `userid` via bare `get_user_by_username`, gated only by a
    /// bespoke `caller.role == "admin"` shortcut. Admins bypassed the
    /// `expose_system_users` gate; non-admins got a `403 Insufficient
    /// privileges` for any cross-user probe (leaking existence via the
    /// differential vs a genuine 404); zero audit lines. This wrapper
    /// closes all three.
    ///
    /// The username→id resolution happens here so the target isn't
    /// leaked through the audit line as a plaintext username on failure:
    /// the `target_username_not_found` event carries the string
    /// (unavoidable — we resolved it, we log it), but every other
    /// downstream event keys off `target_id` after resolution, matching
    /// the id-based endpoint.
    pub async fn get_user_profile_by_username_with_perms(
        &self,
        caller_id: Uuid,
        username: &str,
        expose_system_users: bool,
        pool: &sqlx::PgPool,
    ) -> Result<UserDto, DomainError> {
        let target = match self.user_storage.get_user_by_username(username).await {
            Ok(u) => u,
            Err(e) if e.kind == ErrorKind::NotFound => {
                tracing::info!(
                    target: "audit",
                    event = "user_profile.rejected",
                    reason = "target_username_not_found",
                    caller_id = %caller_id,
                    target_username = %username,
                    "👮🏻‍♂️ user-profile rejected: username '{}' does not exist (caller {})",
                    username,
                    caller_id,
                );
                return Err(DomainError::new(
                    ErrorKind::NotFound,
                    "User",
                    "User not found",
                ));
            }
            Err(e) => return Err(e),
        };
        self.get_user_profile(caller_id, target.id(), expose_system_users, pool)
            .await
    }

    // New method to get user by username - needed for admin user handling
    pub async fn get_user_by_username(&self, username: &str) -> Result<UserDto, DomainError> {
        let user = self.user_storage.get_user_by_username(username).await?;
        Ok(UserDto::from(user))
    }

    // Method to count how many admin users exist in the system
    // Used to determine if we have multiple admins or just the default one
    pub async fn count_admin_users(&self) -> Result<i64, DomainError> {
        // Scalar COUNT(*) — the old form fetched every admin's FULL row (incl.
        // the up-to-512 KiB avatar `image` + `ui_preferences` JSONB) only to
        // call `.len()`, on a status/init endpoint that is polled at bootstrap
        // (benches/ROUND29.md §G).
        self.user_storage.count_users_by_role("admin").await
    }

    /// Lists internal users only. External (grant-only) users are filtered
    /// out so that internal-user surfaces — system address book, OCS
    /// sharee search, etc. — never expose external identities. Admin
    /// surfaces that need the full list should call
    /// [`list_users_including_external_with_perms`] instead.
    pub async fn list_users(&self, limit: i64, offset: i64) -> Result<Vec<UserDto>, DomainError> {
        let users = self.user_storage.list_users(limit, offset, false).await?;
        Ok(users.into_iter().map(UserDto::from).collect())
    }

    /// Admin-only: lists users including external (grant-only) recipients.
    /// Used by the admin user-management UI.
    pub async fn list_users_including_external_with_perms<A: AuthorizationEngine>(
        &self,
        authorization: &A,
        caller_id: Uuid,
        limit: i64,
        offset: i64,
    ) -> Result<Vec<UserDto>, DomainError> {
        self.require_admin_caller(authorization, caller_id).await?;
        let users = self.user_storage.list_users(limit, offset, true).await?;
        Ok(users.into_iter().map(UserDto::from).collect())
    }

    /// Admin-only compact listing.  The detail endpoint retains the complete
    /// [`UserDto`]; this path projects only what the management table renders so
    /// PostgreSQL never detoasts or transfers avatars/preferences for a page.
    pub async fn list_user_summaries_including_external_with_perms<A: AuthorizationEngine>(
        &self,
        authorization: &A,
        caller_id: Uuid,
        limit: i64,
        offset: i64,
    ) -> Result<Vec<AdminUserSummaryDto>, DomainError> {
        self.require_admin_caller(authorization, caller_id).await?;
        let users = self
            .user_storage
            .list_user_summaries(limit, offset, true)
            .await?;
        Ok(users.into_iter().map(AdminUserSummaryDto::from).collect())
    }

    /// Service-layer gate for administrator-scoped user-directory operations.
    /// The route middleware remains a cheap first line of defence, but the
    /// application service is authoritative so alternate callers cannot bypass
    /// policy.  The lookup is the existing single-flight, image-free flags
    /// cache; a hot authorization check does not hydrate the user profile.
    async fn require_admin_caller<A: AuthorizationEngine>(
        &self,
        authorization: &A,
        caller_id: Uuid,
    ) -> Result<(), DomainError> {
        let flags = self.get_user_flags(caller_id).await?;
        authorization.require_system_admin(
            Subject::User(caller_id),
            flags.role,
            flags.is_external,
            flags.active,
        )
    }

    /// Searches internal users only. See [`list_users`] for the rationale.
    pub async fn search_users(&self, query: &str, limit: i64) -> Result<Vec<UserDto>, DomainError> {
        let users = self.user_storage.search_users(query, limit, false).await?;
        Ok(users.into_iter().map(UserDto::from).collect())
    }

    /// Username-only search for the NC sharee autocomplete: identical
    /// predicate / order / limit to [`search_users`], but the repository
    /// projects just `username` — no 21-column hydration (incl. the
    /// up-to-512 KiB avatar `image`) per matched row, per keystroke
    /// (benches/ROUND12.md §1). NULL usernames (email-only signups) are
    /// filtered app-side, exactly like the wide flow's post-limit filter.
    pub async fn search_sharee_usernames(
        &self,
        query: &str,
        limit: i64,
    ) -> Result<Vec<String>, DomainError> {
        let names = self
            .user_storage
            .search_usernames(query, limit, false)
            .await?;
        Ok(names.into_iter().flatten().collect())
    }

    // ========================================================================
    // Admin User Management Methods
    // ========================================================================

    /// Admin-only: create a user bypassing registration guards.
    pub async fn admin_create_user(
        &self,
        dto: crate::application::dtos::settings_dto::AdminCreateUserDto,
    ) -> Result<UserDto, DomainError> {
        // Validate username length
        if dto.username.len() < 3 || dto.username.len() > 254 {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "Username must be between 3 and 254 characters".to_string(),
            ));
        }

        // Check for duplicate username
        if self
            .user_storage
            .get_user_by_username(&dto.username)
            .await
            .is_ok()
        {
            return Err(DomainError::new(
                ErrorKind::AlreadyExists,
                "User",
                format!("User '{}' already exists", dto.username),
            ));
        }

        // Email: use provided or generate placeholder
        let email = dto
            .email
            .filter(|e| !e.trim().is_empty())
            .unwrap_or_else(|| format!("{}@oxicloud.local", dto.username));

        // Check email uniqueness
        if self.user_storage.get_user_by_email(&email).await.is_ok() {
            return Err(DomainError::new(
                ErrorKind::AlreadyExists,
                "User",
                format!("Email '{}' is already registered", email),
            ));
        }

        // Validate password
        if dto.password.len() < 8 {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "Password must be at least 8 characters long".to_string(),
            ));
        }

        // Determine role
        let role = match dto.role.as_deref() {
            Some("admin") => UserRole::Admin,
            _ => UserRole::User,
        };

        let is_external = dto.is_external.unwrap_or(false);

        // Forbid external + admin combo. The DB `users_external_not_admin`
        // CHECK constraint would catch this too, but a 400 with an
        // explanatory message is friendlier than a generic 500 from a
        // constraint violation. See the CHECK definition in
        // migrations/20260612000002_auth_users_is_external.sql for the
        // rationale.
        if is_external && matches!(role, UserRole::Admin) {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "External users cannot be admins. To promote an external user to admin, \
                 first convert them to internal (set is_external = false), then update \
                 the role separately."
                    .to_string(),
            ));
        }

        // External users never own storage. The DB `users_external_no_storage`
        // CHECK constraint enforces this; setting quota=0 here keeps the
        // domain consistent and matches `User::new(..., is_external = true)`.
        let quota = if is_external {
            0
        } else {
            dto.quota_bytes.unwrap_or_else(|| self.capped_quota(&role))
        };

        // Hash password (kept for both internal and external users — for
        // external users it's currently unused since they authenticate via
        // magic-link / OIDC, but the DB column is NOT NULL).
        let password_hash = self.password_hasher.hash_password(&dto.password).await?;

        // Create domain entity. External users are created with
        // is_external=true and role forced to User (the admin+external
        // combo was rejected above). For external users the supplied
        // password hash is persisted so the audit trail is preserved,
        // even though they authenticate via magic-link / OIDC.
        let user = if is_external {
            User::new(
                email,
                Some(dto.username.clone()),
                Some(password_hash),
                None,
                None,
                UserRole::User,
                0,
                true,
            )
        } else {
            User::new(
                email,
                Some(dto.username.clone()),
                Some(password_hash),
                None,
                None,
                role,
                quota,
                false,
            )
        }
        .map_err(|e| {
            DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                format!("Error creating user: {}", e),
            )
        })?;

        // Admin fiat counts as verification. When
        // `OXICLOUD_REQUIRE_VERIFIED_EMAIL` is set, admin-created users
        // still get to log in without a magic-link round-trip — the
        // operator explicitly vouched for the address at creation. This
        // mirrors the OIDC-JIT convention (see `redeem_pending_oidc_token`
        // and `login_oidc_callback` which also stamp
        // `email_verified_at` on first sight).
        let mut user = user;
        user.mark_email_verified();

        // Persist
        let created = self.user_storage.create_user(user).await?;

        // Deactivate if requested (User::new always sets active=true)
        if let Some(false) = dto.active {
            self.user_storage
                .set_user_active_status(created.id(), false)
                .await?;
        }

        // Lifecycle: PersonalDriveLifecycleHook handles the home-folder
        // provisioning (idempotent + short-circuits on is_external).
        // Audit logs the creation event.
        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_created(&created).await;
        }

        tracing::info!(
            "Admin created user: {} ({}, is_external={})",
            dto.username,
            created.id(),
            created.is_external()
        );
        Ok(UserDto::from(created))
    }

    /// Admin-only: reset a user's password.
    pub async fn admin_reset_password(
        &self,
        user_id: Uuid,
        new_password: &str,
    ) -> Result<(), DomainError> {
        // Block password reset for OIDC-provisioned users
        let user = self.user_storage.get_user_by_id(user_id).await?;
        if user.is_oidc_user() {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "Auth",
                "Cannot reset password for SSO/OIDC accounts. The user's password is managed by their identity provider.",
            ));
        }

        if new_password.len() < 8 {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "Password must be at least 8 characters long".to_string(),
            ));
        }
        let hash = self.password_hasher.hash_password(new_password).await?;
        self.user_storage.change_password(user_id, &hash).await?;

        // Invalidate all existing sessions so the user must re-login
        // with the new password.  Mirrors the behaviour of change_password().
        self.session_storage
            .revoke_all_user_sessions(user_id)
            .await?;

        tracing::info!(user_id = %user_id, "Admin reset password — all sessions revoked");
        Ok(())
    }

    /// Get a single user by ID (for admin panel)
    pub async fn get_user_admin(&self, user_id: Uuid) -> Result<UserDto, DomainError> {
        let user = self.user_storage.get_user_by_id(user_id).await?;
        Ok(UserDto::from(user))
    }

    /// Delete a user by ID (admin only).
    ///
    /// Runs the whole flow in a single transaction so the lifecycle
    /// hooks (`SessionRevocationLifecycleHook` revoking sessions with
    /// audit, `AuthzCacheLifecycleHook` invalidating the Moka cache,
    /// `PersonalDriveLifecycleHook` for future trash policy, …) can do
    /// their work atomically with the user DELETE. If any hook returns
    /// `Err`, the transaction rolls back and the user remains intact.
    pub async fn delete_user_admin(&self, user_id: Uuid) -> Result<(), DomainError> {
        let user = self.user_storage.get_user_by_id(user_id).await?;
        tracing::info!(
            "Admin deleting user: {} ({})",
            user.display_for_audit(),
            user_id
        );

        let mut tx = self
            .user_storage
            .pool()
            .begin()
            .await
            .map_err(|e| DomainError::internal_error("Auth", format!("begin tx: {}", e)))?;

        // Hooks run inside the tx, BEFORE the user DELETE. They see the
        // row still present and can write cleanup queries against the
        // same tx (e.g. session revocation with per-session audit).
        if let Some(lc) = &self.user_lifecycle {
            lc.dispatch_deleted(&user, DeletionMode::AdminDelete, &mut tx)
                .await?;
        }

        // Now the DELETE — FK CASCADE handles the downstream cleanup
        // (sessions, folders, files, …) for anything the hooks didn't
        // explicitly remove.
        sqlx::query("DELETE FROM auth.users WHERE id = $1")
            .bind(user_id)
            .execute(&mut *tx)
            .await
            .map_err(|e| DomainError::internal_error("Auth", format!("delete user: {}", e)))?;

        tx.commit()
            .await
            .map_err(|e| DomainError::internal_error("Auth", format!("commit: {}", e)))?;

        Ok(())
    }

    /// Activate or deactivate a user (admin only)
    pub async fn set_user_active(&self, user_id: Uuid, active: bool) -> Result<(), DomainError> {
        self.user_storage
            .set_user_active_status(user_id, active)
            .await?;
        self.user_flags_cache.invalidate(&user_id).await;
        Ok(())
    }

    /// Change user role (admin only).
    ///
    /// Refuses `role = "admin"` when the target is external (grant-only).
    /// The DB CHECK `users_external_not_admin` would also refuse this at
    /// COMMIT, but surfacing it here yields a clean `InvalidInput` error
    /// with an audit line naming the reason, instead of a bare
    /// constraint-violation stringified out of Postgres.
    pub async fn change_user_role(&self, user_id: Uuid, role: &str) -> Result<(), DomainError> {
        if role != "admin" && role != "user" {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                format!("Invalid role: {}. Must be 'admin' or 'user'", role),
            ));
        }

        if role == "admin" {
            let target = self.user_storage.get_user_by_id(user_id).await?;
            if target.is_external() {
                tracing::info!(
                    target: "audit",
                    event = "user.role_change_rejected",
                    reason = "external_cannot_be_admin",
                    target_id = %user_id,
                    "👮🏻‍♂️ role change refused: external users cannot hold the admin role",
                );
                return Err(DomainError::new(
                    ErrorKind::InvalidInput,
                    "User",
                    "External accounts cannot hold the admin role. Promote the user to internal first.",
                ));
            }
        }

        self.user_storage.change_role(user_id, role).await?;
        self.user_flags_cache.invalidate(&user_id).await;
        Ok(())
    }

    /// Update user's storage quota (admin only)
    pub async fn update_user_quota(
        &self,
        user_id: Uuid,
        quota_bytes: i64,
    ) -> Result<(), DomainError> {
        if quota_bytes < 0 {
            return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "User",
                "Quota must be non-negative".to_string(),
            ));
        }
        self.user_storage
            .update_storage_quota(user_id, quota_bytes)
            .await
    }

    /// Check if a user has enough quota for an upload of the given size
    pub async fn check_quota(
        &self,
        user_id: Uuid,
        additional_bytes: i64,
    ) -> Result<bool, DomainError> {
        let user = self.user_storage.get_user_by_id(user_id).await?;
        let quota = user.storage_quota_bytes();
        if quota <= 0 {
            // 0 or negative means unlimited
            return Ok(true);
        }
        Ok(user.storage_used_bytes() + additional_bytes <= quota)
    }

    /// Count users efficiently
    pub async fn count_users_efficient(&self) -> Result<i64, DomainError> {
        self.user_storage.count_users().await
    }

    // ========================================================================
    // OIDC Methods
    // ========================================================================

    /// Prepare the OIDC authorization flow: generates CSRF state, PKCE pair,
    /// nonce, stores them in pending_oidc_flows, and returns the authorize URL.
    pub async fn prepare_oidc_authorize(&self) -> Result<String, DomainError> {
        let oidc = self.oidc_service().ok_or_else(|| {
            DomainError::new(
                ErrorKind::InternalError,
                "OIDC",
                "OIDC service not configured",
            )
        })?;

        // Generate CSRF state token
        use rand_core::{OsRng, RngCore};
        let mut state_bytes = [0u8; 32];
        OsRng.fill_bytes(&mut state_bytes);
        let state_token = hex::encode(state_bytes);

        // Generate nonce for ID token binding
        let mut nonce_bytes = [0u8; 32];
        OsRng.fill_bytes(&mut nonce_bytes);
        let nonce = hex::encode(nonce_bytes);

        // Generate PKCE pair (RFC 7636, S256)
        let mut verifier_bytes = [0u8; 32];
        OsRng.fill_bytes(&mut verifier_bytes);
        let pkce_verifier = base64_url_encode(&verifier_bytes);
        let pkce_challenge = {
            use sha2::{Digest, Sha256};
            let hash = Sha256::digest(pkce_verifier.as_bytes());
            base64_url_encode(&hash)
        };

        // Store pending flow (auto-expires after 10 min via moka TTL)
        self.pending_oidc_flows.insert(
            state_token.clone(),
            PendingOidcFlow {
                pkce_verifier,
                nonce: nonce.clone(),
                nc_flow_token: None,
            },
        );

        // Build authorization URL with state, nonce, and PKCE challenge
        let authorize_url = oidc
            .get_authorize_url(&state_token, &nonce, &pkce_challenge)
            .await?;

        tracing::info!(
            "OIDC authorize flow prepared (state={}...)",
            &state_token[..8]
        );

        Ok(authorize_url)
    }

    /// Prepare an OIDC authorization flow for a Nextcloud Login Flow v2 session.
    ///
    /// Works like [`prepare_oidc_authorize`] but associates the Nextcloud flow
    /// token with the OIDC state so that [`oidc_callback`] can complete the
    /// Nextcloud login flow (app-password + poll result) instead of issuing
    /// internal JWTs.
    pub async fn prepare_oidc_authorize_for_nextcloud(
        &self,
        nc_flow_token: &str,
    ) -> Result<String, DomainError> {
        let oidc = self.oidc_service().ok_or_else(|| {
            DomainError::new(
                ErrorKind::InternalError,
                "OIDC",
                "OIDC service not configured",
            )
        })?;

        use rand_core::{OsRng, RngCore};
        let mut state_bytes = [0u8; 32];
        OsRng.fill_bytes(&mut state_bytes);
        let state_token = hex::encode(state_bytes);

        let mut nonce_bytes = [0u8; 32];
        OsRng.fill_bytes(&mut nonce_bytes);
        let nonce = hex::encode(nonce_bytes);

        let mut verifier_bytes = [0u8; 32];
        OsRng.fill_bytes(&mut verifier_bytes);
        let pkce_verifier = base64_url_encode(&verifier_bytes);
        let pkce_challenge = {
            use sha2::{Digest, Sha256};
            let hash = Sha256::digest(pkce_verifier.as_bytes());
            base64_url_encode(&hash)
        };

        // Store pending flow (auto-expires after 10 min via moka TTL)
        self.pending_oidc_flows.insert(
            state_token.clone(),
            PendingOidcFlow {
                pkce_verifier,
                nonce: nonce.clone(),
                nc_flow_token: Some(nc_flow_token.to_string()),
            },
        );

        let authorize_url = oidc
            .get_authorize_url(&state_token, &nonce, &pkce_challenge)
            .await?;

        tracing::info!(
            "OIDC authorize flow prepared for Nextcloud Login Flow v2 (state={}...)",
            &state_token[..8]
        );

        Ok(authorize_url)
    }

    /// Handle the OIDC callback: validate CSRF state, exchange code with PKCE,
    /// validate ID token nonce, find or create user (JIT provisioning),
    /// issue internal tokens, and return a one-time exchange code.
    ///
    /// If the pending flow carries a Nextcloud flow token, this method returns
    /// `Err(NcOidcComplete { .. })` with a special error kind so the handler
    /// layer can complete the Nextcloud flow instead.
    pub async fn oidc_callback(
        &self,
        code: &str,
        state: &str,
        locale_registry: &crate::common::locale::LocaleRegistry,
    ) -> Result<OidcCallbackResult, DomainError> {
        // 0. Validate CSRF state and retrieve PKCE verifier + nonce + optional NC token
        //    (entry is auto-expired by moka TTL — remove returns None if expired)
        let flow = match self.pending_oidc_flows.remove(state) {
            Some(flow) => flow,
            None => {
                if let Some(exchange_code) = self.completed_oidc_logins.get(state) {
                    tracing::info!(
                        target: "audit",
                        event = "oidc.callback_replayed",
                        reason = "duplicate_callback",
                        "👮🏻‍♂️ Replayed a recently-completed OIDC login for a duplicate callback (consumed state)",
                    );
                    return Ok(OidcCallbackResult::WebLogin { exchange_code });
                }
                tracing::warn!(
                    target: "audit",
                    event = "oidc.callback_rejected",
                    reason = "invalid_or_expired_state",
                    "👮🏻‍♂️ OIDC callback with invalid/expired state token",
                );
                return Err(DomainError::new(
                    ErrorKind::AccessDenied,
                    "OIDC",
                    "Invalid or expired OIDC state — possible CSRF attack. Please try logging in again.",
                ));
            }
        };
        let (pkce_verifier, nonce, nc_flow_token) =
            (flow.pkce_verifier, flow.nonce, flow.nc_flow_token);

        // Clone the Arc and config out of the RwLock so we don't hold the lock across await points
        let (oidc, oidc_config) = {
            let state = self.oidc.read().unwrap();
            let svc = state.service.clone().ok_or_else(|| {
                DomainError::new(
                    ErrorKind::InternalError,
                    "OIDC",
                    "OIDC service not configured",
                )
            })?;
            let cfg = state.config.clone().ok_or_else(|| {
                DomainError::new(
                    ErrorKind::InternalError,
                    "OIDC",
                    "OIDC config not available",
                )
            })?;
            (svc, cfg)
        };

        // 1. Exchange authorization code for tokens (with PKCE verifier)
        let token_set = oidc.exchange_code(code, &pkce_verifier).await?;

        // 2. Validate ID token and extract claims (with nonce verification)
        let claims = oidc
            .validate_id_token(&token_set.id_token, Some(&nonce))
            .await?;

        // 3. Try to enrich claims from UserInfo endpoint if email is missing
        let claims = if claims.email.is_none() {
            match oidc.fetch_user_info(&token_set.access_token).await {
                Ok(user_info) => OidcIdClaims {
                    email: user_info.email.or(claims.email),
                    preferred_username: user_info.preferred_username.or(claims.preferred_username),
                    name: user_info.name.or(claims.name),
                    given_name: user_info.given_name.or(claims.given_name),
                    family_name: user_info.family_name.or(claims.family_name),
                    email_verified: user_info.email_verified.or(claims.email_verified),
                    locale: user_info.locale.or(claims.locale),
                    groups: if user_info.groups.is_empty() {
                        claims.groups
                    } else {
                        user_info.groups
                    },
                    ..claims
                },
                Err(e) => {
                    tracing::warn!(
                        "Failed to fetch UserInfo (continuing with ID token claims): {}",
                        e
                    );
                    claims
                }
            }
        } else {
            claims
        };

        let provider_name = oidc.provider_name().to_string();
        // Check email_verified - only if email is present in claims, and email verification is required.
        if self.require_verified_email()
            && let Some(email) = &claims.email
        {
            let verified = claims.email_verified.unwrap_or(false);
            if !verified {
                tracing::warn!(
                    "OIDC login rejected: email not verified (provider: {}, email: {})",
                    provider_name,
                    email
                );
                return Err(DomainError::new(
                    ErrorKind::AccessDenied,
                    "OIDC",
                    "Email verification required. Please verify your email at the identity provider.",
                ));
            }
        }

        // 4. Determine username and email
        let oidc_username = claims
            .preferred_username
            .clone()
            .or(claims.name.clone())
            .unwrap_or_else(|| format!("oidc_{}", &claims.sub[..8.min(claims.sub.len())]));
        let oidc_email = claims
            .email
            .clone()
            .unwrap_or_else(|| format!("{}@oidc.local", oidc_username));

        // 5. Look up existing user by OIDC subject
        let user = match self
            .user_storage
            .get_user_by_oidc_subject(&provider_name, &claims.sub)
            .await
        {
            Ok(mut existing_user) => {
                // User exists — dispatch login BEFORE register_login() so
                // hooks observe `last_login_at = None` on the very first
                // login (see tip #1 in the trait docstring).
                if let Some(lc) = &self.user_lifecycle {
                    lc.dispatch_login(&existing_user).await;
                }
                // Decide BEFORE mutating: the row just fetched already
                // carries the stored avatar + verification stamp, so the
                // repeat-login common case (same IdP picture, already
                // verified) skips the DB entirely — the old shape rewrote
                // all 17 columns per login, and even a guarded UPDATE
                // would ship the avatar over the wire just to compare it
                // (benches/ROUND12.md §3b).
                let needs_profile_sync = existing_user.email_verified_at().is_none()
                    || existing_user.image() != claims.picture.as_deref();
                existing_user.register_login();
                existing_user.set_image(claims.picture.clone());
                // PR 23: retroactive email verification for OIDC users
                // who predate the column. The OIDC callback already
                // enforced `claims.email_verified == true` upstream, so
                // any user reaching this branch has a verified email
                // by the IdP's word; stamping is safe and idempotent.
                existing_user.mark_email_verified();
                // Narrow guarded sync instead of the 17-column row rewrite:
                // persists the IdP avatar + the verification stamp only
                // when either actually changed; `last_login_at` is stamped
                // by `create_session` at the end of this flow
                // (benches/ROUND12.md §3).
                if needs_profile_sync {
                    self.user_storage
                        .sync_oidc_login_profile(existing_user.id(), claims.picture.as_deref())
                        .await?;
                }
                existing_user
            }
            Err(_) => {
                // User doesn't exist — try to match by email
                let matched_user = self.user_storage.get_user_by_email(&oidc_email).await.ok();

                if let Some(_existing) = matched_user {
                    // Email match but no OIDC link — for security, don't auto-link
                    return Err(DomainError::new(
                        ErrorKind::AlreadyExists,
                        "OIDC",
                        format!(
                            "A user with email '{}' already exists. Contact admin to link your OIDC identity.",
                            oidc_email
                        ),
                    ));
                }

                // No match — JIT provision if enabled
                if !oidc_config.auto_provision {
                    return Err(DomainError::new(
                        ErrorKind::AccessDenied,
                        "OIDC",
                        "Auto-provisioning is disabled. Contact admin to create your account.",
                    ));
                }

                // Determine role from OIDC groups
                let role = self.map_oidc_role(&claims.groups, &oidc_config);

                let quota = self.capped_quota(&role);

                // Sanitize username: if it looks like an email, extract the local part
                // (some OIDC providers like Keycloak use email as the preferred username)
                let base_username = if oidc_username.contains('@') {
                    oidc_username.split('@').next().unwrap_or(&oidc_username)
                } else {
                    &oidc_username
                };

                // Filter to valid username characters only, then truncate to 32 chars
                let mut username = base_username
                    .chars()
                    .filter(|c| c.is_ascii_alphanumeric() || *c == '-' || *c == '_' || *c == '.')
                    .take(32)
                    .collect::<String>();

                // Filter helper: removes any chars that are not valid in a username
                let filter_username_chars = |s: &str| {
                    s.chars()
                        .filter(|c| {
                            c.is_ascii_alphanumeric() || *c == '-' || *c == '_' || *c == '.'
                        })
                        .take(32)
                        .collect::<String>()
                };

                // Ensure minimum length (the padding suffix must also be filtered)
                if username.len() < 3 {
                    let filtered_sub = filter_username_chars(&claims.sub);
                    username = format!("user_{}", &filtered_sub[..filtered_sub.len().min(8)]);
                }

                // Check for username collision
                if self
                    .user_storage
                    .get_user_by_username(&username)
                    .await
                    .is_ok()
                {
                    let filtered_sub = filter_username_chars(&claims.sub);
                    let suffix = &filtered_sub[..filtered_sub.len().min(4)];
                    username = format!("{}_{}", &username[..username.len().min(27)], suffix);
                }

                let mut new_user = User::new(
                    oidc_email,
                    Some(username.clone()),
                    None,
                    Some(provider_name.clone()),
                    Some(claims.sub.clone()),
                    role,
                    quota,
                    false,
                )
                .map_err(|e| {
                    DomainError::new(
                        ErrorKind::InvalidInput,
                        "OIDC",
                        format!("Failed to create OIDC user: {}", e),
                    )
                })?;
                new_user.set_image(claims.picture.clone());
                new_user.set_given_name(claims.given_name.clone());
                new_user.set_family_name(claims.family_name.clone());
                // PR C: provision the user's preferred_locale from the
                // OIDC `locale` claim AT JIT ONLY. Subsequent logins
                // never re-apply this — a UI-driven choice ("I prefer
                // English even though my IdP says fr-CA") must not be
                // silently overwritten on the next sign-in. We validate
                // the claim against the registry so an obscure or
                // malformed code (e.g. `klingon`, `fr-FR-x-private`)
                // doesn't end up stored only to fail at render time;
                // unresolvable claims fall through to NULL → server
                // default.
                if let Some(claim) = claims.locale.as_deref()
                    && let Some(canonical) = locale_registry.parse(claim)
                {
                    new_user.set_preferred_locale(Some(canonical.as_str().to_string()));
                }
                // PR 23: the OIDC callback rejected any caller upstream
                // whose `email_verified` claim wasn't true, so users
                // reaching this branch have an IdP-vetted email. Stamp
                // the verification at JIT-create time.
                new_user.mark_email_verified();

                let created_user = self.user_storage.create_user(new_user).await?;

                // Lifecycle: created (audit + home-folder provisioning) +
                // login (no register_login() for a fresh OIDC user means
                // `last_login_at` is naturally None → first-login detection
                // works). PersonalDriveLifecycleHook creates the home folder.
                if let Some(lc) = &self.user_lifecycle {
                    lc.dispatch_created(&created_user).await;
                    lc.dispatch_login(&created_user).await;
                }

                tracing::info!(
                    "OIDC user provisioned: {} (provider: {}, sub: {})",
                    created_user.id(),
                    provider_name,
                    claims.sub
                );

                created_user
            }
        };

        // ── Branch: Nextcloud Login Flow v2 vs regular web login ──
        if let Some(nc_token) = nc_flow_token {
            // Nextcloud path: return user info so the handler can mint an
            // app-password and complete the NC login flow.
            tracing::info!(
                user = %user.display_for_audit(),
                "OIDC login successful for Nextcloud Login Flow v2"
            );
            return Ok(OidcCallbackResult::NextcloudLogin {
                nc_flow_token: nc_token,
                user_id: user.id(),
                username: user.username().unwrap_or("").to_string(),
            });
        }

        // 6. Issue internal tokens (same as regular login)
        let access_token = self.token_service.generate_access_token(&user)?;
        let refresh_token = self.token_service.generate_refresh_token();

        let mut session = Session::new(
            user.id(),
            refresh_token.clone(),
            None,
            None,
            self.token_service.refresh_token_expiry_days(),
            Uuid::new_v4(),
        )
        .with_oidc_id_token(token_set.id_token.clone());
        // Bind the IdP's session identifier so Back-Channel Logout can
        // revoke this specific device (see auth_ports::OidcLogoutClaims
        // and session_pg_repository::revoke_sessions_by_oidc_sid). IdPs
        // that don't emit sid leave this None; BCL then falls back to
        // sub-based revocation.
        if let Some(sid) = claims.sid.as_ref() {
            session = session.with_oidc_sid(sid.clone());
        }
        self.session_storage.create_session(session).await?;

        let auth_response = AuthResponseDto {
            user: UserDto::from(user),
            access_token,
            refresh_token,
            token_type: "Bearer".to_string(),
            expires_in: self.token_service.refresh_token_expiry_secs(),
        };

        // 7. Store auth response behind a one-time exchange code (Fix #4: no tokens in URL)
        let mut code_bytes = [0u8; 32];
        use rand_core::{OsRng, RngCore};
        OsRng.fill_bytes(&mut code_bytes);
        let exchange_code = hex::encode(code_bytes);

        // Store auth response (auto-expires after 60 s via moka TTL)
        self.pending_oidc_tokens
            .insert(exchange_code.clone(), PendingOidcToken { auth_response });

        self.completed_oidc_logins
            .insert(state.to_string(), exchange_code.clone());

        tracing::info!("OIDC login successful, one-time exchange code generated");

        Ok(OidcCallbackResult::WebLogin { exchange_code })
    }

    /// Exchange a one-time code for the authentication tokens.
    /// The code is single-use and expires after 60 seconds (moka TTL).
    pub fn exchange_oidc_token(&self, one_time_code: &str) -> Result<AuthResponseDto, DomainError> {
        let pending = self
            .pending_oidc_tokens
            .remove(one_time_code)
            .ok_or_else(|| {
                DomainError::new(
                    ErrorKind::AccessDenied,
                    "OIDC",
                    "Invalid or expired exchange code. Please try logging in again.",
                )
            })?;

        Ok(pending.auth_response)
    }

    /// Map OIDC groups to internal role
    fn map_oidc_role(&self, groups: &[String], config: &OidcConfig) -> UserRole {
        if config.admin_groups.is_empty() {
            return UserRole::User;
        }
        let admin_groups: Vec<&str> = config.admin_groups.split(',').map(|s| s.trim()).collect();
        for group in groups {
            if admin_groups.iter().any(|ag| ag.eq_ignore_ascii_case(group)) {
                return UserRole::Admin;
            }
        }
        UserRole::User
    }

    // `create_personal_folder` was removed in PR 3 of the
    // UserLifecycleHook migration — home-folder provisioning is now
    // owned by `PersonalDriveLifecycleHook` in folder_service.rs and runs
    // via `dispatch_created` / `dispatch_login`.
}

/// URL-safe base64 encoding without padding (RFC 4648 §5)
fn base64_url_encode(input: &[u8]) -> String {
    use base64::Engine;
    base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(input)
}