//! REST handlers for the ReBAC grant management endpoints.
//!
//! All endpoints under `/api/grants`. The authenticated caller is taken from
//! the `AuthUser` extractor. Authorization for sharing operations is enforced
//! via `authz.require(caller, Share, resource)` — handlers never embed their
//! own checks (see CLAUDE.md § Authorization).

use axum::{
    Json,
    extract::{Path, Query, State},
    http::StatusCode,
    response::IntoResponse,
};
use serde::Deserialize;
use std::sync::Arc;
use tracing::{error, info};
use utoipa::IntoParams;
use uuid::Uuid;

use crate::application::dtos::grant_dto::{
    CreateGrantDto, GrantDto, PermissionDto, ResourceDto, ResourceTypeDto, SubjectDto,
    UpdateRoleDto,
};
use crate::application::ports::authorization_ports::AuthorizationEngine;
use crate::common::errors::DomainError;
use crate::domain::services::authorization::{Permission, Resource, Subject};
use crate::infrastructure::services::pg_acl_engine::PgAclEngine;
use crate::interfaces::errors::AppError;
use crate::interfaces::middleware::auth::AuthUser;

// ════════════════════════════════════════════════════════════════════════════
// POST /api/grants
// ════════════════════════════════════════════════════════════════════════════

#[utoipa::path(
    post,
    path = "/api/grants",
    request_body = CreateGrantDto,
    responses(
        (status = 201, description = "Grant(s) created", body = Vec<GrantDto>),
        (status = 400, description = "Invalid input (both/neither of permissions+role provided)"),
        (status = 404, description = "Resource not found OR caller lacks Share permission"),
    ),
    tag = "grants"
)]
pub async fn create_grant(
    State(authz): State<Arc<PgAclEngine>>,
    auth_user: AuthUser,
    Json(dto): Json<CreateGrantDto>,
) -> impl IntoResponse {
    let caller_id = auth_user.id;

    // Validate: exactly one of permissions/role
    let permissions: Vec<Permission> = match (dto.permissions, dto.role) {
        (Some(perms), None) if !perms.is_empty() => perms.into_iter().map(Into::into).collect(),
        (None, Some(role)) => role.expand().to_vec(),
        (Some(_), Some(_)) => {
            return AppError::new(
                StatusCode::BAD_REQUEST,
                "Provide either 'permissions' or 'role', not both",
                "InvalidInput",
            )
            .into_response();
        }
        _ => {
            return AppError::new(
                StatusCode::BAD_REQUEST,
                "Either 'permissions' (non-empty) or 'role' is required",
                "InvalidInput",
            )
            .into_response();
        }
    };

    let subject: Subject = dto.subject.into();
    let resource: Resource = dto.resource.into();

    // Caller must have Share on the resource (owners pass via short-circuit).
    if let Err(e) = authz
        .require(Subject::User(caller_id), Permission::Share, resource)
        .await
    {
        return AppError::from(e).into_response();
    }

    let mut results: Vec<GrantDto> = Vec::with_capacity(permissions.len());
    for perm in permissions {
        match authz.grant(caller_id, subject, perm, resource).await {
            Ok(grant) => results.push(grant.into()),
            Err(err) => {
                error!("grant insert failed for {perm:?}: {err}");
                return AppError::from(err).into_response();
            }
        }
    }
    info!(
        "Created {} grant(s) for subject={:?} on resource={:?} by user {}",
        results.len(),
        subject,
        resource,
        caller_id
    );
    (StatusCode::CREATED, Json(results)).into_response()
}

// ════════════════════════════════════════════════════════════════════════════
// DELETE /api/grants/{id}
// ════════════════════════════════════════════════════════════════════════════

#[utoipa::path(
    delete,
    path = "/api/grants/{id}",
    params(("id" = String, Path, description = "Grant UUID")),
    responses(
        (status = 204, description = "Grant revoked (or did not exist)"),
        (status = 404, description = "Caller lacks Share permission on the underlying resource"),
    ),
    tag = "grants"
)]
pub async fn revoke_grant(
    State(authz): State<Arc<PgAclEngine>>,
    auth_user: AuthUser,
    Path(id): Path<String>,
) -> impl IntoResponse {
    let caller_id = auth_user.id;
    let grant_id = match Uuid::parse_str(&id) {
        Ok(u) => u,
        Err(_) => return AppError::not_found(format!("Grant {id} not found")).into_response(),
    };

    // Look up the grant to find the underlying resource (and granter).
    let on_resource = match find_grant_resource(&authz, grant_id).await {
        Ok(Some((res, granter))) => (res, granter),
        Ok(None) => return StatusCode::NO_CONTENT.into_response(), // idempotent
        Err(e) => return AppError::from(e).into_response(),
    };

    // Caller is authorized if they are the granter OR have Share on the resource.
    if on_resource.1 != caller_id
        && let Err(e) = authz
            .require(Subject::User(caller_id), Permission::Share, on_resource.0)
            .await
    {
        return AppError::from(e).into_response();
    }

    if let Err(e) = authz.revoke(grant_id).await {
        return AppError::from(e).into_response();
    }
    info!("Revoked grant {grant_id} (caller {caller_id})");
    StatusCode::NO_CONTENT.into_response()
}

/// Look up a grant by id and return (resource, granted_by) so the caller-auth
/// check in revoke_grant can determine if the caller is the granter or needs
/// the Share permission on the resource. Returns `Ok(None)` if no such grant.
async fn find_grant_resource(
    authz: &PgAclEngine,
    grant_id: Uuid,
) -> Result<Option<(Resource, Uuid)>, DomainError> {
    authz.find_grant_by_id(grant_id).await
}

// ════════════════════════════════════════════════════════════════════════════
// PUT /api/grants/role
// ════════════════════════════════════════════════════════════════════════════

#[utoipa::path(
    put,
    path = "/api/grants/role",
    request_body = UpdateRoleDto,
    responses(
        (status = 200, description = "Role applied; returns the new full grant set", body = Vec<GrantDto>),
        (status = 404, description = "Resource not found or caller lacks Share"),
    ),
    tag = "grants"
)]
pub async fn set_role(
    State(authz): State<Arc<PgAclEngine>>,
    auth_user: AuthUser,
    Json(dto): Json<UpdateRoleDto>,
) -> impl IntoResponse {
    let caller_id = auth_user.id;
    let subject: Subject = dto.subject.into();
    let resource: Resource = dto.resource.into();
    let target_perms: std::collections::HashSet<Permission> =
        dto.role.expand().iter().copied().collect();

    // Caller must have Share on the resource.
    if let Err(e) = authz
        .require(Subject::User(caller_id), Permission::Share, resource)
        .await
    {
        return AppError::from(e).into_response();
    }

    // Fetch current grants on the resource for this subject.
    let current = match authz.list_grants_on_resource(resource).await {
        Ok(g) => g,
        Err(e) => return AppError::from(e).into_response(),
    };
    let current_perms: std::collections::HashSet<Permission> = current
        .iter()
        .filter(|g| g.subject == subject)
        .map(|g| g.permission)
        .collect();

    // Diff and apply.
    let to_add: Vec<Permission> = target_perms.difference(&current_perms).copied().collect();
    let to_remove: Vec<Permission> = current_perms.difference(&target_perms).copied().collect();

    for perm in &to_remove {
        if let Some(g) = current
            .iter()
            .find(|g| g.subject == subject && g.permission == *perm)
            && let Err(e) = authz.revoke(g.id).await
        {
            return AppError::from(e).into_response();
        }
    }
    for perm in &to_add {
        if let Err(e) = authz.grant(caller_id, subject, *perm, resource).await {
            return AppError::from(e).into_response();
        }
    }

    // Return the new full set.
    let after = match authz.list_grants_on_resource(resource).await {
        Ok(g) => g,
        Err(e) => return AppError::from(e).into_response(),
    };
    let mine: Vec<GrantDto> = after
        .into_iter()
        .filter(|g| g.subject == subject)
        .map(Into::into)
        .collect();

    info!(
        "Role applied: caller={} subject={:?} resource={:?} added={:?} removed={:?}",
        caller_id, subject, resource, to_add, to_remove
    );
    (StatusCode::OK, Json(mine)).into_response()
}

// ════════════════════════════════════════════════════════════════════════════
// GET /api/grants/incoming
// ════════════════════════════════════════════════════════════════════════════

#[derive(Debug, Deserialize, IntoParams)]
pub struct IncomingQuery {
    #[serde(default)]
    pub permission: Option<PermissionDto>,
}

#[utoipa::path(
    get,
    path = "/api/grants/incoming",
    params(IncomingQuery),
    responses(
        (status = 200, description = "Direct grants targeting the caller", body = Vec<GrantDto>),
    ),
    tag = "grants"
)]
pub async fn list_incoming(
    State(authz): State<Arc<PgAclEngine>>,
    auth_user: AuthUser,
    Query(q): Query<IncomingQuery>,
) -> impl IntoResponse {
    let caller_id = auth_user.id;
    match authz
        .list_incoming_grants(Subject::User(caller_id), q.permission.map(Into::into))
        .await
    {
        Ok(grants) => {
            let dtos: Vec<GrantDto> = grants.into_iter().map(Into::into).collect();
            (StatusCode::OK, Json(dtos)).into_response()
        }
        Err(e) => AppError::from(e).into_response(),
    }
}

// ════════════════════════════════════════════════════════════════════════════
// GET /api/grants/outgoing
// ════════════════════════════════════════════════════════════════════════════

#[utoipa::path(
    get,
    path = "/api/grants/outgoing",
    responses(
        (status = 200, description = "Grants the caller has created", body = Vec<GrantDto>),
    ),
    tag = "grants"
)]
pub async fn list_outgoing(
    State(authz): State<Arc<PgAclEngine>>,
    auth_user: AuthUser,
) -> impl IntoResponse {
    let caller_id = auth_user.id;
    match authz.list_outgoing_grants(caller_id).await {
        Ok(grants) => {
            let dtos: Vec<GrantDto> = grants.into_iter().map(Into::into).collect();
            (StatusCode::OK, Json(dtos)).into_response()
        }
        Err(e) => AppError::from(e).into_response(),
    }
}

// ════════════════════════════════════════════════════════════════════════════
// GET /api/grants?resource_type=...&resource_id=...
// (list grants on a specific resource — requires Share on it)
// ════════════════════════════════════════════════════════════════════════════

#[derive(Debug, Deserialize, IntoParams)]
pub struct OnResourceQuery {
    pub resource_type: ResourceTypeDto,
    pub resource_id: Uuid,
}

#[utoipa::path(
    get,
    path = "/api/grants",
    params(OnResourceQuery),
    responses(
        (status = 200, description = "Grants on the specified resource", body = Vec<GrantDto>),
        (status = 404, description = "Resource not found or caller lacks Share"),
    ),
    tag = "grants"
)]
pub async fn list_on_resource(
    State(authz): State<Arc<PgAclEngine>>,
    auth_user: AuthUser,
    Query(q): Query<OnResourceQuery>,
) -> impl IntoResponse {
    let caller_id = auth_user.id;
    let resource: Resource = ResourceDto {
        kind: q.resource_type,
        id: q.resource_id,
    }
    .into();

    if let Err(e) = authz
        .require(Subject::User(caller_id), Permission::Share, resource)
        .await
    {
        return AppError::from(e).into_response();
    }

    match authz.list_grants_on_resource(resource).await {
        Ok(grants) => {
            let dtos: Vec<GrantDto> = grants.into_iter().map(Into::into).collect();
            (StatusCode::OK, Json(dtos)).into_response()
        }
        Err(e) => AppError::from(e).into_response(),
    }
}

// Silence unused-import warnings for SubjectDto when only certain endpoints
// touch it directly.
#[allow(dead_code)]
fn _ensure_subject_dto_compiles(_: SubjectDto) {}