use chrono::{DateTime, Duration, Utc};
use uuid::Uuid;

/// How a session was originally minted. Set at INSERT by the login
/// handler; carried over on refresh (a rotation doesn't change how the
/// user first authenticated). Stored as `text` server-side with a CHECK
/// constraint — see `migrations/20261013000000_sessions_origin.sql`.
///
/// `serde(rename_all = "snake_case")` so the wire values match the
/// column values one-to-one: `password | opaque | magic_link | oidc |
/// unknown`. `Unknown` is the fallback for pre-migration rows and any
/// future login path that hasn't been taught to stamp an origin yet.
#[derive(
    Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize, utoipa::ToSchema,
)]
#[serde(rename_all = "snake_case")]
pub enum SessionOrigin {
    Password,
    Opaque,
    MagicLink,
    Oidc,
    /// RFC 8628 device authorization grant — CLI, TV apps, headless
    /// clients that can't run a WebCrypto keypair. Always unbound at
    /// the DPoP middleware. Distinct origin because admin operators
    /// want to know "this login came from a headless device flow", not
    /// conflate it with browser password entry.
    Device,
    Unknown,
}

impl SessionOrigin {
    /// Wire / column string form. Kept out of `Display` to avoid
    /// accidental use in log lines where the Debug form is fine.
    pub fn as_str(self) -> &'static str {
        match self {
            Self::Password => "password",
            Self::Opaque => "opaque",
            Self::MagicLink => "magic_link",
            Self::Oidc => "oidc",
            Self::Device => "device",
            Self::Unknown => "unknown",
        }
    }

    /// Parse from the column / wire string. Any unrecognised value
    /// maps to `Unknown` — matches the CHECK constraint's failure
    /// mode (impossible on well-behaved writes, defensive on load).
    /// Named `from_wire` (not `from_str`) to avoid shadowing the
    /// standard `std::str::FromStr::from_str` trait method, which
    /// would force us to pick a meaningless `Err` type when this
    /// helper is intentionally infallible.
    pub fn from_wire(s: &str) -> Self {
        match s {
            "password" => Self::Password,
            "opaque" => Self::Opaque,
            "magic_link" => Self::MagicLink,
            "oidc" => Self::Oidc,
            "device" => Self::Device,
            _ => Self::Unknown,
        }
    }
}

#[derive(Debug, Clone)]
pub struct Session {
    id: Uuid,
    user_id: Uuid,
    refresh_token: String,
    expires_at: DateTime<Utc>,
    ip_address: Option<String>,
    user_agent: Option<String>,
    created_at: DateTime<Utc>,
    revoked: bool,
    /// Groups all tokens issued from the same original login.
    /// Replaying a revoked token from this family triggers full-family revocation.
    family_id: Uuid,
    /// ID token from the OIDC login exchange. Used as `id_token_hint` on the
    /// RP-initiated logout URL so the IdP can terminate its own SSO session.
    /// `None` for password / magic-link sessions.
    oidc_id_token: Option<String>,
    /// OIDC session identifier (sid claim). Populated only when the IdP
    /// emits it. Enables per-device Back-Channel Logout — without it, a
    /// BCL notification would revoke all of the user's sessions rather
    /// than just the one that logged out on the far end.
    oidc_sid: Option<String>,
    /// DPoP JWK thumbprint (RFC 7638, base64url-encoded SHA-256) binding
    /// this session to a browser-held keypair. `None` for app-password
    /// / Nextcloud-client / pre-DPoP / unbound sessions — the DPoP
    /// middleware exempts them (see `docs/plan/dpop.md`).
    ///
    /// Immutable per-session: set at construction time, never updated.
    /// Downgrading a bound session by clearing the thumbprint would let
    /// a stolen cookie replay without the private key — the whole point
    /// of the binding is to prevent that.
    dpop_jkt: Option<String>,
    /// How this row was minted — see [`SessionOrigin`]. Required at
    /// construction so a callsite can't forget to record it (the
    /// admin sessions panel filters on this).
    origin: SessionOrigin,
}

impl Session {
    #[allow(clippy::too_many_arguments)]
    pub fn new(
        user_id: Uuid,
        refresh_token: String,
        ip_address: Option<String>,
        user_agent: Option<String>,
        expires_in_days: i64,
        family_id: Uuid,
        origin: SessionOrigin,
    ) -> Self {
        if refresh_token.is_empty() {
            panic!("Session refresh_token cannot be empty");
        }

        let now = Utc::now();
        Self {
            id: Uuid::new_v4(),
            user_id,
            refresh_token,
            expires_at: now + Duration::days(expires_in_days),
            ip_address,
            user_agent,
            created_at: now,
            revoked: false,
            family_id,
            oidc_id_token: None,
            oidc_sid: None,
            dpop_jkt: None,
            origin,
        }
    }

    /// Bind the session to a DPoP-Nonce browser keypair. Called by every
    /// login handler when the client presented a well-formed thumbprint
    /// in its login request. Absent → session stays unbound (fail-open).
    ///
    /// Immutable once set: this method panics if called on a session
    /// that already has a thumbprint, so a callsite mistake can't
    /// silently overwrite the binding.
    pub fn with_dpop_jkt(mut self, jkt: String) -> Self {
        if self.dpop_jkt.is_some() {
            panic!("Session.dpop_jkt is immutable — call at construction time only");
        }
        self.dpop_jkt = Some(jkt);
        self
    }

    /// Attach an OIDC ID token — call on sessions minted via the OIDC exchange.
    /// The token is persisted with the session and re-emitted at logout as
    /// `id_token_hint` so the IdP can end its own SSO session.
    pub fn with_oidc_id_token(mut self, id_token: String) -> Self {
        self.oidc_id_token = Some(id_token);
        self
    }

    /// Attach the OIDC session identifier from the id_token's `sid` claim.
    /// Optional even for OIDC sessions — only present when the IdP emits
    /// sid (Keycloak requires "Backchannel Logout Session Required" on the
    /// client). Without it, Back-Channel Logout falls back to sub-based
    /// revocation which is coarser (all of the user's OxiCloud sessions).
    pub fn with_oidc_sid(mut self, sid: String) -> Self {
        self.oidc_sid = Some(sid);
        self
    }

    #[allow(clippy::too_many_arguments)]
    pub fn from_raw(
        id: Uuid,
        user_id: Uuid,
        refresh_token: String,
        expires_at: DateTime<Utc>,
        ip_address: Option<String>,
        user_agent: Option<String>,
        created_at: DateTime<Utc>,
        revoked: bool,
        family_id: Uuid,
        oidc_id_token: Option<String>,
        oidc_sid: Option<String>,
        dpop_jkt: Option<String>,
        origin: SessionOrigin,
    ) -> Self {
        Self {
            id,
            user_id,
            refresh_token,
            expires_at,
            ip_address,
            user_agent,
            created_at,
            revoked,
            family_id,
            oidc_id_token,
            oidc_sid,
            dpop_jkt,
            origin,
        }
    }

    // Getters
    pub fn id(&self) -> Uuid {
        self.id
    }

    pub fn user_id(&self) -> Uuid {
        self.user_id
    }

    pub fn refresh_token(&self) -> &str {
        &self.refresh_token
    }

    pub fn expires_at(&self) -> DateTime<Utc> {
        self.expires_at
    }

    pub fn ip_address(&self) -> Option<&str> {
        self.ip_address.as_deref()
    }

    pub fn user_agent(&self) -> Option<&str> {
        self.user_agent.as_deref()
    }

    pub fn created_at(&self) -> DateTime<Utc> {
        self.created_at
    }

    pub fn is_expired(&self) -> bool {
        Utc::now() > self.expires_at
    }

    pub fn is_revoked(&self) -> bool {
        self.revoked
    }

    pub fn revoke(&mut self) {
        self.revoked = true;
    }

    pub fn family_id(&self) -> Uuid {
        self.family_id
    }

    pub fn oidc_id_token(&self) -> Option<&str> {
        self.oidc_id_token.as_deref()
    }

    pub fn oidc_sid(&self) -> Option<&str> {
        self.oidc_sid.as_deref()
    }

    pub fn dpop_jkt(&self) -> Option<&str> {
        self.dpop_jkt.as_deref()
    }

    pub fn origin(&self) -> SessionOrigin {
        self.origin
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn fresh_session() -> Session {
        Session::new(
            Uuid::new_v4(),
            "refresh-token".to_string(),
            None,
            None,
            30,
            Uuid::new_v4(),
            SessionOrigin::Unknown,
        )
    }

    #[test]
    fn new_session_has_no_dpop_binding() {
        assert_eq!(fresh_session().dpop_jkt(), None);
    }

    #[test]
    fn with_dpop_jkt_stores_thumbprint() {
        let s = fresh_session().with_dpop_jkt("abc123".to_string());
        assert_eq!(s.dpop_jkt(), Some("abc123"));
    }

    #[test]
    #[should_panic(expected = "Session.dpop_jkt is immutable")]
    fn with_dpop_jkt_rejects_double_bind() {
        fresh_session()
            .with_dpop_jkt("first".to_string())
            .with_dpop_jkt("second".to_string());
    }

    #[test]
    fn from_raw_round_trips_dpop_jkt() {
        let s = Session::from_raw(
            Uuid::new_v4(),
            Uuid::new_v4(),
            "token".to_string(),
            Utc::now(),
            None,
            None,
            Utc::now(),
            false,
            Uuid::new_v4(),
            None,
            None,
            Some("thumbprint-xyz".to_string()),
            SessionOrigin::Unknown,
        );
        assert_eq!(s.dpop_jkt(), Some("thumbprint-xyz"));
    }

    #[test]
    fn session_origin_round_trip_snake_case_strings() {
        for o in [
            SessionOrigin::Password,
            SessionOrigin::Opaque,
            SessionOrigin::MagicLink,
            SessionOrigin::Oidc,
            SessionOrigin::Device,
            SessionOrigin::Unknown,
        ] {
            assert_eq!(SessionOrigin::from_wire(o.as_str()), o);
        }
        // Unknown catches typos / drift-off-column-values.
        assert_eq!(SessionOrigin::from_wire("bogus"), SessionOrigin::Unknown);
    }
}