use anyhow::Result;
use axum::Router;
use axum::extract::DefaultBodyLimit;
use axum::routing::{delete, get, patch, post};
use tower_http::trace::TraceLayer;
use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};

mod auth;
mod config;
mod db;
mod error;
mod handlers;
mod models;
mod services;
mod state;

use config::AppConfig;
use state::AppState;

/// Hard HTTP body cap for the upload endpoint (576 MiB). Backstop against
/// memory-exhaustion; precise per-class size limits are enforced in the handler.
pub(crate) const MAX_UPLOAD_BYTES: usize = 576 * 1024 * 1024;

/// Largest per-file size limit (MB) an operator may configure for `max_image_size_mb` /
/// `max_video_size_mb`, derived from [`MAX_UPLOAD_BYTES`] rather than written down twice.
///
/// This used to be enforced by a COMMENT — "if an admin raises max_video_size_mb above this,
/// bump MAX_UPLOAD_BYTES" — while `patch_config` happily accepted 10240 and the admin dashboard
/// rendered "Max. Videogröße (MB)" as a bare number field. Set it to 1000 and every video
/// between 576 MB and the new limit is destroyed, in a shape that is much worse than a refusal:
///
///   * The body limit trips mid-upload, inside `field.chunk()`, so `stream_field_to_file` maps
///     it to `AppError::BadRequest` — a 400, not a 413 with a `quota_exceeded` code.
///   * `classifyUploadStatus` (frontend/src/lib/upload-queue.ts) puts every non-401/408/429 4xx
///     in the `terminal` bucket, and `isReversibleLock(400, 'bad_request')` is false — so the
///     queue DELETES the blob from IndexedDB and moves the row to `blocked`, which by design
///     offers no retry button.
///   * All of that after the guest has already pushed 600 MB over cellular, and the message they
///     get names a read failure rather than a limit.
///
/// So the ceiling is enforced where the value is SET (`patch_config`) and again where it is READ
/// (`handlers::upload`), because a value stored before this bound existed — or written by hand
/// into the `config` table — would otherwise walk straight past the first check.
///
/// The subtraction is the multipart envelope: the body carries the file PLUS the boundary
/// framing and the `caption` / `hashtags` / `client_upload_id` fields. 1 MiB is enormously more
/// than those can occupy (see the test below, which pins it against their actual caps) and costs
/// nothing — the alternative is a limit that is satisfiable in theory and off-by-a-header in
/// practice.
pub(crate) const MAX_CONFIGURABLE_UPLOAD_MB: i64 =
    (MAX_UPLOAD_BYTES as i64 - 1024 * 1024) / (1024 * 1024);

#[tokio::main]
async fn main() -> Result<()> {
    dotenvy::dotenv().ok();

    tracing_subscriber::registry()
        .with(
            // `info`, not `debug`. A stock deploy sets RUST_LOG nowhere (it is absent from
            // .env.example and was absent from docker-compose.yml), so this fallback IS the
            // production level — and at `debug` the TraceLayer below emits a line per request
            // AND per response, into a log file that had no rotation. `tower_http=warn`
            // rather than `info` states the intent: those spans are diagnostics, not an
            // access log, and a future `DefaultOnResponse::new().level(Level::INFO)` should
            // not silently re-enable them.
            tracing_subscriber::EnvFilter::try_from_default_env()
                .unwrap_or_else(|_| "eventsnap_backend=info,tower_http=warn".into()),
        )
        .with(tracing_subscriber::fmt::layer())
        .init();

    let config = AppConfig::from_env()?;

    // Prove both media directories are writable BEFORE anything else runs. This is first
    // because everything downstream — the derivative backfill, export recovery, every upload —
    // assumes it silently.
    //
    // This used to be `create_dir_all(&media_path).await.ok()` far below, which discarded the
    // only signal there was, and EXPORT_PATH was never created or probed at all. The failure
    // mode that produced: a wrong bind mount or a root-owned volume left the app booting
    // *green* — `/health` only probes the database — so Caddy routed traffic to it, guests
    // joined, and every single upload failed with EACCES. Existence is not the property we
    // need; writability is, and the only way to know is to write.
    ensure_writable_dir(&config.media_path, "MEDIA_PATH").await?;
    ensure_writable_dir(&config.export_path, "EXPORT_PATH").await?;

    let pool = db::create_pool(&config.database_url).await?;

    // Reset any rows left mid-flight by a previous (possibly crashed) instance —
    // stuck `compression_status='processing'` uploads and `status='running'` export
    // jobs. Must run before the server starts taking requests so clients never see
    // the half-state.
    services::maintenance::startup_recovery(&pool).await;

    let state = AppState::new(pool.clone(), config.clone());

    // Regenerate image derivatives an older pipeline produced: the big-screen display for
    // uploads processed before it existed (v0.17.x), and anything predating the current
    // DERIVATIVES_REV (rev 1 applies the EXIF orientation, without which every portrait
    // phone photo is stored sideways). Fire-and-forget behind the compression semaphore;
    // originals are never touched, so a failure just retries on the next start.
    state.compression.backfill_stale_derivatives().await;

    // Re-extract poster frames for videos a restart interrupted. `startup_recovery` above
    // marks their compression `failed` but nothing re-enqueued them, so `thumbnail_path`
    // stayed NULL for the rest of the event. Shares the attempt budget with the image
    // backfill, so a clip that genuinely yields no frame stops being retried.
    state.compression.backfill_video_posters().await;

    // Re-spawn exports for events that were released but whose keepsake never finished
    // (crash mid-export). Needs the media/export paths + SSE sender, so it runs here
    // rather than inside `startup_recovery`. Fire-and-forget: the workers run in the
    // background; the HTTP server can start accepting requests meanwhile.
    services::export::recover_exports(
        pool.clone(),
        config.media_path.clone(),
        config.export_path.clone(),
        config.comments_enabled,
        state.sse_tx.clone(),
    )
    .await;

    // Hourly background hygiene: prune expired sessions, evict cold rate-limiter
    // keys. Keeps the DB and process from growing unboundedly over multi-day events.
    services::maintenance::spawn_periodic_tasks(
        pool,
        state.rate_limiter.clone(),
        state.sse_tickets.clone(),
        config.media_path.clone(),
    );

    let api = Router::new()
        // Auth
        .route("/api/v1/event", get(handlers::public::get_public_event))
        .route("/api/v1/join", post(auth::handlers::join))
        .route("/api/v1/recover", post(auth::handlers::recover))
        // Forgotten-PIN escape hatch: ask a host to reset it (unauthenticated, throttled).
        .route(
            "/api/v1/recover/request",
            post(auth::handlers::request_pin_reset),
        )
        .route("/api/v1/admin/login", post(auth::handlers::admin_login))
        .route("/api/v1/session", delete(auth::handlers::logout))
        // "Sign out everywhere" — revoke all of the caller's sessions.
        .route("/api/v1/sessions", delete(auth::handlers::logout_all))
        // Upload — HTTP-level body cap as an OOM backstop. The handler still enforces
        // the precise per-class limits from DB config (max_image/video_size_mb); this
        // layer just stops a multi-GB body from being buffered into memory before that
        // check runs. Sized generously above the default 500 MB video limit + multipart
        // overhead. The DB-configured limits can no longer exceed it: both are clamped to
        // MAX_CONFIGURABLE_UPLOAD_MB at write time and at read time — see that constant
        // for why a comment was not enough.
        .route(
            "/api/v1/upload",
            post(handlers::upload::upload).route_layer(DefaultBodyLimit::max(MAX_UPLOAD_BYTES)),
        )
        .route(
            "/api/v1/upload/{id}",
            patch(handlers::upload::edit_upload).delete(handlers::upload::delete_upload),
        )
        .route(
            "/api/v1/upload/{id}/original",
            get(handlers::upload::get_original),
        )
        // Preview/thumbnail variants are gated the same way as originals (visibility
        // check + direct /media block below) so moderation actually revokes access to
        // the displayed images, not just the full-res download.
        .route(
            "/api/v1/upload/{id}/preview",
            get(handlers::upload::get_preview),
        )
        .route(
            "/api/v1/upload/{id}/display",
            get(handlers::upload::get_display),
        )
        .route(
            "/api/v1/upload/{id}/thumbnail",
            get(handlers::upload::get_thumbnail),
        )
        // Current-user endpoints (live quota estimate, profile + privacy note bundle)
        .route("/api/v1/me/context", get(handlers::me::get_context))
        .route("/api/v1/me/quota", get(handlers::me::get_quota))
        // Self-service erasure. There was no user-deletion route at any role, so an erasure
        // request could only be honoured with hand-written SQL against production — and the join
        // page's data notice now promises this exists. See `me::delete_account`.
        .route("/api/v1/me", delete(handlers::me::delete_account))
        // Feed
        .route("/api/v1/feed", get(handlers::feed::feed))
        .route("/api/v1/feed/delta", get(handlers::feed::feed_delta))
        .route("/api/v1/hashtags", get(handlers::feed::hashtags))
        .route("/api/v1/uploaders", get(handlers::feed::uploaders))
        // Social
        .route(
            "/api/v1/upload/{id}/like",
            post(handlers::social::toggle_like),
        )
        .route(
            "/api/v1/upload/{id}/comments",
            get(handlers::social::list_comments).post(handlers::social::add_comment),
        )
        .route(
            "/api/v1/comment/{id}",
            delete(handlers::social::delete_comment),
        )
        // SSE
        .route("/api/v1/stream", get(handlers::sse::stream))
        .route("/api/v1/stream/ticket", post(handlers::sse::issue_ticket))
        // Host Dashboard
        .route("/api/v1/host/event", get(handlers::host::get_event_status))
        .route(
            "/api/v1/host/event/close",
            post(handlers::host::close_event),
        )
        .route("/api/v1/host/event/open", post(handlers::host::open_event))
        .route(
            "/api/v1/host/gallery/release",
            post(handlers::host::release_gallery),
        )
        // Escape hatch: force a keepsake rebuild. Without it a failed export is terminal at runtime
        // (release_gallery refuses an already-released event; recovery only runs at boot).
        .route(
            "/api/v1/host/export/rebuild",
            post(handlers::host::rebuild_export),
        )
        .route("/api/v1/host/users", get(handlers::host::list_users))
        .route(
            "/api/v1/host/users/{id}/ban",
            post(handlers::host::ban_user),
        )
        .route(
            "/api/v1/host/users/{id}/unban",
            post(handlers::host::unban_user),
        )
        .route(
            "/api/v1/host/users/{id}/role",
            patch(handlers::host::set_role),
        )
        .route(
            "/api/v1/host/users/{id}/pin-reset",
            post(handlers::host::reset_user_pin),
        )
        .route(
            "/api/v1/host/pin-reset-requests",
            get(handlers::host::list_pin_reset_requests),
        )
        .route(
            "/api/v1/host/pin-reset-requests/{id}",
            delete(handlers::host::dismiss_pin_reset_request),
        )
        .route(
            "/api/v1/host/upload/{id}",
            delete(handlers::host::host_delete_upload),
        )
        .route(
            "/api/v1/host/comment/{id}",
            delete(handlers::host::host_delete_comment),
        )
        // Export (all authenticated users)
        .route("/api/v1/export/status", get(handlers::admin::export_status))
        .route(
            "/api/v1/export/ticket",
            post(handlers::admin::export_ticket),
        )
        .route("/api/v1/export/zip", get(handlers::admin::download_zip))
        .route("/api/v1/export/html", get(handlers::admin::download_html))
        // Admin Dashboard
        .route("/api/v1/admin/stats", get(handlers::admin::get_stats))
        .route(
            "/api/v1/admin/config",
            get(handlers::admin::get_config).patch(handlers::admin::patch_config),
        )
        .route(
            "/api/v1/admin/export/jobs",
            get(handlers::admin::get_export_jobs),
        );

    // Test-only route: a hard reset for the Playwright E2E harness. The handler
    // is compiled in always, but the route is only attached when
    // `EVENTSNAP_TEST_MODE=1`. In production the call returns 404 — the route
    // simply isn't there.
    let api = if handlers::test_admin::is_test_mode() {
        tracing::warn!(
            "EVENTSNAP_TEST_MODE=1 — registering /api/v1/admin/__truncate. \
             DO NOT enable this in production."
        );
        api.route(
            "/api/v1/admin/__truncate",
            post(handlers::test_admin::truncate_all),
        )
    } else {
        api
    };

    // NOTE: media is deliberately NOT served over HTTP.
    //
    // Files live under `media_path` so the compression worker and the export job can read
    // them off disk, but nothing may pull them straight from `/media/**` — that bypasses
    // the visibility checks (soft-delete + ban-hide) that make a host takedown stick.
    // Every legitimate fetch goes through `/api/v1/upload/{id}/{original,preview,display,
    // thumbnail}`, which filter via `find_visible_media`; those are the only media URLs the
    // backend ever emits (see `handlers::feed`).
    //
    // This used to be a `ServeDir` on `/media` with four `nest_service` blockers on the
    // subtrees above it. That was bypassable: axum routes on the RAW path while `ServeDir`
    // percent-decodes afterwards, so `/media/%70reviews/{id}.jpg` missed every blocker,
    // fell through to the `ServeDir`, and was decoded back to `previews/` on disk — serving
    // a taken-down photo to anyone, unauthenticated. Any single escaped byte worked, in all
    // four subtrees. Deleting the route removes the vector outright rather than racing the
    // decoder; `/media/**` now 404s regardless of encoding.
    let router = Router::new()
        // ONE probe, and it touches the database. The merge of the unattended-blockers work
        // brought a competing design — a dependency-free `/health` for the compose gate plus
        // a DB-backed `/health/ready` for an external monitor. That split is defensible, and
        // it was rejected deliberately:
        //
        //   * `/health` returning a constant "ok" is the exact defect faea555 fixed and
        //     verified live (stop Postgres → 503 → start → 200, with no app restart). Every
        //     request path touches the database, so a constant probe reports healthy while
        //     the app is useless — the disk-full endgame stayed green all the way down.
        //   * The split's motive was that Caddy's `depends_on: app: service_healthy` would
        //     be blocked by a Postgres hiccup at boot. But `app` itself already gates on
        //     `db: service_healthy`, so the DB is up before this probe ever runs, and the
        //     healthcheck carries a 20s start_period plus 5 retries on top.
        //   * The two handlers were the same `SELECT 1` with the same 2s timeout under two
        //     names, so keeping both bought nothing.
        //
        // The external uptime monitor points at this route — DEPLOYMENT_RUNBOOK.md §10.4,
        // which documents the response table and is the only thing in this deployment that
        // can page a human. (That section previously did not exist and this comment claimed
        // it did; if you are removing §10.4, this route loses its only consumer.)
        .route("/health", get(health))
        .merge(api)
        .layer(TraceLayer::new_for_http())
        .with_state(state);

    let listener = tokio::net::TcpListener::bind(("0.0.0.0", config.app_port)).await?;
    tracing::info!("listening on {}", listener.local_addr()?);
    // `into_make_service_with_connect_info` is required by the pre-auth handlers, which
    // extract `ConnectInfo<SocketAddr>` to use the peer address as the rate-limit key when
    // X-Forwarded-For is absent. Without it those extractors fail at runtime.
    axum::serve(
        listener,
        router.into_make_service_with_connect_info::<std::net::SocketAddr>(),
    )
    .with_graceful_shutdown(shutdown_signal())
    .await?;

    Ok(())
}

/// Create `dir` if absent, then prove we can actually write inside it. Hard error otherwise.
///
/// `create_dir_all` succeeding proves nothing: it is a no-op on an existing directory, so a
/// root-owned volume, a read-only bind mount and a full filesystem all "succeed". The probe
/// below is the only thing that distinguishes them, and it is worth the two syscalls once per
/// boot to turn a silent evening of failed uploads into a container that refuses to start.
///
/// `label` is the env var name so the operator gets the name of the knob to fix, not a path
/// they then have to trace back to a variable.
async fn ensure_writable_dir(dir: &std::path::Path, label: &str) -> anyhow::Result<()> {
    use anyhow::Context;

    tokio::fs::create_dir_all(dir)
        .await
        .with_context(|| format!("{label}: cannot create {}", dir.display()))?;

    // A fixed name is fine: this runs once, before the server accepts requests, and two
    // instances sharing one volume would be a misconfiguration in its own right. Removed on
    // both the success and failure paths so a crashed boot cannot leave litter behind.
    let probe = dir.join(".eventsnap-write-probe");
    let result = async {
        let mut f = tokio::fs::File::create(&probe)
            .await
            .with_context(|| format!("{label}: cannot create a file in {}", dir.display()))?;
        // Write and fsync rather than just create: a full filesystem lets the create succeed
        // and fails at the first byte, which is exactly the disk-full endgame this guards.
        tokio::io::AsyncWriteExt::write_all(&mut f, b"ok")
            .await
            .with_context(|| format!("{label}: cannot write to {}", dir.display()))?;
        f.sync_all()
            .await
            .with_context(|| format!("{label}: cannot flush to {}", dir.display()))?;
        anyhow::Ok(())
    }
    .await;
    let _ = tokio::fs::remove_file(&probe).await;

    result.with_context(|| {
        format!(
            "{label} ({}) is not writable. The app refuses to start rather than accept uploads \
             it cannot store — check the bind mount and that the volume is owned by the \
             container's non-root user.",
            dir.display()
        )
    })?;

    tracing::info!(path = %dir.display(), "{label} is writable");
    Ok(())
}

/// How long `/health` waits for the database before calling the app unhealthy. Deliberately
/// short: the point is to answer "can this process actually serve a request right now", and a
/// probe that blocks for the acquire timeout is itself a symptom.
const HEALTH_DB_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(2);

/// Readiness probe — the Docker healthcheck, Caddy's `depends_on` gate, and the runbook's
/// event-day `curl` all hit this.
///
/// It used to return the literal string `"ok"` and touch nothing. Every request in the app needs
/// the database, so that answered a question nobody asked: the container reported healthy while
/// every real request 500'd, and with no operator watching during the event there was no signal
/// at all. Note what this does NOT buy: Compose's `restart: unless-stopped` does not react to
/// healthcheck state, so nothing restarts on a red probe — this is a diagnostic, and it is
/// deliberately not wired to automatic recovery, because the pool already heals itself across a
/// Postgres restart (sqlx revalidates on acquire) and an auto-restart would truncate every
/// in-flight upload to "fix" an outage that was about to clear on its own.
async fn health(
    axum::extract::State(state): axum::extract::State<AppState>,
) -> impl axum::response::IntoResponse {
    use axum::http::StatusCode;
    match tokio::time::timeout(
        HEALTH_DB_TIMEOUT,
        sqlx::query("SELECT 1").execute(&state.pool),
    )
    .await
    {
        Ok(Ok(_)) => (StatusCode::OK, "ok"),
        Ok(Err(e)) => {
            tracing::error!(error = ?e, "health check: database query failed");
            (StatusCode::SERVICE_UNAVAILABLE, "database unavailable")
        }
        Err(_) => {
            tracing::error!(
                timeout_s = HEALTH_DB_TIMEOUT.as_secs(),
                "health check: database did not respond"
            );
            (StatusCode::SERVICE_UNAVAILABLE, "database timeout")
        }
    }
}

/// Hard cap on how long we wait for in-flight connections to drain after a shutdown
/// signal. Uploads (streamed to disk) finish in well under this; the cap exists because
/// long-lived SSE streams never end on their own and would otherwise keep the graceful
/// drain — and thus the process — pending until the orchestrator force-kills it.
const SHUTDOWN_GRACE: std::time::Duration = std::time::Duration::from_secs(10);

/// Resolves on SIGINT (Ctrl-C) or SIGTERM (container stop / deploy). Letting
/// `axum::serve` drain in-flight requests on this signal means a redeploy no longer
/// truncates uploads mid-flight; any background compression/export half-states that a
/// hard kill would leave are already reconciled by `startup_recovery` on the next boot.
///
/// Once the signal fires we also arm a detached backstop that force-exits after
/// [`SHUTDOWN_GRACE`]. Without it, open SSE streams (which have no natural end) would
/// hold the graceful drain open indefinitely; the backstop bounds shutdown regardless
/// of the orchestrator's own kill timeout. If the drain completes first, `main` returns
/// and the process exits before the timer ever fires.
async fn shutdown_signal() {
    let ctrl_c = async {
        let _ = tokio::signal::ctrl_c().await;
    };

    #[cfg(unix)]
    let terminate = async {
        match tokio::signal::unix::signal(tokio::signal::unix::SignalKind::terminate()) {
            Ok(mut sig) => {
                sig.recv().await;
            }
            Err(e) => {
                tracing::warn!(error = ?e, "failed to install SIGTERM handler");
                // Never resolve — fall back to ctrl_c only.
                std::future::pending::<()>().await;
            }
        }
    };

    #[cfg(not(unix))]
    let terminate = std::future::pending::<()>();

    tokio::select! {
        _ = ctrl_c => {}
        _ = terminate => {}
    }

    tracing::info!(
        "shutdown signal received, draining in-flight requests (max {}s)",
        SHUTDOWN_GRACE.as_secs()
    );

    // Backstop: if the graceful drain is still blocked after the grace window (almost
    // always because SSE streams are still open), exit anyway so deploys aren't stalled.
    tokio::spawn(async {
        tokio::time::sleep(SHUTDOWN_GRACE).await;
        tracing::warn!(
            "graceful drain exceeded {}s (likely open SSE streams); forcing exit",
            SHUTDOWN_GRACE.as_secs()
        );
        std::process::exit(0);
    });
}

#[cfg(test)]
mod tests {
    use super::{MAX_CONFIGURABLE_UPLOAD_MB, MAX_UPLOAD_BYTES};
    use crate::handlers::upload::{
        MAX_CAPTION_BYTES, MAX_CLIENT_UPLOAD_ID_BYTES, MAX_HASHTAGS_BYTES,
    };

    /// Boundary lines, `Content-Disposition` / `Content-Type` headers and CRLFs for the four
    /// fields the handler reads. A few hundred bytes in reality; 4 KiB is a deliberately fat
    /// allowance so this test asserts the invariant rather than a precise byte count.
    const MULTIPART_FRAMING_BYTES: usize = 4 * 1024;

    /// Both bounds on `MAX_CONFIGURABLE_UPLOAD_MB`, asserted at COMPILE time.
    ///
    /// `const _: () = assert!(...)` rather than a runtime `assert!`, matching the precedent in
    /// `handlers::upload` and `services::compression`: every operand is a constant, so a
    /// violation is a build failure rather than something that has to be run to be noticed. The
    /// cost is that a const panic takes a static message — the reasoning lives here instead.
    ///
    /// UPPER: a file at the largest configurable limit must still fit inside the body limit the
    /// router enforces, envelope included. If it does not, an operator can set a limit the
    /// handler accepts and the router then refuses MID-BODY — a 400 that the upload queue
    /// classifies as terminal and answers by deleting the guest's only copy of the photo. See
    /// `MAX_CONFIGURABLE_UPLOAD_MB`. Written against the field caps rather than a hardcoded
    /// number, so raising `MAX_CAPTION_LENGTH` (or adding another text field to the envelope)
    /// fails HERE instead of silently eating the margin.
    ///
    /// LOWER: the ceiling must not be so conservative that it forbids the shipped default.
    /// `max_video_size_mb` is seeded at 500 (migration 005), so a bound below that would clamp
    /// every video upload on a stock install and reject the stock config through `patch_config`.
    #[test]
    fn the_configurable_ceiling_is_bounded_at_both_ends() {
        const FILE: usize = MAX_CONFIGURABLE_UPLOAD_MB as usize * 1024 * 1024;
        const ENVELOPE: usize = MAX_CAPTION_BYTES
            + MAX_HASHTAGS_BYTES
            + MAX_CLIENT_UPLOAD_ID_BYTES
            + MULTIPART_FRAMING_BYTES;
        const _: () = {
            assert!(
                FILE + ENVELOPE <= MAX_UPLOAD_BYTES,
                "a file at MAX_CONFIGURABLE_UPLOAD_MB plus its multipart envelope exceeds \
                 MAX_UPLOAD_BYTES — an operator could configure a limit that DESTROYS uploads \
                 (400 mid-body, blob purged as terminal) instead of refusing them"
            );
            assert!(
                MAX_CONFIGURABLE_UPLOAD_MB >= 500,
                "MAX_CONFIGURABLE_UPLOAD_MB must clear the 500 MB max_video_size_mb default \
                 seeded by migration 005, or a stock install clamps every video upload"
            );
        };
    }
}