//! Startup recovery + periodic background hygiene.
//!
//! Two responsibilities:
//!
//! 1. **Startup sweep** — when the server boots, fix rows left in an "in-progress"
//!    state by the previous (possibly crashed) instance. Compression and export jobs
//!    each leave a status row when they begin; if the process is killed mid-run, that
//!    row stays `'processing'` / `'running'` forever, blocking re-tries and leaving
//!    users staring at a spinner. Resetting them on startup recovers gracefully.
//!
//! 2. **Periodic tasks** — pruning that should happen "every hour" rather than per
//!    request: expired sessions (otherwise the table grows unboundedly), and the
//!    rate-limiter's in-memory windows (so keys for IPs that left long ago don't
//!    accumulate).

use std::path::PathBuf;
use std::time::Duration;

use sqlx::PgPool;

use crate::services::rate_limiter::RateLimiter;
use crate::services::sse_tickets::SseTicketStore;

/// Reset rows left in flight by a previous crashed instance. Run once on startup,
/// before the HTTP server starts taking requests, so users never observe the
/// half-state.
pub async fn startup_recovery(pool: &PgPool) {
    // Uploads whose preview generation was interrupted. Marking them 'failed' is
    // safer than re-queueing — the original file is still on disk, the user can
    // delete + re-upload if they care, and we avoid double-processing risk.
    match sqlx::query(
        "UPDATE upload SET compression_status = 'failed'
         WHERE compression_status = 'processing'",
    )
    .execute(pool)
    .await
    {
        Ok(r) if r.rows_affected() > 0 => {
            tracing::warn!(
                "startup recovery: reset {} stuck upload(s) from 'processing' to 'failed'",
                r.rows_affected()
            );
        }
        Ok(_) => {}
        Err(e) => tracing::error!("startup recovery: failed to sweep uploads: {e:#}"),
    }

    // Export jobs interrupted mid-run. Mark 'failed' so the host can re-trigger.
    // The `UNIQUE(event_id, type)` constraint would otherwise block re-release.
    match sqlx::query(
        "UPDATE export_job
         SET status = 'failed',
             error_message = COALESCE(error_message, 'Server-Neustart während des Exports')
         WHERE status = 'running'",
    )
    .execute(pool)
    .await
    {
        Ok(r) if r.rows_affected() > 0 => {
            tracing::warn!(
                "startup recovery: reset {} stuck export job(s) from 'running' to 'failed'",
                r.rows_affected()
            );
        }
        Ok(_) => {}
        Err(e) => tracing::error!("startup recovery: failed to sweep export_job: {e:#}"),
    }
}

/// Spawns a background task that periodically:
/// - deletes session rows whose `expires_at` is more than a day in the past
/// - prunes the in-memory rate-limiter HashMap of empty windows
/// - drops expired SSE tickets (30s TTL but the map keeps the slot until pruned)
///
/// Cadence is 1h — fine for both jobs at our scale.
pub fn spawn_periodic_tasks(
    pool: PgPool,
    rate_limiter: RateLimiter,
    sse_tickets: SseTicketStore,
    media_path: PathBuf,
) {
    tokio::spawn(async move {
        let mut tick = tokio::time::interval(Duration::from_secs(3600));
        // Fire the first tick immediately, then hourly.
        tick.tick().await;
        loop {
            tick.tick().await;
            cleanup_sessions(&pool).await;
            rate_limiter.prune();
            sse_tickets.prune();
            // Reclaim disk for uploads soft-deleted more than the grace period
            // ago, and hard-delete those rows (FKs cascade).
            crate::services::media_fs::reap_deleted(&pool, &media_path).await;
        }
    });
}

async fn cleanup_sessions(pool: &PgPool) {
    match sqlx::query("DELETE FROM session WHERE expires_at < NOW() - INTERVAL '1 day'")
        .execute(pool)
        .await
    {
        Ok(r) if r.rows_affected() > 0 => {
            tracing::info!("cleaned up {} expired session(s)", r.rows_affected());
        }
        Ok(_) => {}
        Err(e) => tracing::warn!("session cleanup failed: {e:#}"),
    }
}