// Scheduler tick — every TICK_INTERVAL_MS scan the recorder_schedules table
// and transition any rows whose window opens or closes. The actual recorder
// start/stop is delegated to the existing /recorders/:id/start|stop routes
// via an in-process HTTP call, so we reuse all of the existing container
// orchestration, growing-files handling, asset row creation, etc.
//
// On schedule completion: a 'daily' or 'weekly' recurring schedule is cloned
// forward by 1 day / 7 days into a new 'pending' row.

import pool from './db/pool.js';
import { syncToAmpp } from './routes/upload.js';

const TICK_INTERVAL_MS = parseInt(process.env.SCHEDULER_TICK_MS || '15000', 10);
const SELF_URL = process.env.MAM_API_SELF_URL || `http://127.0.0.1:${process.env.PORT || 3000}`;

let _tickRunning = false;
let _interval = null;

async function callSelf(path, method = 'POST') {
  const res = await fetch(`${SELF_URL}${path}`, {
    method,
    headers: { 'Content-Type': 'application/json' },
    signal: AbortSignal.timeout(30000),
  });
  if (!res.ok) {
    const text = await res.text().catch(() => '');
    throw new Error(`${method} ${path} → HTTP ${res.status}: ${text.slice(0, 200)}`);
  }
  return res.json().catch(() => ({}));
}

// Issue #103 — every mam-api replica runs the same tick on the same interval,
// so a multi-node deploy would double-fire recorder starts/stops. We guard
// the whole tick with a PG advisory lock (1 = scheduler) so exactly one
// replica processes a given interval. Pure-Postgres, no extra infra.
const SCHEDULER_LOCK_KEY = 8210301; // arbitrary, must be stable across replicas

async function tryAcquireSchedulerLock(client) {
  const r = await client.query('SELECT pg_try_advisory_lock($1) AS got', [SCHEDULER_LOCK_KEY]);
  return !!r.rows[0]?.got;
}
async function releaseSchedulerLock(client) {
  await client.query('SELECT pg_advisory_unlock($1)', [SCHEDULER_LOCK_KEY]).catch(() => {});
}

async function tick() {
  if (_tickRunning) return;
  _tickRunning = true;

  const client = await pool.connect();
  let haveLock = false;
  try {
    haveLock = await tryAcquireSchedulerLock(client);
    if (!haveLock) {
      // Another replica is processing this interval — bail silently.
      return;
    }

    // 1) Atomically claim pending schedules whose window has opened. The
    //    UPDATE...RETURNING flips status to 'running' in the same statement
    //    so even if another replica got past the lock (it can't, but
    //    belt-and-braces) each row can only be claimed once.
    const dueStart = await client.query(
      `UPDATE recorder_schedules
          SET status = 'starting', updated_at = NOW()
        WHERE id IN (
          SELECT id FROM recorder_schedules
           WHERE status = 'pending' AND start_at <= NOW() AND end_at > NOW()
        ORDER BY start_at ASC
           FOR UPDATE SKIP LOCKED
        )
       RETURNING *`
    );
    for (const s of dueStart.rows) {
      try {
        const result = await callSelf(`/api/v1/recorders/${s.recorder_id}/start`);
        await client.query(
          `UPDATE recorder_schedules
           SET status = 'running', last_asset_id = NULL, updated_at = NOW()
           WHERE id = $1`,
          [s.id]
        );
        console.log(`[scheduler] started schedule "${s.name}" on recorder ${s.recorder_id} (session=${result.current_session_id || '?'})`);
      } catch (err) {
        await client.query(
          `UPDATE recorder_schedules
           SET status = 'failed', error_message = $2, updated_at = NOW()
           WHERE id = $1`,
          [s.id, err.message.slice(0, 500)]
        );
        console.error(`[scheduler] start failed for schedule ${s.id}: ${err.message}`);
      }
    }

    // 2) Atomically claim running schedules whose window has closed.
    const dueStop = await client.query(
      `UPDATE recorder_schedules
          SET status = 'stopping', updated_at = NOW()
        WHERE id IN (
          SELECT id FROM recorder_schedules
           WHERE status = 'running' AND end_at <= NOW()
        ORDER BY end_at ASC
           FOR UPDATE SKIP LOCKED
        )
       RETURNING *`
    );
    for (const s of dueStop.rows) {
      try {
        await callSelf(`/api/v1/recorders/${s.recorder_id}/stop`);
        await pool.query(
          `UPDATE recorder_schedules SET status = 'completed', updated_at = NOW()
           WHERE id = $1`,
          [s.id]
        );
        console.log(`[scheduler] stopped schedule "${s.name}" on recorder ${s.recorder_id}`);
        await enqueueNextOccurrence(s, client);
      } catch (err) {
        // Stop failed — flag as failed but don't keep trying forever.
        await client.query(
          `UPDATE recorder_schedules
           SET status = 'failed', error_message = $2, updated_at = NOW()
           WHERE id = $1`,
          [s.id, ('stop: ' + err.message).slice(0, 500)]
        );
        console.error(`[scheduler] stop failed for schedule ${s.id}: ${err.message}`);
      }
    }

    // 3) If a schedule was cancelled while running, stop the recorder.
    const cancelledRunning = await client.query(
      `SELECT s.* FROM recorder_schedules s
       JOIN recorders r ON r.id = s.recorder_id
       WHERE s.status = 'cancelled' AND r.status = 'recording'
         AND s.updated_at > NOW() - INTERVAL '5 minutes'`
    );
    for (const s of cancelledRunning.rows) {
      try {
        await callSelf(`/api/v1/recorders/${s.recorder_id}/stop`);
        console.log(`[scheduler] cancelled schedule "${s.name}" — stopped recorder ${s.recorder_id}`);
      } catch (err) {
        console.warn(`[scheduler] cancel-stop failed for ${s.id}: ${err.message}`);
      }
    }

    // 4) Mark stale live assets as 'error' (#66).
    // If a capture container crashes without calling mark-empty/mark-complete,
    // the asset row stays status='live' indefinitely. Timeout after 2 hours.
    const LIVE_TIMEOUT_MINUTES = parseInt(process.env.LIVE_ASSET_TIMEOUT_MINUTES || '120', 10);
    const staleResult = await client.query(
      `UPDATE assets
       SET status = 'error',
           updated_at = NOW()
       WHERE status = 'live'
         AND created_at < NOW() - ($1 || ' minutes')::INTERVAL
       RETURNING id, display_name`,
      [LIVE_TIMEOUT_MINUTES]
    );
    if (staleResult.rows.length > 0) {
      for (const row of staleResult.rows) {
        console.warn(`[scheduler] marked stale live asset as error: ${row.id} (${row.display_name})`);
      }
    }

    // 5) AMPP sync retry (#77). Pick up any pending/failed rows whose
    //    next-attempt time has arrived and retry them. Cap per tick so we
    //    don't burn budget on a single rough interval.
    const ampps = await client.query(
      `SELECT id, project_id, bin_id FROM assets
        WHERE ampp_sync_status IN ('pending', 'failed')
          AND (ampp_sync_next_attempt_at IS NULL OR ampp_sync_next_attempt_at <= NOW())
          AND ampp_sync_attempts < 8
        ORDER BY ampp_sync_next_attempt_at NULLS FIRST
        LIMIT 25`
    );
    for (const row of ampps.rows) {
      await syncToAmpp(row.id, row.project_id, row.bin_id);
    }
  } catch (err) {
    console.error('[scheduler] tick error:', err);
  } finally {
    if (haveLock) await releaseSchedulerLock(client);
    client.release();
    _tickRunning = false;
  }
}

async function enqueueNextOccurrence(schedule, client) {
  if (schedule.recurrence === 'none') return;
  const days = schedule.recurrence === 'weekly' ? 7 : 1;
  const start = new Date(schedule.start_at);
  const end   = new Date(schedule.end_at);
  start.setUTCDate(start.getUTCDate() + days);
  end.setUTCDate(end.getUTCDate() + days);
  const q = client || pool;
  await q.query(
    `INSERT INTO recorder_schedules
       (name, recorder_id, start_at, end_at, recurrence, status)
     VALUES ($1, $2, $3, $4, $5, 'pending')`,
    [schedule.name, schedule.recorder_id, start.toISOString(), end.toISOString(), schedule.recurrence]
  );
  console.log(`[scheduler] queued next "${schedule.name}" → ${start.toISOString()}`);
}

export function startSchedulerLoop() {
  if (_interval) return;
  console.log(`[scheduler] tick loop started (interval=${TICK_INTERVAL_MS}ms)`);
  // Fire once on startup so a window that opened while the API was down
  // doesn't have to wait a full interval.
  setTimeout(() => tick().catch(() => {}), 2000);
  _interval = setInterval(() => tick().catch(() => {}), TICK_INTERVAL_MS);
}

export function stopSchedulerLoop() {
  if (_interval) { clearInterval(_interval); _interval = null; }
}