'use strict';

const { getDb } = require('../db/database');
const { getBankSyncConfig } = require('./bankSyncConfigService');
const { syncDataSource } = require('./bankSyncService');

const DEFAULT_INTERVAL_HOURS = 4;
// Skip a source if it was synced less than this long ago (catches recent manual syncs)
const MIN_SYNC_AGE_MS = 60 * 60 * 1000; // 1 hour
// Pause between each source to avoid hammering SimpleFIN
const STAGGER_DELAY_MS = 3000;

let timer = null;
let running = false;
let lastRunAt = null;
let nextRunAt = null;

function intervalMs() {
  const hours = parseFloat(process.env.SIMPLEFIN_SYNC_INTERVAL_HOURS);
  return Number.isFinite(hours) && hours >= 0.5
    ? Math.round(hours * 3600000)
    : DEFAULT_INTERVAL_HOURS * 3600000;
}

function needsSync(source) {
  if (!source.last_sync_at) return true;
  const age = Date.now() - new Date(source.last_sync_at).getTime();
  return age >= MIN_SYNC_AGE_MS;
}

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function runCycle() {
  if (running) return;

  const { enabled } = getBankSyncConfig();
  if (!enabled) return;

  let db, sources;
  try {
    db = getDb();
    sources = db.prepare(`
      SELECT * FROM data_sources
      WHERE type = 'provider_sync' AND provider = 'simplefin'
      ORDER BY last_sync_at ASC
    `).all();
  } catch (err) {
    console.error('[bankSync] Worker failed to load sources:', err.message);
    return;
  }

  if (sources.length === 0) return;

  running = true;
  lastRunAt = new Date().toISOString();

  let synced = 0;
  let skipped = 0;
  let failed = 0;

  for (let i = 0; i < sources.length; i++) {
    const source = sources[i];

    if (!needsSync(source)) {
      skipped++;
      continue;
    }

    try {
      await syncDataSource(db, source.user_id, source.id);
      synced++;
    } catch {
      // syncDataSource already writes last_error to the data_sources row
      failed++;
    }

    // Stagger requests — don't fire them all simultaneously
    if (i < sources.length - 1) await sleep(STAGGER_DELAY_MS);
  }

  if (synced > 0 || failed > 0) {
    console.log(`[bankSync] Auto-sync complete: ${synced} synced, ${failed} failed, ${skipped} skipped`);
  }

  running = false;
}

function scheduleNext() {
  const ms = intervalMs();
  nextRunAt = new Date(Date.now() + ms).toISOString();

  timer = setTimeout(() => {
    runCycle()
      .catch(err => {
        console.error('[bankSync] Worker cycle error:', err.message);
        running = false;
      })
      .finally(scheduleNext);
  }, ms);

  // Don't hold the event loop open if the server is shutting down
  if (timer.unref) timer.unref();
}

function start() {
  if (timer) return;
  scheduleNext();
  const hours = intervalMs() / 3600000;
  console.log(`[bankSync] Auto-sync worker started (interval: ${hours}h)`);
}

function stop() {
  clearTimeout(timer);
  timer = null;
}

function getStatus() {
  return {
    running,
    interval_hours: intervalMs() / 3600000,
    last_run_at: lastRunAt,
    next_run_at: nextRunAt,
  };
}

module.exports = { start, stop, getStatus };