const path = require('path');
const fs = require('fs');
const db = require('./db');

const dataDir = path.join(__dirname, 'data');
const backupDir = path.join(dataDir, 'backups');

const INTERVAL_HOURS = Number(process.env.BACKUP_INTERVAL_HOURS) || 24;
const RETENTION_COUNT = Number(process.env.BACKUP_RETENTION_COUNT) || 14;

function timestamp() {
  return new Date().toISOString().replace(/[:.]/g, '-');
}

async function runBackup() {
  if (!fs.existsSync(backupDir)) fs.mkdirSync(backupDir, { recursive: true });
  const target = path.join(backupDir, `data-${timestamp()}.db`);
  await db.backup(target);
  cleanupOldBackups();
  console.log(`Backup geschrieben: ${target}`);
  return target;
}

function cleanupOldBackups() {
  const files = fs
    .readdirSync(backupDir)
    .filter((f) => f.startsWith('data-') && f.endsWith('.db'))
    .sort();
  const excess = files.length - RETENTION_COUNT;
  for (let i = 0; i < excess; i++) {
    fs.unlinkSync(path.join(backupDir, files[i]));
  }
}

function startBackupScheduler() {
  runBackup().catch((err) => console.error('Backup fehlgeschlagen:', err));
  setInterval(() => {
    runBackup().catch((err) => console.error('Backup fehlgeschlagen:', err));
  }, INTERVAL_HOURS * 60 * 60 * 1000);
}

module.exports = { startBackupScheduler, runBackup };