/**
 * Rollback des Timezone-Fix
 * Macht die Änderungen rückgängig
 */

const mysql = require('mysql2/promise');
const path = require('path');
require('dotenv').config({ path: path.join(__dirname, '.env') });

/**
 * Prüft, ob ein Datum in der Sommerzeit liegt
 */
function isSummertime(date) {
  const year = date.getFullYear();
  
  const marchEnd = new Date(year, 2, 31);
  const marchSunday = 31 - marchEnd.getDay();
  const summerStart = new Date(year, 2, marchSunday, 2, 0, 0);
  
  const octoberEnd = new Date(year, 9, 31);
  const octoberSunday = 31 - octoberEnd.getDay();
  const summerEnd = new Date(year, 9, octoberSunday, 3, 0, 0);
  
  return date >= summerStart && date < summerEnd;
}

async function rollbackTimezones() {
  let connection;
  
  try {
    connection = await mysql.createConnection({
      host: process.env.DB_HOST || 'localhost',
      user: process.env.DB_USER || 'root',
      password: process.env.DB_PASSWORD || '',
      database: process.env.DB_NAME || 'stechuhr2',
      timezone: '+00:00'
    });

    console.log('✅ Datenbankverbindung hergestellt\n');

    const [rows] = await connection.execute(
      'SELECT id, tstamp FROM worklog ORDER BY id ASC'
    );

    console.log(`📊 Gefunden: ${rows.length} Worklog-Einträge\n`);

    console.log('🔄 Wende Rollback an (addiere Offset zurück)...\n');

    let updatedCount = 0;
    for (const row of rows) {
      const storedDate = new Date(row.tstamp);
      
      // Erstelle lokales Datum aus UTC-Komponenten
      const year = storedDate.getUTCFullYear();
      const month = storedDate.getUTCMonth();
      const day = storedDate.getUTCDate();
      const hours = storedDate.getUTCHours();
      const minutes = storedDate.getUTCMinutes();
      const seconds = storedDate.getUTCSeconds();
      
      const localDate = new Date(year, month, day, hours, minutes, seconds);
      const offset = isSummertime(localDate) ? 2 : 1;
      
      // Addiere den Offset ZURÜCK
      const correctedDate = new Date(localDate.getTime() + (offset * 60 * 60 * 1000));
      const correctedISO = correctedDate.toISOString().replace('T', ' ').replace('.000Z', '');
      
      await connection.execute(
        'UPDATE worklog SET tstamp = ? WHERE id = ?',
        [correctedISO, row.id]
      );
      updatedCount++;
      
      if (updatedCount % 100 === 0) {
        console.log(`   ${updatedCount}/${rows.length} aktualisiert...`);
      }
    }
    
    console.log(`\n✅ ${updatedCount} Einträge erfolgreich zurückgesetzt!`);

  } catch (error) {
    console.error('❌ Fehler:', error);
    process.exit(1);
  } finally {
    if (connection) {
      await connection.end();
      console.log('\n🔌 Datenbankverbindung geschlossen');
    }
  }
}

rollbackTimezones().then(() => {
  process.exit(0);
}).catch(err => {
  console.error('Fataler Fehler:', err);
  process.exit(1);
});