/**
 * Structured logging for email worker with daily rotation AND retention
 *
 * Uses pino for high-performance JSON logging.
 * Includes logic to delete logs older than X days.
 */

import pino from 'pino';
import { 
  existsSync, 
  mkdirSync, 
  createWriteStream, 
  type WriteStream, 
  readdirSync, 
  statSync, 
  unlinkSync 
} from 'node:fs';
import { join } from 'node:path';

// ---------------------------------------------------------------------------
// Configuration
// ---------------------------------------------------------------------------
const LOG_DIR = '/var/log/email-worker';
const LOG_FILE_PREFIX = 'worker';
const RETENTION_DAYS = 14; // Logs älter als 14 Tage löschen

// ---------------------------------------------------------------------------
// File stream & Retention Logic
// ---------------------------------------------------------------------------
let fileStream: WriteStream | null = null;
let currentDateStr = '';

function getDateStr(): string {
  return new Date().toISOString().slice(0, 10); // YYYY-MM-DD
}

/**
 * Löscht alte Log-Dateien basierend auf RETENTION_DAYS
 */
function cleanUpOldLogs(): void {
  try {
    if (!existsSync(LOG_DIR)) return;

    const files = readdirSync(LOG_DIR);
    const now = Date.now();
    const maxAgeMs = RETENTION_DAYS * 24 * 60 * 60 * 1000;

    for (const file of files) {
      // Prüfen ob es eine unserer Log-Dateien ist
      if (!file.startsWith(LOG_FILE_PREFIX) || !file.endsWith('.log')) continue;

      const filePath = join(LOG_DIR, file);
      try {
        const stats = statSync(filePath);
        const ageMs = now - stats.mtimeMs;

        if (ageMs > maxAgeMs) {
          unlinkSync(filePath);
          // Einmalig auf stdout loggen, damit man sieht, dass aufgeräumt wurde
          process.stdout.write(`[INFO] Deleted old log file: ${file}\n`);
        }
      } catch (err) {
        // Ignorieren, falls Datei gerade gelöscht wurde oder Zugriff verweigert
      }
    }
  } catch (err) {
    process.stderr.write(`[WARN] Failed to clean up old logs: ${err}\n`);
  }
}

function ensureFileStream(): WriteStream | null {
  const today = getDateStr();
  
  // Wenn wir bereits einen Stream für heute haben, zurückgeben
  if (fileStream && currentDateStr === today) return fileStream;

  try {
    if (!existsSync(LOG_DIR)) mkdirSync(LOG_DIR, { recursive: true });

    // Wenn sich das Datum geändert hat (oder beim ersten Start): Aufräumen
    if (currentDateStr !== today) {
        cleanUpOldLogs();
    }

    // Alten Stream schließen, falls vorhanden
    if (fileStream) {
        fileStream.end();
    }

    const filePath = join(LOG_DIR, `${LOG_FILE_PREFIX}.${today}.log`);
    fileStream = createWriteStream(filePath, { flags: 'a' });
    currentDateStr = today;
    
    return fileStream;
  } catch {
    // Silently continue without file logging (e.g. permission issue)
    return null;
  }
}

// ---------------------------------------------------------------------------
// Pino logger
// ---------------------------------------------------------------------------
const logger = pino({
  level: 'info',
  formatters: {
    level(label) {
      return { level: label };
    },
  },
  timestamp: pino.stdTimeFunctions.isoTime,
});

// ---------------------------------------------------------------------------
// Log level mapping
// ---------------------------------------------------------------------------
type LogLevel = 'DEBUG' | 'INFO' | 'WARNING' | 'ERROR' | 'CRITICAL' | 'SUCCESS';

const LEVEL_MAP: Record<LogLevel, keyof pino.Logger> = {
  DEBUG: 'debug',
  INFO: 'info',
  WARNING: 'warn',
  ERROR: 'error',
  CRITICAL: 'fatal',
  SUCCESS: 'info',
};

// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------
export function log(
  message: string,
  level: LogLevel = 'INFO',
  workerName = 'unified-worker',
): void {
  const prefix = level === 'SUCCESS' ? '[SUCCESS] ' : '';
  const formatted = `[${workerName}] ${prefix}${message}`;

  // Pino (stdout/json)
  const method = LEVEL_MAP[level] ?? 'info';
  (logger as any)[method](formatted);

  // File (plain text)
  const stream = ensureFileStream();
  if (stream) {
    const ts = new Date().toISOString().replace('T', ' ').slice(0, 19);
    const line = `[${ts}] [${level}] [${workerName}] ${prefix}${message}\n`;
    stream.write(line);
  }
}