import 'dart:io';

class MarketQuestionLogger {
  MarketQuestionLogger._();

  static const String _logFilePrefix = 'market_questions_';
  static const String _logFileSuffix = '.log';

  /// Log an answered market question to a date-stamped file with a 2-day rotation.
  static Future<void> logAnswer({
    required String questionId,
    required String userId,
    required String symbol,
    required num response,
    required num correctAnswer,
    required bool isInverted,
    DateTime? now,
  }) async {
    final DateTime time = now ?? DateTime.now().toUtc();
    final String dateString = _formatDate(time);
    
    // Construct today's and yesterday's file names
    final String todayFileName = '$_logFilePrefix$dateString$_logFileSuffix';
    final String yesterdayFileName = '$_logFilePrefix${_formatDate(time.subtract(const Duration(days: 1)))}$_logFileSuffix';

    // 1. Write the log entry
    final String logLine = '[${time.toIso8601String()}] '
        'Question ID: $questionId, '
        'User ID: $userId, '
        'Symbol: $symbol, '
        'Response: $response, '
        'Correct: $correctAnswer, '
        'Inverted: $isInverted\n';

    final File logFile = File(todayFileName);
    try {
      await logFile.writeAsString(logLine, mode: FileMode.append, flush: true);
    } catch (e) {
      stderr.writeln('Failed to write market question log: $e');
    }

    // 2. Perform rotation (delete any log files that are not today's or yesterday's)
    try {
      final Directory currentDir = Directory.current;
      final List<FileSystemEntity> entities = currentDir.listSync();
      for (final FileSystemEntity entity in entities) {
        if (entity is File) {
          final String name = entity.uri.pathSegments.last;
          if (name.startsWith(_logFilePrefix) && name.endsWith(_logFileSuffix)) {
            if (name != todayFileName && name != yesterdayFileName) {
              await entity.delete();
            }
          }
        }
      }
    } catch (e) {
      stderr.writeln('Failed to rotate market question logs: $e');
    }
  }

  static String _formatDate(DateTime dt) {
    final String y = dt.year.toString().padLeft(4, '0');
    final String m = dt.month.toString().padLeft(2, '0');
    final String d = dt.day.toString().padLeft(2, '0');
    return '$y-$m-$d';
  }
}