import 'package:http/http.dart' as http;

class CalendarEvent {
  final String? summary;
  final String? description;
  final String? location;
  final DateTime? startTime;
  final DateTime? endTime;
  final bool isAllDay;

  CalendarEvent({
    this.summary,
    this.description,
    this.location,
    this.startTime,
    this.endTime,
    this.isAllDay = false,
  });
}

class GoogleCalendarService {
  static const String calendarId =
      'b9c267252d5be63d5cdc880be499885a88421eefd0e34e1392890daba0d8471e@group.calendar.google.com';

  final http.Client _httpClient = http.Client();

  Future<List<CalendarEvent>> getEvents({
    DateTime? startDate,
    DateTime? endDate,
  }) async {
    try {
      // Use the public iCal feed URL
      final url = Uri.parse(
          'https://calendar.google.com/calendar/ical/$calendarId/public/basic.ics');

      final response = await _httpClient.get(url);

      if (response.statusCode == 200) {
        final allEvents = _parseICalendar(response.body);

        // Filter events by date range if provided
        if (startDate != null || endDate != null) {
          return allEvents.where((event) {
            if (event.startTime == null) return false;

            if (startDate != null && event.startTime!.isBefore(startDate)) {
              return false;
            }

            if (endDate != null && event.startTime!.isAfter(endDate)) {
              return false;
            }

            return true;
          }).toList();
        }

        return allEvents;
      } else {
        throw Exception('Failed to load calendar: ${response.statusCode}');
      }
    } catch (e) {
      throw Exception('Error fetching events: $e');
    }
  }

  List<CalendarEvent> _parseICalendar(String icalData) {
    final events = <CalendarEvent>[];
    final lines = icalData.split('\n');

    String? summary;
    String? description;
    String? location;
    DateTime? startTime;
    DateTime? endTime;
    bool isAllDay = false;

    for (var i = 0; i < lines.length; i++) {
      var line = lines[i].trim();

      // Handle line continuations
      while (i + 1 < lines.length && lines[i + 1].startsWith(' ')) {
        i++;
        line += lines[i].trim();
      }

      if (line.startsWith('BEGIN:VEVENT')) {
        summary = null;
        description = null;
        location = null;
        startTime = null;
        endTime = null;
        isAllDay = false;
      } else if (line.startsWith('SUMMARY:')) {
        summary = _unescapeText(line.substring(8));
      } else if (line.startsWith('DESCRIPTION:')) {
        description = _unescapeText(line.substring(12));
      } else if (line.startsWith('LOCATION:')) {
        location = _unescapeText(line.substring(9));
      } else if (line.startsWith('DTSTART')) {
        final dateStr = line.split(':')[1];
        if (line.contains('VALUE=DATE')) {
          isAllDay = true;
          startTime = _parseDate(dateStr);
        } else {
          startTime = _parseDateTime(dateStr);
        }
      } else if (line.startsWith('DTEND')) {
        final dateStr = line.split(':')[1];
        if (line.contains('VALUE=DATE')) {
          endTime = _parseDate(dateStr);
        } else {
          endTime = _parseDateTime(dateStr);
        }
      } else if (line.startsWith('END:VEVENT')) {
        events.add(CalendarEvent(
          summary: summary,
          description: description,
          location: location,
          startTime: startTime,
          endTime: endTime,
          isAllDay: isAllDay,
        ));
      }
    }

    return events;
  }

  String _unescapeText(String text) {
    return text
        .replaceAll('\\n', '\n')
        .replaceAll('\\,', ',')
        .replaceAll('\\;', ';')
        .replaceAll('\\\\', '\\');
  }

  DateTime? _parseDate(String dateStr) {
    try {
      // Format: YYYYMMDD
      final year = int.parse(dateStr.substring(0, 4));
      final month = int.parse(dateStr.substring(4, 6));
      final day = int.parse(dateStr.substring(6, 8));
      return DateTime(year, month, day);
    } catch (e) {
      return null;
    }
  }

  DateTime? _parseDateTime(String dateStr) {
    try {
      // Format: YYYYMMDDTHHMMSSZ or YYYYMMDDTHHMMSS
      final year = int.parse(dateStr.substring(0, 4));
      final month = int.parse(dateStr.substring(4, 6));
      final day = int.parse(dateStr.substring(6, 8));
      final hour = int.parse(dateStr.substring(9, 11));
      final minute = int.parse(dateStr.substring(11, 13));
      final second = int.parse(dateStr.substring(13, 15));

      if (dateStr.endsWith('Z')) {
        return DateTime.utc(year, month, day, hour, minute, second);
      } else {
        return DateTime(year, month, day, hour, minute, second);
      }
    } catch (e) {
      return null;
    }
  }

  void dispose() {
    _httpClient.close();
  }
}