import 'package:flutter/services.dart';

import '../domain/course_occurrence.dart';
import '../domain/course.dart';
import 'calendar_service.dart';

class CalendarRecord {
  const CalendarRecord({
    required this.id,
    required this.key,
    required this.calendarId,
    required this.owned,
  });
  final String id, key, calendarId;
  final bool owned;
}

class CalendarEventDraft {
  const CalendarEventDraft({
    required this.key,
    required this.calendarId,
    required this.title,
    required this.room,
    required this.description,
    required this.startMs,
    required this.endMs,
  });
  final String key, calendarId, title, room, description;
  final int startMs, endMs;
  Map<String, Object> toMap() => {
    'key': key,
    'calendarId': calendarId,
    'title': title,
    'room': room,
    'description': description,
    'startMs': startMs,
    'endMs': endMs,
    'timeZone': 'Asia/Shanghai',
  };
}

abstract class CalendarGateway {
  Future<bool> requestAccess();
  Future<List<DeviceCalendar>> calendars();
  Future<List<CalendarRecord>> ownedEvents(String calendarId);
  Future<String> save(CalendarEventDraft event, String? eventId);
  Future<void> delete(String eventId, String expectedKey);
}

class AndroidCalendarService extends CalendarService {
  AndroidCalendarService(this.gateway);
  final CalendarGateway gateway;
  @override
  Future<Map<String, String>> ownedEventIds(String calendarId) async => {
    for (final event in await gateway.ownedEvents(calendarId))
      if (event.owned && event.calendarId == calendarId) event.key: event.id,
  };
  @override
  Future<bool> requestAccess() => gateway.requestAccess();
  @override
  Future<List<DeviceCalendar>> listWritableCalendars() => gateway.calendars();
  @override
  Future<Map<String, String>> sync(
    List<CourseOccurrence> occurrences,
    String calendarId,
    Map<String, String> knownEventIds,
  ) async {
    if (!(await gateway.calendars()).any((c) => c.id == calendarId)) {
      throw StateError('所选日历不可写入');
    }
    final existing = (await gateway.ownedEvents(calendarId))
        .where((e) => e.owned && e.calendarId == calendarId)
        .toList();
    final result = <String, String>{};
    for (final occurrence in occurrences.where(
      (e) => e.course.source != CourseSource.demo,
    )) {
      final matches = existing.where((e) => e.key == occurrence.key).toList();
      matches.sort(
        (a, b) => (a.id == knownEventIds[occurrence.key] ? -1 : 0).compareTo(
          b.id == knownEventIds[occurrence.key] ? -1 : 0,
        ),
      );
      result[occurrence.key] = await gateway.save(
        CalendarEventDraft(
          key: occurrence.key,
          calendarId: calendarId,
          title: occurrence.course.name,
          room: occurrence.course.room,
          description: '任课老师：${occurrence.course.teacher}\n河畔Everyday',
          startMs: occurrence.start.millisecondsSinceEpoch,
          endMs: occurrence.end.millisecondsSinceEpoch,
        ),
        matches.isEmpty ? null : matches.first.id,
      );
    }
    for (final old in existing) {
      if (result[old.key] != old.id) {
        await gateway.delete(old.id, old.key);
      }
    }
    return result;
  }

  @override
  Future<void> deleteOwned(Map<String, String> eventIds) async {
    for (final entry in eventIds.entries) {
      await gateway.delete(entry.value, entry.key);
    }
  }
}

class MethodCalendarGateway extends CalendarGateway {
  static const channel = MethodChannel('hepan_everyday/calendar');
  @override
  Future<bool> requestAccess() async =>
      await channel.invokeMethod<bool>('requestAccess') ?? false;
  @override
  Future<List<DeviceCalendar>> calendars() async {
    final rows =
        await channel.invokeMethod<List<dynamic>>('listCalendars') ?? [];
    return rows
        .map((r) => DeviceCalendar(r['id'] as String, r['name'] as String))
        .toList();
  }

  @override
  Future<List<CalendarRecord>> ownedEvents(String calendarId) async {
    final rows =
        await channel.invokeMethod<List<dynamic>>('ownedEvents', {
          'calendarId': calendarId,
        }) ??
        [];
    return rows
        .map(
          (r) => CalendarRecord(
            id: r['id'] as String,
            key: r['key'] as String,
            calendarId: r['calendarId'] as String,
            owned: r['owned'] as bool,
          ),
        )
        .toList();
  }

  @override
  Future<String> save(CalendarEventDraft event, String? eventId) async =>
      (await channel.invokeMethod<String>('saveEvent', {
        ...event.toMap(),
        'eventId': eventId,
      }))!;
  @override
  Future<void> delete(String eventId, String expectedKey) => channel
      .invokeMethod<void>('deleteEvent', {'id': eventId, 'key': expectedKey});
}