import 'dart:core';
import 'dart:convert';
import 'dart:developer';
import 'package:flutter/material.dart';
import 'package:intl/intl.dart' show DateFormat;

import 'package:flutter/services.dart';

class ScheduleService {
  static const Duration dayOffset = Duration(hours: 4);

  Future<Map<String, dynamic>> getSchema() async {
    final source = await rootBundle
        .loadString('assets/schedule.json');
    return jsonDecode(source);
  }

  Future<Map<String, dynamic>?> getRule(DateTime day) async {
    final Map<String, dynamic> schema = await getSchema();
    if(!schema.containsKey('rules')) return null;

    for(final Map<String, dynamic> rule in (schema['rules'] as List<dynamic>)) {
      final DateTime after = DateTime.parse(rule['after']);
      final DateTime? before = rule['before'] != null
        ? DateTime.parse(rule['before'])
        : null;

      if(day.isAfter(after) && (before == null || day.isBefore(before)))
      { return rule; }
    }

    return null;
  }

  Future<Map<String, String>?> getDataset(DateTime day) async {
    final Map<String, dynamic>? rule = await getRule(day);

    if(rule == null || !rule.containsKey('dataset')) return null;

    return (rule['dataset'] as Map<String, dynamic>).map((key, value) {
      return MapEntry(key, value.toString());
    });
  }

  String datetimeWeekdayToDatasetKey(int weekday) {
    switch(weekday){
      case DateTime.monday:   return 'monday';
      case DateTime.tuesday:  return 'tuesday';
      case DateTime.wednesday:return 'wednesday';
      case DateTime.thursday: return 'thursday';
      case DateTime.friday:   return 'friday';
      case DateTime.saturday: return 'saturday';
      case DateTime.sunday:   return 'sunday';
    }

    return 'monday';
  }

  Future<List<Map<String, dynamic>>?> getScheduleByKey(String key) async {
    final Map<String, dynamic> schema = await getSchema();
    if(!schema.containsKey('schedules')) return null;
    if(!(schema['schedules'] as Map<String, dynamic>).containsKey(key)) return null;

    return (schema['schedules'][key] as List<dynamic>).map((element) {
      return element as Map<String, dynamic>;
    }).toList();
  }

  Future<List<Map<String, dynamic>>?> getScheduleByDate(DateTime datetime, {bool force = false}) async {
    final dateStart = datetime.copyWith(hour: 0, minute: 0, second: 0, microsecond: 0, millisecond: 0);
    final dateEnd   = datetime.copyWith(hour: 23, minute: 59, second: 59, microsecond: 999, millisecond: 999);
    final datetimeStartWithOffset = dateStart.copyWith().add(dayOffset);

    final DateTime usedScheduleDatetime = datetime.isAfter(datetimeStartWithOffset)
        ? datetime
        : datetime.copyWith().subtract(const Duration(days: 1));

    final Map<String, String>? dataset = await getDataset(usedScheduleDatetime);
    if(dataset == null) return null;

    final String dayKey = DateFormat('y-M-d').format(usedScheduleDatetime);
    final String weekdayKey = datetimeWeekdayToDatasetKey(usedScheduleDatetime.weekday);

    String? scheduleKey;
    if(dataset.containsKey(dayKey)) { scheduleKey = dataset[dayKey]; }
    else if(dataset.containsKey(weekdayKey)) { scheduleKey = dataset[weekdayKey]; }

    if(scheduleKey == null) return null;

    List<Map<String, dynamic>>? schedule = await getScheduleByKey(scheduleKey);
    if(schedule == null) return null;

    int durationOffset = 0;
    for (var i = 0; i < schedule.length; i++) {
      final scheduleItem = schedule[i];
      final int duration = (scheduleItem['duration'] as int);
      DateTime start = datetimeStartWithOffset.copyWith().add(Duration(minutes: durationOffset));
      DateTime end = datetimeStartWithOffset.copyWith().add(Duration(minutes: durationOffset + duration));
      durationOffset += duration;

      if(!force) {
        if(i == 0) {
          final schedulePrevDay = await getScheduleByDate(datetime.copyWith().subtract(const Duration(days: 1)), force: true);
          final lastScheduleElement = schedulePrevDay?.last;
          if(lastScheduleElement != null && (lastScheduleElement['direction'] as String) == (scheduleItem['direction'] as String)) {
            start = start.subtract(Duration(minutes: lastScheduleElement['duration'] as int));
          }
        }

        if(i == (schedule.length -1)) {
          final scheduleNextDay = await getScheduleByDate(datetime.copyWith().add(const Duration(days: 1)), force: true);
          final firstScheduleElement = scheduleNextDay?.first;
          if(firstScheduleElement != null && (firstScheduleElement['direction'] as String) == (scheduleItem['direction'] as String)) {
            end = end.add(Duration(minutes: firstScheduleElement['duration'] as int));
          }
        }
      }

      schedule[i]['start'] = start;
      schedule[i]['show_start_date'] = !(start.isAfter(dateStart) && start.isBefore(dateEnd));
      schedule[i]['end'] = end;
      schedule[i]['show_end_date'] = !(end.isAfter(dateStart) && end.isBefore(dateEnd));
    }

    return schedule;
  }

  Future<Map<String, dynamic>?> getCurrentStatus() async {
    final DateTime now = DateTime.now();
    final List<Map<String, dynamic>>? schedule = await getScheduleByDate(now);
    if(schedule == null) return null;

    for(var i = 0; i < schedule.length; i++) {
      final start = schedule[i]['start'];
      final end = schedule[i]['end'];

      if(now.isAfter(start) && now.isBefore(end)) {
        return schedule[i];
      }
    }

    return null;
  }

  static String formatDirection(String direction) {
    switch(direction) {
      case 'in_city': return 'В город';
      case 'out_city': return 'Из города';
      default: return 'Переключение';
    }
  }

  static IconData getIconByDirection(String? direction) {
    switch(direction) {
      case 'in_city': return Icons.input_outlined;
      case 'out_city': return Icons.output_outlined;
      default: return Icons.change_circle_outlined;
    }
  }
}