import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:shared_preferences/shared_preferences.dart';

import '../models/availability.dart';
import 'session_controller.dart';

/// Availability is stored as `yyyy-mm-dd` -> the blocks switched on that day.
typedef AvailabilityMap = Map<String, Set<DayBlock>>;

String dayKey(DateTime d) =>
    '${d.year}-${d.month.toString().padLeft(2, '0')}-${d.day.toString().padLeft(2, '0')}';

class AvailabilityController extends Notifier<AvailabilityMap> {
  static const _key = 'availability';

  SharedPreferences get _prefs => ref.read(prefsProvider);

  @override
  AvailabilityMap build() {
    final raw = _prefs.getStringList(_key) ?? const <String>[];
    final map = <String, Set<DayBlock>>{};
    for (final entry in raw) {
      // Stored as "2026-08-14:morning,evening".
      final parts = entry.split(':');
      if (parts.length != 2) continue;
      final blocks = parts[1]
          .split(',')
          .where((s) => s.isNotEmpty)
          .map(
            (name) => DayBlock.values.firstWhere(
              (b) => b.name == name,
              orElse: () => DayBlock.morning,
            ),
          )
          .toSet();
      if (blocks.isNotEmpty) map[parts[0]] = blocks;
    }
    return map;
  }

  void _persist(AvailabilityMap map) {
    _prefs.setStringList(_key, [
      for (final e in map.entries)
        if (e.value.isNotEmpty)
          '${e.key}:${e.value.map((b) => b.name).join(',')}',
    ]);
    state = map;
  }

  Set<DayBlock> blocksFor(DateTime day) => state[dayKey(day)] ?? <DayBlock>{};

  bool isDayOff(DateTime day) => blocksFor(day).isEmpty;

  void toggleBlock(DateTime day, DayBlock block) {
    final map = {
      for (final e in state.entries) e.key: {...e.value},
    };
    final key = dayKey(day);
    final blocks = map[key] ?? <DayBlock>{};
    if (!blocks.remove(block)) blocks.add(block);
    if (blocks.isEmpty) {
      map.remove(key);
    } else {
      map[key] = blocks;
    }
    _persist(map);
  }

  /// The day toggle: all three blocks on, or the day cleared.
  void setDayAvailable(DateTime day, bool available) {
    final map = {
      for (final e in state.entries) e.key: {...e.value},
    };
    final key = dayKey(day);
    if (available) {
      map[key] = DayBlock.values.toSet();
    } else {
      map.remove(key);
    }
    _persist(map);
  }

  /// Presets across the visible week: all days, weekdays only, weekends only.
  void applyPreset(
    List<DateTime> week, {
    required bool Function(DateTime) test,
  }) {
    final map = {
      for (final e in state.entries) e.key: {...e.value},
    };
    for (final day in week) {
      final key = dayKey(day);
      if (test(day)) {
        map[key] = DayBlock.values.toSet();
      } else {
        map.remove(key);
      }
    }
    _persist(map);
  }

  void clearWeek(List<DateTime> week) {
    final map = {
      for (final e in state.entries) e.key: {...e.value},
    };
    for (final day in week) {
      map.remove(dayKey(day));
    }
    _persist(map);
  }
}

final availabilityProvider =
    NotifierProvider<AvailabilityController, AvailabilityMap>(
      AvailabilityController.new,
    );

/// How many days in the coming week have at least one block switched on.
final daysSetProvider = Provider<int>((ref) {
  final map = ref.watch(availabilityProvider);
  final now = DateTime.now();
  var count = 0;
  for (var i = 0; i < 7; i++) {
    final d = now.add(Duration(days: i));
    if ((map[dayKey(d)] ?? const <DayBlock>{}).isNotEmpty) count++;
  }
  return count;
});