import 'dart:async';

import 'package:flutter/material.dart';

import '../../data/repositories/settings_repository.dart';
import 'theme_preference.dart';

/// Resolves the light/dark choice, including the fixed time-of-day schedule.
///
/// Automatic mode is dark from [nightStartMinutes] until [nightEndMinutes],
/// wrapping around midnight (19:00 -> 07:00 by default). A timer wakes exactly
/// at the next boundary so the app can switch without polling.
class ThemeController extends ChangeNotifier {
  ThemeController(this._settings) {
    _preference = _settings.themePreference;
    _nightStartMinutes = _settings.nightStartMinutes;
    _nightEndMinutes = _settings.nightEndMinutes;
    _resolvedDark = _computeDark(DateTime.now());
    _scheduleBoundary();
  }

  final SettingsRepository _settings;

  ThemePreference _preference = ThemePreference.automatic;
  int _nightStartMinutes = 19 * 60;
  int _nightEndMinutes = 7 * 60;
  bool _resolvedDark = false;
  Timer? _boundaryTimer;
  bool _disposed = false;

  ThemePreference get preference => _preference;
  int get nightStartMinutes => _nightStartMinutes;
  int get nightEndMinutes => _nightEndMinutes;
  bool get isDark => _resolvedDark;
  ThemeMode get themeMode => _resolvedDark ? ThemeMode.dark : ThemeMode.light;

  Future<void> setPreference(ThemePreference preference) async {
    if (_preference == preference) return;
    _preference = preference;
    _resolvedDark = _computeDark(DateTime.now());
    await _settings.setThemePreference(preference);
    _scheduleBoundary();
    _notify();
  }

  Future<void> setNightWindow({
    required int startMinutes,
    required int endMinutes,
  }) async {
    _nightStartMinutes = startMinutes.clamp(0, 1439);
    _nightEndMinutes = endMinutes.clamp(0, 1439);
    await _settings.setNightWindow(
      startMinutes: _nightStartMinutes,
      endMinutes: _nightEndMinutes,
    );
    _resolvedDark = _computeDark(DateTime.now());
    _scheduleBoundary();
    _notify();
  }

  /// Re-evaluates the schedule after the app resumes or a settings page closes.
  void refreshNow() {
    if (_preference != ThemePreference.automatic) return;
    final next = _computeDark(DateTime.now());
    if (next != _resolvedDark) {
      _resolvedDark = next;
      _notify();
    }
    _scheduleBoundary();
  }

  bool _computeDark(DateTime now) {
    switch (_preference) {
      case ThemePreference.light:
        return false;
      case ThemePreference.dark:
        return true;
      case ThemePreference.automatic:
        final minutes = now.hour * 60 + now.minute;
        if (_nightStartMinutes == _nightEndMinutes) return false;
        if (_nightStartMinutes < _nightEndMinutes) {
          return minutes >= _nightStartMinutes && minutes < _nightEndMinutes;
        }
        return minutes >= _nightStartMinutes || minutes < _nightEndMinutes;
    }
  }

  void _scheduleBoundary() {
    _boundaryTimer?.cancel();
    _boundaryTimer = null;
    if (_preference != ThemePreference.automatic) return;

    final now = DateTime.now();
    final next = _nextBoundary(now);
    if (next == null) return;
    _boundaryTimer = Timer(
      next.difference(now) + const Duration(seconds: 1),
      () {
        _resolvedDark = _computeDark(DateTime.now());
        _notify();
        _scheduleBoundary();
      },
    );
  }

  DateTime? _nextBoundary(DateTime now) {
    DateTime at(int minutes) {
      return DateTime(
        now.year,
        now.month,
        now.day,
        minutes ~/ 60,
        minutes % 60,
      );
    }

    final candidates = <DateTime>[];
    for (final minutes in {_nightStartMinutes, _nightEndMinutes}) {
      var candidate = at(minutes);
      if (!candidate.isAfter(now)) {
        candidate = candidate.add(const Duration(days: 1));
      }
      candidates.add(candidate);
    }
    if (candidates.isEmpty) return null;
    candidates.sort();
    return candidates.first;
  }

  void _notify() {
    if (!_disposed) notifyListeners();
  }

  @override
  void dispose() {
    _disposed = true;
    _boundaryTimer?.cancel();
    super.dispose();
  }
}