import 'dart:async';

import 'package:flutter/foundation.dart';

import '../../data/models/app_entry.dart';
import '../../data/models/slot_assignment.dart';
import '../../data/models/slot_type.dart';
import '../../data/repositories/settings_repository.dart';
import '../../data/services/native_bridge.dart';

/// Owns installed apps, shortcut assignments and the default-home state.
class LauncherController extends ChangeNotifier {
  LauncherController(this._platform, this._settings);

  final LauncherPlatform _platform;
  final SettingsRepository _settings;

  static const maxHomeButtons = 16;

  final Map<SlotType, SlotAssignment> _slots = {};
  final Map<SlotType, bool> _slotEnabled = {};
  final List<SlotAssignment> _pinnedApps = [];
  List<AppEntry> _apps = const [];
  bool _appsLoaded = false;
  bool _loadingApps = false;
  Object? _appsError;
  DateTime? _lastAppsLoad;
  bool _defaultHome = false;
  bool _defaultHomeKnown = false;
  Timer? _stateTimer;
  bool _disposed = false;

  List<AppEntry> get apps => _apps;
  bool get isLoadingApps => _loadingApps;
  bool get appsLoaded => _appsLoaded;
  Object? get appsError => _appsError;
  bool get isDefaultHome => _defaultHome;
  bool get defaultHomeKnown => _defaultHomeKnown;

  SlotAssignment? assignmentFor(SlotType slot) => _slots[slot];

  bool isSlotEnabled(SlotType slot) => _slotEnabled[slot] ?? true;

  /// Settings and All apps are always present; the three fixed slots count only
  /// while enabled, and each pinned app adds one.
  int get homeButtonCount =>
      2 + SlotType.values.where(isSlotEnabled).length + _pinnedApps.length;

  int get enabledSlotCount => SlotType.values.where(isSlotEnabled).length;

  List<SlotAssignment> get pinnedApps => List.unmodifiable(_pinnedApps);

  bool isPinned(SlotAssignment assignment) => _pinnedApps.contains(assignment);

  AppEntry? appForAssignment(SlotAssignment assignment) {
    for (final app in _apps) {
      if (app.matches(assignment)) return app;
    }
    return null;
  }

  /// Loads persisted choices synchronously, then refreshes platform state in
  /// the background so the first frame is not blocked by package enumeration.
  void initialize() {
    for (final slot in SlotType.values) {
      _slotEnabled[slot] = _settings.slotEnabled(slot);
      final assignment = _settings.slot(slot);
      if (assignment != null) _slots[slot] = assignment;
    }

    _pinnedApps.addAll(_settings.pinnedApps);
    final loadedCount = homeButtonCount;
    var trimmed = false;
    while (homeButtonCount > maxHomeButtons && _pinnedApps.isNotEmpty) {
      _pinnedApps.removeLast();
      trimmed = true;
    }
    if (trimmed || loadedCount != homeButtonCount) {
      unawaited(_settings.setPinnedApps(_pinnedApps));
    }

    _notify();

    unawaited(refreshDefaultHome());
    unawaited(loadApps());
  }

  Future<void> loadApps({bool force = false}) async {
    if (_loadingApps) return;
    if (_appsLoaded && !force) return;

    _loadingApps = true;
    _appsError = null;
    _notify();

    try {
      final loaded = await _platform.listApps();
      _apps = List<AppEntry>.unmodifiable(loaded);
      _appsLoaded = true;
      _lastAppsLoad = DateTime.now();
      await _validateAssignments();
    } catch (error) {
      _appsError = error;
    } finally {
      _loadingApps = false;
      _notify();
    }
  }

  /// Called when the launcher returns to the foreground. The package list is
  /// refreshed at most once a minute unless [forceApps] is set.
  Future<void> refresh({bool forceApps = false}) async {
    await refreshDefaultHome();
    final last = _lastAppsLoad;
    if (forceApps ||
        last == null ||
        DateTime.now().difference(last).inSeconds > 60) {
      await loadApps(force: true);
    }
  }

  Future<void> _validateAssignments() async {
    final installed = _apps
        .map((app) => '${app.packageName}/${app.activityName}')
        .toSet();
    final missing = <SlotType>[];
    _slots.forEach((slot, assignment) {
      if (!installed.contains(
        '${assignment.packageName}/${assignment.activityName}',
      )) {
        missing.add(slot);
      }
    });
    for (final slot in missing) {
      _slots.remove(slot);
      await _settings.clearSlot(slot);
    }

    final missingPinned = _pinnedApps
        .where(
          (assignment) => !installed.contains(
            '${assignment.packageName}/${assignment.activityName}',
          ),
        )
        .toList(growable: false);
    if (missingPinned.isNotEmpty) {
      _pinnedApps.removeWhere(missingPinned.contains);
      await _settings.setPinnedApps(_pinnedApps);
    }
  }

  Future<void> assign(SlotType slot, AppEntry app) async {
    final assignment = app.toAssignment();
    _slots[slot] = assignment;
    await _settings.setSlot(slot, assignment);
    _notify();
  }

  Future<void> clearSlot(SlotType slot) async {
    _slots.remove(slot);
    await _settings.clearSlot(slot);
    _notify();
  }

  /// Hides or shows a predefined home button. Disabled slots keep their app
  /// assignment, so re-enabling restores the same shortcut.
  Future<String?> setSlotEnabled(SlotType slot, bool enabled) async {
    if (isSlotEnabled(slot) == enabled) return null;
    if (enabled && homeButtonCount >= maxHomeButtons) {
      return 'Home screen is full ($maxHomeButtons buttons). '
          'Remove an app or turn off another button first.';
    }
    _slotEnabled[slot] = enabled;
    await _settings.setSlotEnabled(slot, enabled);
    _notify();
    return null;
  }

  /// Pins an app from All Apps to the home screen. Returns an error message
  /// when the app is already present or the 16-button limit is reached.
  Future<String?> addPinnedApp(AppEntry app) async {
    final assignment = app.toAssignment();
    final alreadyPinned = _pinnedApps.contains(assignment);
    final alreadyInVisibleSlot = SlotType.values.any(
      (slot) => isSlotEnabled(slot) && _slots[slot] == assignment,
    );
    if (alreadyPinned || alreadyInVisibleSlot) {
      return '${app.label} is already on the Home screen.';
    }
    if (homeButtonCount >= maxHomeButtons) {
      return 'Home screen is full ($maxHomeButtons buttons). '
          'Remove a button first.';
    }
    _pinnedApps.add(assignment);
    await _settings.setPinnedApps(_pinnedApps);
    _notify();
    return null;
  }

  Future<void> removePinnedApp(SlotAssignment assignment) async {
    if (!_pinnedApps.remove(assignment)) return;
    await _settings.setPinnedApps(_pinnedApps);
    _notify();
  }

  Future<String?> launchSlot(SlotType slot) async {
    final assignment = _slots[slot];
    if (assignment == null) return null;
    return launchAssignment(assignment);
  }

  Future<String?> launchAssignment(SlotAssignment assignment) async {
    try {
      await _platform.launchApp(
        packageName: assignment.packageName,
        activityName: assignment.activityName,
      );
      return null;
    } on LauncherPlatformException catch (error) {
      return error.message;
    } catch (_) {
      return 'Could not open ${assignment.label.isEmpty ? 'this app' : assignment.label}.';
    }
  }

  Future<String?> launchAppEntry(AppEntry app) async {
    try {
      await _platform.launchApp(
        packageName: app.packageName,
        activityName: app.activityName,
      );
      return null;
    } on LauncherPlatformException catch (error) {
      return error.message;
    } catch (_) {
      return 'Could not open ${app.label}.';
    }
  }

  Future<void> refreshDefaultHome() async {
    try {
      _defaultHome = await _platform.isDefaultHome();
    } catch (_) {
      _defaultHome = false;
    }
    _defaultHomeKnown = true;
    _notify();
  }

  Future<bool> requestDefaultHome() async {
    final launched = await _platform.requestDefaultHome();
    if (launched) {
      // The system dialog will pause us; refresh again after it closes.
      _stateTimer?.cancel();
      _stateTimer = Timer(const Duration(seconds: 2), () {
        unawaited(refreshDefaultHome());
      });
    }
    return launched;
  }

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

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