import 'package:flutter/material.dart';

/// Locks once the app returns after being in the background for at least
/// [gracePeriod], so a quick trip to the image picker or installer doesn't.
class AppLifecycleLockObserver extends WidgetsBindingObserver {
  final VoidCallback onLock;
  final VoidCallback? onBackground;
  final VoidCallback? onForeground;
  final bool Function()? shouldLock;
  final Duration gracePeriod;
  final DateTime Function() _clock;

  DateTime? _backgroundedAt;

  AppLifecycleLockObserver({
    required this.onLock,
    this.onBackground,
    this.onForeground,
    this.shouldLock,
    this.gracePeriod = const Duration(seconds: 30),
    DateTime Function()? clock,
  }) : _clock = clock ?? DateTime.now;

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    switch (state) {
      case AppLifecycleState.inactive:
        break;
      case AppLifecycleState.hidden:
      case AppLifecycleState.paused:
      case AppLifecycleState.detached:
        if (_backgroundedAt != null) return;
        _backgroundedAt = _clock();
        onBackground?.call();
      case AppLifecycleState.resumed:
        final backgroundedAt = _backgroundedAt;
        if (backgroundedAt == null) return;
        _backgroundedAt = null;

        final away = _clock().difference(backgroundedAt);
        if (away >= gracePeriod && (shouldLock?.call() ?? true)) onLock();
        onForeground?.call();
    }
  }
}