import 'package:flutter/material.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:app_settings/app_settings.dart';
import 'logger.dart';

class PermissionUtil {
  static final PermissionUtil instance = PermissionUtil._();
  PermissionUtil._();

  OverlayEntry? _explanationOverlayEntry;

  Future<bool> requestPermission({
    required BuildContext context,
    required Permission permissionType,
    required String permissionName,
    required String explanationText,
    required String permanentDenialText,
    String settingsButtonText = '前往设置',
    String cancelButtonText = '取消',
  }) async {
    try {
      final PermissionStatus status = await permissionType.status;
      Logger.d('PermissionUtil', '初始权限状态 [$permissionName]: $status');

      // 处理已授权状态（包括授予状态和临时通知权限）
      if (status == PermissionStatus.granted ||
          status == PermissionStatus.provisional) {
        Logger.i('PermissionUtil', '$permissionName 权限已授予或临时授权');
        return true;
      }

      // 处理永久拒绝状态
      if (status == PermissionStatus.permanentlyDenied) {
        Logger.w('PermissionUtil', '$permissionName 权限被永久拒绝，显示引导对话框');
        await _showPermanentDenialDialog(
          context: context,
          permissionName: permissionName,
          permanentDenialText: permanentDenialText,
          settingsButtonText: settingsButtonText,
          cancelButtonText: cancelButtonText,
        );
        return false;
      }

      // 处理初始拒绝/未决定状态
      if (status == PermissionStatus.denied) {
        Logger.d('PermissionUtil', '$permissionName 权限被拒绝或未决定，显示说明横幅并请求');
        _showExplanationOverlay(
          context: context,
          permissionName: permissionName,
          explanationText: explanationText,
        );

        final PermissionStatus newStatus = await permissionType.request();
        Logger.d('PermissionUtil', '请求后 $permissionName 的新权限状态: $newStatus');

        _hideExplanationOverlay();

        // 处理请求后的状态
        if (newStatus == PermissionStatus.granted ||
            newStatus == PermissionStatus.provisional) {
          Logger.i('PermissionUtil', '$permissionName 权限在请求后被授予');
          return true;
        } else if (newStatus == PermissionStatus.permanentlyDenied) {
          Logger.w('PermissionUtil', '$permissionName 权限在请求后被永久拒绝');
          await _showPermanentDenialDialog(
            context: context,
            permissionName: permissionName,
            permanentDenialText: permanentDenialText,
            settingsButtonText: settingsButtonText,
            cancelButtonText: cancelButtonText,
          );
        }
        return false;
      }

      // 处理受限状态
      if (status == PermissionStatus.restricted ||
          status == PermissionStatus.limited) {
        Logger.w('PermissionUtil', '$permissionName 权限受限或受限访问: $status');
        await _showRestrictedPermissionDialog(context, permissionName);
        return false;
      }

      // 其他未知状态处理
      Logger.e('PermissionUtil', '$permissionName 处于未知状态: $status');
      return false;
    } catch (e, stackTrace) {
      Logger.e(
        'PermissionUtil',
        '请求 $permissionName 权限失败: $e',
        e,
        stackTrace,
      );
      _hideExplanationOverlay();
      return false;
    }
  }

  /// 显示权限解释横幅（漂浮在UI顶部的说明性UI）
  ///
  /// 在请求权限前显示，向用户解释为什么需要这个权限
  void _showExplanationOverlay({
    required BuildContext context,
    required String permissionName,
    required String explanationText,
  }) {
    _hideExplanationOverlay(); // 确保移除旧叠加层

    _explanationOverlayEntry = OverlayEntry(
      builder: (context) => Positioned(
        top: MediaQuery.of(context).padding.top + 10,
        left: 16,
        right: 16,
        child: Material(
          borderRadius: BorderRadius.circular(12),
          elevation: 4,
          color: Theme.of(context).colorScheme.background,
          child: Padding(
            padding: const EdgeInsets.all(16),
            child: Column(
              mainAxisSize: MainAxisSize.min,
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text(
                  '需要$permissionName权限',
                  style: const TextStyle(
                    fontWeight: FontWeight.bold,
                    fontSize: 16,
                  ),
                ),
                const SizedBox(height: 8),
                Text(
                  explanationText,
                  style: const TextStyle(fontSize: 14),
                ),
              ],
            ),
          ),
        ),
      ),
    );

    Future.delayed(Duration.zero, () {
      if (_explanationOverlayEntry != null) {
        Overlay.of(context).insert(_explanationOverlayEntry!);
        Logger.i('PermissionUtil', '权限说明叠加层已显示 ($permissionName)');
      }
    });
  }

  /// 隐藏权限解释横幅
  void _hideExplanationOverlay() {
    if (_explanationOverlayEntry != null) {
      _explanationOverlayEntry?.remove();
      _explanationOverlayEntry = null;
      Logger.d('PermissionUtil', '权限说明叠加层已移除');
    }
  }

  /// 显示永久拒绝后的设置引导对话框
  ///
  /// 在权限被永久拒绝时调用，提示用户前往设置手动开启权限
  Future<void> _showPermanentDenialDialog({
    required BuildContext context,
    required String permissionName,
    required String permanentDenialText,
    required String settingsButtonText,
    required String cancelButtonText,
  }) async {
    Logger.i('PermissionUtil', '显示永久拒绝对话框 ($permissionName)');

    await showDialog<void>(
      context: context,
      barrierDismissible: false,
      builder: (context) => AlertDialog(
        title: Text('需要$permissionName权限'),
        content: Text(permanentDenialText),
        actions: [
          TextButton(
            onPressed: () {
              Logger.d('PermissionUtil', '用户取消设置 ($permissionName)');
              Navigator.pop(context);
            },
            child: Text(cancelButtonText),
          ),
          ElevatedButton(
            onPressed: () {
              Logger.d('PermissionUtil', '用户同意前往设置 ($permissionName)');
              Navigator.pop(context);
              AppSettings.openAppSettings();
            },
            child: Text(settingsButtonText),
          ),
        ],
      ),
    );
  }

  /// 显示受限权限对话框
  ///
  /// 在权限受限状态（如iOS上的受限照片访问）时调用
  Future<void> _showRestrictedPermissionDialog(
      BuildContext context, String permissionName) async {
    Logger.w('PermissionUtil', '显示受限权限对话框 ($permissionName)');
    await showDialog(
      context: context,
      builder: (context) => AlertDialog(
        title: Text('$permissionName权限受限'),
        content: const Text('此功能在当前设备上不可用或受限，请检查设备设置或系统限制'),
        actions: [
          TextButton(
            onPressed: () {
              Logger.d('PermissionUtil', '用户确认受限权限 ($permissionName)');
              Navigator.pop(context);
            },
            child: const Text('确定'),
          ),
        ],
      ),
    );
  }
}