import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter/foundation.dart' show kIsWeb, defaultTargetPlatform;
import 'package:flutter/foundation.dart' show TargetPlatform;
import '../providers/time_tracking_provider.dart';
import '../widgets/error_state_widget.dart';

class PermissionScreen extends ConsumerWidget {
  const PermissionScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final permissionStatus = ref.watch(permissionStatusProvider);
    final theme = Theme.of(context);

    return Scaffold(
      appBar: AppBar(
        title: const Text('权限设置'),
      ),
      body: SingleChildScrollView(
        padding: const EdgeInsets.all(24),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            // 图标
            Icon(
              Icons.security,
              size: 80,
              color: theme.colorScheme.primary,
            ),
            const SizedBox(height: 24),

            // 标题
            Text(
              '我们需要访问您的应用使用数据',
              style: theme.textTheme.headlineSmall?.copyWith(
                fontWeight: FontWeight.bold,
              ),
              textAlign: TextAlign.center,
            ),
            const SizedBox(height: 16),

            // 说明
            Text(
              _getPermissionDescription(),
              style: theme.textTheme.bodyLarge?.copyWith(
                color: theme.colorScheme.onSurface.withOpacity(0.7),
              ),
              textAlign: TextAlign.center,
            ),
            const SizedBox(height: 32),

            // 权限状态
            permissionStatus.when(
              data: (hasPermission) {
                if (hasPermission) {
                  return _buildPermissionGranted(context, theme);
                } else {
                  return _buildPermissionRequest(context, ref, theme);
                }
              },
              loading: () => const Center(child: CircularProgressIndicator()),
              error: (error, stack) => ErrorStateWidget.generic(
                message: '检查权限时出错，请重试',
                onRetry: () {
                  ref.invalidate(permissionStatusProvider);
                },
              ),
            ),

            const SizedBox(height: 32),

            // 隐私说明
            _buildPrivacyInfo(theme),
          ],
        ),
      ),
    );
  }

  String _getPermissionDescription() {
    if (kIsWeb) {
      return 'Web 平台暂不支持时间追踪功能。\n\n'
          '请使用 iOS 或 Android 应用。';
    } else if (defaultTargetPlatform == TargetPlatform.iOS) {
      return '这样我们才能自动追踪您的应用使用情况，无需手动操作。\n\n'
          '• 完全自动化，无需手动操作\n'
          '• 数据仅存储在本地\n'
          '• 不会上传到服务器';
    } else {
      return '这样我们才能自动追踪您的应用使用情况，无需手动操作。\n\n'
          '• 完全自动化，无需手动操作\n'
          '• 数据仅存储在本地\n'
          '• 不会上传到服务器';
    }
  }

  Widget _buildPermissionRequest(BuildContext context, WidgetRef ref, ThemeData theme) {
    return Column(
      children: [
        Container(
          padding: const EdgeInsets.all(16),
          decoration: BoxDecoration(
            color: theme.colorScheme.errorContainer,
            borderRadius: BorderRadius.circular(12),
          ),
          child: Row(
            children: [
              Icon(
                Icons.warning_amber_rounded,
                color: theme.colorScheme.error,
              ),
              const SizedBox(width: 12),
              Expanded(
                child: Text(
                  '权限未授予',
                  style: theme.textTheme.bodyLarge?.copyWith(
                    color: theme.colorScheme.error,
                    fontWeight: FontWeight.w600,
                  ),
                ),
              ),
            ],
          ),
        ),
        const SizedBox(height: 24),
        ElevatedButton(
          onPressed: () async {
            final service = ref.read(timeTrackingServiceProvider);
            final granted = await service.requestPermission();
            
            if (granted) {
              ref.invalidate(permissionStatusProvider);
              if (context.mounted) {
                ScaffoldMessenger.of(context).showSnackBar(
                  const SnackBar(content: Text('权限已授予')),
                );
              }
            } else {
              if (context.mounted) {
                ScaffoldMessenger.of(context).showSnackBar(
                  const SnackBar(content: Text('权限授予失败，请前往设置中手动开启')),
                );
              }
            }
          },
          style: ElevatedButton.styleFrom(
            padding: const EdgeInsets.symmetric(vertical: 16),
            shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(12),
            ),
          ),
          child: const Text(
            '去设置',
            style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600),
          ),
        ),
        const SizedBox(height: 12),
        TextButton(
          onPressed: () {
            Navigator.of(context).pop();
          },
          child: const Text('稍后再说'),
        ),
      ],
    );
  }

  Widget _buildPermissionGranted(BuildContext context, ThemeData theme) {
    return Container(
      padding: const EdgeInsets.all(16),
      decoration: BoxDecoration(
        color: theme.colorScheme.primaryContainer,
        borderRadius: BorderRadius.circular(12),
      ),
      child: Row(
        children: [
          Icon(
            Icons.check_circle,
            color: theme.colorScheme.primary,
          ),
          const SizedBox(width: 12),
          Expanded(
            child: Text(
              '权限已授予',
              style: theme.textTheme.bodyLarge?.copyWith(
                color: theme.colorScheme.primary,
                fontWeight: FontWeight.w600,
              ),
            ),
          ),
        ],
      ),
    );
  }


  Widget _buildPrivacyInfo(ThemeData theme) {
    return Container(
      padding: const EdgeInsets.all(16),
      decoration: BoxDecoration(
        color: theme.cardColor,
        borderRadius: BorderRadius.circular(12),
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(
            '隐私说明',
            style: theme.textTheme.titleMedium?.copyWith(
              fontWeight: FontWeight.w600,
            ),
          ),
          const SizedBox(height: 8),
          Text(
            '• 所有数据仅存储在您的设备本地\n'
            '• 我们不会收集或上传任何数据到服务器\n'
            '• 您可以随时删除所有数据\n'
            '• 应用使用数据仅用于统计和分析',
            style: theme.textTheme.bodySmall?.copyWith(
              color: theme.colorScheme.onSurface.withOpacity(0.7),
            ),
          ),
        ],
      ),
    );
  }
}