import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';
import 'package:go_router/go_router.dart';
import 'package:url_launcher/url_launcher.dart';
import 'package:webview_flutter/webview_flutter.dart';

import '../application/web_navigation_policy.dart';

/// Shared HTTPS WebView host. Mall-specific residency and attribution are
/// layered above this page so ordinary H5 links never receive mall state.
class AppWebPage extends StatefulWidget {
  const AppWebPage({
    super.key,
    required this.initialUri,
    this.hideTitle = false,
  });

  final Uri initialUri;
  final bool hideTitle;

  @override
  State<AppWebPage> createState() => _AppWebPageState();
}

class _AppWebPageState extends State<AppWebPage> {
  late final WebViewController _controller;
  var _progress = 0;
  String? _error;
  String _title = '';

  @override
  void initState() {
    super.initState();
    _controller =
        WebViewController(
            // Ordinary pages never receive camera/microphone or other protected
            // resources. MallWebHost owns its separate permission policy.
            onPermissionRequest: (request) => unawaited(request.deny()),
          )
          ..setJavaScriptMode(JavaScriptMode.unrestricted)
          ..addJavaScriptChannel(
            'JinzhiBridge',
            onMessageReceived: (message) {
              if (message.message == 'close' && mounted) context.pop();
            },
          )
          ..setNavigationDelegate(
            NavigationDelegate(
              onProgress: (progress) => setState(() => _progress = progress),
              onPageFinished: (_) async {
                final title = await _controller.getTitle();
                if (mounted && title != null && title.trim().isNotEmpty) {
                  setState(() => _title = title.trim());
                }
              },
              onWebResourceError: (error) {
                if (error.isForMainFrame == true && mounted) {
                  setState(() => _error = error.description);
                }
              },
              onNavigationRequest: _onNavigationRequest,
            ),
          )
          ..loadRequest(widget.initialUri);
  }

  NavigationDecision _onNavigationRequest(NavigationRequest request) {
    final uri = Uri.tryParse(request.url);
    if (uri != null && shouldOpenWebUrlExternally(request.url)) {
      launchUrl(uri, mode: LaunchMode.externalApplication);
      return NavigationDecision.prevent;
    }
    if (uri == null || !_isAllowedWebUri(uri)) {
      return NavigationDecision.prevent;
    }
    // Align with jinzhi-flutter-app: a normal HTTPS navigation stays in this
    // WebView even when its host changes. H5 opts into an external handoff
    // through `out`, which is handled above.
    return NavigationDecision.navigate;
  }

  Future<bool> _onPop() async {
    if (await _controller.canGoBack()) {
      await _controller.goBack();
      return false;
    }
    return true;
  }

  @override
  Widget build(BuildContext context) {
    final body = _error == null
        ? Stack(
            children: [
              WebViewWidget(controller: _controller),
              if (_progress < 100)
                LinearProgressIndicator(value: _progress / 100),
            ],
          )
        : Center(
            child: Padding(
              padding: const EdgeInsets.all(24),
              child: Text('页面加载失败\n$_error', textAlign: TextAlign.center),
            ),
          );
    return PopScope(
      canPop: false,
      onPopInvokedWithResult: (didPop, _) async {
        if (!didPop && await _onPop() && context.mounted) context.pop();
      },
      child: Scaffold(
        appBar: widget.hideTitle
            ? null
            : AppBar(title: Text(_title.isEmpty ? '加载中' : _title)),
        body: body,
      ),
    );
  }
}

Uri? parseSafeWebUri(String? raw) {
  final uri = Uri.tryParse(raw?.trim() ?? '');
  return uri != null && _isAllowedWebUri(uri) ? uri : null;
}

bool _isAllowedWebUri(Uri uri) {
  if (!uri.hasAuthority || uri.host.isEmpty) return false;
  if (uri.scheme.toLowerCase() == 'https') return true;
  if (kReleaseMode || uri.scheme.toLowerCase() != 'http') return false;
  return const {
    'localhost',
    '127.0.0.1',
    '::1',
  }.contains(uri.host.toLowerCase());
}