import 'dart:async';

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

import '../application/mall_web_host_controller.dart';

/// 常驻在 Tab Shell 上层的商城 H5 宿主。
class MallWebHost extends StatefulWidget {
  const MallWebHost({super.key, required this.onExit});
  final VoidCallback onExit;

  @override
  State<MallWebHost> createState() => _MallWebHostState();
}

class _MallWebHostState extends State<MallWebHost> {
  final _host = MallWebHostController.instance;
  WebViewController? _controller;
  String? _loadedUrl;
  String? _error;
  int _progress = 0;

  @override
  void initState() {
    super.initState();
    _host.state.addListener(_sync);
    _host.attachBackHandler(_goBack);
    _sync();
  }

  @override
  void dispose() {
    _host.state.removeListener(_sync);
    _host.detachBackHandler();
    super.dispose();
  }

  void _sync() {
    final url = _host.state.value.url;
    if (url != null && url != _loadedUrl) _load(url);
    if (mounted) setState(() {});
  }

  void _load(String rawUrl) {
    final uri = Uri.tryParse(rawUrl);
    if (uri == null || (uri.scheme != 'https' && uri.scheme != 'http')) {
      _error = '商城链接不可用';
      return;
    }
    _error = null;
    _progress = 0;
    _loadedUrl = rawUrl;
    _controller ??= WebViewController()
      ..setJavaScriptMode(JavaScriptMode.unrestricted)
      ..addJavaScriptChannel(
        'JinzhiBridge',
        onMessageReceived: (message) {
          if (message.message == 'close') widget.onExit();
        },
      )
      ..setNavigationDelegate(
        NavigationDelegate(
          onProgress: (value) {
            if (mounted) setState(() => _progress = value);
          },
          onWebResourceError: (error) {
            if (error.isForMainFrame == false) return;
            if (mounted) setState(() => _error = error.description);
          },
          onNavigationRequest: (request) async {
            final target = Uri.tryParse(request.url);
            if (target == null ||
                target.scheme == 'http' ||
                target.scheme == 'https') {
              return NavigationDecision.navigate;
            }
            if (await canLaunchUrl(target)) {
              await launchUrl(target, mode: LaunchMode.externalApplication);
            }
            return NavigationDecision.prevent;
          },
        ),
      );
    unawaited(_controller!.loadRequest(uri));
  }

  Future<void> _goBack() async {
    final controller = _controller;
    if (controller != null && await controller.canGoBack()) {
      await controller.goBack();
    }
  }

  @override
  Widget build(BuildContext context) {
    final current = _host.state.value;
    if (current.url == null) return const SizedBox.shrink();
    return ColoredBox(
      color: Theme.of(context).scaffoldBackgroundColor,
      child: Stack(
        children: [
          if (_controller != null)
            Positioned.fill(child: WebViewWidget(controller: _controller!)),
          if (_error != null)
            Center(
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  const Icon(Icons.wifi_off_rounded, size: 32),
                  const SizedBox(height: 12),
                  const Text('商城加载失败'),
                  const SizedBox(height: 8),
                  TextButton(
                    onPressed: () => _load(_loadedUrl ?? ''),
                    child: const Text('重新加载'),
                  ),
                ],
              ),
            ),
          if (_error == null && _progress < 100)
            const Align(
              alignment: Alignment.topCenter,
              child: LinearProgressIndicator(minHeight: 2),
            ),
        ],
      ),
    );
  }
}