import 'dart:async';
import 'dart:convert';

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

import 'config/app_config.dart';

const _shellBackground = Color(0xFFF8FBFF);
const _shellAccent = Color(0xFF0089FF);
const _shellSubText = Color(0xFF8E9AB0);
const _shellBrandingChannel =
    MethodChannel('io.openim.flutter.im_webview_app/shell_branding');

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  SystemChrome.setSystemUIOverlayStyle(
    const SystemUiOverlayStyle(
      statusBarColor: Colors.transparent,
      statusBarIconBrightness: Brightness.dark,
      systemNavigationBarColor: _shellBackground,
      systemNavigationBarIconBrightness: Brightness.dark,
    ),
  );
  runApp(const ImWebViewApp());
}

class ShellBranding {
  const ShellBranding({
    required this.appName,
    required this.appLogo,
  });

  static const fallback = ShellBranding(
    appName: AppConfig.appName,
    appLogo: AppConfig.appLogo,
  );

  final String appName;
  final String appLogo;

  static Future<ShellBranding> load() async {
    try {
      final data = await _shellBrandingChannel
          .invokeMapMethod<String, String>('getShellBranding');
      final appName = _trim(data?['appName']);
      final appLogo = _trim(data?['appLogo']);

      return ShellBranding(
        appName: appName.isNotEmpty ? appName : fallback.appName,
        appLogo: appLogo.isNotEmpty ? appLogo : fallback.appLogo,
      );
    } catch (_) {
      return fallback;
    }
  }

  static String _trim(String? value) => value?.trim() ?? '';
}

class ImWebViewApp extends StatelessWidget {
  const ImWebViewApp({
    super.key,
    this.shellBranding = ShellBranding.fallback,
  });

  final ShellBranding shellBranding;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: shellBranding.appName,
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: const Color(0xFF1F6FEB)),
        scaffoldBackgroundColor: _shellBackground,
        useMaterial3: true,
      ),
      home: H5ShellPage(initialShellBranding: shellBranding),
    );
  }
}

class H5ShellPage extends StatefulWidget {
  const H5ShellPage({super.key, required this.initialShellBranding});

  final ShellBranding initialShellBranding;

  @override
  State<H5ShellPage> createState() => _H5ShellPageState();
}

class _H5ShellPageState extends State<H5ShellPage> {
  late final WebViewController _controller;

  int _progress = 0;
  String? _loadError;
  bool _showShellCover = true;
  bool _shellBrandingLoaded = false;
  Timer? _shellCoverFallbackTimer;
  late ShellBranding _shellBranding;

  @override
  void initState() {
    super.initState();
    _shellBranding = widget.initialShellBranding;
    _controller = _buildController();
    unawaited(_loadHome());
  }

  WebViewController _buildController() {
    return WebViewController()
      ..setJavaScriptMode(JavaScriptMode.unrestricted)
      ..addJavaScriptChannel(
        'OpenIMShell',
        onMessageReceived: _handleShellMessage,
      )
      ..setBackgroundColor(_shellBackground)
      ..setNavigationDelegate(
        NavigationDelegate(
          onProgress: (progress) {
            if (mounted) {
              setState(() => _progress = progress);
            }
          },
          onPageStarted: (_) {
            _shellCoverFallbackTimer?.cancel();
            if (mounted) {
              setState(() {
                _loadError = null;
                _progress = 0;
                _showShellCover = true;
              });
            }
          },
          onPageFinished: (_) {
            unawaited(_handlePageFinished());
          },
          onWebResourceError: (error) {
            if (error.isForMainFrame ?? true) {
              _shellCoverFallbackTimer?.cancel();
              if (mounted) {
                setState(() {
                  _loadError = error.description;
                  _showShellCover = false;
                });
              }
            }
          },
          onNavigationRequest: _handleNavigationRequest,
        ),
      );
  }

  @override
  void dispose() {
    _shellCoverFallbackTimer?.cancel();
    super.dispose();
  }

  Future<void> _runJavaScriptSafely(String source) async {
    try {
      await _controller.runJavaScript(source);
    } catch (_) {
      // WebView can reject JavaScript while a page is still navigating.
    }
  }

  String _freshHomeUrl() {
    return AppConfig.homeUrl();
  }

  Future<void> _handlePageFinished() async {
    await _loadShellBrandingIfNeeded();
    await _syncShellBranding();
    if (mounted) {
      setState(() {
        _progress = 100;
      });
    }
    _scheduleShellCoverFallback();
  }

  void _handleShellMessage(JavaScriptMessage message) {
    try {
      final decoded = jsonDecode(message.message);
      if (decoded is Map && decoded['type'] == 'first-screen-ready') {
        _hideShellCover();
      }
    } catch (_) {
      if (message.message == 'first-screen-ready') {
        _hideShellCover();
      }
    }
  }

  void _scheduleShellCoverFallback() {
    _shellCoverFallbackTimer?.cancel();
    _shellCoverFallbackTimer = Timer(
      const Duration(seconds: 4),
      _hideShellCover,
    );
  }

  void _hideShellCover() {
    _shellCoverFallbackTimer?.cancel();
    if (!mounted || !_showShellCover) {
      return;
    }

    setState(() {
      _progress = 100;
      _showShellCover = false;
    });
  }

  Future<void> _loadShellBrandingIfNeeded() async {
    if (_shellBrandingLoaded) {
      return;
    }

    final shellBranding = await ShellBranding.load();
    _shellBrandingLoaded = true;
    if (!mounted) {
      _shellBranding = shellBranding;
      return;
    }

    setState(() {
      _shellBranding = shellBranding;
    });
  }

  Future<void> _syncShellBranding() {
    final payload = jsonEncode({
      'name': _shellBranding.appName,
      'logo': _shellBranding.appLogo,
    });
    final script = '''
(() => {
  try {
    const brand = $payload;
    window.sessionStorage.setItem('OPENIM_FLUTTER_SHELL_BRAND', JSON.stringify(brand));
    window.dispatchEvent(new CustomEvent('openim-shell-branding-updated', { detail: brand }));
  } catch (_) {}
})();
''';
    return _runJavaScriptSafely(script);
  }

  Future<void> _loadHome() async {
    await _loadUrl(_freshHomeUrl());
  }

  Future<void> _loadUrl(String url) async {
    final targetUrl = AppConfig.canonicalizeMainFrameUrl(url);

    if (mounted) {
      _shellCoverFallbackTimer?.cancel();
      setState(() {
        _loadError = null;
        _progress = 0;
        _showShellCover = true;
      });
    }

    await _controller.loadRequest(Uri.parse(targetUrl));
  }

  Future<NavigationDecision> _handleNavigationRequest(
    NavigationRequest request,
  ) async {
    final uri = Uri.tryParse(request.url);
    if (uri == null) {
      return NavigationDecision.prevent;
    }

    const webSchemes = {'http', 'https', 'about', 'data'};
    if (webSchemes.contains(uri.scheme)) {
      if (request.isMainFrame &&
          AppConfig.shouldRewriteMainFrameUrl(request.url)) {
        unawaited(_loadUrl(AppConfig.canonicalizeMainFrameUrl(request.url)));
        return NavigationDecision.prevent;
      }
      return NavigationDecision.navigate;
    }

    try {
      await launchUrl(uri, mode: LaunchMode.externalApplication);
    } catch (_) {
      // Ignore unsupported custom schemes so the WebView does not navigate to
      // an error page.
    }
    return NavigationDecision.prevent;
  }

  Future<void> _handleBackNavigation() async {
    if (await _controller.canGoBack()) {
      await _controller.goBack();
    } else {
      await SystemNavigator.pop();
    }
  }

  @override
  Widget build(BuildContext context) {
    return PopScope(
      canPop: false,
      onPopInvokedWithResult: (didPop, _) {
        if (!didPop) {
          unawaited(_handleBackNavigation());
        }
      },
      child: Scaffold(
        backgroundColor: _shellBackground,
        body: SafeArea(
          bottom: false,
          child: Stack(
            children: [
              Positioned.fill(child: _ShellFallback(progress: _progress)),
              WebViewWidget(controller: _controller),
              if (_showShellCover)
                Positioned.fill(
                  child: IgnorePointer(
                    child: _ShellFallback(progress: _progress),
                  ),
                ),
              if (!_showShellCover && _progress < 100)
                LinearProgressIndicator(
                  value: _progress == 0 ? null : _progress / 100,
                  minHeight: 2,
                ),
              if (_loadError != null)
                _ErrorPanel(
                  message: _loadError!,
                  onRetry: () => unawaited(_loadHome()),
                ),
            ],
          ),
        ),
      ),
    );
  }
}

class _ErrorPanel extends StatelessWidget {
  const _ErrorPanel({required this.message, required this.onRetry});

  final String message;
  final VoidCallback onRetry;

  @override
  Widget build(BuildContext context) {
    return ColoredBox(
      color: Colors.white,
      child: Center(
        child: Padding(
          padding: const EdgeInsets.all(24),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const Icon(Icons.wifi_off_rounded, size: 44),
              const SizedBox(height: 16),
              const Text(
                '页面加载失败',
                style: TextStyle(fontSize: 18, fontWeight: FontWeight.w600),
              ),
              const SizedBox(height: 8),
              Text(
                message,
                textAlign: TextAlign.center,
                style: Theme.of(context).textTheme.bodyMedium,
              ),
              const SizedBox(height: 20),
              FilledButton(
                onPressed: onRetry,
                child: const Text('重新加载'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class _ShellFallback extends StatelessWidget {
  const _ShellFallback({required this.progress});

  final int progress;

  @override
  Widget build(BuildContext context) {
    final progressValue =
        progress <= 0 ? 0.42 : (0.18 + progress.clamp(0, 100) * 0.0074);

    return CustomPaint(
      painter: const _H5LoadingBackgroundPainter(),
      child: LayoutBuilder(
        builder: (context, constraints) {
          final markSize = (constraints.maxWidth * 0.37).clamp(118.0, 152.0);
          final contentTop = constraints.maxHeight * 0.29;
          final progressWidth =
              (constraints.maxWidth * 0.28).clamp(104.0, 132.0);

          return Align(
            alignment: Alignment.topCenter,
            child: Padding(
              padding: EdgeInsets.only(top: contentTop),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  _ShellMark(size: markSize),
                  SizedBox(height: markSize * 0.16),
                  const Text(
                    '心有回响',
                    style: TextStyle(
                      color: _shellAccent,
                      fontSize: 24,
                      height: 1.2,
                      fontWeight: FontWeight.w700,
                      letterSpacing: 0,
                    ),
                  ),
                  const SizedBox(height: 8),
                  const Text(
                    '正在为你唤醒会话',
                    style: TextStyle(
                      color: _shellSubText,
                      fontSize: 12,
                      height: 1.2,
                      letterSpacing: 0,
                    ),
                  ),
                  const SizedBox(height: 30),
                  _H5LoadingProgress(
                    width: progressWidth,
                    value: progressValue.clamp(0.18, 0.96),
                  ),
                ],
              ),
            ),
          );
        },
      ),
    );
  }
}

class _ShellMark extends StatelessWidget {
  const _ShellMark({required this.size});

  final double size;

  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      size: Size(size, size * 0.92),
      painter: const _BubbleCheckPainter(),
    );
  }
}

class _H5LoadingProgress extends StatelessWidget {
  const _H5LoadingProgress({required this.width, required this.value});

  final double width;
  final double value;

  @override
  Widget build(BuildContext context) {
    return ClipRRect(
      borderRadius: BorderRadius.circular(99),
      child: SizedBox(
        width: width,
        height: 4,
        child: Stack(
          fit: StackFit.expand,
          children: [
            const ColoredBox(color: Color(0xFFDCEEFF)),
            TweenAnimationBuilder<double>(
              tween: Tween<double>(end: value),
              duration: const Duration(milliseconds: 260),
              curve: Curves.easeOutCubic,
              builder: (context, animatedValue, _) {
                return FractionallySizedBox(
                  alignment: Alignment.centerLeft,
                  widthFactor: animatedValue,
                  child: const ColoredBox(color: _shellAccent),
                );
              },
            ),
          ],
        ),
      ),
    );
  }
}

class _H5LoadingBackgroundPainter extends CustomPainter {
  const _H5LoadingBackgroundPainter();

  static const _sourceSize = Size(1080, 2400);

  @override
  void paint(Canvas canvas, Size size) {
    final scale =
        (size.width / _sourceSize.width) > (size.height / _sourceSize.height)
            ? size.width / _sourceSize.width
            : size.height / _sourceSize.height;
    final dx = (size.width - _sourceSize.width * scale) / 2;
    final dy = (size.height - _sourceSize.height * scale) / 2;

    canvas.save();
    canvas.translate(dx, dy);
    canvas.scale(scale);

    final pageRect = Offset.zero & _sourceSize;
    final pagePaint = Paint()
      ..shader = const LinearGradient(
        begin: Alignment.topCenter,
        end: Alignment.bottomCenter,
        colors: [
          Color(0xFFE7F4FF),
          _shellBackground,
          Colors.white,
        ],
        stops: [0, 0.46, 1],
      ).createShader(pageRect);
    canvas.drawRect(pageRect, pagePaint);

    final topWave = Path()
      ..moveTo(0, 0)
      ..lineTo(1080, 0)
      ..lineTo(1080, 318)
      ..cubicTo(920, 246, 780, 246, 660, 318)
      ..cubicTo(512, 407, 387, 410, 284, 348)
      ..cubicTo(174, 282, 79, 281, 0, 344)
      ..close();
    canvas.drawPath(
      topWave,
      Paint()..color = const Color(0xFFDDF1FF).withValues(alpha: 0.68),
    );

    final bottomWave = Path()
      ..moveTo(1080, 855)
      ..lineTo(1080, 2400)
      ..lineTo(0, 2400)
      ..lineTo(0, 1942)
      ..cubicTo(124, 1854, 265, 1834, 423, 1883)
      ..cubicTo(598, 1937, 744, 1905, 862, 1788)
      ..cubicTo(934, 1717, 1007, 1678, 1080, 1672)
      ..close();
    canvas.drawPath(
      bottomWave,
      Paint()..color = const Color(0xFFF4FAFF).withValues(alpha: 0.86),
    );

    canvas.restore();
  }

  @override
  bool shouldRepaint(covariant _H5LoadingBackgroundPainter oldDelegate) {
    return false;
  }
}

class _BubbleCheckPainter extends CustomPainter {
  const _BubbleCheckPainter();

  static const _viewBox = Size(400, 363.33);

  @override
  void paint(Canvas canvas, Size size) {
    final scale =
        (size.width / _viewBox.width) < (size.height / _viewBox.height)
            ? size.width / _viewBox.width
            : size.height / _viewBox.height;
    final dx = (size.width - _viewBox.width * scale) / 2;
    final dy = (size.height - _viewBox.height * scale) / 2;

    canvas.save();
    canvas.translate(dx, dy);
    canvas.scale(scale);

    final bubble = Path()
      ..moveTo(200, 0)
      ..cubicTo(89.54, 0, 0, 81.33, 0, 181.67)
      ..cubicTo(0, 282, 89.54, 363.33, 200, 363.33)
      ..cubicTo(237.89, 363.33, 273.32, 353.77, 303.52, 337.16)
      ..lineTo(386.67, 363.33)
      ..lineTo(355.95, 290.69)
      ..cubicTo(383.61, 260.37, 400, 222.36, 400, 181.67)
      ..cubicTo(400, 81.33, 310.46, 0, 200, 0)
      ..close();

    final shadowPaint = Paint()
      ..color = const Color(0xFF026CD5).withValues(alpha: 0.18)
      ..maskFilter = const MaskFilter.blur(BlurStyle.normal, 34);
    canvas.save();
    canvas.translate(0, 30);
    canvas.drawPath(bubble, shadowPaint);
    canvas.restore();

    final bubblePaint = Paint()
      ..shader = const LinearGradient(
        begin: Alignment.topLeft,
        end: Alignment.bottomRight,
        colors: [
          Color(0xFFA8DDFF),
          _shellAccent,
          Color(0xFF0066E8),
        ],
        stops: [0, 0.48, 1],
      ).createShader(Offset.zero & _viewBox);
    canvas.drawPath(bubble, bubblePaint);

    final highlightPaint = Paint()
      ..shader = LinearGradient(
        begin: Alignment.topLeft,
        end: Alignment.bottomRight,
        colors: [
          Colors.white.withValues(alpha: 0.38),
          Colors.white.withValues(alpha: 0),
        ],
      ).createShader(Offset.zero & _viewBox);
    canvas.drawPath(bubble, highlightPaint);

    final check = Path()
      ..moveTo(101, 163.5)
      ..lineTo(170.5, 233)
      ..lineTo(306, 97.5);
    canvas.drawPath(
      check,
      Paint()
        ..color = Colors.white
        ..style = PaintingStyle.stroke
        ..strokeWidth = 58
        ..strokeCap = StrokeCap.round
        ..strokeJoin = StrokeJoin.round,
    );

    canvas.restore();
  }

  @override
  bool shouldRepaint(covariant _BubbleCheckPainter oldDelegate) {
    return false;
  }
}