import 'dart:async';
import 'dart:convert';
import 'dart:ui_web' as ui;

import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:universal_html/html.dart' as html;

class GrapesEmailEditorController {
  _GrapesEmailEditorState? _state;

  void _bind(_GrapesEmailEditorState state) => _state = state;

  void _unbind(_GrapesEmailEditorState state) {
    if (_state == state) _state = null;
  }

  bool get isReady => _state?.isReady ?? false;

  String get currentHtml => _state?.currentHtml ?? '';

  Future<String> exportHtml() => _state?.exportHtml() ?? Future.value('');

  void loadHtml(String html) => _state?.loadHtml(html);

  void insertToken(String token) => _state?.insertToken(token);
}

class GrapesEmailEditor extends StatefulWidget {
  final String html;
  final GrapesEmailEditorController? controller;
  final ValueChanged<String>? onHtmlChanged;

  const GrapesEmailEditor({
    super.key,
    required this.html,
    this.controller,
    this.onHtmlChanged,
  });

  @override
  State<GrapesEmailEditor> createState() => _GrapesEmailEditorState();
}

class _GrapesEmailEditorState extends State<GrapesEmailEditor> {
  static int _instanceCounter = 0;

  late final String _viewType;
  html.IFrameElement? _iframe;
  StreamSubscription<html.MessageEvent>? _messageSub;
  bool _isReady = false;
  bool _isDisposed = false;
  String _currentHtml = '';
  int _requestCounter = 0;
  final Map<int, Completer<String>> _pendingExports = {};

  bool get isReady => _isReady;

  String get currentHtml => _currentHtml;

  @override
  void initState() {
    super.initState();
    _currentHtml = widget.html;
    widget.controller?._bind(this);
    _instanceCounter += 1;
    _viewType = 'grapes-email-editor-$_instanceCounter';
    if (kIsWeb) {
      _registerView();
      _messageSub = html.window.onMessage.listen(_onMessage);
    }
  }

  @override
  void dispose() {
    _isDisposed = true;
    _messageSub?.cancel();
    _messageSub = null;
    _pendingExports.clear();
    try {
      _postToEditor({'action': 'destroy'});
      _iframe?.src = 'about:blank';
    } catch (_) {}
    widget.controller?._unbind(this);
    super.dispose();
  }

  void _registerView() {
    ui.platformViewRegistry.registerViewFactory(_viewType, (int viewId) {
      final iframe = html.IFrameElement()
        ..src = 'email-editor.html'
        ..style.border = 'none'
        ..style.width = '100%'
        ..style.height = '100%'
        ..style.display = 'block';

      _iframe = iframe;
      return iframe;
    });
  }

  void _postToEditor(Map<String, dynamic> payload) {
    if (_isDisposed) return;
    final win = _iframe?.contentWindow;
    if (win == null) return;
    try {
      final message = jsonEncode({
        'source': 'nhance-email-editor-host',
        ...payload,
      });
      (win as dynamic).postMessage(message, '*');
    } catch (_) {}
  }

  Map<String, dynamic>? _readPayload(Object? data) {
    if (data == null) return null;
    if (data is String) {
      try {
        final decoded = jsonDecode(data);
        if (decoded is Map) {
          return Map<String, dynamic>.from(decoded);
        }
      } catch (_) {
        return null;
      }
    }
    if (data is Map) {
      return Map<String, dynamic>.from(data);
    }
    try {
      final dynamic raw = data;
      final source = raw['source']?.toString();
      if (source == null) return null;
      return {
        'source': source,
        'action': raw['action']?.toString(),
        'html': raw['html']?.toString(),
        'requestId': raw['requestId'],
        'message': raw['message']?.toString(),
      };
    } catch (_) {
      return null;
    }
  }

  void _onMessage(html.MessageEvent event) {
    if (_isDisposed || !mounted) return;

    Map<String, dynamic>? data;
    try {
      data = _readPayload(event.data);
    } catch (_) {
      return;
    }
    if (data == null || data['source'] != 'nhance-email-editor') return;

    try {
      switch (data['action']) {
        case 'ready':
          if (_isDisposed || !mounted) return;
          _isReady = true;
          loadHtml(_currentHtml);
          break;
        case 'change':
          if (_isDisposed || !mounted) return;
          final htmlContent = data['html']?.toString() ?? '';
          if (htmlContent.isEmpty || htmlContent == _currentHtml) return;
          _currentHtml = htmlContent;
          widget.onHtmlChanged?.call(htmlContent);
          break;
        case 'html':
          if (_isDisposed) return;
          final requestId = int.tryParse(data['requestId']?.toString() ?? '');
          if (requestId != null) {
            _pendingExports.remove(requestId)?.complete(
              data['html']?.toString() ?? '',
            );
          }
          break;
      }
    } catch (_) {}
  }

  void loadHtml(String html) {
    if (_isDisposed) return;
    _currentHtml = html;
    _postToEditor({'action': 'load', 'html': html});
  }

  Future<String> exportHtml() async {
    if (_isDisposed) return _currentHtml;
    if (!_isReady) return _currentHtml;
    final requestId = ++_requestCounter;
    final completer = Completer<String>();
    _pendingExports[requestId] = completer;
    _postToEditor({'action': 'export', 'requestId': requestId});
    try {
      final result = await completer.future.timeout(const Duration(seconds: 5));
      if (!_isDisposed) _currentHtml = result;
      return result;
    } catch (_) {
      return _currentHtml;
    } finally {
      _pendingExports.remove(requestId);
    }
  }

  void insertToken(String token) {
    _postToEditor({'action': 'insertToken', 'token': token});
  }

  @override
  Widget build(BuildContext context) {
    if (!kIsWeb) {
      return Center(
        child: Padding(
          padding: const EdgeInsets.all(16),
          child: Text(
            'Drag-and-drop email editor is available on web.',
            style: GoogleFonts.poppins(fontSize: 13, color: Colors.black54),
            textAlign: TextAlign.center,
          ),
        ),
      );
    }

    return ClipRect(
      clipBehavior: Clip.hardEdge,
      child: SizedBox.expand(
        child: HtmlElementView(viewType: _viewType),
      ),
    );
  }
}