import 'dart:async';
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:shared_preferences/shared_preferences.dart';
import '../core/network/api_config.dart';
import 'story_detail_page.dart';

class StoryLoadingPage extends StatefulWidget {
  /// Selected story elements from the generator modal
  final List<String> characters;
  final List<String> scenes;
  final List<String> props;

  const StoryLoadingPage({
    super.key,
    this.characters = const [],
    this.scenes = const [],
    this.props = const [],
  });

  @override
  State<StoryLoadingPage> createState() => _StoryLoadingPageState();
}

class _StoryLoadingPageState extends State<StoryLoadingPage> {
  double _progress = 0.0;
  String _loadingText = '正在收集灵感碎片...';
  bool _hasError = false;

  @override
  void initState() {
    super.initState();
    _generateStory();
  }

  Future<String?> _getToken() async {
    final prefs = await SharedPreferences.getInstance();
    return prefs.getString('access_token');
  }

  Future<void> _generateStory() async {
    try {
      final token = await _getToken();

      final request = http.Request(
        'POST',
        Uri.parse('${ApiConfig.fullBaseUrl}/stories/generate/'),
      );
      request.headers['Content-Type'] = 'application/json';
      if (token != null) {
        request.headers['Authorization'] = 'Bearer $token';
      }
      request.body = jsonEncode({
        'characters': widget.characters,
        'scenes': widget.scenes,
        'props': widget.props,
      });

      final client = http.Client();
      final response = await client.send(request).timeout(
        const Duration(seconds: 180),
      );

      if (response.statusCode != 200) {
        _showError('服务器响应异常 (${response.statusCode})');
        client.close();
        return;
      }

      // ── Parse SSE stream ──
      String buffer = '';
      String? storyTitle;
      String? storyContent;

      await for (final chunk in response.stream.transform(utf8.decoder)) {
        buffer += chunk;

        while (buffer.contains('\n\n')) {
          final idx = buffer.indexOf('\n\n');
          final block = buffer.substring(0, idx).trim();
          buffer = buffer.substring(idx + 2);

          // Extract the data line from the SSE block (may contain event: + data:)
          String? jsonStr;
          for (final line in block.split('\n')) {
            if (line.startsWith('data: ')) {
              jsonStr = line.substring(6);
              break;
            }
          }
          if (jsonStr == null) continue;

          try {
            final event = jsonDecode(jsonStr) as Map<String, dynamic>;
            final stage = event['stage'] as String? ?? '';
            final progress = (event['progress'] as num?)?.toDouble() ?? 0;
            final message = event['message'] as String? ?? '';

            if (!mounted) return;

            switch (stage) {
              case 'connecting':
                _updateProgress(progress / 100, '正在收集灵感碎片...');
                break;
              case 'generating':
                _updateProgress(progress / 100, '故事正在诞生...');
                break;
              case 'parsing':
                _updateProgress(progress / 100, '正在编制最后的魔法...');
                break;
              case 'done':
                storyTitle = event['title'] as String? ?? '卡皮巴拉的故事';
                storyContent = event['content'] as String? ?? '';
                _updateProgress(1.0, '大功告成！');
                break;
              case 'error':
                _showError(message.isNotEmpty ? message : '故事生成失败，请重试');
                client.close();
                return;
            }
          } catch (e) {
            debugPrint('SSE parse error: $e');
          }
        }
      }

      client.close();

      // ── Navigate to story detail ──
      if (!mounted) return;

      if (storyTitle != null && storyContent != null && storyContent.isNotEmpty) {
        // Brief pause to show "大功告成！"
        await Future.delayed(const Duration(milliseconds: 600));
        if (!mounted) return;

        final result = await Navigator.of(context).push<dynamic>(
          MaterialPageRoute(
            builder: (context) => StoryDetailPage(
              mode: StoryMode.generated,
              story: {
                'title': storyTitle,
                'content': storyContent,
              },
            ),
          ),
        );

        // Pass the story data back to DeviceControlPage
        if (mounted) {
          if (result == 'saved') {
            Navigator.of(context).pop({
              'action': 'saved',
              'title': storyTitle,
              'content': storyContent,
            });
          } else {
            Navigator.of(context).pop(result);
          }
        }
      } else {
        _showError('AI 返回了空故事，请重试');
      }
    } catch (e) {
      debugPrint('Story generation error: $e');
      if (mounted) {
        _showError('网络开小差了，再试一次~');
      }
    }
  }

  void _updateProgress(double progress, String text) {
    if (!mounted) return;
    setState(() {
      _progress = progress.clamp(0.0, 1.0);
      _loadingText = text;
    });
  }

  void _showError(String message) {
    if (!mounted) return;
    setState(() {
      _hasError = true;
      _loadingText = message;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: const Color(0xFFFDF9F3),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            // Image
            Image.asset(
              'assets/www/kapi_writing.png',
              width: 200,
              height: 200,
              errorBuilder: (c, e, s) => const Icon(
                Icons.edit_note,
                size: 100,
                color: Color(0xFFD1D5DB),
              ),
            ),
            const SizedBox(height: 32),

            // Text
            Text(
              _loadingText,
              style: const TextStyle(
                fontSize: 18,
                color: Color(0xFF4B2404),
                fontWeight: FontWeight.w600,
              ),
              textAlign: TextAlign.center,
            ),
            const SizedBox(height: 24),

            // Progress Bar
            Container(
              width: 280,
              height: 12,
              decoration: BoxDecoration(
                color: const Color(0xFFC99672).withOpacity(0.2),
                borderRadius: BorderRadius.circular(6),
              ),
              child: ClipRRect(
                borderRadius: BorderRadius.circular(6),
                child: FractionallySizedBox(
                  alignment: Alignment.centerLeft,
                  widthFactor: _progress.clamp(0.0, 1.0),
                  child: Container(
                    decoration: const BoxDecoration(
                      gradient: LinearGradient(
                        colors: [Color(0xFFECCFA8), Color(0xFFC99672)],
                      ),
                    ),
                  ),
                ),
              ),
            ),

            // Retry button (shown on error)
            if (_hasError) ...[
              const SizedBox(height: 32),
              TextButton(
                onPressed: () => Navigator.of(context).pop(),
                child: const Text(
                  '返回重试',
                  style: TextStyle(
                    fontSize: 16,
                    color: Color(0xFFC99672),
                    fontWeight: FontWeight.w600,
                  ),
                ),
              ),
            ],
          ],
        ),
      ),
    );
  }
}