import 'dart:convert';

import 'package:dio/dio.dart';

import '../models/conversation.dart';
import '../models/message.dart';
import 'api_client.dart';

class ChatApi {
  final Dio _dio;
  const ChatApi(this._dio);

  Future<List<Conversation>> getConversations() async {
    try {
      final response = await _dio.get('/api/chat/conversations');
      final data = response.data as Map<String, dynamic>;
      final list = data['conversations'] as List<dynamic>;
      return list
          .map((e) => Conversation.fromJson(e as Map<String, dynamic>))
          .toList();
    } on DioException catch (e) {
      throw dioToApp(e);
    }
  }

  Future<Conversation> createConversation(String title) async {
    try {
      final response = await _dio.post('/api/chat/conversations', data: {
        'title': title,
      });
      return Conversation.fromJson(response.data as Map<String, dynamic>);
    } on DioException catch (e) {
      throw dioToApp(e);
    }
  }

  Future<void> deleteConversation(int id) async {
    try {
      await _dio.delete('/api/chat/conversations/$id');
    } on DioException catch (e) {
      throw dioToApp(e);
    }
  }

  // Messages are embedded in the conversation detail response.
  Future<List<Message>> getMessages(int conversationId) async {
    try {
      final response =
          await _dio.get('/api/chat/conversations/$conversationId');
      final conv = response.data as Map<String, dynamic>;
      final list = conv['messages'] as List<dynamic>? ?? [];
      return list
          .map((e) => Message.fromJson(e as Map<String, dynamic>))
          .where((m) => m.status != 'generating') // skip in-flight placeholders
          .toList();
    } on DioException catch (e) {
      throw dioToApp(e);
    }
  }

  // Step 1: POST the user message — server starts background generation.
  Future<void> sendMessage(int conversationId, String content) async {
    try {
      await _dio.post(
        '/api/chat/conversations/$conversationId/messages',
        data: {'content': content},
      );
    } on DioException catch (e) {
      throw dioToApp(e);
    }
  }

  // Step 2: GET the SSE stream and yield text chunks.
  Stream<String> streamGeneration(int conversationId) async* {
    try {
      final response = await _dio.get(
        '/api/chat/conversations/$conversationId/generation/stream',
        options: Options(
          responseType: ResponseType.stream,
          headers: {'Accept': 'text/event-stream'},
        ),
      );

      final stream = (response.data as ResponseBody).stream;
      final buf = StringBuffer();
      String currentEvent = '';

      await for (final chunk in stream) {
        buf.write(utf8.decode(chunk));
        final raw = buf.toString();
        final lines = raw.split('\n');

        // Keep the last (potentially incomplete) line in the buffer.
        buf.clear();
        buf.write(lines.last);

        for (final line in lines.sublist(0, lines.length - 1)) {
          if (line.startsWith('event: ')) {
            currentEvent = line.substring(7).trim();
          } else if (line.startsWith('data: ')) {
            final jsonStr = line.substring(6).trim();
            if (currentEvent == 'chunk') {
              try {
                final data = json.decode(jsonStr) as Map<String, dynamic>;
                final text = data['text'] as String? ?? '';
                if (text.isNotEmpty) yield text;
              } catch (_) {}
            } else if (currentEvent == 'done' || currentEvent == 'error') {
              return;
            }
          } else if (line.isEmpty) {
            currentEvent = ''; // blank line = SSE event separator
          }
        }
      }
    } on DioException catch (e) {
      throw dioToApp(e);
    }
  }
}