import 'dart:convert';

import 'package:dio/dio.dart';

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

sealed class ChatStreamEvent {}

class ChatTextChunk extends ChatStreamEvent {
  final String text;
  ChatTextChunk(this.text);
}

class ChatStatusUpdate extends ChatStreamEvent {
  final String status; // empty string = clear status
  ChatStatusUpdate(this.status);
}

/// A single tool call fired during generation. Mirrors the `tool_call` SSE
/// event emitted by `generation_task.py` and the `tool_calls` array persisted
/// on the assistant Message row — same shape either way so the UI can render
/// live chips during streaming and re-render them from storage after reload.
class ChatToolCall extends ChatStreamEvent {
  final Map<String, dynamic> toolCall;
  ChatToolCall(this.toolCall);
}

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);
    }
  }

  // Returns the conversation metadata AND its messages in a single request.
  Future<(Conversation, 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 conversation = Conversation.fromJson(conv);
      final list = conv['messages'] as List<dynamic>? ?? [];
      final messages = list
          .map((e) => Message.fromJson(e as Map<String, dynamic>))
          .toList();
      return (conversation, messages);
    } 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 typed events (text chunks + status updates).
  Stream<ChatStreamEvent> streamGeneration(int conversationId) async* {
    try {
      final response = await _dio.get(
        '/api/chat/conversations/$conversationId/generation/stream',
        options: Options(
          responseType: ResponseType.stream,
          receiveTimeout: Duration.zero, // SSE streams run indefinitely
          sendTimeout: Duration.zero,
          headers: {
            'Accept': 'text/event-stream',
            'Cache-Control': 'no-cache',
          },
        ),
      );

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

      await for (final chunk in stream) {
        buf.write(utf8.decode(chunk, allowMalformed: true));
        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 data = line.substring(6).trim();
            if (data == '[DONE]') return;
            if (currentEvent == 'done' || currentEvent == 'error') return;

            if (currentEvent == 'chunk' || currentEvent.isEmpty) {
              try {
                final obj = json.decode(data) as Map<String, dynamic>;
                final text = obj['text'] as String? ?? '';
                if (text.isNotEmpty) yield ChatTextChunk(text);
              } catch (_) {
                if (data.isNotEmpty) yield ChatTextChunk(data);
              }
            } else if (currentEvent == 'status') {
              try {
                final obj = json.decode(data) as Map<String, dynamic>;
                final status = obj['status'] as String? ?? '';
                yield ChatStatusUpdate(status);
              } catch (_) {
                // Ignore malformed status events
              }
            } else if (currentEvent == 'tool_call') {
              try {
                final obj = json.decode(data) as Map<String, dynamic>;
                final tc = obj['tool_call'];
                if (tc is Map<String, dynamic>) yield ChatToolCall(tc);
              } catch (_) {
                // Ignore malformed tool_call events
              }
            }
          } else if (line.isEmpty) {
            currentEvent = ''; // blank line = SSE event separator
          }
        }
      }
    } on DioException catch (e) {
      throw dioToApp(e);
    }
  }

  /// POST /api/chat/from-article/{itemId}
  /// Creates or retrieves a chat conversation seeded with the article.
  /// Returns the conversation_id.
  Future<int> openArticleInChat(int itemId) async {
    try {
      final response =
          await _dio.post('/api/chat/from-article/$itemId', data: <String, dynamic>{});
      final data = response.data as Map<String, dynamic>;
      return data['conversation_id'] as int;
    } on DioException catch (e) {
      throw dioToApp(e);
    }
  }
}