sendMessageStream method

Stream<String> sendMessageStream(
  1. String message
)

Sends a message to the AI service and returns a stream of responses.

This method enables real-time streaming of AI responses, allowing the UI to display responses as they are generated.

The message parameter is the user's input text.

Returns a Stream<String> that yields response chunks as they arrive.

Throws an Exception if:

  • API key is not set
  • Network request fails
  • API returns an error response

Example:

final stream = aiService.sendMessageStream('Tell me a story');
await for (final chunk in stream) {
  print(chunk); // Print each chunk as it arrives
}

Implementation

Stream<String> sendMessageStream(String message) async* {
  if (apiKey == null || apiKey!.isEmpty) {
    throw Exception('API key not set. Please configure your OpenAI API key.');
  }

  try {
    final request = http.Request(
      'POST',
      Uri.parse('$_baseUrl/chat/completions'),
    );

    request.headers['Content-Type'] = 'application/json';
    request.headers['Authorization'] = 'Bearer $apiKey';

    request.body = jsonEncode({
      'model': _model,
      'messages': [
        {
          'role': 'user',
          'content': message,
        },
      ],
      'max_tokens': 1000,
      'temperature': 0.7,
      'stream': true,
    });

    final streamedResponse = await request.send();

    if (streamedResponse.statusCode == 200) {
      await for (final chunk
          in streamedResponse.stream.transform(utf8.decoder)) {
        final lines = chunk.split('\n');
        for (final line in lines) {
          if (line.startsWith('data: ')) {
            final data = line.substring(6);
            if (data == '[DONE]') break;

            try {
              final json = jsonDecode(data);
              final content = json['choices'][0]['delta']['content'];
              if (content != null) {
                yield content as String;
              }
            } on FormatException {
              // Skip malformed JSON chunks
              continue;
            }
          }
        }
      }
    } else {
      final errorResponse = await streamedResponse.stream.bytesToString();
      final error = jsonDecode(errorResponse);
      throw Exception('API Error: ${error['error']['message']}');
    }
  } on FormatException catch (e) {
    throw Exception('Invalid response format: $e');
  } on Exception {
    rethrow;
  } catch (e) {
    throw Exception('Network error: $e');
  }
}