streamEvents method

@override Stream<ProviderEvent> streamEvents(List<ChatMessage> conversation)

Streams structured events for conversation's next assistant turn.

conversation is oldest-first; its last element is the new user turn.

Implementation

@override
Stream<ProviderEvent> streamEvents(List<ChatMessage> conversation) async* {
  final request = http.Request('POST', _endpoint)
    ..headers['Authorization'] = 'Bearer $apiKey'
    ..headers['Content-Type'] = 'application/json'
    ..headers['Accept'] = 'text/event-stream'
    ..body = jsonEncode({
      'model': model,
      'stream': true,
      'messages': _toOpenAiMessages(conversation),
      if (tools != null) 'tools': tools,
      ...?extraParams,
    });

  final response = await _httpClient.send(request);
  if (response.statusCode < 200 || response.statusCode >= 300) {
    final body = await response.stream.bytesToString();
    throw AgentProviderException(response.statusCode, body);
  }

  final pendingCalls = <int, _PendingToolCall>{};

  await for (final payload in sseDataEvents(response.stream)) {
    if (payload == '[DONE]') break;
    if (payload.isEmpty) continue;

    final Map<String, Object?> json;
    try {
      json = jsonDecode(payload) as Map<String, Object?>;
    } on FormatException {
      // OpenRouter occasionally sends non-JSON keep-alive comments; skip
      // rather than aborting the whole stream.
      continue;
    }

    final choices = json['choices'] as List<Object?>?;
    final delta = choices == null || choices.isEmpty
        ? null
        : (choices.first as Map<String, Object?>)['delta']
            as Map<String, Object?>?;
    if (delta == null) continue;

    final content = delta['content'] as String?;
    if (content != null && content.isNotEmpty) {
      yield TextDelta(content);
    }

    final toolCalls = delta['tool_calls'] as List<Object?>?;
    if (toolCalls != null) {
      for (final raw in toolCalls) {
        final entry = raw as Map<String, Object?>;
        final index = entry['index'] as int? ?? 0;
        final function = entry['function'] as Map<String, Object?>?;
        final pending = pendingCalls.putIfAbsent(index, _PendingToolCall.new);
        final id = entry['id'] as String?;
        if (id != null) pending.id = id;
        final name = function?['name'] as String?;
        if (name != null) pending.name = name;
        final argsChunk = function?['arguments'] as String?;
        if (argsChunk != null) pending.arguments.write(argsChunk);
      }
    }
  }

  for (final pending in pendingCalls.values) {
    final call = pending.toToolCall();
    if (call != null) yield ToolCallEvent(call);
  }
}