Streaming API

emitStreamStart(messageId: string, conversationId: string): void;
emitStreamChunk(messageId: string, chunk: string, accumulated: string): void;
emitStreamEnd(message: Message & { type: "ai" }): Promise<void>;
emitStreamError(messageId: string, conversationId: string, error: ChatError): void;

emitStreamStart
  -> emitStreamChunk (repeat N times)
  -> emitStreamEnd
or
  -> emitStreamError

import type { ChatEngine } from '@kaira/chat-core';
 
import { createChatError } from '@kaira/chat-core';
 
export async function streamAssistantReply(
  engine: ChatEngine,
  params: {
    readonly conversationId: string;
    readonly messageId: string;
    readonly chunks: AsyncIterable<string>;
  },
): Promise<void> {
  const { conversationId, messageId, chunks } = params;
  engine.emitStreamStart(messageId, conversationId);
 
  let accumulated = '';
  try {
    for await (const chunk of chunks) {
      accumulated += chunk;
      engine.emitStreamChunk(messageId, chunk, accumulated);
    }
 
    await engine.emitStreamEnd({
      id: messageId,
      conversationId,
      sender: { id: 'assistant', role: 'assistant' },
      timestamp: Date.now(),
      status: 'sent',
      type: 'ai',
      content: accumulated,
      streamState: 'complete',
    });
  } catch (error: unknown) {
    engine.emitStreamError(
      messageId,
      conversationId,
      createChatError('transport', 'AI streaming failed', { cause: error }),
    );
  }
}