mio-ai/src/platforms/openai/features/chat-completion.ts

import {
  FinishableChoiceBase,
  ConsumeStream,
  DataEventId,
  DoFetch,
  PlatformError,
  PlatformResponse,
} from '../common';
import {
  UsageMetadata,
} from '../usage';
import { ChatCompletionModel } from '../models';
import { normalizeChatMessage, Message, MessageObject } from '../chat';

export interface CreateChatCompletionParams {
  messages: Message | Message[];
  model: ChatCompletionModel;
  temperature?: number;
  topP?: number;
  n?: number;
  stop?: string | string[];
  maxTokens?: number;
  presencePenalty?: number;
  frequencyPenalty?: number;
  logitBias?: Record<string, number>;
  user?: string;
}

export interface ChatCompletionChunkChoice extends FinishableChoiceBase {
  delta: Partial<MessageObject>;
}

export interface ChatCompletionChoice extends FinishableChoiceBase {
  message: Partial<Message>;
}

export enum DataEventObjectType {
  CHAT_COMPLETION_CHUNK = 'chat.completion.chunk',
  CHAT_COMPLETION = 'chat.completion',
}

export interface CreateChatCompletionDataEvent<
  C extends Partial<FinishableChoiceBase>
> extends PlatformResponse {
  id: DataEventId;
  object: DataEventObjectType;
  model: ChatCompletionModel;
  choices: C[];
}

export interface ChatCompletion
  extends CreateChatCompletionDataEvent<Partial<ChatCompletionChoice>>, UsageMetadata {}

export type ChatCompletionChunkDataEvent = CreateChatCompletionDataEvent<ChatCompletionChunkChoice>;

export function createChatCompletion(
  this: NodeJS.EventEmitter,
  doFetch: DoFetch,
  consumeStream: ConsumeStream,
  params: CreateChatCompletionParams,
) {
  doFetch('POST', '/chat/completions', {
    messages: normalizeChatMessage(params.messages),
    model: params.model ?? ChatCompletionModel.GPT_3_5_TURBO,
    temperature: params.temperature ?? 1,
    top_p: params.topP ?? 1,
    n: params.n ?? 1,
    stop: params.stop ?? null,
    stream: true,
    max_tokens: params.maxTokens,
    presence_penalty: params.presencePenalty ?? 0,
    frequency_penalty: params.frequencyPenalty ?? 0,
    logit_bias: params.logitBias ?? {},
    user: params.user,
  })
    .then(async (response) => {
      if (!response.ok) {
        this.emit('error', new PlatformError(
          // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
          `Create chat completion returned with status: ${response.status}`,
          response,
        ));
        this.emit('end');
        return;
      }

      await consumeStream(response);
      this.emit('end');
    })
    .catch((err) => {
      this.emit('error', err as Error);
      this.emit('end');
    });

  return this;
}