typesafe-function-calling .ts

import type { ZodObject, ZodRawShape } from "zod";
import { zodToJsonSchema } from "zod-to-json-schema";

/**
 * zod と zod-to-json-schema を使って型安全に completion 結果を得るコード
 */
export const createChatCompletionWithFunction = async <T extends ZodRawShape>(
  messages: ChatCompletionRequestMessage[],
  functionName: string,
  schema: ZodObject<T>
) => {
  const configuration = new Configuration({
    apiKey: process.env.API_KEY,
  });
  const openaiClient = new OpenAIApi(configuration);

  const fn: ChatCompletionFunctions = {
    name: functionName,
    parameters: zodToJsonSchema(schema),
  };
  const result = await openaiClient.createChatCompletion({
    model: "gpt-4-0613",
    messages,
    functions: [fn],
  });

  const functionCallArguments =
    result?.data.choices.at(0)?.message?.function_call?.arguments;
  if (!functionCallArguments) {
    throw new Error(
      "Failed to chat completion, function call arguments is not found"
    );
  }

  return await schema.parseAsync(JSON.parse(functionCallArguments));
};