const jokeSubjectGenerator = defineTool(
  {
    name: 'jokeSubjectGenerator',
    description: 'can be called to generate a subject for a joke',
  },
  async () => {
    return 'banana';
  }
);

export const toolCaller = defineFlow(
  {
    name: 'toolCaller',
    outputSchema: z.string(),
  },
  async (_, streamingCallback) => {
    if (!streamingCallback) {
      throw new Error('this flow only works in streaming mode');
    }

    const { response, stream } = await generateStream({
      model: gemini15ProPreview,
      config: {
        temperature: 1,
      },
      tools: [jokeSubjectGenerator],
      prompt: `tell me a joke`,
    });

    for await (const chunk of stream()) {
      streamingCallback(chunk);
    }

    return (await response()).text();
  }
);