OpenAI Assistants API with Threads

import OpenAI from 'openai';

const openai = new OpenAI();

export async function createAssistant() {
  return openai.beta.assistants.create({
    name: 'Code Reviewer',
    instructions: 'You are a senior developer. Review code for bugs, security issues, and best practices.',
    model: 'gpt-4o',
    tools: [{ type: 'code_interpreter' }],
  });
}

export async function chat(assistantId: string, threadId: string | null, message: string) {
  // Create or reuse thread
  const thread = threadId
    ? { id: threadId }
    : await openai.beta.threads.create();

  // Add user message
  await openai.beta.threads.messages.create(thread.id, {
    role: 'user',
    content: message,
  });

  // Run and poll for completion
  const run = await openai.beta.threads.runs.createAndPoll(thread.id, {
    assistant_id: assistantId,
  });

  if (run.status === 'completed') {
    const messages = await openai.beta.threads.messages.list(thread.id);
    const last = messages.data[0];
    const text = last.content[0].type === 'text' ? last.content[0].text.value : '';
    return { threadId: thread.id, response: text };
  }

  throw new Error(`Run failed with status: ${run.status}`);
}