index.js

const express = require('express');
const { verifyKeyMiddleware, InteractionType, InteractionResponseType } = require('discord-interactions');
const OpenAI = require('openai');

const app = express();
const openai = new OpenAI({ apiKey: process.env.OPENAI_KEY });

app.post('/interactions', verifyKeyMiddleware(process.env.DISCORD_PUBLIC_KEY), async (req, res) => {
  const interaction = req.body;

  if (interaction.type === InteractionType.PING) {
    return res.send({ type: InteractionResponseType.PONG });
  }

  if (interaction.type === InteractionType.APPLICATION_COMMAND) {
    const userMsg = interaction.data.options?.[0]?.value || '';
    
    res.send({ type: InteractionResponseType.DEFERRED_CHANNEL_MESSAGE_WITH_SOURCE });

    const completion = await openai.chat.completions.create({
      model: 'gpt-3.5-turbo',
      max_tokens: 500,
      messages: [{ role: 'user', content: userMsg }]
    });

    const reply = completion.choices[0].message.content;

    await fetch(`https://discord.com/api/v10/webhooks/${process.env.DISCORD_APP_ID}/${interaction.token}/messages/@original`, {
      method: 'PATCH',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ content: reply })
    });
  }
});

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => console.log(`Bot running on port ${PORT}`));