server.ts

import express, { Request, Response } from 'express';
import path from 'path';
import { fileURLToPath } from 'url';

const app = express();
const PORT = 7860;

const MODEL_ID = "amiguel/qwen2.5-7b-instruct-ai_llm-sft";
// OpenAI-compatible chat completions endpoint — handles PEFT adapters,
// applies the model's own chat template, and streams in standard SSE format.
const API_URL = `https://api-inference.huggingface.co/models/${MODEL_ID}/v1/chat/completions`;

app.use(express.json());

const __dirname = path.dirname(fileURLToPath(import.meta.url));
app.use(express.static(path.join(__dirname, 'dist')));

app.post('/api/chat', async (req: Request, res: Response) => {
  const { messages } = req.body;
  const hfToken = process.env.HF_TOKEN;

  if (!hfToken) {
    return res.status(401).json({ error: "HF_TOKEN environment variable not set." });
  }

  try {
    const response = await fetch(API_URL, {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${hfToken}`,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        model: MODEL_ID,
        messages,
        max_tokens: 1024,
        stream: true,
        temperature: 0.7,
      }),
    });

    if (!response.ok) {
      const errorText = await response.text();
      console.error("HF API Error:", errorText);
      return res.status(response.status).json({ error: errorText });
    }

    res.setHeader('Content-Type', 'text/event-stream');
    res.setHeader('Cache-Control', 'no-cache');
    res.setHeader('Connection', 'keep-alive');

    const reader = response.body?.getReader();
    const decoder = new TextDecoder();

    if (!reader) {
      return res.end();
    }

    while (true) {
      const { done, value } = await reader.read();
      if (done) break;

      const chunk = decoder.decode(value, { stream: true });
      res.write(chunk);
    }

    res.end();
  } catch (error) {
    console.error("Server Error:", error);
    res.status(500).json({ error: "Internal Server Error" });
  }
});

// SPA fallback
app.get('*', (_req, res) => {
  res.sendFile(path.join(__dirname, 'dist', 'index.html'));
});

app.listen(PORT, () => {
  console.log(`Server running on http://0.0.0.0:${PORT}`);
});