server.js

/**
 * src/server.js   —  RENDER-OPTIMISED (stateless)
 * ─────────────────────────────────────────────────
 * Changes from the original:
 *   • POST /api/chat now expects { message, history } — the frontend
 *     owns and replays the conversation so nothing is stored server-side.
 *   • DELETE /api/chat is removed (nothing to clear).
 *   • GET  /api/health exposes queue depth for easy monitoring.
 *
 * GITHUB PATH  →  src/server.js
 */

"use strict";

require("dotenv").config();
const express = require("express");
const cors    = require("cors");
const path    = require("path");
const { chat } = require("./geminiClient");

const app  = express();
const PORT = process.env.PORT || 3000;

// ── Middleware ───────────────────────────────────────────────────────────────
app.use(cors());
app.use(express.json());
app.use(express.static(path.join(__dirname, "..", "public")));

// ── Health / queue-depth probe ───────────────────────────────────────────────
app.get("/api/health", (_req, res) => {
  res.json({
    status : "ok",
    model  : "gemini-1.5-flash",
    approach: "long-context-stateless"
  });
});

// ── Chat endpoint ────────────────────────────────────────────────────────────
/**
 * POST /api/chat
 *
 * Body:
 *   {
 *     "message" : "How do I book?",
 *     "history" : [                          ← can be []
 *       { "role": "user",      "text": "Hi" },
 *       { "role": "assistant", "text": "Hello! …" }
 *     ]
 *   }
 *
 * Returns:
 *   { "answer": "…", "matchedSections": ["2. Customer FAQ"] }
 */
app.post("/api/chat", async (req, res) => {
  const { message, history } = req.body;

  if (!message) {
    return res.status(400).json({ error: "Missing 'message' in request body." });
  }

  try {
    const result = await chat(history || [], message);
    res.json(result);
  } catch (err) {
    console.error("[/api/chat] Error:", err.message);
    res.status(500).json({ error: "Something went wrong. Please try again." });
  }
});

// ── Catch-all: SPA fallback ──────────────────────────────────────────────────
app.get("*", (_req, res) => {
  res.sendFile(path.join(__dirname, "..", "public", "index.html"));
});

// ── Start ────────────────────────────────────────────────────────────────────
app.listen(PORT, () => {
  console.log(`\n🚀  Skedulelt RAG  —  http://localhost:${PORT}`);
  console.log(`    Model    : gemini-1.5-flash`);
  console.log(`    Approach : Long Context, stateless, queued\n`);
});