server.js

/**
 * ============================================================
 * Parent Teacher Communication Smart Dashboard - Server Entry
 * ============================================================
 * Express app with MongoDB, JWT auth, role-based routing,
 * static frontend serving, and global error handling.
 */

const express = require('express');
const mongoose = require('mongoose');
const cors = require('cors');
const morgan = require('morgan');
const path = require('path');
require('dotenv').config();

// ─── Import Routes ────────────────────────────────────────────────────────────
const authRoutes = require('./routes/auth');
const mentorRoutes = require('./routes/mentor');
const subjectRoutes = require('./routes/subject');
const parentRoutes = require('./routes/parent');
const chatRoutes = require('./routes/chat');

const app = express();
const PORT = process.env.PORT || 5000;

// ─── Middleware ────────────────────────────────────────────────────────────────
app.use(cors());
app.use(express.json());
app.use(express.urlencoded({ extended: true }));

// HTTP request logging (only in development)
if (process.env.NODE_ENV !== 'production') {
    app.use(morgan('dev'));
}

// ─── Serve Static Frontend ─────────────────────────────────────────────────────
app.use(express.static(path.join(__dirname, 'frontend')));

// ─── API Routes ───────────────────────────────────────────────────────────────
app.use('/api', authRoutes);
app.use('/api/mentor', mentorRoutes);
app.use('/api/subject', subjectRoutes);
app.use('/api/parent', parentRoutes);
app.use('/api/chat', chatRoutes);

// ─── Health Check Endpoint ────────────────────────────────────────────────────
app.get('/api/health', (req, res) => {
    res.json({ status: 'ok', message: 'Parent Teacher Dashboard API is running.' });
});

// ─── Frontend Catch-all (SPA fallback) ────────────────────────────────────────
// Redirect root to login page
app.get('/', (req, res) => {
    res.sendFile(path.join(__dirname, 'frontend', 'login.html'));
});

// ─── 404 Handler ─────────────────────────────────────────────────────────────
app.use((req, res, next) => {
    res.status(404).json({ message: `Route not found: ${req.method} ${req.originalUrl}` });
});

// ─── Global Error Handler ─────────────────────────────────────────────────────
// eslint-disable-next-line no-unused-vars
app.use((err, req, res, next) => {
    console.error('❌ Global Error:', err.stack || err.message);

    // Mongoose validation error
    if (err.name === 'ValidationError') {
        const messages = Object.values(err.errors).map((e) => e.message);
        return res.status(400).json({ message: 'Validation Error', errors: messages });
    }

    // Mongoose cast error (invalid ObjectId)
    if (err.name === 'CastError') {
        return res.status(400).json({ message: 'Invalid ID format.' });
    }

    // Duplicate key error
    if (err.code === 11000) {
        const field = Object.keys(err.keyValue)[0];
        return res.status(409).json({ message: `${field} already exists.` });
    }

    res.status(err.status || 500).json({
        message: err.message || 'Internal server error.',
    });
});

// ─── Connect to MongoDB and Start Server ──────────────────────────────────────
const startServer = async () => {
    try {
        await mongoose.connect(process.env.MONGO_URI, {
            useNewUrlParser: true,
            useUnifiedTopology: true,
        });
        console.log('✅ Connected to MongoDB');

        app.listen(PORT, () => {
            console.log(`🚀 Server running on http://localhost:${PORT}`);
            console.log(`📚 Frontend:  http://localhost:${PORT}/login.html`);
            console.log(`🔑 API Docs:  http://localhost:${PORT}/api/health`);
        });
    } catch (error) {
        console.error('❌ MongoDB connection failed:', error.message);
        process.exit(1);
    }
};

startServer();