server.js

const express = require('express');
const cors = require('cors');

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

app.use(cors());
app.use(express.json());
app.use(express.static(__dirname));

app.get('/api/health', (req, res) => {
    res.json({ ok: true });
});

// Simple SSE stream that emits ship positions along a predefined route (fallback demo)
app.get('/api/ship/stream', (req, res) => {
    const mmsi = String(req.query.mmsi || '000000000');
    res.setHeader('Content-Type', 'text/event-stream');
    res.setHeader('Cache-Control', 'no-cache');
    res.setHeader('Connection', 'keep-alive');
    res.flushHeaders && res.flushHeaders();

    // MMSI-specific demo routes (water-safe corridors)
    const routesByMmsi = {
        '211331640': [
            { lat: 53.5461, lng: 9.9662 },
            { lat: 51.0, lng: 2.0 },
            { lat: 48.7, lng: -4.5 },
            { lat: 36.0, lng: -5.5 },
            { lat: 31.2, lng: 32.3 },
            { lat: 29.9, lng: 32.55 },
            { lat: 12.5, lng: 43.2 },
            { lat: 15.0, lng: 46.0 },
            { lat: 9.0, lng: 70.0 },
            { lat: 5.0, lng: 90.0 },
            { lat: 1.26, lng: 103.84 },
            { lat: 10.0, lng: 112.0 },
            { lat: 22.5, lng: 120.5 },
            { lat: 31.2304, lng: 121.4737 }
        ],
        '366982000': [
            { lat: 33.7329, lng: -118.2710 },
            { lat: 25.0, lng: -112.0 },
            { lat: 8.95, lng: -79.55 },
            { lat: 9.35, lng: -79.9 },
            { lat: 20.0, lng: -78.0 },
            { lat: 25.7781, lng: -80.1794 },
            { lat: 31.0, lng: -76.0 },
            { lat: 40.6711, lng: -74.0456 }
        ],
        'DEFAULT': [
            { lat: 35.6762, lng: 139.6503 },
            { lat: 35.0951, lng: 129.0390 },
            { lat: 22.3193, lng: 114.1694 },
            { lat: 1.2966, lng: 103.7764 },
            { lat: -15.0, lng: 70.0 },
            { lat: -36.0, lng: 20.0 },
            { lat: 51.4631, lng: 0.3336 }
        ]
    };
    const route = routesByMmsi[mmsi] || routesByMmsi.DEFAULT;

    let legIndex = 0;
    let t = 0; // 0..1 along current leg
    const legDurationMs = 60000; // 60s per leg (slower)
    let lastTick = Date.now();

    const send = (obj) => {
        res.write(`data: ${JSON.stringify(obj)}\n\n`);
    };

    send({ type: 'hello', mmsi });

    const interval = setInterval(() => {
        const now = Date.now();
        const dt = now - lastTick;
        lastTick = now;

        const from = route[legIndex];
        const to = route[legIndex + 1] || route[legIndex];
        if (!to) return;

        t += dt / legDurationMs;
        if (t > 1) {
            t = 0;
            legIndex++;
            if (legIndex >= route.length - 1) legIndex = 0; // loop
        }

        const lat = from.lat + (to.lat - from.lat) * t;
        const lng = from.lng + (to.lng - from.lng) * t;

        // Rough course and speed
        const course = Math.atan2(
            (to.lng - from.lng) * Math.cos((from.lat + to.lat) * Math.PI / 360),
            (to.lat - from.lat)
        ) * 180 / Math.PI;
        const speed = 18 + Math.sin(now / 5000) * 2; // ~18±2 knots demo

        send({
            type: 'position',
            mmsi,
            name: 'Live Vessel',
            lat,
            lng,
            speed: Number(speed.toFixed(1)),
            course: Math.round((course + 360) % 360),
            timestamp: new Date().toISOString()
        });
    }, 1000);

    req.on('close', () => {
        clearInterval(interval);
        res.end();
    });
});

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