/**
 * Satelliten-Layer: Orbitale Positionen berechnet aus TLE-Daten.
 * Vereinfachte Kreisbahn-Berechnung (kein SGP4, reicht fuer Visualisierung).
 */
const SatellitesLayer = {
    _viewer: null,
    _points: null,
    _orbits: null,
    _interval: null,
    _count: 0,
    _data: [],
    _animFrame: null,

    start(viewer) {
        if (this._points) return;
        this._viewer = viewer;
        this._points = viewer.scene.primitives.add(new Cesium.PointPrimitiveCollection());
        this._orbits = viewer.scene.primitives.add(new Cesium.PolylineCollection());
        this._fetch();
        var self = this;
        // Positionen alle 2s aktualisieren (Satelliten bewegen sich schnell)
        this._interval = setInterval(function() { self._updatePositions(); }, 2000);
    },

    stop() {
        if (this._interval) { clearInterval(this._interval); this._interval = null; }
        if (this._points && this._viewer) { this._viewer.scene.primitives.remove(this._points); this._points = null; }
        if (this._orbits && this._viewer) { this._viewer.scene.primitives.remove(this._orbits); this._orbits = null; }
        this._count = 0; this._data = [];
    },

    _fetch() {
        var self = this;
        var loadEl = document.getElementById('loading-satellites');
        var statusEl = document.getElementById('status-satellites');
        if (loadEl) loadEl.classList.add('active');
        if (statusEl) { statusEl.textContent = 'Lade Orbitdaten...'; statusEl.classList.add('active'); }
        fetch('/api/satellites')
        .then(function(r) { return r.json(); })
        .then(function(data) {
            self._data = data.satellites || [];
            self._count = self._data.length;
            self._updatePositions();
            self._drawOrbits();
            if (statusEl) statusEl.textContent = self._count + ' Satelliten';
        })
        .catch(function(e) { console.warn('Satellites error:', e); if (statusEl) statusEl.textContent = 'Fehler'; })
        .finally(function() { if (loadEl) loadEl.classList.remove('active'); setTimeout(function() { if (statusEl) statusEl.classList.remove('active'); }, 5000); });
    },

    _calcPosition(sat, time) {
        // Vereinfachte Kreisbahn aus Kepler-Elementen
        var n = sat.meanMotion; // Umlaeufe pro Tag
        if (!n || n <= 0) return null;
        var period = 86400 / n; // Umlaufzeit in Sekunden
        var a = Math.pow(398600.4418 * Math.pow(period / (2 * Math.PI), 2), 1/3); // Semi-major axis in km
        var altitude = a - 6371; // Hoehe ueber Erdoberflaeche in km
        if (altitude < 100 || altitude > 50000) return null;

        var epochMs = new Date(sat.epoch).getTime();
        var elapsed = (time - epochMs) / 1000; // Sekunden seit Epoch
        var M = (sat.meanAnomaly || 0) + (360 * n / 86400) * elapsed; // Aktuelle Mean Anomaly
        M = ((M % 360) + 360) % 360; // Normalisieren

        var inc = (sat.inclination || 0) * Math.PI / 180;
        var raan = (sat.raOfAscNode || 0) * Math.PI / 180;
        var argP = (sat.argOfPericenter || 0) * Math.PI / 180;
        var nu = M * Math.PI / 180; // True anomaly ≈ Mean anomaly fuer kleine Exzentrizitaet

        // Position im Orbital-Frame
        var u = argP + nu;
        var r = a; // Kreisbahn-Naeherung

        // ECI -> ECEF (vereinfacht: Erdrotation ignoriert fuer Visualisierung)
        var x = r * (Math.cos(raan) * Math.cos(u) - Math.sin(raan) * Math.sin(u) * Math.cos(inc));
        var y = r * (Math.sin(raan) * Math.cos(u) + Math.cos(raan) * Math.sin(u) * Math.cos(inc));
        var z = r * Math.sin(u) * Math.sin(inc);

        // Erdrotation beruecksichtigen (grob)
        var gmst = elapsed * 7.2921159e-5; // Sternzeit-Winkel
        var xr = x * Math.cos(gmst) + y * Math.sin(gmst);
        var yr = -x * Math.sin(gmst) + y * Math.cos(gmst);

        var lon = Math.atan2(yr, xr) * 180 / Math.PI;
        var lat = Math.asin(z / r) * 180 / Math.PI;

        return { lat: lat, lon: lon, alt: altitude * 1000 }; // alt in Metern
    },

    _updatePositions() {
        if (!this._points || !this._data.length) return;
        this._points.removeAll();
        var now = Date.now();
        var colors = {
            'stations': Cesium.Color.fromCssColorString('#ff4444'),
            'gps-ops': Cesium.Color.fromCssColorString('#ffaa00'),
            'galileo': Cesium.Color.fromCssColorString('#44aaff'),
            'weather': Cesium.Color.fromCssColorString('#aa44ff'),
            'resource': Cesium.Color.fromCssColorString('#44ffaa'),
            'starlink': Cesium.Color.fromCssColorString('#888888'),
        };
        for (var i = 0; i < this._data.length; i++) {
            var pos = this._calcPosition(this._data[i], now);
            if (!pos) continue;
            var color = colors[this._data[i].group] || Cesium.Color.WHITE;
            this._points.add({
                position: Cesium.Cartesian3.fromDegrees(pos.lon, pos.lat, pos.alt),
                pixelSize: this._data[i].group === 'starlink' ? 1.5 : 3,
                color: color,
            });
        }
    },

    _drawOrbits() {
        if (!this._orbits || !this._data.length) return;
        this._orbits.removeAll();
        var now = Date.now();
        var colors = {
            'stations': Cesium.Color.fromCssColorString('#ff4444').withAlpha(0.4),
            'gps-ops': Cesium.Color.fromCssColorString('#ffaa00').withAlpha(0.15),
            'galileo': Cesium.Color.fromCssColorString('#44aaff').withAlpha(0.15),
        };
        // Nur Orbits fuer Stationen, GPS, Galileo zeichnen (nicht Starlink — zu viele)
        for (var i = 0; i < this._data.length; i++) {
            var sat = this._data[i];
            if (!colors[sat.group]) continue;
            var positions = [];
            var period = 86400000 / (sat.meanMotion || 14); // Umlaufzeit in ms
            for (var t = 0; t <= period; t += period / 60) {
                var pos = this._calcPosition(sat, now + t);
                if (pos) positions.push(Cesium.Cartesian3.fromDegrees(pos.lon, pos.lat, pos.alt));
            }
            if (positions.length > 10) {
                this._orbits.add({
                    positions: positions,
                    width: sat.group === 'stations' ? 1.5 : 0.5,
                    material: Cesium.Material.fromType('Color', { color: colors[sat.group] }),
                });
            }
        }
    },
};