// QR code scanner interop (html5-qrcode) for Blazor.
// Usage from .NET: qrScanner.start(elementId, dotNetRef) / qrScanner.stop()
window.qrScanner = (function () {
    let scanner = null;
    let lastText = null;
    let lastTime = 0;

    async function ensureLib() {
        if (window.Html5Qrcode) return;
        await new Promise((resolve, reject) => {
            const s = document.createElement('script');
            s.src = 'lib/html5-qrcode/html5-qrcode.min.js';
            s.onload = resolve;
            s.onerror = () => reject(new Error('QR-Bibliothek konnte nicht geladen werden.'));
            document.head.appendChild(s);
        });
    }

    async function start(elementId, dotNetRef) {
        await stop();
        await ensureLib();

        if (!navigator.mediaDevices || !navigator.mediaDevices.getUserMedia) {
            throw new Error('Kamera wird von diesem Browser nicht unterstützt (HTTPS erforderlich).');
        }

        scanner = new Html5Qrcode(elementId, {
            formatsToSupport: [Html5QrcodeSupportedFormats.QR_CODE],
            verbose: false
        });

        const config = {
            fps: 10,
            qrbox: (w, h) => {
                const size = Math.max(180, Math.min(w, h) * 0.7);
                return { width: size, height: size };
            },
            aspectRatio: 1.0
        };

        const onSuccess = (text) => {
            const now = Date.now();
            if (text === lastText && now - lastTime < 2500) return;
            lastText = text;
            lastTime = now;
            dotNetRef.invokeMethodAsync('OnQrScanned', text);
        };

        try {
            await scanner.start({ facingMode: 'environment' }, config, onSuccess, () => { });
        } catch (e) {
            // Fallback: any camera
            const cams = await Html5Qrcode.getCameras();
            if (!cams || cams.length === 0) throw new Error('Keine Kamera gefunden.');
            await scanner.start(cams[0].id, config, onSuccess, () => { });
        }
    }

    async function stop() {
        if (!scanner) return;
        try {
            if (scanner.isScanning) await scanner.stop();
            scanner.clear();
        } catch (e) { /* ignore */ }
        scanner = null;
        lastText = null;
    }

    // Short audio feedback ("success" | "error") via Web Audio, no asset required.
    function playSound(type) {
        try {
            const Ctx = window.AudioContext || window.webkitAudioContext;
            if (!Ctx) return;
            const ctx = new Ctx();
            const osc = ctx.createOscillator();
            const gain = ctx.createGain();
            osc.type = 'sine';
            osc.frequency.value = type === 'error' ? 220 : 880;
            gain.gain.value = 0.08;
            osc.connect(gain).connect(ctx.destination);
            osc.start();
            osc.stop(ctx.currentTime + (type === 'error' ? 0.25 : 0.12));
            osc.onended = () => ctx.close().catch(() => { });
        } catch (e) { /* audio is best-effort */ }
    }

    return { start, stop, playSound };
})();