// Camera-based QR scanning (mobile/claude.md web stub: "Scans QR codes via
// the browser MediaDevices camera API"). Decode library: jsQR — pure JS,
// no WASM, the standard lightweight choice for in-browser barcode reading;
// not a crypto primitive, so it isn't subject to crypto.md's pinned-library
// list.

import jsQR from 'jsqr';

export interface ScannerHandle {
    stop: () => void;
}

/**
 * Opens the camera and polls frames via requestAnimationFrame until a QR
 * code decodes, then calls `onDecode` once and stops polling on its own
 * (the caller is still responsible for calling `stop()` to release the
 * camera stream once it's done with the decoded content).
 */
export async function startScanner(
    video: HTMLVideoElement,
    canvas: HTMLCanvasElement,
    onDecode: (content: string) => void,
): Promise<ScannerHandle> {
    const stream = await navigator.mediaDevices.getUserMedia({ video: { facingMode: 'environment' } });
    video.srcObject = stream;
    await video.play();

    const ctx = canvas.getContext('2d', { willReadFrequently: true });
    if (!ctx) throw new Error('2D canvas context unavailable');

    let stopped = false;
    let decoded = false;

    function tick(): void {
        if (stopped || decoded) return;
        if (video.readyState === video.HAVE_ENOUGH_DATA) {
            canvas.width = video.videoWidth;
            canvas.height = video.videoHeight;
            ctx!.drawImage(video, 0, 0, canvas.width, canvas.height);
            const frame = ctx!.getImageData(0, 0, canvas.width, canvas.height);
            const code = jsQR(frame.data, frame.width, frame.height);
            if (code) {
                decoded = true;
                onDecode(code.data);
                return;
            }
        }
        requestAnimationFrame(tick);
    }
    requestAnimationFrame(tick);

    return {
        stop: () => {
            stopped = true;
            stream.getTracks().forEach((track) => track.stop());
        },
    };
}