import SwiftUI
import AVFoundation

struct QRScannerView: UIViewControllerRepresentable {
    let onScan: (String) -> Void

    func makeUIViewController(context: Context) -> ScannerViewController {
        let vc = ScannerViewController()
        vc.onScan = onScan
        return vc
    }

    func updateUIViewController(_ uiViewController: ScannerViewController, context: Context) {}
}

final class ScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
    var onScan: ((String) -> Void)?

    private let session = AVCaptureSession()
    private var previewLayer: AVCaptureVideoPreviewLayer?

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .black
        setupCapture()
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        previewLayer?.frame = view.bounds
    }

    private func setupCapture() {
        guard let device = AVCaptureDevice.default(for: .video),
              let input = try? AVCaptureDeviceInput(device: device),
              session.canAddInput(input) else { return }

        session.addInput(input)

        let output = AVCaptureMetadataOutput()
        guard session.canAddOutput(output) else { return }
        session.addOutput(output)
        output.setMetadataObjectsDelegate(self, queue: .main)
        output.metadataObjectTypes = [.qr]

        let layer = AVCaptureVideoPreviewLayer(session: session)
        layer.videoGravity = .resizeAspectFill
        view.layer.addSublayer(layer)
        previewLayer = layer

        DispatchQueue.global(qos: .userInitiated).async { self.session.startRunning() }
    }

    func metadataOutput(_ output: AVCaptureMetadataOutput,
                        didOutput objects: [AVMetadataObject],
                        from connection: AVCaptureConnection) {
        guard let obj = objects.first as? AVMetadataMachineReadableCodeObject,
              let value = obj.stringValue else { return }
        session.stopRunning()
        onScan?(value)
    }
}