import SwiftUI
import AVFoundation

struct QRScannerSheet: View {
    var onResult: (String) -> Void
    @Environment(\.dismiss) private var dismiss

    var body: some View {
        NavigationStack {
            QRCameraView(onResult: { result in
                dismiss()
                onResult(result)
            })
            .ignoresSafeArea()
            .navigationTitle("Scan QR Code")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .navigationBarLeading) {
                    Button("Cancel") { dismiss() }
                        .foregroundStyle(.white)
                }
            }
        }
    }
}

private struct QRCameraView: UIViewRepresentable {
    var onResult: (String) -> Void

    func makeUIView(context: Context) -> UIView {
        let view = UIView()
        view.backgroundColor = .black

        let session = AVCaptureSession()
        guard let device = AVCaptureDevice.default(for: .video),
              let input  = try? AVCaptureDeviceInput(device: device) else {
            return view
        }
        if session.canAddInput(input) { session.addInput(input) }

        let output = AVCaptureMetadataOutput()
        if session.canAddOutput(output) {
            session.addOutput(output)
            output.setMetadataObjectsDelegate(context.coordinator, queue: .main)
            output.metadataObjectTypes = [.qr]
        }

        let preview = AVCaptureVideoPreviewLayer(session: session)
        preview.videoGravity = .resizeAspectFill
        preview.frame = view.bounds
        view.layer.addSublayer(preview)
        context.coordinator.previewLayer = preview

        DispatchQueue.global(qos: .userInitiated).async { session.startRunning() }
        context.coordinator.session = session
        return view
    }

    func updateUIView(_ uiView: UIView, context: Context) {
        context.coordinator.previewLayer?.frame = uiView.bounds
    }

    func makeCoordinator() -> Coordinator { Coordinator(onResult: onResult) }

    final class Coordinator: NSObject, AVCaptureMetadataOutputObjectsDelegate {
        var onResult: (String) -> Void
        var session: AVCaptureSession?
        var previewLayer: AVCaptureVideoPreviewLayer?
        private var didCapture = false

        init(onResult: @escaping (String) -> Void) {
            self.onResult = onResult
        }

        func metadataOutput(_ output: AVCaptureMetadataOutput,
                            didOutput objects: [AVMetadataObject],
                            from connection: AVCaptureConnection) {
            guard !didCapture,
                  let obj = objects.first as? AVMetadataMachineReadableCodeObject,
                  let str = obj.stringValue else { return }
            didCapture = true
            session?.stopRunning()
            DispatchQueue.main.async { self.onResult(str) }
        }
    }
}