// Native iOS QR capture for the join page — AVCaptureMetadataOutput does QR
// detection in hardware-adjacent fashion on iOS (no Vision pass needed, unlike
// the macOS scanner). Emits every decoded payload; the caller decides what to
// do (and when to dismiss).

import SwiftUI
import AVFoundation

struct QRScanView: UIViewControllerRepresentable {
    let onCode: (String) -> Void

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

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

    final class ScannerController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
        var onCode: ((String) -> Void)?
        private let session = AVCaptureSession()
        private let sessionQueue = DispatchQueue(label: "tva.qr-scan")

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

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

            AVCaptureDevice.requestAccess(for: .video) { [weak self] granted in
                guard granted, let self else { return }
                self.sessionQueue.async { self.configure() }
            }
        }

        override func viewDidLayoutSubviews() {
            super.viewDidLayoutSubviews()
            view.layer.sublayers?.first?.frame = view.bounds
        }

        override func viewWillDisappear(_ animated: Bool) {
            super.viewWillDisappear(animated)
            sessionQueue.async { [session] in
                if session.isRunning { session.stopRunning() }
            }
        }

        private func configure() {
            guard session.inputs.isEmpty,
                  let camera = AVCaptureDevice.default(for: .video),
                  let input = try? AVCaptureDeviceInput(device: camera),
                  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]
            session.startRunning()
        }

        func metadataOutput(_ output: AVCaptureMetadataOutput,
                            didOutput metadataObjects: [AVMetadataObject],
                            from connection: AVCaptureConnection) {
            guard let payload = (metadataObjects.first as? AVMetadataMachineReadableCodeObject)?
                .stringValue else { return }
            onCode?(payload)
        }
    }
}