import AVFoundation
import SwiftUI

class BarcodeScanner: NSObject, ObservableObject {
    @Published var scannedCode: String?
    @Published var isScanning = false
    @Published var error: String?

    private var captureSession: AVCaptureSession?
    private let metadataOutput = AVCaptureMetadataOutput()

    // Supported barcode types for food products
    private let supportedTypes: [AVMetadataObject.ObjectType] = [
        .ean8,
        .ean13,
        .upce,
        .code128,
        .code39,
        .code93,
        .itf14
    ]

    override init() {
        super.init()
    }

    // MARK: - Public Interface
    func checkPermission() async -> Bool {
        switch AVCaptureDevice.authorizationStatus(for: .video) {
        case .authorized:
            return true
        case .notDetermined:
            return await AVCaptureDevice.requestAccess(for: .video)
        default:
            return false
        }
    }

    func setupSession() {
        guard captureSession == nil else { return }

        let session = AVCaptureSession()
        session.sessionPreset = .high

        guard let videoDevice = AVCaptureDevice.default(for: .video),
              let videoInput = try? AVCaptureDeviceInput(device: videoDevice) else {
            error = "Camera not available"
            return
        }

        if session.canAddInput(videoInput) {
            session.addInput(videoInput)
        }

        if session.canAddOutput(metadataOutput) {
            session.addOutput(metadataOutput)
            metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            metadataOutput.metadataObjectTypes = supportedTypes.filter {
                metadataOutput.availableMetadataObjectTypes.contains($0)
            }
        }

        captureSession = session
    }

    func startScanning() {
        guard let session = captureSession else {
            setupSession()
            startScanning()
            return
        }

        scannedCode = nil
        error = nil

        DispatchQueue.global(qos: .userInitiated).async { [weak self] in
            session.startRunning()
            DispatchQueue.main.async {
                self?.isScanning = true
            }
        }
    }

    func stopScanning() {
        captureSession?.stopRunning()
        isScanning = false
    }

    func reset() {
        scannedCode = nil
        error = nil
    }

    var previewLayer: AVCaptureVideoPreviewLayer? {
        guard let session = captureSession else { return nil }
        let layer = AVCaptureVideoPreviewLayer(session: session)
        layer.videoGravity = .resizeAspectFill
        return layer
    }
}

// MARK: - AVCaptureMetadataOutputObjectsDelegate
extension BarcodeScanner: AVCaptureMetadataOutputObjectsDelegate {
    func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
        guard let metadataObject = metadataObjects.first as? AVMetadataMachineReadableCodeObject,
              let code = metadataObject.stringValue,
              scannedCode == nil else { return }

        // Haptic feedback
        let generator = UIImpactFeedbackGenerator(style: .medium)
        generator.impactOccurred()

        scannedCode = code
        stopScanning()
    }
}

// MARK: - Camera Preview View
struct CameraPreviewView: UIViewRepresentable {
    let scanner: BarcodeScanner

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

        if let previewLayer = scanner.previewLayer {
            previewLayer.frame = view.bounds
            view.layer.addSublayer(previewLayer)
        }

        return view
    }

    func updateUIView(_ uiView: UIView, context: Context) {
        DispatchQueue.main.async {
            if let sublayer = uiView.layer.sublayers?.first as? AVCaptureVideoPreviewLayer {
                sublayer.frame = uiView.bounds
            } else if let previewLayer = scanner.previewLayer {
                previewLayer.frame = uiView.bounds
                uiView.layer.addSublayer(previewLayer)
            }
        }
    }
}