import SwiftUI
import AVFoundation

#if os(iOS)
import UIKit

// MARK: - iOS 扫码界面（SwiftUI sheet，替代 macOS 的独立 NSWindow 控制器）

/// 使用 AVCaptureSession + AVCaptureMetadataOutput 扫描包含媒体 URL 的二维码。
/// 扫到有效 http/https URL 后调用 `bridge.addURL`（自动入库 + 播放）并关闭。
struct QRScannerSheet: View {
    @ObservedObject var bridge: PlayerBridge
    let onDismiss: () -> Void

    @State private var statusText: String = ""
    @State private var statusColor: Color = .white
    @State private var isAuthorized = false
    @State private var hasCamera = true

    var body: some View {
        VStack(spacing: 0) {
            HStack {
                Text(L.scanQRCode).font(.headline).foregroundColor(.white)
                Spacer()
                Button(L.cancel) { onDismiss() }
                    .foregroundColor(.white)
            }
            .padding()
            .background(Color.black)

            ZStack {
                Color.black
                if isAuthorized && hasCamera {
                    QRCaptureRepresentable(onCode: handleCode)
                        .ignoresSafeArea(edges: .horizontal)
                } else {
                    VStack(spacing: 12) {
                        Image(systemName: hasCamera ? "lock.shield" : "video.slash")
                            .font(.system(size: 40))
                            .foregroundColor(.white.opacity(0.6))
                        Text(hasCamera ? "Camera access required" : "No camera available")
                            .foregroundColor(.white.opacity(0.8))
                    }
                }
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)

            VStack(spacing: 6) {
                Text(statusText.isEmpty ? L.scanHint : statusText)
                    .font(.system(size: 12, design: .monospaced))
                    .foregroundColor(statusColor.opacity(0.9))
                    .multilineTextAlignment(.center)
                    .lineLimit(3)
                    .truncationMode(.middle)
                    .padding(.horizontal)
            }
            .frame(maxWidth: .infinity)
            .padding(.vertical, 12)
            .background(Color.black)
        }
        .background(Color.black)
        .onAppear(perform: checkPermission)
    }

    private func checkPermission() {
        hasCamera = AVCaptureDevice.default(for: .video) != nil
        guard hasCamera else { return }
        switch AVCaptureDevice.authorizationStatus(for: .video) {
        case .authorized:
            isAuthorized = true
        case .notDetermined:
            AVCaptureDevice.requestAccess(for: .video) { granted in
                DispatchQueue.main.async { isAuthorized = granted }
            }
        default:
            isAuthorized = false
        }
    }

    private func handleCode(_ code: String) {
        statusText = code
        // 解析 JSON 载荷（含频道信息）或纯 URL → 入库 + 播放
        if bridge.handleScannedCode(code) {
            statusColor = .green
            DispatchQueue.main.asyncAfter(deadline: .now() + 1.2) { onDismiss() }
        } else {
            statusColor = .red
        }
    }
}

// MARK: - UIKit 摄像头预览桥接（AVCaptureVideoPreviewLayer）

private struct QRCaptureRepresentable: UIViewRepresentable {
    let onCode: (String) -> Void

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

    func makeUIView(context: Context) -> QRCaptureView {
        let v = QRCaptureView()
        v.coordinator = context.coordinator
        v.configure()
        return v
    }

    func updateUIView(_ uiView: QRCaptureView, context: Context) {}

    static func dismantleUIView(_ uiView: QRCaptureView, coordinator: Coordinator) {
        coordinator.stop()
    }

    final class Coordinator: NSObject, AVCaptureMetadataOutputObjectsDelegate {
        let onCode: (String) -> Void
        private var lastCode: String?
        private var lastTime = Date.distantPast

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

        func metadataOutput(_ output: AVCaptureMetadataOutput,
                            didOutput metadataObjects: [AVMetadataObject],
                            from connection: AVCaptureConnection) {
            guard let m = metadataObjects.first as? AVMetadataMachineReadableCodeObject,
                  let code = m.stringValue else { return }
            let now = Date()
            if code == lastCode, now.timeIntervalSince(lastTime) < 3 { return }
            lastCode = code
            lastTime = now
            DispatchQueue.main.async { self.onCode(code) }
        }

        func stop() {}
    }

    /// 承载 AVCaptureVideoPreviewLayer 的 UIView
    final class QRCaptureView: UIView {
        weak var coordinator: Coordinator?
        private let session = AVCaptureSession()
        private var previewLayer: AVCaptureVideoPreviewLayer?

        func configure() {
            // 摄像头配置是同步硬件 I/O，必须放到后台线程，否则主线程冻结
            DispatchQueue.global(qos: .userInitiated).async { [weak self] in
                guard let self else { return }
                self.session.sessionPreset = .high

                guard let device = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back)
                        ?? AVCaptureDevice.default(for: .video),
                      let input = try? AVCaptureDeviceInput(device: device),
                      self.session.canAddInput(input) else { return }
                self.session.addInput(input)

                let output = AVCaptureMetadataOutput()
                guard self.session.canAddOutput(output) else { return }
                self.session.addOutput(output)
                output.setMetadataObjectsDelegate(self.coordinator, queue: .main)
                self.session.startRunning()
                // availableMetadataObjectTypes 在 startRunning 之后才非空
                if output.availableMetadataObjectTypes.contains(.qr) {
                    output.metadataObjectTypes = [.qr]
                }

                DispatchQueue.main.async { [weak self] in
                    guard let self else { return }
                    let pl = AVCaptureVideoPreviewLayer(session: self.session)
                    pl.videoGravity = .resizeAspectFill
                    pl.frame = self.bounds
                    self.layer.addSublayer(pl)
                    self.previewLayer = pl
                }
            }
        }

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

        deinit { session.stopRunning() }
    }
}
#endif