import SwiftUI
import AVFoundation
import UIKit
import Combine

/// 异常项快拍 · 局部相机。
/// 实时预览 + 居中小框 + 快门 → **裁剪到小框区域**的 UIImage 回调。
/// 只在真机可用(模拟器无相机,QuickRegionCaptureFlow 退化到 PhotoPicker)。
///
/// 裁剪原理:`previewLayer.metadataOutputRectConverted(fromLayerRect:)` 把屏上小框换算成
/// 归一化(0-1)裁剪 rect;先把拍到的照片方向 bake 成 `.up`,再按归一化 rect 裁 CGImage。
struct RegionCameraView: View {
    let onCapture: (UIImage) -> Void
    let onCancel: () -> Void

    @StateObject private var controller = RegionCameraController()
    @State private var authState: AuthState = .checking
    @State private var isCapturing = false
    @State private var flash = false

    enum AuthState { case checking, authorized, denied }

    var body: some View {
        ZStack {
            Color.black.ignoresSafeArea()

            switch authState {
            case .checking:
                ProgressView().tint(.white)
            case .denied:
                deniedView
            case .authorized:
                cameraStack
            }

            if flash {
                Color.white.ignoresSafeArea().transition(.opacity)
            }
        }
        .task { await resolveAuth() }
    }

    // MARK: - 相机 + 小框 + 控件

    private var cameraStack: some View {
        GeometryReader { proxy in
            let box = RegionFraming.box(in: proxy.size)
            ZStack {
                RegionCameraPreview(controller: controller)
                    .ignoresSafeArea()

                // 框外压暗(even-odd 挖空),只突出小框内
                Canvas { ctx, size in
                    var path = Path(CGRect(origin: .zero, size: size))
                    path.addPath(Path(roundedRect: box, cornerRadius: Tj.Radius.md))
                    ctx.fill(path, with: .color(.black.opacity(0.5)), style: FillStyle(eoFill: true))
                }
                .ignoresSafeArea()
                .allowsHitTesting(false)

                // 小框边
                RoundedRectangle(cornerRadius: Tj.Radius.md, style: .continuous)
                    .strokeBorder(Color.white.opacity(0.95),
                                  style: StrokeStyle(lineWidth: 2, dash: [8, 6]))
                    .frame(width: box.width, height: box.height)
                    .position(x: box.midX, y: box.midY)
                    .allowsHitTesting(false)

                // 提示
                Text("把异常项放进框里 · 对准一两行")
                    .font(.system(size: 13, weight: .medium))
                    .foregroundStyle(.white)
                    .padding(.horizontal, 12)
                    .padding(.vertical, 6)
                    .background(Capsule().fill(.black.opacity(0.4)))
                    .position(x: box.midX, y: box.minY - 22)
                    .allowsHitTesting(false)

                controlsOverlay
            }
        }
    }

    private var controlsOverlay: some View {
        VStack {
            HStack {
                Button {
                    onCancel()
                } label: {
                    Text("取消")
                        .font(.system(size: 16, weight: .medium))
                        .foregroundStyle(.white)
                        .padding(.horizontal, 14)
                        .padding(.vertical, 8)
                        .background(Capsule().fill(.black.opacity(0.35)))
                }
                Spacer()
            }
            .padding(.horizontal, 18)
            .padding(.top, 8)

            Spacer()

            shutterButton
                .padding(.bottom, 36)
        }
    }

    private var shutterButton: some View {
        Button {
            capture()
        } label: {
            ZStack {
                Circle().fill(.white).frame(width: 72, height: 72)
                Circle().strokeBorder(.white.opacity(0.6), lineWidth: 3).frame(width: 84, height: 84)
                if isCapturing {
                    ProgressView().tint(.black)
                }
            }
        }
        .disabled(isCapturing)
        .accessibilityLabel("拍摄异常项")
    }

    private var deniedView: some View {
        VStack(spacing: 16) {
            Image(systemName: "camera.fill")
                .font(.system(size: 40))
                .foregroundStyle(.white.opacity(0.8))
            Text("相机权限未开启")
                .font(.tjH2())
                .foregroundStyle(.white)
            Text("异常项快拍需要相机。去「设置 → 康康 → 相机」打开后再回来。")
                .font(.system(size: 13))
                .foregroundStyle(.white.opacity(0.7))
                .multilineTextAlignment(.center)
                .padding(.horizontal, 36)
            HStack(spacing: 12) {
                Button("取消") { onCancel() }
                    .font(.system(size: 15))
                    .foregroundStyle(.white)
                    .padding(.horizontal, 18).padding(.vertical, 10)
                    .background(Capsule().strokeBorder(.white.opacity(0.5), lineWidth: 1))
                Button("去设置") {
                    if let url = URL(string: UIApplication.openSettingsURLString) {
                        UIApplication.shared.open(url)
                    }
                }
                .font(.system(size: 15, weight: .semibold))
                .foregroundStyle(.black)
                .padding(.horizontal, 18).padding(.vertical, 10)
                .background(Capsule().fill(.white))
            }
        }
    }

    // MARK: - 行为

    private func capture() {
        guard !isCapturing else { return }
        isCapturing = true
        withAnimation(.easeOut(duration: 0.08)) { flash = true }
        controller.capture { image in
            withAnimation(.easeIn(duration: 0.15)) { flash = false }
            isCapturing = false
            guard let image else { return }
            onCapture(image)
        }
    }

    private func resolveAuth() async {
        switch AVCaptureDevice.authorizationStatus(for: .video) {
        case .authorized:
            authState = .authorized
        case .notDetermined:
            let granted = await AVCaptureDevice.requestAccess(for: .video)
            authState = granted ? .authorized : .denied
        default:
            authState = .denied
        }
    }
}

// MARK: - 小框几何(UIView 与 SwiftUI 覆盖层共用,保证坐标一致)

enum RegionFraming {
    /// 居中、略高于中心的小框。宽 84% 屏宽,高取 160 与 28% 屏高的较小值。
    static func box(in size: CGSize) -> CGRect {
        guard size.width > 0, size.height > 0 else { return .zero }
        let w = size.width * 0.84
        let h = min(160, size.height * 0.28)
        let x = (size.width - w) / 2
        let y = (size.height - h) / 2 - size.height * 0.06
        return CGRect(x: x, y: y, width: w, height: h)
    }
}

// MARK: - 裁剪纯函数

enum RegionImageCropper {
    /// 按归一化 rect(原点左上、范围 0-1、与显示方向一致)裁剪 `.up` 方向的图。
    /// 入参 image 须已 bake 成 `.up`(见 `UIImage.normalizedUp()`)。越界自动夹紧;失败回退原图。
    static func crop(_ image: UIImage, normalizedRect: CGRect) -> UIImage {
        guard let cg = image.cgImage else { return image }
        let w = CGFloat(cg.width), h = CGFloat(cg.height)
        let nx = max(0, min(1, normalizedRect.origin.x))
        let ny = max(0, min(1, normalizedRect.origin.y))
        let nw = max(0, min(1 - nx, normalizedRect.size.width))
        let nh = max(0, min(1 - ny, normalizedRect.size.height))
        let rect = CGRect(x: nx * w, y: ny * h, width: nw * w, height: nh * h).integral
        guard rect.width >= 1, rect.height >= 1, let cropped = cg.cropping(to: rect) else { return image }
        return UIImage(cgImage: cropped, scale: image.scale, orientation: .up)
    }
}

extension UIImage {
    /// 把 EXIF 方向 bake 进像素,返回 `.up` 方向图,便于按归一化 rect 直接裁 CGImage。
    func normalizedUp() -> UIImage {
        if imageOrientation == .up { return self }
        let format = UIGraphicsImageRendererFormat.default()
        format.scale = scale
        let renderer = UIGraphicsImageRenderer(size: size, format: format)
        return renderer.image { _ in draw(in: CGRect(origin: .zero, size: size)) }
    }
}

// MARK: - AVFoundation 桥接

/// SwiftUI 持有,作为快门触发的句柄(weak 指向真正的 UIView)。
final class RegionCameraController: ObservableObject {
    weak var view: RegionPreviewUIView?
    func capture(_ completion: @escaping (UIImage?) -> Void) {
        guard let view else { completion(nil); return }
        view.capture(completion: completion)
    }
}

struct RegionCameraPreview: UIViewRepresentable {
    let controller: RegionCameraController

    func makeUIView(context: Context) -> RegionPreviewUIView {
        let v = RegionPreviewUIView()
        controller.view = v
        return v
    }

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

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

/// 实时预览 + 单张拍摄,拍完按小框裁剪。
final class RegionPreviewUIView: UIView, AVCapturePhotoCaptureDelegate {
    private let session = AVCaptureSession()
    private let output = AVCapturePhotoOutput()
    private var previewLayer: AVCaptureVideoPreviewLayer?
    private var setupDone = false
    private var captureCompletion: ((UIImage?) -> Void)?

    override func didMoveToWindow() {
        super.didMoveToWindow()
        guard !setupDone, window != nil else { return }
        setupDone = true
        configure()
    }

    private func configure() {
        session.beginConfiguration()
        session.sessionPreset = .photo
        guard let device = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back),
              let input = try? AVCaptureDeviceInput(device: device),
              session.canAddInput(input) else {
            session.commitConfiguration()
            return
        }
        session.addInput(input)
        if session.canAddOutput(output) { session.addOutput(output) }
        session.commitConfiguration()

        let preview = AVCaptureVideoPreviewLayer(session: session)
        preview.videoGravity = .resizeAspectFill
        preview.frame = bounds
        layer.addSublayer(preview)
        self.previewLayer = preview
        applyPortrait(preview.connection)

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

    /// 锁竖屏(iOS 17+ 用 videoRotationAngle,避免 videoOrientation 弃用告警)。
    private func applyPortrait(_ connection: AVCaptureConnection?) {
        guard let connection else { return }
        if connection.isVideoRotationAngleSupported(90) {
            connection.videoRotationAngle = 90
        }
    }

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

    func capture(completion: @escaping (UIImage?) -> Void) {
        guard session.isRunning else { completion(nil); return }
        captureCompletion = completion
        applyPortrait(output.connection(with: .video))
        output.capturePhoto(with: AVCapturePhotoSettings(), delegate: self)
    }

    func stop() {
        guard session.isRunning else { return }
        DispatchQueue.global(qos: .userInitiated).async { [weak self] in
            self?.session.stopRunning()
        }
    }

    func photoOutput(_ output: AVCapturePhotoOutput,
                     didFinishProcessingPhoto photo: AVCapturePhoto,
                     error: Error?) {
        let completion = captureCompletion
        captureCompletion = nil
        // 代理回调在 AVFoundation 私有队列,SwiftUI 状态更新必须切回主线程。
        let deliver: (UIImage?) -> Void = { result in
            DispatchQueue.main.async { completion?(result) }
        }
        guard error == nil,
              let data = photo.fileDataRepresentation(),
              let image = UIImage(data: data) else {
            deliver(nil)
            return
        }
        let upright = image.normalizedUp()
        guard let preview = previewLayer else {
            deliver(upright)
            return
        }
        // metadataOutputRectConverted 读 previewLayer 几何,回主线程算更稳。
        DispatchQueue.main.async {
            let box = RegionFraming.box(in: self.bounds.size)
            let normalized = preview.metadataOutputRectConverted(fromLayerRect: box)
            let cropped = RegionImageCropper.crop(upright, normalizedRect: normalized)
            completion?(cropped)
        }
    }
}