import SwiftUI
import PhotosUI

struct SinglePhotoPicker: View {
    @State private var selectedItem: PhotosPickerItem?
    @State private var selectedImage: Image?

    var body: some View {
        VStack {
            if let selectedImage {
                selectedImage
                    .resizable()
                    .scaledToFit()
                    .frame(maxHeight: 300)
            }

            PhotosPicker("Select Photo", selection: $selectedItem, matching: .images)
        }
        .onChange(of: selectedItem) { _, newItem in
            Task {
                if let data = try? await newItem?.loadTransferable(type: Data.self),
                   let uiImage = UIImage(data: data) {
                    selectedImage = Image(uiImage: uiImage)
                }
            }
        }
    }
}

struct MultiPhotoPicker: View {
    @State private var selectedItems: [PhotosPickerItem] = []
    @State private var selectedImages: [Image] = []

    var body: some View {
        VStack {
            ScrollView(.horizontal) {
                HStack {
                    ForEach(selectedImages.indices, id: \.self) { index in
                        selectedImages[index]
                            .resizable()
                            .scaledToFill()
                            .frame(width: 100, height: 100)
                            .clipShape(.rect(cornerRadius: 8))
                    }
                }
            }

            PhotosPicker(
                "Select Photos",
                selection: $selectedItems,
                maxSelectionCount: 5,
                matching: .images
            )
        }
        .onChange(of: selectedItems) { _, newItems in
            Task {
                selectedImages = []
                for item in newItems {
                    if let data = try? await item.loadTransferable(type: Data.self),
                       let uiImage = UIImage(data: data) {
                        selectedImages.append(Image(uiImage: uiImage))
                    }
                }
            }
        }
    }
}

// Images only
PhotosPicker(selection: $items, matching: .images)

// Videos only
PhotosPicker(selection: $items, matching: .videos)

// Live Photos only
PhotosPicker(selection: $items, matching: .livePhotos)

// Screenshots only
PhotosPicker(selection: $items, matching: .screenshots)

// Images and videos combined
PhotosPicker(selection: $items, matching: .any(of: [.images, .videos]))

// Images excluding screenshots
PhotosPicker(selection: $items, matching: .all(of: [.images, .not(.screenshots)]))

struct PickedImage: Transferable {
    let data: Data
    let image: Image

    static var transferRepresentation: some TransferRepresentation {
        DataRepresentation(importedContentType: .image) { data in
            guard let uiImage = UIImage(data: data) else {
                throw TransferError.importFailed
            }
            return PickedImage(data: data, image: Image(uiImage: uiImage))
        }
    }
}

enum TransferError: Error {
    case importFailed
}

// Usage
if let picked = try? await item.loadTransferable(type: PickedImage.self) {
    selectedImage = picked.image
}

import Photos

func requestPhotoLibraryAccess() async -> PHAuthorizationStatus {
    let status = PHPhotoLibrary.authorizationStatus(for: .readWrite)

    switch status {
    case .notDetermined:
        return await PHPhotoLibrary.requestAuthorization(for: .readWrite)
    case .authorized, .limited:
        return status
    case .denied, .restricted:
        return status
    @unknown default:
        return status
    }
}

import AVFoundation

func requestCameraAccess() async -> Bool {
    let status = AVCaptureDevice.authorizationStatus(for: .video)

    switch status {
    case .notDetermined:
        return await AVCaptureDevice.requestAccess(for: .video)
    case .authorized:
        return true
    case .denied, .restricted:
        return false
    @unknown default:
        return false
    }
}

struct PermissionDeniedView: View {
    let message: String
    @Environment(\.openURL) private var openURL

    var body: some View {
        ContentUnavailableView {
            Label("Access Denied", systemImage: "lock.shield")
        } description: {
            Text(message)
        } actions: {
            Button("Open Settings") {
                if let url = URL(string: UIApplication.openSettingsURLString) {
                    openURL(url)
                }
            }
        }
    }
}

import SwiftUI
import AVFoundation

struct CameraPreview: UIViewRepresentable {
    let session: AVCaptureSession

    func makeUIView(context: Context) -> PreviewView {
        let view = PreviewView()
        view.previewLayer.session = session
        view.previewLayer.videoGravity = .resizeAspectFill
        return view
    }

    func updateUIView(_ uiView: PreviewView, context: Context) {
        if uiView.previewLayer.session !== session {
            uiView.previewLayer.session = session
        }
    }
}

final class PreviewView: UIView {
    override class var layerClass: AnyClass { AVCaptureVideoPreviewLayer.self }
    var previewLayer: AVCaptureVideoPreviewLayer { layer as! AVCaptureVideoPreviewLayer }
}

struct CameraScreen: View {
    @State private var cameraManager = CameraManager()

    var body: some View {
        ZStack(alignment: .bottom) {
            CameraPreview(session: cameraManager.session)
                .ignoresSafeArea()

            Button {
                // Capture photo -- see references/camera-capture.md
            } label: {
                Circle()
                    .fill(.white)
                    .frame(width: 72, height: 72)
                    .overlay(Circle().stroke(.gray, lineWidth: 3))
            }
            .padding(.bottom)
        }
        .task {
            await cameraManager.configure()
            cameraManager.start()
        }
        .onDisappear {
            cameraManager.stop()
        }
    }
}

AsyncImage(url: imageURL) { phase in
    switch phase {
    case .empty:
        ProgressView()
    case .success(let image):
        image
            .resizable()
            .scaledToFill()
    case .failure:
        Image(systemName: "photo")
            .foregroundStyle(.secondary)
    @unknown default:
        EmptyView()
    }
}
.frame(width: 200, height: 200)
.clipShape(.rect(cornerRadius: 12))

import ImageIO
import UIKit

func downsample(data: Data, to pointSize: CGSize, scale: CGFloat = UITraitCollection.current.displayScale) -> UIImage? {
    let maxDimensionInPixels = max(pointSize.width, pointSize.height) * scale

    let options: [CFString: Any] = [
        kCGImageSourceCreateThumbnailFromImageAlways: true,
        kCGImageSourceShouldCacheImmediately: true,
        kCGImageSourceCreateThumbnailWithTransform: true,
        kCGImageSourceThumbnailMaxPixelSize: maxDimensionInPixels
    ]

    guard let source = CGImageSourceCreateWithData(data as CFData, nil),
          let cgImage = CGImageSourceCreateThumbnailAtIndex(source, 0, options as CFDictionary) else {
        return nil
    }

    return UIImage(cgImage: cgImage)
}

// Original: display the image as-is with its original colors
Image("photo")
    .renderingMode(.original)

// Template: treat the image as a mask, colored by foregroundStyle
Image(systemName: "heart.fill")
    .renderingMode(.template)
    .foregroundStyle(.red)