Caps-iOS/Caps/Camera/CameraView.swift

import SwiftUI
import SFSafeSymbols

struct CameraView: View {

    static let cameraImagePadding: CGFloat = 300

    private static let circleSize: CGFloat = 180
    private var circleSize: CGFloat {
        CameraView.circleSize
    }

    static var circleCropFactor: CGFloat {
        let fullWidth = UIScreen.main.bounds.width + 2 * cameraImagePadding
        return circleSize / fullWidth
    }

    private let circleStrength: CGFloat = 3

    private let circleColor: Color = .green

    private let captureButtonSize: CGFloat = 110
    private let captureButtonHeight: CGFloat = 40
    private let captureButtonWidth: CGFloat = 50

    private let cancelButtonSize: CGFloat = 75
    private let cancelIconSize: CGFloat = 25

    @Binding
    var isPresented: Bool

    @Binding
    var image: UIImage?

    @Binding
    var capId: Int?

    @StateObject
    private var model = ContentViewModel()

    @EnvironmentObject
    var database: Database

    var body: some View {
        ZStack {
            FrameView(image: model.frame)
                .edgesIgnoringSafeArea(.all)
                .padding(-CameraView.cameraImagePadding)

            ErrorView(error: model.error)
            VStack {
                Spacer()
                HStack {
                    Spacer()
                    Button(action: dismiss) {
                        Image(systemSymbol: .xmark)
                            .resizable()
                            .frame(width: cancelIconSize, height: cancelIconSize)
                            .padding((cancelButtonSize-cancelIconSize)/2)
                            .background(.thinMaterial)
                            .cornerRadius(cancelButtonSize/2)
                    }.padding()
                }
            }
            VStack {
                Spacer()
                HStack {
                    Spacer()
                    Button(action: capture) {
                        Image(systemSymbol: .camera)
                            .resizable()
                            .frame(width: captureButtonWidth, height: captureButtonHeight)
                            .padding(.horizontal, (captureButtonSize - captureButtonWidth)/2)
                            .padding(.vertical, (captureButtonSize - captureButtonHeight)/2)
                            .background(.thinMaterial)
                            .cornerRadius(captureButtonSize / 2)
                    }.padding()
                    Spacer()
                }
            }
            VStack {
                Spacer()
                HStack {
                    Spacer()
                    Text("")
                        .frame(width: circleSize, height: circleSize, alignment: .center)
                        .overlay(RoundedRectangle(cornerRadius: circleSize/2)
                            .stroke(lineWidth: circleStrength)
                            .foregroundColor(circleColor))
                        .background(Color(white: 1, opacity: 0.01))
                        .onAppear(perform: didTapCircle)
                    Spacer()
                }
                Spacer()
            }.ignoresSafeArea()

        }
        .onAppear() {
            model.startCapture()
        }
        .onDisappear {
            model.endCapture()
        }.onChange(of: model.image) { image in
            if let capId = capId, let image = image {
                database.save(image, for: capId)
            } else {
                database.image = image
            }
            dismiss()
        }
    }

    private func dismiss() {
        isPresented = false
    }

    private func capture() {
        model.captureImage()
    }

    private func didTapCircle() {
        model.continuouslyFocusOnMiddle()
    }
}

struct CameraView_Previews: PreviewProvider {
    static var previews: some View {
        CameraView(isPresented: .constant(true),
                   image: .constant(nil),
                   capId: .constant(nil))
    }
}