ScanOverlayView.swift

import UIKit
import Shared

final class ScanOverlayView: UIView {
    private let cropView = UIView()
    private let scanViewLength = 266.0
    private let maskLayer = CAShapeLayer()
    private let topLeftLayer = CAShapeLayer()
    private let topRightLayer = CAShapeLayer()
    private let bottomLeftLayer = CAShapeLayer()
    private let bottomRightLayer = CAShapeLayer()

    init() {
        super.init(frame: .zero)
        backgroundColor = Asset.neutralDark.color.withAlphaComponent(0.5)

        addSubview(cropView)

        cropView.snp.makeConstraints {
            $0.width.equalTo(scanViewLength)
            $0.centerY.equalToSuperview().offset(-50)
            $0.centerX.equalToSuperview()
            $0.height.equalTo(scanViewLength)
        }

        maskLayer.fillRule = .evenOdd
        layer.mask = maskLayer
        layer.masksToBounds = true

        [topLeftLayer, topRightLayer, bottomLeftLayer, bottomRightLayer].forEach {
            $0.strokeColor = Asset.brandPrimary.color.cgColor
            $0.fillColor = UIColor.clear.cgColor
            $0.lineWidth = 3.0
            $0.lineCap = .round
            layer.addSublayer($0)
        }
    }

    required init?(coder: NSCoder) { nil }

    override func layoutSubviews() {
        super.layoutSubviews()

        maskLayer.frame = bounds
        let path = UIBezierPath(rect: bounds)
        path.append(UIBezierPath(roundedRect: cropView.frame, cornerRadius: 30.0))
        maskLayer.path = path.cgPath

        topLeftLayer.frame = bounds
        topRightLayer.frame = bounds
        bottomRightLayer.frame = bounds
        bottomLeftLayer.frame = bounds

        topLeftLayer.path = topLeftPath()
        topRightLayer.path = topRightPath()
        bottomRightLayer.path = bottomRightPath()
        bottomLeftLayer.path = bottomLeftPath()
    }

    func updateCornerColor(_ color: UIColor) {
        [topLeftLayer, topRightLayer, bottomLeftLayer, bottomRightLayer].forEach {
            $0.strokeColor = color.cgColor
        }
    }

    func topLeftPath() -> CGPath {
        let path = UIBezierPath()

        let vert0X = cropView.frame.minX - 15
        let vert0Y = cropView.frame.minY + 45
        let vert0 = CGPoint(x: vert0X, y: vert0Y)
        path.move(to: vert0)

        let vertNX = cropView.frame.minX - 15
        let vertNY = cropView.frame.minY + 15
        let vertN = CGPoint(x: vertNX, y: vertNY)
        path.addLine(to: vertN)

        let arcCenterX = cropView.frame.minX + 15
        let arcCenterY = cropView.frame.minY + 15
        let arcCenter = CGPoint(x: arcCenterX , y: arcCenterY)
        path.addArc(center: arcCenter, startAngle: .pi)

        let horizX = cropView.frame.minX + 45
        let horizY = cropView.frame.minY - 15
        let horiz = CGPoint(x: horizX, y: horizY)
        path.addLine(to: horiz)

        return path.cgPath
    }

    func topRightPath() -> CGPath {
        let path = UIBezierPath()

        let horiz0X = cropView.frame.maxX - 45
        let horiz0Y = cropView.frame.minY - 15
        let horiz0 = CGPoint(x: horiz0X, y: horiz0Y)
        path.move(to: horiz0)

        let horizNX = cropView.frame.maxX - 15
        let horizNY = cropView.frame.minY - 15
        let horizN = CGPoint(x: horizNX, y: horizNY)
        path.addLine(to: horizN)

        let arcCenterX = cropView.frame.maxX - 15
        let arcCenterY = cropView.frame.minY + 15
        let arcCenter = CGPoint(x: arcCenterX, y: arcCenterY)
        path.addArc(center: arcCenter, startAngle: 3 * .pi/2)

        let vertX = cropView.frame.maxX + 15
        let vertY = cropView.frame.minY + 45
        let vert = CGPoint(x: vertX, y: vertY)
        path.addLine(to: vert)

        return path.cgPath
    }

    func bottomRightPath() -> CGPath {
        let path = UIBezierPath()

        let vert0X = cropView.frame.maxX + 15
        let vert0Y = cropView.frame.maxY - 45
        let vert0 = CGPoint(x: vert0X, y: vert0Y)
        path.move(to: vert0)

        let vertNX = cropView.frame.maxX + 15
        let vertNY = cropView.frame.maxY - 15
        let vertN = CGPoint(x: vertNX, y: vertNY)
        path.addLine(to: vertN)

        let arcCenterX = cropView.frame.maxX - 15
        let arcCenterY = cropView.frame.maxY - 15
        let arcCenter = CGPoint(x: arcCenterX, y: arcCenterY)
        path.addArc(center: arcCenter, startAngle: 0)

        let horizX = cropView.frame.maxX - 45
        let horizY = cropView.frame.maxY + 15
        let horiz = CGPoint(x: horizX, y: horizY)
        path.addLine(to: horiz)

        return path.cgPath
    }

    func bottomLeftPath() -> CGPath {
        let path = UIBezierPath()

        let horiz0X = cropView.frame.minX + 45
        let horiz0Y = cropView.frame.maxY + 15
        let horiz0 = CGPoint(x: horiz0X, y: horiz0Y)
        path.move(to: horiz0)

        let horizNX = cropView.frame.minX + 15
        let horizNY = cropView.frame.maxY + 15
        let horizN = CGPoint(x: horizNX, y: horizNY)
        path.addLine(to: horizN)

        let arcCenterX = cropView.frame.minX + 15
        let arcCenterY = cropView.frame.maxY - 15
        let arcCenter = CGPoint(x: arcCenterX, y: arcCenterY)
        path.addArc(center: arcCenter, startAngle: .pi/2)

        let vertX = cropView.frame.minX - 15
        let vertY = cropView.frame.maxY - 45
        let vert = CGPoint(x: vertX, y: vertY)
        path.addLine(to: vert)

        return path.cgPath
    }
}

private extension UIBezierPath {
    func addArc(center: CGPoint, startAngle: CGFloat) {
        addArc(
            withCenter: center,
            radius: 30,
            startAngle: startAngle,
            endAngle: startAngle + .pi/2,
            clockwise: true
        )
    }
}