//
//  GradientBorderedView.swift
//  DiaryOfBloodPressure
//
//  Created by Aleksandr Smetannikov on 04/10/2019.
//  Copyright © 2019 AlexSmetannikov. All rights reserved.
//

import UIKit

class GradientBorderedView: UIView {
    private var gradientLayer = CAGradientLayer()
    private var borderLayer = CAShapeLayer()

    var colors: [UIColor] = []

    var borderWidth: CGFloat = 1 {
        didSet {
            setNeedsDisplay()
        }
    }

    var cornerRadius: CGFloat = 4 {
        didSet {
            layer.cornerRadius = cornerRadius
            setNeedsDisplay()
        }
    }

    override var frame: CGRect {
        didSet {
            setNeedsDisplay()
        }
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)

        layer.addSublayer(gradientLayer)
    }

    override init(frame: CGRect) {
        super.init(frame: frame)

        layer.addSublayer(gradientLayer)
    }

    override func draw(_ rect: CGRect) {
        makeGradietBorder()

        super.draw(rect)
    }

    private func makeGradietBorder() {
        gradientLayer.transform = CATransform3DMakeRotation( -CGFloat.pi / 2, 0, 0, 1)
        gradientLayer.frame = CGRect(origin: .zero, size: frame.size)
        gradientLayer.colors = colors.isEmpty ? [] : colors.map { $0.cgColor }

        borderLayer.borderWidth = borderWidth
        borderLayer.cornerRadius = cornerRadius
        borderLayer.path = UIBezierPath(rect: gradientLayer.bounds).cgPath
        borderLayer.strokeColor = UIColor.black.cgColor
        borderLayer.fillColor = UIColor.clear.cgColor

        gradientLayer.mask = borderLayer
    }
}