Shadows+UIKit.swift

//
//  Vitamin iOS
//  Apache License 2.0
//

import UIKit
import VitaminCore

extension UIView {
    /// Drops a shadow below this view.
    /// - Parameters shadowType : the `VitaminShadow`you wqnt to drop
    /// Since the shadow os added to the layer of the view, the background color is
    /// forwarded from the view to the view'layer not to overlay the shadow
    public func dropShadow(shadowType: VitaminShadow) {
        layer.applyShadow(
            color: shadowType.color,
            opacity: shadowType.opacity,
            shadowSize: shadowType.size,
            blur: shadowType.blur,
            spread: shadowType.spread)

        if let backgroundCGColor = backgroundColor?.cgColor, shadowType != .none {
            backgroundColor = nil
            layer.backgroundColor = backgroundCGColor
        }
    }

    /// Remove any shadow from this view by resetting all shadow properties on the view's layer
    /// The layer background color is set back to the view if the layer color is not nil and the view's one is nil
    public func removeShadow() {
        dropShadow(shadowType: .none)

        if let backgroundCGColor = backgroundColor?.cgColor, backgroundColor == nil {
            layer.backgroundColor = nil
            backgroundColor = UIColor(cgColor: backgroundCGColor)
        }
    }
}

extension CALayer {
    /// Convenience mathod to apply a shadow on a CALayer
    /// - Parameters:
    ///     - color: the `UIColor` of the shadow
    ///     - opacity: the opacity of the shadow
    ///     - shadowSize: a `CGSize`defining the position of the light source
    ///     - blur: blur of the shadow, as defined in Figma
    ///     - spread: spread of the shadow, as defined in Figma
    func applyShadow(
        color: UIColor = .black,
        opacity: Float = 0.5,
        shadowSize: CGSize = CGSize(width: 0, height: 2),
        blur: CGFloat = 4,
        spread: CGFloat = 0
    ) {
            masksToBounds = false
            shadowColor = color.cgColor
            shadowOpacity = opacity
            shadowOffset = shadowSize
            // the shadow radius in iOS is equals to the blur divided by the screen scale
            shadowRadius = blur / UIScreen.main.scale
            if spread == 0 {
                shadowPath = nil
            } else {
                let deltaX = -spread
                let rect = bounds.insetBy(dx: deltaX, dy: deltaX)
                shadowPath = UIBezierPath(rect: rect).cgPath
            }
    }
}