ScrollContentIndicator.swift

//
//  ScrollContentIndicator.swift
//
//  Made with ❤️ by Novum
//
//  Copyright © Telefonica. All rights reserved.
//

import UIKit

public class ScrollContentIndicator: Button {
    private enum Constants {
        static let shadowOpacity: Float = 0.2
        static let shadowRadius: CGFloat = 12
        static let defaultMargin: CGFloat = 24
        static let defaultHeight: CGFloat = 40
        static let animationDuration: TimeInterval = 0.3
    }

    public init(title: String, loadingTitle: String? = nil, isSmall: Bool = false) {
        super.init(style: .primaryClear, title: title, loadingTitle: loadingTitle, isSmall: isSmall)
        setUp()
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        style = .primaryClear
        setUp()
    }

    public func addToView(_ view: UIView) {
        view.addSubview(self, constraints: [
            centerXAnchor.constraint(equalTo: view.centerXAnchor),
            heightAnchor.constraint(equalToConstant: Constants.defaultHeight),
            topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: Constants.defaultMargin)
        ])
    }

    public func show() {
        isHidden = false
        UIView.animate(
            withDuration: Constants.animationDuration,
            delay: 0.0,
            options: .curveEaseOut,
            animations: {
                self.transform = .identity
                self.alpha = 1
            }
        )
    }

    public func hide() {
        UIView.animate(
            withDuration: Constants.animationDuration,
            delay: 0.0,
            options: .curveEaseIn,
            animations: {
                // Due to the maths behind Affine Transformation matrix we have to use 0.001 instead 0.0 for the down scale to work properly.
                // More info: https://medium.com/@sarthak.tayade/problem-when-animating-a-uiview-to-scale-to-zero-using-cgaffinetransform-on-ios-2f50717add18
                self.transform = CGAffineTransform(scaleX: 0.001, y: 0.001)
                self.alpha = 0
            },
            completion: { _ in
                self.isHidden = true
            }
        )
    }
}

private extension ScrollContentIndicator {
    var cornerRadius: CGFloat {
        Constants.defaultHeight / 2
    }

    func setUp() {
        removeBorder()
        addBackgroundView()
        makeRounded(cornerRadius: cornerRadius)
        addShadow()
        transform = CGAffineTransform(scaleX: 0.0, y: 0.0)
        alpha = 0
        isHidden = true
        setContentCompressionResistancePriority(.required, for: .horizontal)
    }

    func addBackgroundView() {
        let backgroundView = UIView()
        backgroundView.backgroundColor = .brand
        backgroundView.makeRounded(cornerRadius: cornerRadius)
        backgroundView.isUserInteractionEnabled = false
        insertSubview(backgroundView, at: 0, constraints: backgroundView.constraintsForEdges(to: self))
    }

    func addShadow() {
        layer.shadowColor = UIColor.backgroundOverlay.cgColor
        layer.shadowOpacity = Constants.shadowOpacity
        layer.shadowOffset = .zero
        layer.shadowRadius = Constants.shadowRadius
        layer.masksToBounds = false
    }
}