AnimatedControl.swift

//
//  AnimatedControl.swift
//  lottie-swift
//
//  Created by Brandon Withrow on 2/4/19.
//

import Foundation
import UIKit

/**
 Lottie comes prepacked with a two Animated Controls, `AnimatedSwitch` and
 `AnimatedButton`. Both of these controls are built on top of `AnimatedControl`
 
 `AnimatedControl` is a subclass of `UIControl` that provides an interactive
 mechanism for controlling the visual state of an animation in response to
 user actions.
 
 The `AnimatedControl` will show and hide layers depending on the current
 `UIControl.State` of the control.
 
 Users of `AnimationControl` can set a Layer Name for each `UIControl.State`.
 When the state is change the `AnimationControl` will change the visibility
 of its layers.
 
 NOTE: Do not initialize directly. This is intended to be subclassed.
 */
open class AnimatedControl: UIControl {
  
  // MARK: Public
  
  /// The animation backing the animated control.
  public var animation: Animation? {
    didSet {
      animationView.animation = animation
      animationView.bounds = animation?.bounds ?? .zero
      setNeedsLayout()
      updateForState()
      animationDidSet()
    }
  }
  
  /// Sets which Animation Layer should be visible for the given state.
  public func setLayer(named: String, forState: UIControl.State) {
    stateMap[forState.rawValue] = named
    updateForState()
  }

  /// Sets a ValueProvider for the specified keypath
  public func setValueProvider(_ valueProvider: AnyValueProvider, keypath: AnimationKeypath) {
    animationView.setValueProvider(valueProvider, keypath: keypath)
  }
  
  // MARK: Initializers
  
  public init(animation: Animation) {
    self.animationView = AnimationView(animation: animation)
    super.init(frame: animation.bounds)
    commonInit()
  }
  
  public init() {
    self.animationView = AnimationView()
    super.init(frame: .zero)
    commonInit()
  }
  
  required public init?(coder aDecoder: NSCoder) {
    self.animationView = AnimationView()
    super.init(coder: aDecoder)
    commonInit()
  }
  
  // MARK: UIControl Overrides
  
  open override var isEnabled: Bool {
    didSet {
      updateForState()
    }
  }
  
  open override var isSelected: Bool {
    didSet {
      updateForState()
    }
  }
  
  open override var isHighlighted: Bool {
    didSet {
      updateForState()
    }
  }
  
  open override func beginTracking(_ touch: UITouch, with event: UIEvent?) -> Bool {
    updateForState()
    return super.beginTracking(touch, with: event)
  }
  
  open override func continueTracking(_ touch: UITouch, with event: UIEvent?) -> Bool {
    updateForState()
    return super.continueTracking(touch, with: event)
  }
  
  open override func endTracking(_ touch: UITouch?, with event: UIEvent?) {
    updateForState()
    return super.endTracking(touch, with: event)
  }
  
  open override func cancelTracking(with event: UIEvent?) {
    updateForState()
    super.cancelTracking(with: event)
  }
  
  open override var intrinsicContentSize: CGSize {
    return animationView.intrinsicContentSize
  }
  
  open func animationDidSet() {
    
  }
  
  // MARK: Private
  
  let animationView: AnimationView
  var stateMap: [UInt : String] = [:]
  
  fileprivate func commonInit() {
    animationView.clipsToBounds = false
    clipsToBounds = true
    animationView.translatesAutoresizingMaskIntoConstraints = false
    animationView.backgroundBehavior = .forceFinish
    addSubview(animationView)
    animationView.contentMode = .scaleAspectFit
    animationView.isUserInteractionEnabled = false
    animationView.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true
    animationView.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true
    animationView.topAnchor.constraint(equalTo: topAnchor).isActive = true
    animationView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
  }
  
  func updateForState() {
    guard let animationLayer = animationView.animationLayer else { return }
    if let layerName = stateMap[state.rawValue],
        let stateLayer = animationLayer.layer(for: AnimationKeypath(keypath: layerName)) {
      for layer in animationLayer.animationLayers {
        layer.isHidden = true
      }
      stateLayer.isHidden = false
    } else {
      for layer in animationLayer.animationLayers {
        layer.isHidden = false
      }
    }
  }
  
}