import AVFoundation
import UIKit

import CommonCore
import LayoutKit

extension AnimationBlock {
  static func makeBlockView() -> BlockView {
    AnimationBlockView()
  }

  func canConfigureBlockView(_ view: BlockView) -> Bool {
    view is AnimationBlockView
  }

  func configureBlockView(
    _ view: BlockView,
    observer _: ElementStateObserver?,
    overscrollDelegate _: ScrollDelegate?,
    renderingDelegate _: RenderingDelegate?
  ) {
    let lottieView = view as! AnimationBlockView
    if lottieView.animationHolder !== holder {
      lottieView.animatableView = animatableView.value
      lottieView.animationHolder = holder
    }
  }
}

private final class AnimationBlockView: BlockView {
  var animatableView: AnimatableView? {
    didSet {
      if let animatablView = animatableView {
        oldValue?.removeFromSuperview()
        addSubview(animatablView)
      }
    }
  }
  
  private var animationRequest: Cancellable?
  var animationHolder: AnimationHolder? {
    didSet {
      animationRequest?.cancel()

      let newValue = animationHolder
      animationRequest = animationHolder?.requestAnimationWithCompletion { [weak self] animationSource in
        guard let self = self,
              newValue === self.animationHolder, let animationSource = animationSource else {
          return
        }
        
        self.animatableView?.setSource(animationSource)
        self.animatableView?.play()
      }
    }
  }

  init() {
    super.init(frame: .zero)
  }
  
  override func layoutSubviews() {
    super.layoutSubviews()
    animatableView?.frame = bounds
  }

  @available(*, unavailable)
  required init?(coder _: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

  let effectiveBackgroundColor: UIColor? = nil
}

extension AnimationBlockView: VisibleBoundsTrackingLeaf { }