ActionSheetAnimator.swift

import UIKit

///
/// `ActionSheetAnimator` is used to handle the presentation and dismissal animation of `ActionSheet`
///
final class ActionSheetAnimator: NSObject {
    let isPresentation: Bool

    init(isPresentation: Bool) {
        self.isPresentation = isPresentation
        super.init()
    }
}

extension ActionSheetAnimator: UIViewControllerAnimatedTransitioning {
    func transitionDuration(
        using transitionContext: UIViewControllerContextTransitioning?
    ) -> TimeInterval {
        return ActionSheetConstants.animationDuration
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let key: UITransitionContextViewControllerKey = isPresentation ? .to : .from
        guard let controller = transitionContext.viewController(forKey: key)
            else { return }

        if isPresentation {
            transitionContext.containerView.addSubview(controller.view)
        }

        let presentedFrame = transitionContext.finalFrame(for: controller)
        var dismissedFrame = presentedFrame

        // adding 50 to offset a weird UIKit bug that doesn't place the view off screen
        dismissedFrame.origin.y = transitionContext.containerView.frame.size.height + 50

        let initialFrame = isPresentation ? dismissedFrame : presentedFrame
        let finalFrame = isPresentation ? presentedFrame : dismissedFrame

        let animationDuration = transitionDuration(using: transitionContext)
        controller.view.frame = initialFrame
        UIView.animate(withDuration: animationDuration,
                       delay: 0,
                       options: .curveEaseInOut) {
            controller.view.frame = finalFrame
        } completion: { finished in
            if !self.isPresentation {
                controller.view.removeFromSuperview()
            }
            transitionContext.completeTransition(finished)
        }
    }
}