element-ios/Riot/Modules/SlidingModal/SlidingModalPresentationAnimator.swift

/*
Copyright 2019-2024 New Vector Ltd.

SPDX-License-Identifier: AGPL-3.0-only
Please see LICENSE in the repository root for full details.
 */

import UIKit

/// `SlidingModalPresentationAnimator` handles the animations for a custom sliding view controller transition.
final class SlidingModalPresentationAnimator: NSObject {
    
    // MARK: - Constants
    
    private enum AnimationDuration {
        static let presentation: TimeInterval = 0.2
        static let dismissal: TimeInterval = 0.3
    }
    
    // MARK: - Properties

    private let isPresenting: Bool
    private let options: SlidingModalOption
    
    // MARK: - Setup
    
    /// Instantiate a SlidingModalPresentationAnimator object.
    ///
    /// - Parameter isPresenting: true to animate presentation or false to animate dismissal
    /// - Parameter isSpanning: true to remove left, bottom and right spaces between the screen edges and the content view
    required public init(isPresenting: Bool, options: SlidingModalOption) {
        self.isPresenting = isPresenting
        self.options = options
        super.init()
    }
    
    // MARK: - Private
    
    // Animate presented view controller presentation
    private func animatePresentation(using transitionContext: UIViewControllerContextTransitioning) {
        guard let presentedViewController = transitionContext.viewController(forKey: .to),
            transitionContext.viewController(forKey: .from) != nil else {
                return
        }
        
        guard let presentedViewControllerView = presentedViewController.view else {
            return
        }
        
        let containerView = transitionContext.containerView
        
        // Spanning not available for iPad
        let slidingModalContainerView = options.contains(.spanning) && UIDevice.current.userInterfaceIdiom != .pad ? SpanningSlidingModalContainerView.instantiate() : SlidingModalContainerView.instantiate()
        slidingModalContainerView.blurBackground = options.contains(.blurBackground)
        slidingModalContainerView.centerInScreen = options.contains(.centerInScreen)
        slidingModalContainerView.alpha = 0
        slidingModalContainerView.updateDimmingViewAlpha(0.0)
        
        // Add presented view controller view to slidingModalContainerView content view
        slidingModalContainerView.setContentView(presentedViewControllerView)
        
        // Add slidingModalContainerView to container view
        containerView.vc_addSubViewMatchingParent(slidingModalContainerView)
        containerView.layoutIfNeeded()
        
        // Adapt slidingModalContainerView content view height from presentedViewControllerView height 
        if let slidingModalPresentable = presentedViewController as? SlidingModalPresentable {
            let slidingModalContainerViewContentViewWidth = slidingModalContainerView.contentViewFrame.width
            let presentableHeight = slidingModalPresentable.layoutHeightFittingWidth(slidingModalContainerViewContentViewWidth)
            slidingModalContainerView.updateContentViewMaxHeight(presentableHeight)
            slidingModalContainerView.updateContentViewLayout()
        }
        
        // Hide slidingModalContainerView content view
        slidingModalContainerView.prepareDismissAnimation()
        containerView.layoutIfNeeded()
        
        let animationDuration = self.transitionDuration(using: transitionContext)
        
        slidingModalContainerView.preparePresentAnimation()
        slidingModalContainerView.alpha = 1
        
        UIView.animate(withDuration: animationDuration, animations: {
            containerView.layoutIfNeeded()
            slidingModalContainerView.updateDimmingViewAlpha(1.0)
        }, completion: { completed in
            transitionContext.completeTransition(completed)
        })
    }
    
    // Animate presented view controller dismissal
    private func animateDismissal(using transitionContext: UIViewControllerContextTransitioning) {
        
        let containerView = transitionContext.containerView
        
        let slidingModalContainerView = self.slidingModalContainerView(from: transitionContext)
        
        let animationDuration = self.transitionDuration(using: transitionContext)
        
        slidingModalContainerView?.prepareDismissAnimation()
        
        UIView.animate(withDuration: animationDuration, animations: {
            containerView.layoutIfNeeded()
            slidingModalContainerView?.updateDimmingViewAlpha(0.0)
        }, completion: { completed in
            transitionContext.completeTransition(completed)
        })
    }
    
    private func slidingModalContainerView(from transitionContext: UIViewControllerContextTransitioning) -> SlidingModalContainerView? {
        let modalContentView = transitionContext.containerView.subviews.first(where: { view -> Bool in
            view is SlidingModalContainerView
        }) as? SlidingModalContainerView
        return modalContentView
    }
}

// MARK: - UIViewControllerAnimatedTransitioning
extension SlidingModalPresentationAnimator: UIViewControllerAnimatedTransitioning {
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return self.isPresenting ? AnimationDuration.presentation : AnimationDuration.dismissal
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        if self.isPresenting {
            self.animatePresentation(using: transitionContext)
        } else {
            self.animateDismissal(using: transitionContext)
        }
    }
}