//
//  FullScreenTransitionManager.swift
//

import Foundation
import UIKit

// MARK: FullScreenPresentationController

final class FullScreenPresentationController: UIPresentationController {
    private let backgroundView: UIView = {
        let view = UIView()
        view.backgroundColor = .systemBackground
        view.alpha = 0
        return view
    }()
    
    private lazy var tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(onTap))
    
    @objc private func onTap(_ gesture: UITapGestureRecognizer) {
        presentedViewController.dismiss(animated: true)
    }
}
    
// MARK: UIPresentationController
    
extension FullScreenPresentationController {
    override func presentationTransitionWillBegin() {
        guard let containerView = containerView else { return }
        
        containerView.addGestureRecognizer(tapGestureRecognizer)
        
        containerView.addSubview(backgroundView)
        backgroundView.frame = containerView.frame
        
        guard let transitionCoordinator = presentingViewController.transitionCoordinator else { return }
        
        transitionCoordinator.animate(alongsideTransition: { context in
            self.backgroundView.alpha = 1
        })
    }
    
    override func presentationTransitionDidEnd(_ completed: Bool) {
        if !completed {
            backgroundView.removeFromSuperview()
            containerView?.removeGestureRecognizer(tapGestureRecognizer)
        }
    }
    
    override func dismissalTransitionWillBegin() {
        guard let transitionCoordinator = presentingViewController.transitionCoordinator else { return }
        
        transitionCoordinator.animate(alongsideTransition: { context in
            self.backgroundView.alpha = 0
        })
    }
    
    override func dismissalTransitionDidEnd(_ completed: Bool) {
        if completed {
            backgroundView.removeFromSuperview()
            containerView?.removeGestureRecognizer(tapGestureRecognizer)
        }
    }
    
    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        guard let containerView = containerView else { return }
        coordinator.animate(alongsideTransition: { context in
            self.backgroundView.frame = containerView.frame
        })
    }
}

// MARK: FullScreenTransitionManager

final class FullScreenTransitionManager: NSObject, UIViewControllerTransitioningDelegate {
    fileprivate enum AnimationState {
        case present
        case dismiss
    }
    
    private weak var anchorView: UIView?
    
    private var animationState: AnimationState = .present
    private var animationDuration: TimeInterval = Resources.animation.duration
    private var anchorViewFrame: CGRect = .zero
    
    private var propertyAnimator: UIViewPropertyAnimator?
    
    init(anchorView: UIView) {
        self.anchorView = anchorView
    }
    
    func presentationController(forPresented presented: UIViewController,
                                presenting: UIViewController?,
                                source: UIViewController) -> UIPresentationController? {
        FullScreenPresentationController(presentedViewController: presented, presenting: presenting)
    }
    
    func animationController(forPresented presented: UIViewController,
                             presenting: UIViewController,
                             source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        prepare(animationState: .present)
    }

    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        // Starting the animation here, since UIKit do not update safe area insets after UIViewController.viewWillDisappear() is called
        defer {
            propertyAnimator = dismissAnimator(animating: dismissed)
        }
        return prepare(animationState: .dismiss)
    }
}

// MARK: UIViewControllerAnimatedTransitioning

extension FullScreenTransitionManager: UIViewControllerAnimatedTransitioning {
    private func prepare(animationState: AnimationState,
                         animationDuration: TimeInterval = Resources.animation.duration) -> UIViewControllerAnimatedTransitioning? {
        guard let anchorView = anchorView else { return nil }
        
        self.animationState = animationState
        self.animationDuration = animationDuration
        self.anchorViewFrame = anchorView.safeAreaLayoutGuide.layoutFrame
        
        return self
    }
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        animationDuration
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        switch animationState {
        case .present:
            guard
                let toViewController = transitionContext.viewController(forKey: .to)
            else {
                return transitionContext.completeTransition(false)
            }
            propertyAnimator = presentAnimator(with: transitionContext, animating: toViewController)
        case .dismiss:
            guard
                let fromViewController = transitionContext.viewController(forKey: .from)
            else {
                return transitionContext.completeTransition(false)
            }
            propertyAnimator = updatedDismissAnimator(with: transitionContext, animating: fromViewController)
        }
    }
    
    private func presentAnimator(with transitionContext: UIViewControllerContextTransitioning,
                                 animating viewController: UIViewController) -> UIViewPropertyAnimator {
        transitionContext.containerView.addSubview(viewController.view)
        let finalFrame = transitionContext.finalFrame(for: viewController)
        viewController.view.frame = anchorViewFrame
        viewController.view.layoutIfNeeded()
        return UIViewPropertyAnimator.runningPropertyAnimator(withDuration: transitionDuration(using: transitionContext),
                                                              delay: 0,
                                                              options: [.curveEaseInOut],
                                                              animations: {
            viewController.view.frame = finalFrame
            viewController.view.layoutIfNeeded()
        }, completion: { _ in
            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
        })
    }
    
    private func dismissAnimator(animating viewController: UIViewController) -> UIViewPropertyAnimator {
        let finalFrame = anchorViewFrame
        return UIViewPropertyAnimator.runningPropertyAnimator(withDuration: animationDuration,
                                                              delay: 0,
                                                              options: [.curveEaseInOut],
                                                              animations: {
            viewController.view.frame = finalFrame
            viewController.view.layoutIfNeeded()
        })
    }
    
    private func updatedDismissAnimator(with transitionContext: UIViewControllerContextTransitioning,
                                        animating viewController: UIViewController) -> UIViewPropertyAnimator {
        let propertyAnimator = self.propertyAnimator ?? dismissAnimator(animating: viewController)
        propertyAnimator.addCompletion({ _ in
            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
        })
        self.propertyAnimator = propertyAnimator
        return propertyAnimator
    }
}