frenzy-ios/Reader/StretchyMenuInteraction.swift

//
//  StretchyMenuInteraction.swift
//  Reader
//
//  Created by Shadowfacts on 1/11/22.
//

import UIKit

struct StretchyMenuItem {
    let title: String
    let subtitle: String?
    let action: () -> Void
}

protocol StretchyMenuInteractionDelegate: AnyObject {
    func stretchyMenuTitle() -> String?
    func stretchyMenuItems() -> [StretchyMenuItem]
}

class StretchyMenuInteraction: NSObject, UIInteraction {
    
    weak var delegate: StretchyMenuInteractionDelegate?
    
    private(set) weak var view: UIView? = nil
    
    private let menuHintView = MenuHintView()
    fileprivate let feedbackGenerator = UIImpactFeedbackGenerator(style: .medium)
    private var snapshot: UIView?
    private var menuView: MenuView?
    
    private let menuOpenThreshold: CGFloat = 100
    
    fileprivate var isShowingMenu = false
    
    init(delegate: StretchyMenuInteractionDelegate) {
        self.delegate = delegate
        
        menuHintView.translatesAutoresizingMaskIntoConstraints = false
    }
    
    func willMove(to view: UIView?) {
        if self.view != nil {
            fatalError("removing StretchyMenuInteraction from view is unsupported")
        }
    }
    
    func didMove(to view: UIView?) {
        self.view = view
        
        guard let view = view else {
            return
        }

        let panRecognizer = UIPanGestureRecognizer(target: self, action: #selector(panGestureRecognized))
        panRecognizer.delegate = self
        panRecognizer.allowedScrollTypesMask = [.continuous]
        view.addGestureRecognizer(panRecognizer)
    }
    
    private var prevTranslation: CGFloat = 0
    
    @objc private func panGestureRecognized(_ recognizer: UIPanGestureRecognizer) {
        guard let view = view,
              !isShowingMenu,
              let delegate = delegate else {
            return
        }
        
        let prevTranslation = self.prevTranslation
        let translation = recognizer.translation(in: view)
        self.prevTranslation = translation.x

        switch recognizer.state {
        case .began:
            snapshot = view.snapshotView(afterScreenUpdates: false)
            let effectiveTranslation = 0.5 * max(0, -translation.x)
            snapshot!.transform = CGAffineTransform(translationX: -effectiveTranslation, y: 0)
            view.addSubview(snapshot!)
            view.insertSubview(menuHintView, belowSubview: snapshot!)
            menuHintView.backgroundColor = view.backgroundColor
            menuHintView.frame = CGRect(x: view.bounds.width - effectiveTranslation, y: 0, width: effectiveTranslation, height: view.bounds.height)
            menuHintView.updateForProgress(0, animate: false)
            feedbackGenerator.prepare()
            
        case .changed:
            let effectiveTranslation = 0.5 * max(0, -translation.x)
            snapshot!.transform = CGAffineTransform(translationX: -effectiveTranslation, y: 0)
            if -prevTranslation < menuOpenThreshold && -translation.x >= menuOpenThreshold {
                feedbackGenerator.impactOccurred()
            }
            menuHintView.frame = CGRect(x: view.bounds.width - effectiveTranslation, y: 0, width: effectiveTranslation, height: view.bounds.height)
            menuHintView.updateForProgress(-translation.x / menuOpenThreshold, animate: true)
            
        case .ended:
            UIView.animate(withDuration: 0.2, delay: 0, options: .curveEaseInOut) {
                self.snapshot!.transform = .identity
            } completion: { _ in
                self.snapshot!.removeFromSuperview()
                self.menuHintView.removeFromSuperview()
            }

            
            if -translation.x > menuOpenThreshold {
                guard let rootView = view.window?.rootViewController?.view else {
                    return
                }
                let menuView = MenuView(title: delegate.stretchyMenuTitle(), items: delegate.stretchyMenuItems(), owner: self)
                self.menuView = menuView
                menuView.translatesAutoresizingMaskIntoConstraints = false
                menuView.layer.zPosition = 102
                rootView.addSubview(menuView)
                NSLayoutConstraint.activate([
                    menuView.leadingAnchor.constraint(equalTo: rootView.leadingAnchor),
                    menuView.trailingAnchor.constraint(equalTo: rootView.trailingAnchor),
                    menuView.topAnchor.constraint(equalTo: rootView.topAnchor),
                    menuView.bottomAnchor.constraint(equalTo: rootView.bottomAnchor),
                ])
                rootView.layoutIfNeeded()
                menuView.animateIn()
                
                isShowingMenu = true
                feedbackGenerator.prepare()
            }
            
        default:
            break
        }
    }
    
    func hideMenu(completion: (() -> Void)? = nil) {
        guard let menuView = menuView else {
            return
        }

        menuView.animateOut() {
            menuView.removeFromSuperview()
            self.isShowingMenu = false
            completion?()
        }
    }
}

extension StretchyMenuInteraction: UIGestureRecognizerDelegate {
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return otherGestureRecognizer.name == AppNavigationController.panRecognizerName
    }
}

private class MenuHintView: UIView {
    private let pill = UIView()
    private var progress: CGFloat = 0
    
    private var animator: UIViewPropertyAnimator?
    
    init() {
        super.init(frame: .zero)
        
        pill.frame = CGRect(x: 0, y: 0, width: 5, height: 50)
        pill.backgroundColor = .systemGray
        pill.layer.cornerRadius = 2.5
        addSubview(pill)
        
        pill.backgroundColor = .systemGray
        pill.frame.size.height = 50
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        let width: CGFloat = 5
        pill.frame.origin.x = bounds.midX - width / 2
        pill.frame.origin.y = bounds.midY - pill.frame.height / 2
    }
    
    func updateForProgress(_ progress: CGFloat, animate: Bool) {
        let oldCompleted = self.progress >= 1
        let completed = progress >= 1
        
        self.progress = progress
        
        if oldCompleted != completed {
            func updatePill() {
                pill.backgroundColor = completed ? .tintColor : .systemGray
                let height: CGFloat = completed ? 75 : 50
                pill.frame.origin.y = bounds.midY - height / 2
                pill.frame.size.height = height
            }
            
            animator?.stopAnimation(true)
            if animate {
                animator = UIViewPropertyAnimator(duration: 0.5, dampingRatio: 0.5, animations: updatePill)
                animator!.startAnimation()
            } else {
                updatePill()
            }
        }
    }
}

private class MenuView: UIView {
    
    weak var owner: StretchyMenuInteraction?
    
    private let blurEffect = UIBlurEffect(style: .systemUltraThinMaterialDark)
    private var blurView: UIView!
    private let optionsStack = UIStackView()
    
    private let items: [StretchyMenuItem]
    
    init(title: String?, items: [StretchyMenuItem], owner: StretchyMenuInteraction) {
        self.items = items
        self.owner = owner
        
        super.init(frame: .zero)
        
        blurView = UIVisualEffectView(effect: blurEffect)
        blurView.translatesAutoresizingMaskIntoConstraints = false
        addSubview(blurView)
        
        optionsStack.axis = .vertical
        optionsStack.alignment = .fill
        optionsStack.spacing = 2
        optionsStack.translatesAutoresizingMaskIntoConstraints = false
        for item in items {
            optionsStack.addArrangedSubview(MenuItemView(item: item, owner: owner))
        }
        addSubview(optionsStack)
        
        if let title = title {
            let titleLabel = UILabel()
            titleLabel.translatesAutoresizingMaskIntoConstraints = false
            titleLabel.text = title
            titleLabel.textAlignment = .right
            titleLabel.font = .preferredFont(forTextStyle: .title1)
            let vibrancyView = UIVisualEffectView(effect: UIVibrancyEffect(blurEffect: blurEffect, style: .label))
            vibrancyView.contentView.addSubview(titleLabel)
            optionsStack.insertArrangedSubview(vibrancyView, at: 0)
            
            NSLayoutConstraint.activate([
                titleLabel.leadingAnchor.constraint(equalToSystemSpacingAfter: vibrancyView.contentView.leadingAnchor, multiplier: 1),
                vibrancyView.contentView.trailingAnchor.constraint(equalToSystemSpacingAfter: titleLabel.trailingAnchor, multiplier: 1),
                titleLabel.topAnchor.constraint(equalTo: vibrancyView.contentView.topAnchor),
                titleLabel.bottomAnchor.constraint(equalTo: vibrancyView.contentView.bottomAnchor),
            ])
        }
        
        NSLayoutConstraint.activate([
            blurView.leadingAnchor.constraint(equalTo: leadingAnchor),
            blurView.trailingAnchor.constraint(equalTo: trailingAnchor),
            blurView.topAnchor.constraint(equalTo: topAnchor),
            blurView.bottomAnchor.constraint(equalTo: bottomAnchor),
            
            optionsStack.leadingAnchor.constraint(equalTo: leadingAnchor),
            optionsStack.trailingAnchor.constraint(equalTo: trailingAnchor),
            optionsStack.centerYAnchor.constraint(equalTo: centerYAnchor),
        ])
        
        blurView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(blurTapped)))
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func animateIn() {
        blurView.layer.opacity = 0
        let count = optionsStack.arrangedSubviews.count
        for (index, item) in optionsStack.arrangedSubviews.enumerated() {
            let multiplier = (1 + CGFloat(index) * 1 / CGFloat(count - 1))
            item.transform = CGAffineTransform(translationX: bounds.width * multiplier, y: 0)
        }
        
        UIView.animate(withDuration: 0.35, delay: 0, options: .curveEaseInOut) {
            self.blurView.layer.opacity = 1
            for item in self.optionsStack.arrangedSubviews {
                item.transform = .identity
            }
        }
    }
    
    func animateOut(completion: @escaping () -> Void) {
        UIView.animate(withDuration: 0.35, delay: 0, options: .curveEaseInOut) {
            self.blurView.layer.opacity = 0
            let count = self.optionsStack.arrangedSubviews.count
            for (index, item) in self.optionsStack.arrangedSubviews.enumerated() {
                let multiplier = (1 + CGFloat(index) * 1 / CGFloat(count - 1))
                item.transform = CGAffineTransform(translationX: self.bounds.width * -multiplier, y: 0)
            }
        } completion: { _ in
            completion()
        }
    }
    
    @objc private func blurTapped() {
        owner?.hideMenu()
    }
    
}

private class MenuItemView: UIView {
    weak var owner: StretchyMenuInteraction?
    
    private let item: StretchyMenuItem
    
    init(item: StretchyMenuItem, owner: StretchyMenuInteraction) {
        self.item = item
        self.owner = owner
        
        super.init(frame: .zero)
        
        backgroundColor = .appBackground
        
        let titleLabel = UILabel()
        titleLabel.translatesAutoresizingMaskIntoConstraints = false
        titleLabel.text = item.title
        titleLabel.textColor = .tintColor
        titleLabel.textAlignment = .right
        titleLabel.font = .preferredFont(forTextStyle: .title2)
        addSubview(titleLabel)
        
        NSLayoutConstraint.activate([
            titleLabel.topAnchor.constraint(equalTo: topAnchor, constant: 4),
            titleLabel.leadingAnchor.constraint(equalToSystemSpacingAfter: leadingAnchor, multiplier: 1),
            trailingAnchor.constraint(equalToSystemSpacingAfter: titleLabel.trailingAnchor, multiplier: 1),
            
            heightAnchor.constraint(greaterThanOrEqualToConstant: 44),
        ])
        
        if let subtitle = item.subtitle {
            let subtitleLabel = UILabel()
            subtitleLabel.translatesAutoresizingMaskIntoConstraints = false
            subtitleLabel.text = subtitle
            subtitleLabel.textColor = .secondaryLabel
            subtitleLabel.textAlignment = .right
            addSubview(subtitleLabel)
            NSLayoutConstraint.activate([
                subtitleLabel.leadingAnchor.constraint(equalToSystemSpacingAfter: leadingAnchor, multiplier: 1),
                trailingAnchor.constraint(equalToSystemSpacingAfter: subtitleLabel.trailingAnchor, multiplier: 1),
                subtitleLabel.topAnchor.constraint(equalTo: titleLabel.bottomAnchor),
                bottomAnchor.constraint(equalTo: subtitleLabel.bottomAnchor, constant: 4),
            ])
        } else {
            NSLayoutConstraint.activate([
                bottomAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant: 4),
            ])
        }
        
        addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(itemTapped)))
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    @objc private func itemTapped() {
        owner?.feedbackGenerator.impactOccurred()
        
        UIView.animateKeyframes(withDuration: 0.15, delay: 0, options: []) {
            UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 0.5) {
                self.backgroundColor = .appSecondaryBackground
            }
            UIView.addKeyframe(withRelativeStartTime: 0.5, relativeDuration: 0.5) {
                self.backgroundColor = .appBackground
            }
        } completion: { _ in
            self.owner?.hideMenu() {
                self.item.action()
            }
        }
    }
    
    func addBorders(top: Bool, bottom: Bool) {
        if top {
            let view = UIView()
            view.translatesAutoresizingMaskIntoConstraints = false
            view.backgroundColor = .systemGray
            addSubview(view)
            NSLayoutConstraint.activate([
                view.heightAnchor.constraint(equalToConstant: 1),
                view.topAnchor.constraint(equalTo: topAnchor),
                view.leadingAnchor.constraint(equalTo: leadingAnchor),
                view.trailingAnchor.constraint(equalTo: trailingAnchor),
            ])
        }
        
        if bottom {
            let view = UIView()
            view.translatesAutoresizingMaskIntoConstraints = false
            view.backgroundColor = .systemGray
            addSubview(view)
            NSLayoutConstraint.activate([
                view.heightAnchor.constraint(equalToConstant: 1),
                view.bottomAnchor.constraint(equalTo: bottomAnchor),
                view.leadingAnchor.constraint(equalTo: leadingAnchor),
                view.trailingAnchor.constraint(equalTo: trailingAnchor),
            ])
        }
    }
    
}