alpha-wallet-ios/AlphaWallet/Extensions/UIGestureRecognizer+Closure.swift

// Copyright SIX DAY LLC. All rights reserved.

import Foundation
import UIKit

extension UIGestureRecognizer {
    @discardableResult convenience init(addToView targetView: UIView,
                                        closure: @escaping () -> Void) {
        self.init()

        GestureTarget.add(gesture: self,
                          closure: closure,
                          toView: targetView)
    }
}

private class GestureTarget: UIView {
    class ClosureContainer {
        weak var gesture: UIGestureRecognizer?
        let closure: (() -> Void)

        init(closure: @escaping () -> Void) {
            self.closure = closure
        }
    }

    var containers = [ClosureContainer]()

    convenience init() {
        self.init(frame: .zero)
        isHidden = true
    }

    class func add(
        gesture: UIGestureRecognizer,
        closure: @escaping () -> Void,
        toView targetView: UIView
    ) {
        let target: GestureTarget
        if let existingTarget = existingTarget(inTargetView: targetView) {
            target = existingTarget
        } else {
            target = GestureTarget()
            targetView.addSubview(target)
        }
        let container = ClosureContainer(closure: closure)
        container.gesture = gesture
        target.containers.append(container)

        gesture.addTarget(target, action: #selector(GestureTarget.target(gesture:)))
        targetView.addGestureRecognizer(gesture)
    }

    class func existingTarget(inTargetView targetView: UIView) -> GestureTarget? {
        for subview in targetView.subviews {
            if let target = subview as? GestureTarget {
                return target
            }
        }
        return nil
    }

    func cleanUpContainers() {
        containers = containers.filter({ $0.gesture != nil })
    }

    @objc func target(gesture: UIGestureRecognizer) {
        cleanUpContainers()

        for container in containers {
            guard let containerGesture = container.gesture else {
                continue
            }

            if gesture === containerGesture {
                container.closure()
            }
        }
    }
}