/// Copyright (c) 2022 Razeware LLC
/// 
/// Permission is hereby granted, free of charge, to any person obtaining a copy
/// of this software and associated documentation files (the "Software"), to deal
/// in the Software without restriction, including without limitation the rights
/// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
/// copies of the Software, and to permit persons to whom the Software is
/// furnished to do so, subject to the following conditions:
/// 
/// The above copyright notice and this permission notice shall be included in
/// all copies or substantial portions of the Software.
/// 
/// Notwithstanding the foregoing, you may not use, copy, modify, merge, publish,
/// distribute, sublicense, create a derivative work, and/or sell copies of the
/// Software in any work that is designed, intended, or marketed for pedagogical or
/// instructional purposes related to programming, coding, application development,
/// or information technology.  Permission for such use, copying, modification,
/// merger, publication, distribution, sublicensing, creation of derivative works,
/// or sale is expressly withheld.
/// 
/// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
/// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
/// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
/// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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/// THE SOFTWARE.

import Foundation
import UIKit

class TickleGestureRecognizer: UIGestureRecognizer {
  // 1
  private let requiredTickles = 2
  private let distanceForTickleGesture: CGFloat = 25

  // 2
  enum TickleDirection {
    case unknown
    case left
    case right
  }

  // 3
  private var tickleCount = 0
  private var tickleStartLocation: CGPoint = .zero
  private var latestDirection: TickleDirection = .unknown
    
    override func reset() {
      tickleCount = 0
      latestDirection = .unknown
      tickleStartLocation = .zero

      if state == .possible {
        state = .failed
      }
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
      guard let touch = touches.first else {
        return
      }

      tickleStartLocation = touch.location(in: view)
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
      guard let touch = touches.first else {
        return
      }

      let tickleLocation = touch.location(in: view)

      let horizontalDifference = tickleLocation.x - tickleStartLocation.x

      if abs(horizontalDifference) < distanceForTickleGesture {
        return
      }

      let direction: TickleDirection

      if horizontalDifference < 0 {
        direction = .left
      } else {
        direction = .right
      }

      if latestDirection == .unknown ||
        (latestDirection == .left && direction == .right) ||
        (latestDirection == .right && direction == .left) {

        tickleStartLocation = tickleLocation
        latestDirection = direction
        tickleCount += 1

        if state == .possible && tickleCount > requiredTickles {
          state = .ended
        }
      }
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent) {
      reset()
    }

    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent) {
      reset()
    }

    
    
}

