// Free to copy, use and modify for all types of software projects

import UIKit

// ************** Protocol ***************
/// Closurable protocol
protocol Closurable: class {}
// restrict protocol to only classes => can refer to the class instance in the protocol extension
extension Closurable {

  // Create container for closure, store it and return it
  func getContainer(for closure: @escaping (Self) -> Void) -> ClosureContainer<Self> {
    weak var weakSelf = self
    let container = ClosureContainer(closure: closure, caller: weakSelf)
    // store the container so that it can be called later, we do not need to explicitly retrieve it.
    objc_setAssociatedObject(self, Unmanaged.passUnretained(self).toOpaque(), container as AnyObject!, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
    return container
  }
}

/// Container class for closures, so that closure can be stored as an associated object
final class ClosureContainer<T: Closurable> {

  var closure: (T) -> Void
  var caller: T?

  init(closure: @escaping (T) -> Void, caller: T?) {
    self.closure = closure
    self.caller = caller
  }

  // method for the target action, visible to UIKit classes via @objc
  @objc func processHandler() {
    if let caller = caller {
      closure(caller)
    }
  }

  // target action
  var action: Selector { return #selector(processHandler) }
}

// ************** UIKit extensions ***************
/// extension for UIButton - actions with closure
extension UIButton: Closurable {

  func addTarget(forControlEvents: UIControlEvents = .touchUpInside, closure: @escaping (UIButton) -> Void) {
    let container = getContainer(for: closure)
    addTarget(container, action: container.action, for: forControlEvents)
  }
}

/// extension for UIPageControl - actions with closure
extension UIPageControl: Closurable {

  func addTarget(forControlEvents: UIControlEvents = .valueChanged, closure: @escaping (UIPageControl) -> Void) {
    let container = getContainer(for: closure)
    addTarget(container, action: container.action, for: forControlEvents)
  }
}

/// extension for UIGestureRecognizer - actions with closure
extension UIGestureRecognizer: Closurable {

  convenience init(closure: @escaping (UIGestureRecognizer) -> Void) {
    self.init()
    let container = getContainer(for: closure)
    addTarget(container, action: container.action)
  }
}

/// extension for UIBarButtonItem - actions with closure
extension UIBarButtonItem: Closurable {

  convenience init(image: UIImage?, style: UIBarButtonItemStyle = .plain, closure: @escaping (UIBarButtonItem) -> Void) {
    self.init(image: image, style: style, target: nil, action: nil)
    let container = getContainer(for: closure)
    target = container
    action = container.action
  }

  convenience init(title: String?, style: UIBarButtonItemStyle = .plain, closure: @escaping (UIBarButtonItem) -> Void) {
    self.init(title: title, style: style, target: nil, action: nil)
    let container = getContainer(for: closure)
    target = container
    action = container.action
  }
}