//
//  UIGestureRecognizer.swift
//  VDS
//
//  Created by Matt Bruce on 8/31/22.
//

import Foundation
import UIKit
import Combine

extension UIView {
    
    public func publisher<G>(for gestureRecognizer: G) -> UIGestureRecognizer.Publisher<G> where G: UIGestureRecognizer {
        UIGestureRecognizer.Publisher(gestureRecognizer: gestureRecognizer, view: self)
    }
}

extension UIGestureRecognizer {
    
    public struct Publisher<G>: Combine.Publisher where G: UIGestureRecognizer {
        
        public typealias Output = G
        public typealias Failure = Never
        
        public let gestureRecognizer: G
        public let view: UIView
        
        public func receive<S>(subscriber: S) where S : Subscriber, Failure == S.Failure, Output == S.Input {
            subscriber.receive(
                subscription: Subscription(subscriber: subscriber, gestureRecognizer: gestureRecognizer, on: view)
            )
        }
    }
    
    public class Subscription<G: UIGestureRecognizer, S: Subscriber>: Combine.Subscription where S.Input == G, S.Failure == Never {
        
        public var subscriber: S?
        public let gestureRecognizer: G
        public let view: UIView
        
        public init(subscriber: S, gestureRecognizer: G, on view: UIView) {
            self.subscriber = subscriber
            self.gestureRecognizer = gestureRecognizer
            self.view = view
            gestureRecognizer.addTarget(self, action: #selector(gestureHandler))
            view.addGestureRecognizer(gestureRecognizer)
        }
        
        @objc private func gestureHandler(_ gesture: UIGestureRecognizer) {
            _ = subscriber?.receive(gestureRecognizer)
        }
        
        public func cancel() {
            view.removeGestureRecognizer(gestureRecognizer)
        }
        
        public func request(_ demand: Subscribers.Demand) { }
    }
}