//
//  UIView+Gesture.swift
//  Mastodon
//
//  Created by sxiaojian on 2021/4/14.
//

import Combine
import Foundation
import UIKit

struct GesturePublisher: Publisher {
    typealias Output = GestureType
    typealias Failure = Never
    private let view: UIView
    private let gestureType: GestureType
    init(view: UIView, gestureType: GestureType) {
        self.view = view
        self.gestureType = gestureType
    }

    func receive<S>(subscriber: S) where S: Subscriber,
        GesturePublisher.Failure == S.Failure, GesturePublisher.Output
        == S.Input
    {
        let subscription = GestureSubscription(
            subscriber: subscriber,
            view: view,
            gestureType: gestureType
        )
        subscriber.receive(subscription: subscription)
    }
}

enum GestureType {
    case tap(UITapGestureRecognizer = .init())
    case swipe(UISwipeGestureRecognizer = .init())
    case longPress(UILongPressGestureRecognizer = .init())
    case pan(UIPanGestureRecognizer = .init())
    case pinch(UIPinchGestureRecognizer = .init())
    case edge(UIScreenEdgePanGestureRecognizer = .init())
    func get() -> UIGestureRecognizer {
        switch self {
        case let .tap(tapGesture):
            return tapGesture
        case let .swipe(swipeGesture):
            return swipeGesture
        case let .longPress(longPressGesture):
            return longPressGesture
        case let .pan(panGesture):
            return panGesture
        case let .pinch(pinchGesture):
            return pinchGesture
        case let .edge(edgePanGesture):
            return edgePanGesture
        }
    }
}

class GestureSubscription<S: Subscriber>: Subscription where S.Input == GestureType, S.Failure == Never {
    private var subscriber: S?
    private var gestureType: GestureType
    private var view: UIView
    init(subscriber: S, view: UIView, gestureType: GestureType) {
        self.subscriber = subscriber
        self.view = view
        self.gestureType = gestureType
        configureGesture(gestureType)
    }

    private func configureGesture(_ gestureType: GestureType) {
        let gesture = gestureType.get()
        gesture.addTarget(self, action: #selector(handler))
        view.addGestureRecognizer(gesture)
    }

    func request(_ demand: Subscribers.Demand) {}
    func cancel() {
        subscriber = nil
    }

    @objc
    private func handler() {
        _ = subscriber?.receive(gestureType)
    }
}

extension UIView {
    func gesture(_ gestureType: GestureType = .tap()) -> GesturePublisher {
        isUserInteractionEnabled = true
        return GesturePublisher(view: self, gestureType: gestureType)
    }
}