DelayScheduler.swift

//
//  DelayScheduler.swift
//
//  Created by Daniel Tartaglia on 4/20/17.
//  Copyright © 2017 Daniel Tartaglia. MIT License.
//

final class DelayScheduler: ImmediateSchedulerType {

    init(delay: TimeInterval, queue: DispatchQueue = .main) {
        self.queue = queue
        dispatchDelay = delay
    }

    func schedule<StateType>(_ state: StateType, action: @escaping (StateType) -> Disposable) -> Disposable {
        let cancel = SingleAssignmentDisposable()
        lastDispatch = max(lastDispatch + dispatchDelay, .now())
        queue.asyncAfter(deadline: lastDispatch) {
            guard cancel.isDisposed == false else { return }
            cancel.setDisposable(action(state))
        }
        return cancel
    }

    private var lastDispatch: DispatchTime = .now()
    private let queue: DispatchQueue
    private let dispatchDelay: TimeInterval
}