Timer.swift

// Copyright 2021 Cii
//
// This file is part of Shikishi.
//
// Shikishi is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Shikishi is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Shikishi.  If not, see <http://www.gnu.org/licenses/>.

import Dispatch

final class RunTimer {
    private(set) var workItem: DispatchWorkItem?
    private var cancelClosure: (() -> ())?
    func run(afterTime: Double,
             dispatchQueue: DispatchQueue,
             beginClosure: () -> (),
             waitClosure: () -> (),
             cancelClosure: @escaping () -> (),
             endClosure: @escaping () -> ()) {
        if isWait {
            self.workItem?.cancel()
            self.workItem = nil
            waitClosure()
        } else {
            beginClosure()
        }
        var workItem: DispatchWorkItem!
        workItem = DispatchWorkItem(block: { [weak self] in
            if !(workItem?.isCancelled ?? false) {
                workItem = nil
                self?.workItem = nil
                endClosure()
            } else {
                workItem = nil
                self?.workItem = nil
            }
        })
        dispatchQueue.asyncAfter(deadline: DispatchTime.now() + afterTime,
                                 execute: workItem)
        self.workItem = workItem
        self.cancelClosure = cancelClosure
    }
    var isWait: Bool {
        if let workItem = workItem {
            return !workItem.isCancelled
        } else {
            return false
        }
    }
    func cancel() {
        if isWait {
            workItem?.cancel()
            workItem = nil
            cancelClosure?()
        }
    }
}