61 lines
1.4 KiB
Swift
61 lines
1.4 KiB
Swift
//
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// FetchRequestQueue.swift
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// NetNewsWire
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//
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// Created by Brent Simmons on 6/20/19.
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// Copyright © 2019 Ranchero Software. All rights reserved.
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//
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import Foundation
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@MainActor final class FetchRequestQueue {
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private var pendingRequests = [FetchRequestOperation]()
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private var currentRequest: FetchRequestOperation? = nil
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var isAnyCurrentRequest: Bool {
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if let currentRequest = currentRequest {
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return !currentRequest.isCanceled
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}
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return false
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}
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func cancelAllRequests() {
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precondition(Thread.isMainThread)
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for request in pendingRequests {
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request.isCanceled = true
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}
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currentRequest?.isCanceled = true
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pendingRequests = [FetchRequestOperation]()
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}
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func add(_ fetchRequestOperation: FetchRequestOperation) {
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precondition(Thread.isMainThread)
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pendingRequests.append(fetchRequestOperation)
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runNextRequestIfNeeded()
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}
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}
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private extension FetchRequestQueue {
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func runNextRequestIfNeeded() {
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precondition(Thread.isMainThread)
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removeCanceledAndFinishedRequests()
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guard currentRequest == nil, let requestToRun = pendingRequests.first else {
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return
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}
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currentRequest = requestToRun
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pendingRequests.removeFirst()
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currentRequest!.run { (fetchRequestOperation) in
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precondition(fetchRequestOperation === self.currentRequest)
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self.currentRequest = nil
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self.runNextRequestIfNeeded()
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}
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}
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func removeCanceledAndFinishedRequests() {
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pendingRequests = pendingRequests.filter{ !$0.isCanceled && !$0.isFinished }
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}
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}
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