// // FetchRequestOperation.swift // NetNewsWire // // Created by Brent Simmons on 6/20/19. // Copyright © 2019 Ranchero Software. All rights reserved. // import Foundation import RSCore import Account import Articles // Main thread only. // Runs an asynchronous fetch. typealias FetchRequestOperationResultBlock = (Set
, FetchRequestOperation) -> Void final class FetchRequestOperation { let id: Int let readFilter: Bool let resultBlock: FetchRequestOperationResultBlock var isCanceled = false var isFinished = false private let representedObjects: [Any] init(id: Int, readFilter: Bool, representedObjects: [Any], resultBlock: @escaping FetchRequestOperationResultBlock) { precondition(Thread.isMainThread) self.id = id self.readFilter = readFilter self.representedObjects = representedObjects self.resultBlock = resultBlock } func run(_ completion: @escaping (FetchRequestOperation) -> Void) { precondition(Thread.isMainThread) precondition(!isFinished) var didCallCompletion = false func callCompletionIfNeeded() { if !didCallCompletion { didCallCompletion = true completion(self) } } if isCanceled { callCompletionIfNeeded() return } let articleFetchers = representedObjects.compactMap{ $0 as? ArticleFetcher } if articleFetchers.isEmpty { isFinished = true resultBlock(Set
(), self) callCompletionIfNeeded() return } let numberOfFetchers = articleFetchers.count var fetchersReturned = 0 var fetchedArticles = Set
() func process(_ articles: Set
) { precondition(Thread.isMainThread) guard !self.isCanceled else { callCompletionIfNeeded() return } assert(!self.isFinished) fetchedArticles.formUnion(articles) fetchersReturned += 1 if fetchersReturned == numberOfFetchers { self.isFinished = true self.resultBlock(fetchedArticles, self) callCompletionIfNeeded() } } for articleFetcher in articleFetchers { if readFilter { articleFetcher.fetchUnreadArticlesAsync { articleSetResult in let articles = (try? articleSetResult.get()) ?? Set
() process(articles) } } else { articleFetcher.fetchArticlesAsync { articleSetResult in let articles = (try? articleSetResult.get()) ?? Set
() process(articles) } } } } }