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//
// ExclusivityController.swift
// MullvadVPN
//
// Created by pronebird on 06/07/2020.
// Copyright © 2020 Mullvad VPN AB. All rights reserved.
//
import Foundation
class ExclusivityController<Category> where Category: Hashable {
private let operationQueue: OperationQueue
private let lock = NSRecursiveLock()
private var operations: [Category: [Operation]] = [:]
private var observers: [Operation: NSObjectProtocol] = [:]
init(operationQueue: OperationQueue) {
self.operationQueue = operationQueue
}
func addOperation(_ operation: Operation, categories: [Category]) {
addOperations([operation], categories: categories)
}
func addOperations(_ operations: [Operation], categories: [Category]) {
lock.withCriticalBlock {
for operation in operations {
for category in categories {
addDependencies(operation: operation, category: category)
}
observers[operation] = operation.observe(\.isFinished, options: [.initial, .new]) { [weak self] (op, change) in
if let isFinished = change.newValue, isFinished {
self?.operationDidFinish(op, categories: categories)
}
}
}
operationQueue.addOperations(operations, waitUntilFinished: false)
}
}
private func addDependencies(operation: Operation, category: Category) {
var exclusiveOperations = self.operations[category] ?? []
if let dependency = exclusiveOperations.last, !operation.dependencies.contains(dependency) {
operation.addDependency(dependency)
}
exclusiveOperations.append(operation)
self.operations[category] = exclusiveOperations
}
private func operationDidFinish(_ operation: Operation, categories: [Category]) {
lock.withCriticalBlock {
for category in categories {
var exclusiveOperations = self.operations[category] ?? []
exclusiveOperations.removeAll { (storedOperation) -> Bool in
return operation == storedOperation
}
self.operations[category] = exclusiveOperations
}
self.observers.removeValue(forKey: operation)
}
}
}
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