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//
// TransformOperation.swift
// Operations
//
// Created by pronebird on 31/05/2022.
// Copyright © 2022 Mullvad VPN AB. All rights reserved.
//
import Foundation
import protocol MullvadTypes.Cancellable
public final class TransformOperation<Input, Output>: ResultOperation<Output>, InputOperation {
public typealias InputBlock = () -> Input?
private let nslock = NSLock()
public var input: Input? {
return _input
}
private var __input: Input?
private var _input: Input? {
get {
nslock.lock()
defer { nslock.unlock() }
return __input
}
set {
nslock.lock()
__input = newValue
nslock.unlock()
}
}
private var inputBlock: InputBlock?
private var executor: ((Input, @escaping (Result<Output, Error>) -> Void) -> Cancellable?)?
private var cancellableTask: Cancellable?
public init(
dispatchQueue: DispatchQueue? = nil,
input: Input? = nil,
block: @escaping (_ input: Input, _ finish: @escaping (Result<Output, Error>) -> Void) -> Void
) {
super.init(dispatchQueue: dispatchQueue)
__input = input
executor = { input, finish in
block(input, finish)
return nil
}
}
public init(
dispatchQueue: DispatchQueue? = nil,
input: Input? = nil,
throwingBlock: @escaping (_ input: Input) throws -> Output
) {
super.init(dispatchQueue: dispatchQueue)
__input = input
executor = { input, finish in
finish(Result { try throwingBlock(input) })
return nil
}
}
public init(
dispatchQueue: DispatchQueue? = nil,
input: Input? = nil,
cancellableTask: @escaping (_ input: Input, _ finish: @escaping (Result<Output, Error>) -> Void) -> Cancellable
) {
super.init(dispatchQueue: dispatchQueue)
__input = input
executor = cancellableTask
}
override public func main() {
if let inputBlock {
_input = inputBlock()
}
guard let inputValue = _input else {
finish(result: .failure(OperationError.unsatisfiedRequirement))
return
}
let executor = executor
self.executor = nil
assert(executor != nil)
cancellableTask = executor?(inputValue, self.finish)
}
override public func operationDidCancel() {
cancellableTask?.cancel()
}
override public func operationDidFinish() {
executor = nil
cancellableTask = nil
}
// MARK: - Input injection
public func setInputBlock(_ block: @escaping () -> Input?) {
dispatchQueue.async {
self.inputBlock = block
}
}
}
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