import Foundation

final class RDEPUBMetadataParseCancellationController {

    let token: UUID

    private let lock = NSLock()

    private weak var queue: OperationQueue?

    private var cancelled = false

    init(token: UUID) {
        self.token = token
    }

    func attach(queue: OperationQueue) {
        let shouldCancelImmediately: Bool
        lock.lock()
        self.queue = queue
        shouldCancelImmediately = cancelled
        lock.unlock()

        if shouldCancelImmediately {
            queue.cancelAllOperations()
        }
    }

    func cancel() {
        let queueToCancel: OperationQueue?
        lock.lock()
        cancelled = true
        queueToCancel = queue
        lock.unlock()
        queueToCancel?.cancelAllOperations()
    }

    var isCancelled: Bool {
        lock.lock()
        let value = cancelled
        lock.unlock()
        return value
    }
}