Emcee

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import CLTExtensions
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import Dispatch
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import Foundation
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public final class EventBus {
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    private var streams = [EventStream]()
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    private let lock = NSLock()
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    private let eventDeliveryQueue = DispatchQueue(label: "ru.avito.EventBus.eventDeliveryQueue")
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    public init() {}
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    public func add(stream: EventStream) {
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        lock.whileLocked {
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            streams.append(stream)
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        }
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    }
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    public func post(event: BusEvent) {
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        lock.whileLocked {
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            streams.forEach { stream in
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                eventDeliveryQueue.async {
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                    stream.process(event: event)
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                }
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            }
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        }
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    }
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    public func uponDeliveryOfAllEvents(work: @escaping () -> ()) {
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        eventDeliveryQueue.async {
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            work()
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        }
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    }
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    public func tearDown() {
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        post(event: .tearDown)
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        eventDeliveryQueue.sync(flags: .barrier) {}
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    }
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}
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