CombineStream.swift

import Combine

public final class CurrentValueStream<T: Sendable>: @unchecked Sendable {

    public init() {
        subject = CurrentValueSubject<T?, Never>(nil)
    }

    public init(initialValue: T) {
        subject = CurrentValueSubject<T?, Never>(initialValue)
    }

    public func sendValue(_ value: T) {
        subject.send(value)
    }

    public func terminate() {
        subject.send(completion: .finished)
    }

    public var stream: AsyncStream<T> {
        AsyncStream { continuation in
            let subscription = subject.sink(receiveCompletion: { _ in
                continuation.finish()
            }, receiveValue: { value in
                guard let value = value else { return }
                continuation.yield(value)
            })

            continuation.onTermination = { _ in
                // Store the subscription until the stream is termianted.
                _ = subscription
            }
        }
    }

    // CurrentValueSubject is not sendable, but since we never use the `value` accessor we can consider ourselves sendable.
    private let subject: CurrentValueSubject<T?, Never>
}

public func +=<T: Sendable> (lhs: CurrentValueStream<T>, rhs: T) {
    lhs.sendValue(rhs)
}