import Foundation
import RastrilloApple

/// The transport supplier a window hands its workspace, for one account.
///
/// A workspace's model can outlive a session of its account, so it asks for
/// the connection's current client on every request instead of keeping one.
/// It must never be handed another account's session, even for a moment:
/// SwiftUI can still be finishing a request or holding a stream for the old
/// workspace after the window switches accounts.
public enum DocsAccountTransport {
    @MainActor public static func supplier(account: String?,
                                           active: @escaping @MainActor () -> String?,
                                           client: @escaping @MainActor () -> NativeTransport?) -> @MainActor () -> NativeTransport? {
        return {
            // Checked on every request, not when the supplier is made: a
            // switch can land while a save or stream reconnect is in flight.
            guard let account, active() == account else { return nil }
            return client()
        }
    }
}