import Foundation

/// The bridge that carries ``RecordingCommand``s from outside the feature's UI into the recording flow.
///
/// The commander exists because the senders of the commands — the App Intents behind a Live Activity's buttons — are instantiated
/// by the system, out of reach of the feature's dependency injection: they send through the process-wide ``shared`` instance, and the
/// feature's model listens to ``commands``, translating every received command into the button press it mirrors. Unit tests create
/// commanders of their own and inject them into the model, leaving the shared instance untouched.
@MainActor
public final class RecordingCommander {

    // MARK: Constants

    /// The process-wide commander the recording flow listens to by default.
    public static let shared = RecordingCommander()

    // MARK: Properties

    /// The stream of commands sent through the commander.
    public let commands: AsyncStream<RecordingCommand>

    /// The continuation that feeds ``commands``.
    private let continuation: AsyncStream<RecordingCommand>.Continuation

    // MARK: Initializers

    /// Creates a commander with an empty stream of commands.
    public init() {
        (commands, continuation) = AsyncStream.makeStream(of: RecordingCommand.self)
    }

    // MARK: Methods

    /// Sends a command to the recording flow listening to the commander.
    ///
    /// - Parameter command: The command to send.
    public func send(
        _ command: RecordingCommand
    ) {
        continuation.yield(command)
    }

}