using System;
using System.Threading;
using System.Threading.Tasks;

namespace MediaBrowser.Controller.Session;

/// <summary>
/// Point-to-point delivery between instances: every instance listens on a channel of its own, so a
/// message can be addressed to the one instance holding a given connection.
/// </summary>
public interface IPodMessageBus
{
    /// <summary>
    /// Gets the identity of this instance.
    /// </summary>
    string PodId { get; }

    /// <summary>
    /// Sends a message to one instance and waits for that instance to report what it did with it. The
    /// number of subscribers only proves the target's connection to the broker is up, so delivery is
    /// taken from the acknowledgement of the instance that has to act on the message.
    /// </summary>
    /// <param name="targetPod">The instance to deliver to.</param>
    /// <param name="message">The message.</param>
    /// <param name="cancellationToken">The cancellation token.</param>
    /// <returns><c>true</c> if the target acknowledged having carried the message out.</returns>
    Task<bool> RequestAsync(string targetPod, PodMessage message, CancellationToken cancellationToken = default);

    /// <summary>
    /// Registers a handler for the messages addressed to this instance. Whatever the handler returns is
    /// sent back to the origin as the acknowledgement.
    /// </summary>
    /// <param name="handler">The handler.</param>
    void Subscribe(Func<PodMessage, Task<bool>> handler);
}