CRS 2 Design

[clegendre]

Main interface ICommandHandler is renamed to IRequestHandler (to support commands and events...) and does no longer returns a result (but Task obviously).

    public interface IRequestHandler<T>
    {
        Task HandleAsync( T request, ICommandContext context );
    }

This enforces to treat impacts of a command like pure events.
What are your thoughts about that?
Is it really what we want?
Should CRS still offers a way to return "synchronous" results of a command or should we left this usage for simple REST-like interactions ?

[clegendre]

The question is: should we consider the result of a command or only its impact on the system?

[clegendre]

Command 
     -> CommandHandler 
          -> Can emit Events -> EventHandler 
                   ->  Can dispatch WebSocketEvent -> WebSocket client handler
          -> Can dispatch WebSocketEvent -> WebSocket client handler

There is one constraint: WebSocketEvents can only be published by the CRS endpoint, which holds the WebSocket connection.

[clegendre]

The kernel supports now both command handlers with and without results, and event handlers.
The runtime is shipped with a default asynchronous, in-memory, non-resilient implementation of IBus interface.

    public interface ICommandHandler<T> : ICommandHandler
    {
        /// <summary>
        /// Handles a request with the given <see cref="ICommandContext"/>.
        /// </summary>
        /// <remarks>
        /// If the request is like a Command, the context is the one of this command. 
        /// If the request is like an Event, the context is the original command that raises this event.</remarks>
        /// <param name="request">The request to handle.</param>
        /// <param name="context">The command context. See remarks.</param>
        /// <returns></returns>
        Task HandleAsync( T request, ICommandContext context );
    }

    public interface ICommandHandler<T, TResult> : ICommandHandlerWithResult
    {
        /// <summary>
        /// Handles a request with the given <see cref="ICommandContext"/>.
        /// </summary>
        /// <remarks>
        /// If the request is like a Command, the context is the one of this command. 
        /// If the request is like an Event, the context is the original command that raises this event.</remarks>
        /// <param name="request">The request to handle.</param>
        /// <param name="context">The command context. See remarks.</param>
        /// <returns></returns>
        Task<TResult> HandleAsync( T request, ICommandContext context );
    }

    public interface IEventHandler<T>: IEventHandler
    {
        Task HandleAsync( T request, ICommandContext context );
    }