Sequential control

A method is provided to control the behavior of async handlers when they can be executed in duplicate.

It is possible to specify CommandOrdering at each level, such as per Router instance, SubscribeAwait argument, Route method, etc.

public enum CommandOrdering
{
    /// <summary>
    /// If commands are published simultaneously, subscribers are called in parallel.
    /// </summary>
    Parallel,

    /// <summary>
    /// If commands are published simultaneously, wait until the subscriber has processed the first command.
    /// </summary>
    Sequential,

    /// <summary>
    /// If commands are published simultaneously, ignore commands that come later.
    /// </summary>
    Drop,

    /// <summary>
    /// If the previous asynchronous method is running, it is cancelled and the next asynchronous method is executed.
    /// </summary>
    Switch,
}

Parallel

Sequential

Drop

Switch

How to set

// Set sequential constraint to the globally.
Router.Default.AddFilter(CommandOrdering.Sequential);

// Or
var fifoRouter = new Router(CommandOrdering.Sequential);

// Or Configure sequential routing via DI
builder.RegisterVitalRouter(routing => 
{
    routing.CommandOrdering = CommandOrdering.Sequential;
});

// Command ordering per class level
[Routes(CommandOrdering.Sequential)]
public FooPresenter
{
    public async UniTask On(FooCommand cmd)
    {
    }
}

[Routes]
public FooPresenter
{
    // Command ordering per method level
    [Route(CommandOrdering.Sequential)]
    public async UniTask On(FooCommand cmd)
    {
    }
}

// Command ordering per per lambda expressions
router.SubscribeAwait(async (cmd, ctx) => 
{
    /* ... */
}, CommandOrdering.Sequential);