# Intent.FastEndpoints.Dispatch.Mediator

Wires FastEndpoints endpoints to dispatch Commands and Queries through Mediator's `ISender`, so each endpoint hands its request to the handler generated by `Intent.Application.Mediator`.


## What This Module Does

The module has no templates of its own. It replaces the registration of the `EndpointTemplate` from `Intent.FastEndpoints` and extends the result:

- `EndpointTemplateRegistration` creates one endpoint per Command or Query that has HTTP settings in the Services designer. FastEndpoints is one class per operation, so endpoints are not grouped by folder.
- `MediatorEndpointExtension` adds a `Mediator.ISender _sender` constructor parameter (with a null guard) to each of those endpoints and emits the dispatch call in `HandleAsync`.

## Generated Dispatch

The request is sent with `ISender.Send`. The response type is inferred from the Command or Query contract, so there is no type argument.

For a Command that returns a value, followed by the endpoint's normal response (illustrative):

```csharp
public class CreateProductCommandEndpoint : Endpoint<CreateProductCommand, Guid>
{
    private readonly ISender _sender;

    public CreateProductCommandEndpoint(ISender sender)
    {
        _sender = sender ?? throw new ArgumentNullException(nameof(sender));
    }

    public override async Task HandleAsync(CreateProductCommand req, CancellationToken ct)
    {
        var result = Guid.Empty;
        result = await _sender.Send(req, ct);
        // ... response statement from Intent.FastEndpoints
    }
}
```

For a void Command the call is `await _sender.Send(req, ct);` with no result. For a Query with no route or query-string parameters (no `req`), the request is created inline:

```csharp
result = await _sender.Send(new GetProductsQuery(), ct);
```

The dispatch statement carries a `mediator-dispatch` metadata tag so other modules can find it.

## One Dispatch Module Per Application

`Intent.FastEndpoints.Dispatch.Mediator`, `Intent.FastEndpoints.Dispatch.Wolverine` and `Intent.FastEndpoints.Dispatch.MediatR` each replace FastEndpoints' `EndpointTemplate` registration with their own, built from the same Commands and Queries. They are mutually exclusive: install only one of them in an application. Installing more than one makes them compete over the same endpoint files and produces conflicting output.

## Prerequisites

- `Intent.FastEndpoints` - generates the endpoint classes this module extends.
- `Intent.Application.Mediator` - generates the Commands, Queries and handlers, and brings in the `Mediator` library that provides `ISender`.
- `Intent.Modelers.Services.CQRS` - the Command and Query designer elements.

Installing `Intent.FastEndpoints` into an application that already has `Intent.Application.Mediator` installs this module (the core declares it as interoperability).

## Related Modules

- [Intent.FastEndpoints](https://docs.intentarchitect.com/articles/modules-dotnet/intent-fastendpoints/intent-fastendpoints.html) - generates the FastEndpoints endpoint classes this module extends.
- [Intent.FastEndpoints.Dispatch.Wolverine](https://docs.intentarchitect.com/articles/modules-dotnet/intent-fastendpoints-dispatch-wolverine/intent-fastendpoints-dispatch-wolverine.html) - the Wolverine equivalent. Mutually exclusive with this module.
- `Intent.FastEndpoints.Dispatch.MediatR` - the MediatR equivalent (no published page). Mutually exclusive with this module.
- `Intent.AspNetCore.Controllers.Dispatch.Mediator` - equivalent dispatch wiring for ASP.NET Core controllers (no published page yet).
- `Intent.Application.Mediator` - the core module of this family (no published page yet).