Allow users to load their mocked endpoint via json spec file

[phalvesr]

I've just discovered this library recently and it's quite nice, but there is a feature I was wondering if we could get add. The feature would be allow users to load their endpoints using a json file, similarly to what json server does. Thinking about user experience, maybe follow the below example:

var httpServer = new HttpServer();
httpServer.Config.FromJsonFile("path/to/json_spec.json");

Considering a json spec file in the below format:

{
  "Routes": [
      {
        "Method": "GET",
        "Url": "/hello-world",
        "Body": "Hello from route.json!",
        "StatusCode": 200,
        "RequestHeaders": {
          "Authorization": "Bearer ey..."
        },
        "ResponseHeaders": {
          "CorrelationId": "00000000-0000-0000-0000-00000000"
        }
      },
      {
        "Method": "POST",
        "Url": "/hello-world",
        "Body": "{\"Data\": { \"Fullname\": \"JOHN DOE\", \"Age\": 42 }}",
        "StatusCode": 200
      }
    ]
}

We can get the proposed experience with the following changes (using .Net 6 sintax):

• Create a model for the JsonSpec file:

public sealed class JsonSpec
{
    public IEnumerable<JsonSpecItem> Routes { get; init; } = default!;
}

• Create a model for the route definition

public sealed class JsonSpecItem
{
    public string Method { get; init; } = default!;
    public string Url { get; init; } = default!;
    public string Body { get; init; } = default!;
    public int StatusCode { get; init; } = default!;
    public Dictionary<string, string> RequestHeaders { get; init; } = default!;
    public Dictionary<string, string> ResponseHeaders { get; init; } = default!;
} 

• Implement an extension method to handle the route registration

public static void FromJsonFile(this IRequestBuilder builder, string jsonSpecPath)
{
        var specAsJson = File.ReadAllText(jsonSpecPath);

        var spec = JsonSerializer.Deserialize<JsonSpec>(specAsJson);

        foreach (var route in spec.Routes)
        {
            builder.Request(route.Method, route.Url, route.RequestHeaders)
                .Send(route.Body, route.StatusCode, route.ResponseHeaders);
        }
}

Calling the endpoint, for example, the "hello-world" from the json example with the following curl command:

curl -v -H "Authorization: Bearer ey..." http://localhost:5000/hello-world

would produce the following output:

*   Trying 127.0.0.1:5000...
* Connected to localhost (127.0.0.1) port 5000 (#0)
> GET /hello-world HTTP/1.1
> Host: localhost:5000
> User-Agent: curl/7.83.1
> Accept: */*
> Authorization: Bearer ey...
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Server: Kestrel
< Transfer-Encoding: chunked
< CorrelationId: 00000000-0000-0000-0000-00000000
<
Hello from test route.json!

I would be happy to implement the pointed changes (with maybe some changes) in the project 😊

[benyblack]

Sorry for the very late response. Was super busy recently. Looks good to me but a bit difficult to find a time to implement. Pull requests are welcome.