Featurerequest: Add a 'precondition' to Router. about pistache HOT 7 CLOSED

+1

from pistache.

Hello,

Yes, that indeed sounds like a great suggestion. Basically, we need filters.

We could have two kind of filters: before-filters and after-filters. before-filters will be executed before each requests and can read/write the request/response. after-filters will be executed after each requests and can also read and modify the response.

Now we need to come up with a good API for this, feel free to suggest something if you have any idea :)

from pistache.

@oktal How Go does its HTTP middleware may be a good idea here. They're just simple function wrappers, without the explicit need for having pre/post filter APIs.

from pistache.

@knadh could you provide an example on how Go is handling it ?

If you have a clear idea on how to design it as well as the API to provide, feel free to post it here so that we can discuss it

from pistache.

In Go, functions that satisfy http.Handler (which implements the function ServeHTTP(ResponseWriter, *Request)) can act as middleware. A middleware takes a handler and returns a handler (similar to pistache's (const Rest::Request& request, Http::ResponseWriter response)). Here's some pseudocode that illustrates this.

func enforcePOST(next http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    if r.Method != "POST" {
        http.Error(w, "Method not allowed", 405)
        return
    }

    // All good, continue the request.
    next.ServeHTTP(w, r)
  })
}

func validateUser(next http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    if r.Form.Get("user_id") != 1 {
        http.Error(w, "User is not authorized.", 403)
        return
    }

    // All good, continue the request.
    next.ServeHTTP(w, r)
  })
}

func helloHandler (w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello world! You got past the middleware filters")
})

// Bind the route.
http.Handle("/", validateUser(enforcePOST(helloHandler)))

Here, enforcePost() and validateUser() are middleware functions that can decide to fail or continue a request before it gets to the final handler, helloHandler(). Hope that makes sense.

from pistache.

Makes sense. We could have something similar in Pistache, some sort on Middleware concept. I personally would like to call it Pipeline but it's already a common term in the HTTP world so meh.

Anyway, I'll take some time to think about it. Let me know if you are interested in working on it. We could potentially join our effort and start development in a separate branch

from pistache.

we could add the Pipeline feature to project task and close this issue.

from pistache.