Interceptors

[kittinunf]

Introducing Interceptor's concept into Fuel. There are two types of interceptors which are RequestInterceptor and ResponseInterceptor.

RequestInterceptor is in type of (Request) -> Request) -> ((Request) -> Request).

Simple usage of RequestInterceptor is cUrlLoggingInterceptor can be simply implemented as such

fun cUrlLoggingRequestInterceptor() =
        { next: (Request) -> Request ->
            { r: Request ->
                println(r.cUrlString())
                next(r)
            }
        }

And usage will be

//Initialization phase
manager.addRequestInterceptor(cUrlLoggingInterceptor())

manager.request(Method.GET, "https://httpbin.org/get").header("User-Agent", "Fuel").response()

// print
curl -i -H "User-Agent:Fuel" "https://httpbin.org/get"

next is a way to let user customize the behavior of interceptor even more. Without calling next, next interceptor chain will not be called.

For ResponseInterceptor, it is in type of (Request, Response) -> Response -> (Request, Response) -> Response. This makes Redirection to be supported with one type of ResponseInterceptor by checking whether Response type is either 301 or 302. Then, re-request with new URL in location header.