compose handlers in go

composehandlers.go

// CountRequests is middleware for standard handler functions
func (vc *VascoClient) CountRequests(handler http.HandlerFunc) http.HandlerFunc {
    return func(rw http.ResponseWriter, req *http.Request) {
        // we use a recorder as our response writer so we can inspect it
        recorder := httptest.NewRecorder()
        // now call the original handler with our recorder
        handler(recorder, req)

        // switch on the result
        code := recorder.Code
        switch {
        case code >= 400 && code <= 499:
            vc.CountUserError()
        case code >= 500 && code <= 599:
            vc.CountServerError()
        default:
        }
        vc.CountQuery()

        // and now play back the stuff that the handler set
        for k, v := range recorder.Header() {
            rw.Header()[k] = v
        }
        rw.WriteHeader(recorder.Code)
        rw.Write(recorder.Body.Bytes())
    }
}

// LogRequests is middleware
func (vc *VascoClient) LogRequests(handler http.HandlerFunc) http.HandlerFunc {
    return func(rw http.ResponseWriter, req *http.Request) {
        log.Printf("%s %s\n", req.Method, req.URL)
        handler(rw, req)
    }
}

// CL is middleware that composes LogRequests and CountRequests
func (vc *VascoClient) CL(handler http.HandlerFunc) http.HandlerFunc {
    return vc.LogRequests(vc.CountRequests(handler))
}