main.go

package main

import (
	"io/ioutil"
	"log"
	"net/http"
	"os"

	"github.com/gorilla/mux"
)

// DispatchRequest returns response received from target resource
func DispatchRequest(w http.ResponseWriter, r *http.Request) {
	// params := mux.Vars(r) // Need to embed optional slash parsinfg in URL
	params := r.URL.Query()
	targetURL := params.Get("u")

	if targetURL == "" {
		w.Write([]byte("Exiting request. URL not specified."))
		return
	}

	// TBD: Validate `targetURL` structure in preflight request (1).
	// TBD: Allow more params for customized functionality (2).

	response, err := http.Get(targetURL)
	if err != nil {
		w.Write([]byte("Something went wrong :("))
	}
	defer response.Body.Close()
	body, err := ioutil.ReadAll(response.Body)
	w.Header().Set("X-Frame-Options", "SAMEORIGIN")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Write([]byte(string(body)))
}

func main() {
	r := mux.NewRouter()
	port := os.Getenv("PORT")

	if port == "" {
		port = "8080"
	}

	r.
		PathPrefix("/static/").
		Handler(http.StripPrefix("/static/",
			http.FileServer(http.Dir("."+"/static/"))))

	r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		htmlContent, err := ioutil.ReadFile("static/usage.html")
		if err != nil {
			w.Write([]byte("There's a runtime issue with the app :("))
		} else {
			w.Write([]byte(htmlContent))
		}
	}).Methods("GET")

	r.HandleFunc("/proxy", DispatchRequest).Methods("GET")

	log.Fatal(http.ListenAndServe(":"+port, r))
}