Amazon Alexa Simple Account Linking Server by Golang

main.go

package main

import (
	"encoding/json"
	"log"
	"net/http"
	"os"
	"time"

	"golang.org/x/oauth2"
)

const (
	DefaultPort = "3000"
)

func main() {
	http.HandleFunc("/auth", authHandler)
	http.HandleFunc("/token", tokenHandler)

	port := DefaultPort
	if v := os.Getenv("PORT"); len(v) != 0 {
		port = v
	}

	log.Printf("[INFO] Start listening on %s", port)
	if err := http.ListenAndServe(":"+port, nil); err != nil {
		log.Printf("[ERROR] %s", err)
	}
}

func authHandler(w http.ResponseWriter, r *http.Request) {
	username, password, ok := r.BasicAuth()
	if !ok || !(username == AlexaAdminName && password == AlexaAdminPass) {
		w.Header().Set("WWW-Authenticate", `Basic realm="alexa-auth"`)
		w.WriteHeader(http.StatusUnauthorized)
		w.Write([]byte("Unauthorized"))
		return
	}

	if v := r.FormValue("client_id"); v != ClientID {
		log.Printf("[ERROR] Invalid client_id: %q", v)
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("error"))
		return
	}

	if v := r.FormValue("response_type"); v != "code" {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte("Bad request\n"))
		return
	}

	state := r.FormValue("state")
	if len(state) == 0 {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte("Bad request\n"))
		return
	}

	req, err := http.NewRequest("GET", RedirectURL, nil)
	if err != nil {
		log.Printf("[ERROR] %s", err)
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("Internal Server Error\n"))
		return
	}

	values := req.URL.Query()
	values.Add("state", state)
	values.Add("code", AuthorizationCode)
	req.URL.RawQuery = values.Encode()
	log.Printf("[INFO] location: %s", req.URL.String())

	http.Redirect(w, r, req.URL.String(), http.StatusFound)
}

func tokenHandler(w http.ResponseWriter, r *http.Request) {
	username, password, ok := r.BasicAuth()
	if !ok || !(username == ClientID && password == ClientSecret) {
		w.Header().Set("WWW-Authenticate", `Basic realm="alexa-token"`)
		w.WriteHeader(http.StatusUnauthorized)
		w.Write([]byte("Unauthorized"))
		return
	}

	if v := r.FormValue("grant_type"); v != "authorization_code" {
		log.Printf("[ERROR] Invalid grant_type: %s", v)
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte("Bad request\n"))
		return
	}

	if v := r.FormValue("code"); v != AuthorizationCode {
		log.Printf("[ERROR] Invalid code: %s", v)
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte("Bad request\n"))
		return
	}

	token := oauth2.Token{
		AccessToken:  AccessToken,
		RefreshToken: AccessToken,
		TokenType:    "Bearer",
		Expiry:       time.Now().Add(30 * 24 * time.Hour),
	}

	buf, err := json.Marshal(&token)
	if err != nil {
		log.Printf("[ERROR] Marshal: %s", err)
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("error"))
		return
	}

	w.Header().Add("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	w.Write(buf)
}

hi, thanks for posting this code. can I use port 3000 in production? or do I have to use port 443 ?