utilities.go

package main

import (
	"net/http"
	log "github.com/Sirupsen/logrus"
	b64 "encoding/base64"
	"fmt"
	"net/url"
	"bytes"
	"strconv"
	"io/ioutil"
	"encoding/json"
)

type BearerToken struct {
	AccessToken string `json:"access_token"`
}

func (h *HTTPClientHandler) getBearerToken() BearerToken {
	client := h.http.HTTPClient
	//Step 1: Encode consumer key and secret
	encodedKeySecret := b64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s:%s", url.QueryEscape(AppConfig.TwitterKey),
		url.QueryEscape(AppConfig.TwitterSecret))))

	//Step 2: Obtain a bearer token
	//The body of the request must be grant_type=client_credentials
	reqBody := bytes.NewBuffer([]byte(`grant_type=client_credentials`))
	//The request must be a HTTP POST request
	req, err := http.NewRequest("POST", "https://api.twitter.com/oauth2/token", reqBody)
	if err != nil {
		log.Fatal(err, client, req)
	}
	//The request must include an Authorization header formatted as
	//Basic <base64 encoded value from step 1>.
	req.Header.Add("Authorization", fmt.Sprintf("Basic %s", encodedKeySecret))
	//The request must include a Content-Type header with
	//the value of application/x-www-form-urlencoded;charset=UTF-8.
	req.Header.Add("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8")
	req.Header.Add("Content-Length", strconv.Itoa(reqBody.Len()))

	//Issue the request and get the bearer token from the JSON you get back
	resp, err := client.Do(req)
	if err != nil {
		log.Fatal(err, resp)
	}
	defer resp.Body.Close()
	respBody, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		log.Fatal(err, respBody)
	}

	var b BearerToken
	json.Unmarshal(respBody, &b)

	return b
}