Refresh Token for Access Token Google API: R Code - r

Question

I am attempting to retrieve an access token using my refresh token, client id and client secret for the youtube api using R Code.
This is google's example of how to POST a request.
POST /o/oauth2/token HTTP/1.1 Host: accounts.google.com Content-Type: application/x-www-form-urlencoded client_id=21302922996.apps.googleusercontent.com&client_secret=XTHhXh1SlUNgvyWGwDk1EjXB&refresh_token=1/6BMfW9j53gdGImsixUH6kU5RsR4zwI9lUVX-tqf8JXQ&grant_type=refresh_token
This was my r code:
library(httr)
url<- paste("https://accounts.google.com/o/oauth2/token?client_id=", client_id, "&client_secret=", client_secret, "&refresh_token=", refresh_token, "&grant_type=access_token", sep="")
POST(url)
And I keep getting this response:
Response [https://accounts.google.com/o/oauth2/token?client_id=xxxxxxxxxx&client_secret=xxxxxxxx&refresh_token=xxxxxxxxxxxxxxxxxxxxxx&grant_type=refresh_token]
Date: 2015-09-02 16:43
Status: 400
Content-Type: application/json
Size: 102 B
{
"error" : "invalid_request",
"error_description" : "Required parameter is missing: grant_type"
Is there a better way to do this? Maybe using RCurl? If so, what would the format of the request be? I would appreciate help on this!

Answer 1

The RAdwords package has a function to retrieve the refresh token. If you don't want to add the entire package you can just add the following code to your script.
refreshToken = function(google_auth) {
# This function refreshes the access token.
# The access token deprecates after one hour and has to updated
# with the refresh token.
#
# Args:
# access.token$refreh_token and credentials as input
# Returns:
# New access.token with corresponding time stamp
rt = rjson::fromJSON(RCurl::postForm('https://accounts.google.com/o/oauth2/token',
refresh_token=google_auth$access$refresh_token,
client_id=google_auth$credentials$c.id,
client_secret=google_auth$credentials$c.secret,
grant_type="refresh_token",
style="POST",
.opts = list(ssl.verifypeer = FALSE)))
access <- rt
access
}