HTTP API Authentification in R via 0auth - r

Question

I got some problems accessing tracking API via 0auth;
I have sign key, secret and Authorization_key.
Sign key and secret should form a sig file as I understand and authorization_key that should be added as header.
The code:
auth_info <-
read.csv2('./Data/auth_info.csv',
encoding = 'UTF-8',
stringsAsFactors = F)
express <-
oauth_app("express", key = 'Ur1475', secret = auth_info$sign_key)
sig <- sign_oauth1.0(express)
order <-
GET(
"http://www.express.ru/api/v2/getOrder?orderNumber=WEBN3141018",
authenticate("Ur1475", auth_info$sign_key),
add_headers(Authorization = auth_info$auth_key),
sig
)
order_info <- content(order)
order_info
Returns me auth error;
Official api documentation tells that should be formed md5(client key . URL . GET params . POST params . sign key).
Also I've looked at 0auth function code it does not use http.
Could it cause the problem?
Could you please comment on how to get data from API via R?
API doc (in russian)): https://www.express.ru/docs/APIExpressRu.pdf

Answer 1

The major of API's (Google, Twitter, Facebook) need a token that you must to obtain from an oauth authentication. Depending from the API's you must to use the functions GETor POST. And you must to provide your key encoded in base64. So what I think you need is:
First: Authenticate.
if(!require("jsonlite")){library("jsonlite")}
if(!require("httr")){library("httr")}
#Create your own appication key
consumer_key <- "your consumer key" #needed
consumer_secret <- "your consumer secret" #some api's don't need.
#Use basic auth
secret <- jsonlite::base64_enc(paste(consumer_key, consumer_secret, sep = ":"))
req <- httr::POST("https://url.of.your.api/oauth/token", #"oauth" and "token" are not parameters, they are fixed.
httr::add_headers(
"Authorization" = paste("Basic", gsub("\n", "", secret)),
"Content-Type" = "application/x-www-form-urlencoded;charset=UTF-8"
),
body = "grant_type=client_credentials"
)
#Extract the access token
token <- paste("Bearer", httr::content(req)$access_token)
Next: Make a request.
url<-"http://url.of.your.api/search?parameter1=value&parameter2=value"
req <- httr::POST(url, httr::add_headers("Authorization" = token))
json <- httr::content(req)
json
As I said, some API's need GETand others POST, try both.