add GetFitOauth2Token function

.gitignore

@@ -5,3 +5,4 @@
 RGoogleFit.Rproj
 RGoogleFit.Rcheck
 *.tar.gz
+.httr-oauth

RGoogleFit/.Rbuildignore

@@ -1,2 +1,3 @@
 ^.*\.Rproj$
 ^\.Rproj\.user$
+.httr-oauth

RGoogleFit/DESCRIPTION

@@ -1,7 +1,7 @@
 Package: RGoogleFit
 Type: Package
 Title: R Interface to Google Fit API
-Version: 0.1.0
+Version: 0.2.0
 Author: Marcin Szymanski
 Maintainer: Marcin Szymanski <[email protected]>
 Description: Provides interface to Google Fit REST API v1 (see <https://developers.google.com/fit/rest/v1/reference/>). 
@@ -11,7 +11,8 @@ Depends:
     R (>= 3.0),
     RCurl,
     jsonlite,
-    bit64
+    bit64,
+    httr
 Imports:
     utils
 RoxygenNote: 5.0.1

RGoogleFit/NAMESPACE

@@ -3,8 +3,10 @@
 export(GetFitDataset)
 export(GetFitDatasource)
 export(GetFitDatasources)
+export(GetFitOauth2Token)
 export(NanosToPOSIXct)
 import(RCurl)
 import(bit64)
+import(httr)
 import(jsonlite)
 importFrom(utils,URLencode)

RGoogleFit/NEWS

@@ -0,0 +1,9 @@
+RGoogleFit 0.2.0
+----------------------------------------------------------------
+
+* new function GetFitOauth2Token to simplify OAuth2 authentication
+
+RGoogleFit 0.1.0
+----------------------------------------------------------------
+
+* initial release

RGoogleFit/R/GetFitOAuth2Token.R

@@ -0,0 +1,47 @@
+#' @title GetFitOauth2Token
+#' @rdname GetFitOauth2Token
+#' @description
+#' Retrieves or refreshes an OAuth2 token. Two options must be set:
+#' \code{RGoogleFit.client_id}
+#' \code{RGoogleFit.client_secret}
+#' @export
+GetFitOauth2Token <- function() {
+  client_id = getOption('RGoogleFit.client_id')
+  client_secret = getOption('RGoogleFit.client_secret')
+
+  assert(!is.null(client_id),
+         'Please set \'RGoogleFit.client_id\' option')
+  assert(!is.null(client_secret),
+         'Please set \'RGoogleFit.client_secret\' option')
+
+  oauth2_token <- get0('RGoogleFit.token')
+
+  if (!is.null(oauth2_token)) {
+    if (!oauth2_token$validate()) {
+      oauth2_token$refresh()
+    }
+
+  }
+  else
+  {
+    oauth2_token <- oauth2.0_token(
+      endpoint = oauth_endpoints("google"),
+      app = oauth_app(
+        "google",
+        key = getOption("RGoogleFit.client_id"),
+        secret = getOption("RGoogleFit.client_secret")
+      ),
+      scope = c(
+        "https://www.googleapis.com/auth/fitness.activity.read",
+        "https://www.googleapis.com/auth/fitness.location.read"
+      ) ,
+      use_oob = FALSE,
+      cache = TRUE
+    )
+  }
+
+  assign('RGoogleFit.token', oauth2_token)
+
+  return(oauth2_token$credentials$access_token)
+
+}

RGoogleFit/R/RGoogleFit-package.R

@@ -8,6 +8,6 @@
 #'
 #' @name RGoogleFit-package
 #' @docType package
-#' @import RCurl jsonlite bit64
+#' @import RCurl jsonlite bit64 httr
 #' @importFrom utils URLencode
 invisible(NULL)

RGoogleFit/R/Utils.R

@@ -43,4 +43,7 @@ NanosToPOSIXct <- function(nanos) {
   )
 
 }
-
+
+assert <- function (expr, error) {
+  if (! expr) stop(error, call. = FALSE)
+}