add read / write from / to csv and move checking directory to helpers

R/helpers.R

@@ -3,3 +3,18 @@
 flip <- function(f) function(x, y) f(y, x)
 
 clear_na <- function(xs) xs[!is.na(xs)]
+
+check_directory <- function(path, create=F) {
+    # check if download_dir exists
+    if(file.access(path, mode=0) == -1) {
+        if (create) {
+            tryCatch(dir.create(path),
+                     error = stop_dir_not_creatable,
+                     warning = stop_dir_not_creatable)
+        } else {
+            stop("Directory does not exist. Use create = TRUE if you wish to create the directory.")
+        }
+    } else if (file.access(path, mode=2) == -1) {
+        stop("Directory exists, but is not writeable.")
+    }
+}