Added a better error message when the PRISM web service is down.

#122

NEWS.md

@@ -3,6 +3,7 @@
 * Removed global assignment inside `prism_webservice()`
 * Documented return value for `pd_stack()`, `prism_set_dl_dir()` ,`pd_to_file()`, `pd_get_type()` & `get_prism_*()` functions.
 * Added examples to documentation for `pd_to_file()`, `prism_archive_clean()`, `prism_archive_verify()`, `prism_set_dl_dir()`, & `pd_get_*()` functions.
+* Added a better error message when the PRISM webservice is down (not returning status 200). (#122)
 
 # prism 0.2.1
 

R/prism_webservice.R

@@ -30,6 +30,14 @@ prism_webservice <- function(uri, keepZip = FALSE, returnName = FALSE,
 {
   ## Get file name
   x <- httr::HEAD(uri)
+  x2 <- check_status(x, uri)
+
+  # check status - return NULL if status was not 200
+  if (!isTRUE(x2)) {
+    warning(x2)
+    return(NULL)
+  }
+
   fn <- x$headers[["content-disposition"]]
   fn <- regmatches(fn, regexpr('\\"[a-zA-Z0-9_\\.]+', fn))
   fn <- substr(fn, 2, nchar((fn)))
@@ -98,6 +106,31 @@ prism_webservice <- function(uri, keepZip = FALSE, returnName = FALSE,
   }
 }
 
+check_status <- function(x, uri) {
+  if (x$status_code == as.integer(200)) {
+    # status 200 is request has succeeded
+    return(TRUE)
+  } else {
+    # otherwise - tell user about status
+    y <- paste0(
+      "\nAttempted to download:\n",
+      uri,
+      '\nCould not reach url, with status:\n',
+      x$status_code, "\n",
+      'Please try pasting one or more of the following urls into your web browser:\n',
+      'https://services.nacse.org/prism/data/public/4km/tmin/20090405', '\n',
+      'https://services.nacse.org/prism/data/public/4km/tmin/200904', '\n',
+      'https://services.nacse.org/prism/data/public/4km/tmin/2009', '\n',
+      'https://services.nacse.org/prism/data/public/4km/tmin/1944', '\n',
+      'If you receive the same status code, then the issue is with the PRISM web service.\n',
+      'Please try again later or use the manual downloads at https://prism.oregonstate.edu.\n',
+      'If the status is different or download works, please file a bug at:\n',
+      'https://github.com/ropensci/prism/issues/'
+    )
+    return(y)
+  }
+}
+
 # x is the file to check. 
 # returns TRUE if it is a zip file, and otherwiser returns text that was read
 check_zip_file <- function(x) {