[elpa] externals/repology e1cc934c92 1/2: repology-utils: Add delay between queries

[Nicolas Goaziou]

branch: externals/repology
commit e1cc934c926d01b57e0cbaeae9f39bddb1cfcad9
Author: Nicolas Goaziou <mail@nicolasgoaziou.fr>
Commit: Nicolas Goaziou <mail@nicolasgoaziou.fr>

    repology-utils: Add delay between queries
    
    * repology-utils.el (repology-request-delay):
    (repology--last-request-time): New variables.
    (repology-request): Wait for at least `repology-request-delay' before
    sending a new request, per API's terms of use.
---
 repology-utils.el | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/repology-utils.el b/repology-utils.el
index 0d47364c1d..3e4e618af8 100644
--- a/repology-utils.el
+++ b/repology-utils.el
@@ -43,6 +43,11 @@
     "incorrect" "untrusted" "ignored")
   "List of known status values.")
 
+(defconst repology-request-delay 1.0
+  "Number of seconds between two requests to Repology API.
+The value is defined according to its terms of use.  See URL
+`https://repology.org/api'.")
+
 
 ;;; Packages
 (defun repology-package-p (object)
@@ -324,6 +329,10 @@ Raise an error if REPOSITORY is unknown to Repology."
 
 
 ;;; Requests
+(defvar repology--last-request-time nil
+  "Time for last request to the Repology API, or nil.
+It is updated each time `repology-request' is called.")
+
 (defun repology-request (url &optional extra-headers)
   "Perform a raw HTTP request on URL.
 
@@ -335,6 +344,14 @@ Return a property list with `:code', `:reason', `:header' 
and
 a string explaining the issue."
   (let* ((url-request-method "GET")
          (url-request-extra-headers extra-headers))
+    ;; Make sure to wait at least for `repology-request-delay' seconds
+    ;; between queries.
+    (when (and repology--last-request-time
+               (< (float-time (time-subtract (current-time)
+                                             repology--last-request-time))
+                  repology-request-delay))
+      (sleep-for repology-request-delay))
+    (setq repology--last-request-time (current-time))
     (pcase (condition-case err
                (url-retrieve-synchronously url t)
              (error (error-message-string err)))