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+;;; Copyright © 2019 - 2022 Jakob L. Kreuze <zerodaysfordays@sdf.org>
+;;;
+;;; This program is free software; you can redistribute it and/or
+;;; modify it under the terms of the GNU General Public License as
+;;; published by the Free Software Foundation; either version 3 of the
+;;; License, or (at your option) any later version.
+;;;
+;;; This program is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+;;; General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with this program. If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+(define-module (dynamic logging)
+  #:use-module (ice-9 format)
+  #:use-module (srfi srfi-19)
+  #:export (log-append!))
+
+(define %log-file-name (make-parameter "/var/log/jakob-dynamic.log"))
+(define %log-level (make-parameter 'info))
+
+(define (dominates message-level baseline-level)
+  "Determine if `a' should be shown for baseline log level `b'."
+  (define log-level-hierarchy '(debug info warn error))
+  (>= (list-index log-level-hierarchy message-level)
+      (list-index log-level-hierarchy baseline-level)))
+
+(define (log-append! level message)
+  "Append `message', at `level', to the log buffer."
+  (when (dominates level (%log-level))
+    (call-with-output-file (%log-file-name)
+      (lambda (port)
+        (let ((now (date->string (current-date) "~4")))
+          (format port "[~a] ~a: ~a~%" now level message))))))