;;; Monitoring --- Server monitoring
;;; Copyright © 2021 Masaya Tojo <masaya@tojo.tokyo>
;;;
;;; This file is part of Monitoring.
;;;
;;; Monitoring 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.
;;;
;;; Monitoring 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 Monitoring.  If not, see <http://www.gnu.org/licenses/>.

(define-module (tojo-tokyo monitoring)
  #:use-module (ice-9 popen)
  #:use-module (ice-9 textual-ports)
  #:use-module (ice-9 regex)
  #:use-module ((srfi srfi-1) #:select (any))
  #:use-module (web client))

(define-public current-df-command (make-parameter "df"))
(define-public current-heartbeat-url
  (make-parameter
   (let ((heartbeat-file "/etc/heartbeat-url"))
     (or (and (file-exists? heartbeat-file)
              (call-with-input-file heartbeat-file get-line))
         "https://heartbeat.test"))))

(define (df)
  (let ((port (open-input-pipe (current-df-command))))
    (get-line port)
    (let f ((line (get-line port)))
      (cond ((eof-object? line)
             (close-pipe port)
             '())
            (else
             (cons (map cons
                        '(filesystem 1k-blocks used available use% mounted-on)
                        (map match:substring (list-matches "[^ ]+" line)))
                   (f (get-line port))))))))

(define-public (disk-use%-over? threshold)
  (any (lambda (x)
         (let ((use% (string->number (string-delete #\% (assoc-ref x 'use%)))))
           (< threshold use%)))
       (filter (lambda (x)
                 (let ((fs (assoc-ref x 'filesystem)))
                   (and fs
                        (<= 5 (string-length fs))
                        (string=? (substring fs 0 5) "/dev/"))))
               (df))))

(define-syntax-rule (heartbeat (p? body ...) ...)
  (let ((heartbeat-cancel? #f))
    (when p? body ... (set! heartbeat-cancel? #t)) ...
    (unless heartbeat-cancel?
      (http-request (current-heartbeat-url)))))
(export-syntax heartbeat)