;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
;;; Copyright © 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix 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.
;;;
;;; GNU Guix 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 GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (gnu services admin)
  #:use-module (gnu packages admin)
  #:use-module (gnu packages base)
  #:use-module (gnu services)
  #:use-module (gnu services mcron)
  #:use-module (gnu services shepherd)
  #:use-module (guix gexp)
  #:use-module (guix packages)
  #:use-module (guix records)
  #:use-module (srfi srfi-1)
  #:use-module (ice-9 vlist)
  #:export (%default-rotations
            %rotated-files

            log-rotation
            log-rotation?
            log-rotation-frequency
            log-rotation-files
            log-rotation-options
            log-rotation-post-rotate

            rottlog-configuration
            rottlog-configuration?
            rottlog-service
            rottlog-service-type))

;;; Commentary:
;;;
;;; This module implements configuration of rottlog by writing
;;; /etc/rottlog/{rc,hourly|daily|weekly}.  Example usage
;;;
;;;     (mcron-service)
;;;     (service rottlog-service-type)
;;;
;;; Code:

(define-record-type* <log-rotation> log-rotation make-log-rotation
  log-rotation?
  (files       log-rotation-files)                ;list of strings
  (frequency   log-rotation-frequency             ;symbol
               (default 'weekly))
  (post-rotate log-rotation-post-rotate           ;#f | gexp
               (default #f))
  (options     log-rotation-options               ;list of strings
               (default '())))

(define %rotated-files
  ;; Syslog files subject to rotation.
  '("/var/log/messages" "/var/log/secure" "/var/log/debug"
    "/var/log/maillog"))

(define %default-rotations
  (list (log-rotation                             ;syslog files
         (files %rotated-files)

         ;; Restart syslogd after rotation.
         (options '("sharedscripts"))
         (post-rotate #~(let ((pid (call-with-input-file "/var/run/syslog.pid"
                                     read)))
                          (kill pid SIGHUP))))
        (log-rotation
         (files '("/var/log/guix-daemon.log")))))

(define (log-rotation->config rotation)
  "Return a string-valued gexp representing the rottlog configuration snippet
for ROTATION."
  (define post-rotate
    (let ((post (log-rotation-post-rotate rotation)))
      (and post
           (program-file "rottlog-post-rotate.scm" post))))

  #~(let ((post #$post-rotate))
      (string-append (string-join '#$(log-rotation-files rotation) ",")
                     " {"
                     #$(string-join (log-rotation-options rotation)
                                    "\n  " 'prefix)
                     (if post
                         (string-append "\n  postrotate\n    " post
                                        "\n  endscript\n")
                         "")
                     "\n}\n")))

(define (log-rotations->/etc-entries rotations)
  "Return the list of /etc entries for ROTATIONS, a list of <log-rotation>."
  (define (frequency-file frequency rotations)
    (computed-file (string-append "rottlog." (symbol->string frequency))
                   #~(call-with-output-file #$output
                       (lambda (port)
                         (for-each (lambda (str)
                                     (display str port))
                                   (list #$@(map log-rotation->config
                                                 rotations)))))))

  (let* ((frequencies (delete-duplicates
                       (map log-rotation-frequency rotations)))
         (table       (fold (lambda (rotation table)
                              (vhash-consq (log-rotation-frequency rotation)
                                           rotation table))
                            vlist-null
                            rotations)))
    (map (lambda (frequency)
           `(,(symbol->string frequency)
             ,(frequency-file frequency
                              (vhash-foldq* cons '() frequency table))))
         frequencies)))

(define (default-jobs rottlog)
  (list #~(job '(next-hour '(0))                  ;midnight
               #$(file-append rottlog "/sbin/rottlog"))
        #~(job '(next-hour '(12))                 ;noon
               #$(file-append rottlog "/sbin/rottlog"))))

(define-record-type* <rottlog-configuration>
  rottlog-configuration make-rottlog-configuration
  rottlog-configuration?
  (rottlog            rottlog-rottlog             ;package
                      (default rottlog))
  (rc-file            rottlog-rc-file             ;file-like
                      (default (file-append rottlog "/etc/rc")))
  (rotations          rottlog-rotations           ;list of <log-rotation>
                      (default %default-rotations))
  (jobs               rottlog-jobs                ;list of <mcron-job>
                      (default #f)))

(define (rottlog-etc config)
  `(("rottlog"
     ,(file-union "rottlog"
                  (cons `("rc" ,(rottlog-rc-file config))
                        (log-rotations->/etc-entries
                         (rottlog-rotations config)))))))

(define (rottlog-jobs-or-default config)
  (or (rottlog-jobs config)
      (default-jobs (rottlog-rottlog config))))

(define rottlog-service-type
  (service-type
   (name 'rottlog)
   (description
    "Periodically rotate log files using GNU@tie{}Rottlog and GNU@tie{}mcron.
Old log files are removed or compressed according to the configuration.")
   (extensions (list (service-extension etc-service-type rottlog-etc)
                     (service-extension mcron-service-type
                                        rottlog-jobs-or-default)

                     ;; Add Rottlog to the global profile so users can access
                     ;; the documentation.
                     (service-extension profile-service-type
                                        (compose list rottlog-rottlog))))
   (compose concatenate)
   (extend (lambda (config rotations)
             (rottlog-configuration
              (inherit config)
              (rotations (append (rottlog-rotations config)
                                 rotations)))))
   (default-value (rottlog-configuration))))

;;; admin.scm ends here