;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018 Sou Bunnbu <iyzsong@member.fsf.org>
;;; Copyright © 2018 Gábor Boskovits <boskovits@gmail.com>
;;; Copyright © 2018 Oleg Pykhalov <go.wigust@gmail.com>
;;;
;;; 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 monitoring)
  #:use-module (gnu services)
  #:use-module (gnu services configuration)
  #:use-module (gnu services shepherd)
  #:use-module (gnu packages admin)
  #:use-module (gnu packages monitoring)
  #:use-module (gnu system shadow)
  #:use-module (guix gexp)
  #:use-module (guix packages)
  #:use-module (guix records)
  #:use-module (ice-9 match)
  #:use-module (srfi srfi-26)
  #:export (darkstat-configuration
            prometheus-node-exporter-configuration
            darkstat-service-type
            prometheus-node-exporter-service-type

            zabbix-server-configuration
            zabbix-server-service-type))


;;;
;;; darkstat
;;;

(define-record-type* <darkstat-configuration>
  darkstat-configuration make-darkstat-configuration darkstat-configuration?
  (package      darkstat-configuration-package
                (default darkstat))
  (interface    darkstat-configuration-interface)
  (port         darkstat-configuration-port
                (default "667"))
  (bind-address darkstat-configuration-bind-address
                (default "127.0.0.1"))
  (base         darkstat-configuration-base
                (default "/")))

(define %darkstat-accounts
  (list (user-account
         (name "darkstat")
         (group "darkstat")
         (system? #t)
         (comment "darkstat daemon user")
         (home-directory "/var/lib/darkstat")
         (shell (file-append shadow "/sbin/nologin")))
        (user-group
         (name "darkstat")
         (system? #t))))

(define darkstat-shepherd-service
  (match-lambda
    (($ <darkstat-configuration>
        package interface port bind-address base)
     (shepherd-service
      (documentation "Network statistics gatherer.")
      (provision '(darkstat))
      (requirement '(networking))
      (start #~(make-forkexec-constructor
                (list #$(file-append package "/sbin/darkstat")
                      "-i" #$interface
                      "-p" #$port
                      "-b" #$bind-address
                      "--base" #$base
                      "--syslog" "--no-daemon"
                      "--chroot" "/var/lib/darkstat"
                      "--user" "darkstat"
                      "--import" "darkstat.db"
                      "--export" "darkstat.db")))
      (stop #~(make-kill-destructor))))))

(define darkstat-service-type
  (service-type
   (name 'darkstat)
   (description
    "Run @command{darkstat} to serve network traffic statictics reports over
HTTP.")
   (extensions
    (list (service-extension account-service-type
                             (const %darkstat-accounts))
          (service-extension shepherd-root-service-type
                             (compose list darkstat-shepherd-service))))))

(define-record-type* <prometheus-node-exporter-configuration>
  prometheus-node-exporter-configuration
  make-prometheus-node-exporter-configuration
  prometheus-node-exporter-configuration?
  (package prometheus-node-exporter-configuration-package
           (default go-github-com-prometheus-node-exporter))
  (web-listen-address prometheus-node-exporter-web-listen-address
                      (default ":9100")))

(define prometheus-node-exporter-shepherd-service
  (match-lambda
    (( $ <prometheus-node-exporter-configuration>
         package web-listen-address)
     (shepherd-service
      (documentation "Prometheus node exporter.")
      (provision '(prometheus-node-exporter))
      (requirement '(networking))
      (start #~(make-forkexec-constructor
                (list #$(file-append package "/bin/node_exporter")
                      "--web.listen-address" #$web-listen-address)))
      (stop #~(make-kill-destructor))))))

(define prometheus-node-exporter-service-type
  (service-type
   (name 'prometheus-node-exporter)
   (description
    "Run @command{node_exporter} to serve hardware and OS metrics to
prometheus.")
   (extensions
    (list (service-extension
           shepherd-root-service-type
           (compose list prometheus-node-exporter-shepherd-service))))))


;;;
;;; Zabbix server
;;;

(define (uglify-field-name field-name)
  (apply string-append
         (map (lambda (str)
                (if (member (string->symbol str) '(ca db ssl))
                    (string-upcase str)
                    (string-capitalize str)))
              (string-split (string-delete #\?
                                           (symbol->string field-name))
                            #\-))))

(define (serialize-field field-name val)
  (format #t "~a=~a~%" (uglify-field-name field-name) val))

(define (serialize-number field-name val)
  (serialize-field field-name (number->string val)))

(define (serialize-list field-name val)
  (if (null? val) "" (serialize-field field-name (string-join val ","))))

(define (serialize-string field-name val)
  (if (and (string? val) (string=? val ""))
      ""
      (serialize-field field-name val)))

(define group? string?)

(define serialize-group
  (const ""))

(define include-files? list?)

(define (serialize-include-files field-name val)
  (if (null? val) "" (for-each (cut serialize-field 'include <>) val)))

(define extra-options? string?)

(define (serialize-extra-options field-name val)
  (if (null? val) "" (display val)))

(define-configuration zabbix-server-configuration
  (zabbix-server
   (package zabbix-server)
   "The zabbix-server package.")
  (user
   (string "zabbix")
   "User who will run the Zabbix server.")
  (group ;for zabbix-server-account procedure
   (group "zabbix")
   "Group who will run the Zabbix server.")
  (db-host
   (string "127.0.0.1")
   "Database host name.")
  (db-name
   (string "zabbix")
   "Database name.")
  (db-user
   (string "zabbix")
   "Database user.")
  (db-password
   (string "")
   "Database password.  Please, use @code{include-files} with
@code{DBPassword=SECRET} inside a specified file instead.")
  (db-port
   (number 5432)
   "Database port.")
  (log-type
   (string "")
   "Specifies where log messages are written to:
@itemize
@item @code{system} - syslog.
@item @code{file} - file specified with @code{log-file} parameter.
@item @code{console} - standard output.
@end itemize\n")
  (log-file
   (string "/var/log/zabbix/server.log")
   "Log file name for @code{log-type} @code{file} parameter.")
  (pid-file
   (string  "/var/run/zabbix/zabbix_server.pid")
   "Name of PID file.")
  (ssl-ca-location
   (string "/etc/ssl/certs/ca-certificates.crt")
   "The location of certificate authority (CA) files for SSL server
certificate verification.")
  (ssl-cert-location
   (string "/etc/ssl/certs")
   "Location of SSL client certificates.")
  (extra-options
   (extra-options "")
   "Extra options will be appended to Zabbix server configuration file.")
  (include-files
   (include-files '())
   "You may include individual files or all files in a directory in the
configuration file."))

(define (zabbix-server-account config)
  "Return the user accounts and user groups for CONFIG."
  (let ((zabbix-user (zabbix-server-configuration-user config))
        (zabbix-group (zabbix-server-configuration-group config)))
    (list (user-group (name zabbix-group) (system? #t))
          (user-account
           (name zabbix-user)
           (system? #t)
           (group zabbix-group)
           (comment "zabbix privilege separation user")
           (home-directory (string-append "/var/run/" zabbix-user))
           (shell #~(string-append #$shadow "/sbin/nologin"))))))

(define (zabbix-server-config-file config)
  "Return the zabbix-server configuration file corresponding to CONFIG."
  (computed-file
   "zabbix_server.conf"
   #~(begin
       (call-with-output-file #$output
         (lambda (port)
           (display "# Generated by 'zabbix-server-service'.\n" port)
           (display #$(with-output-to-string
                        (lambda ()
                          (serialize-configuration
                           config zabbix-server-configuration-fields)))
                    port)
           #t)))))

(define (zabbix-server-activation config)
  "Return the activation gexp for CONFIG."
  (with-imported-modules '((guix build utils)
                           (ice-9 rdelim))
    #~(begin
        (use-modules (guix build utils)
                     (ice-9 rdelim))
        (let ((user (getpw #$(zabbix-server-configuration-user config))))
          (for-each (lambda (file)
                      (let ((directory (dirname file)))
                        (mkdir-p directory)
                        (chown directory (passwd:uid user) (passwd:gid user))
                        (chmod directory #o755)))
                    (list #$(zabbix-server-configuration-log-file config)
                          #$(zabbix-server-configuration-pid-file config)
                          "/etc/zabbix/maintenance.inc.php"))))))

(define (zabbix-server-shepherd-service config)
  "Return a <shepherd-service> for Zabbix server with CONFIG."
  (list (shepherd-service
         (provision '(zabbix-server))
         (documentation "Run Zabbix server daemon.")
         (start #~(make-forkexec-constructor
                   (list #$(file-append (zabbix-server-configuration-zabbix-server config)
                                        "/sbin/zabbix_server")
                         "--config" #$(zabbix-server-config-file config)
                         "--foreground")
                   #:user #$(zabbix-server-configuration-user config)
                   #:group #$(zabbix-server-configuration-group config)
                   #:pid-file #$(zabbix-server-configuration-pid-file config)
                   #:environment-variables
                   (list "SSL_CERT_DIR=/run/current-system/profile\
/etc/ssl/certs"
                         "SSL_CERT_FILE=/run/current-system/profile\
/etc/ssl/certs/ca-certificates.crt")))
         (stop #~(make-kill-destructor)))))

(define zabbix-server-service-type
  (service-type
   (name 'zabbix-server)
   (extensions
    (list (service-extension shepherd-root-service-type
                             zabbix-server-shepherd-service)
          (service-extension account-service-type
                             zabbix-server-account)
          (service-extension activation-service-type
                             zabbix-server-activation)))
   (default-value (zabbix-server-configuration))))

(define (generate-zabbix-server-documentation)
  (generate-documentation
   `((zabbix-server-configuration
      ,zabbix-server-configuration-fields))
   'zabbix-server-configuration))