guix/gnu/services/audio.scm

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017 Peter Mikkelsen <petermikkelsen10@gmail.com>
;;; Copyright © 2019 Ricardo Wurmus <rekado@elephly.net>
;;; Copyright © 2020 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2022 Bruno Victal <mirai@makinata.eu>
;;;
;;; 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 audio)
  #:use-module (guix gexp)
  #:use-module (guix deprecation)
  #:use-module (guix diagnostics)
  #:use-module (guix i18n)
  #:use-module (gnu services)
  #:use-module (gnu services configuration)
  #:use-module (gnu services shepherd)
  #:use-module (gnu services admin)
  #:use-module (gnu system shadow)
  #:use-module (gnu packages admin)
  #:use-module (gnu packages mpd)
  #:use-module (guix records)
  #:use-module (ice-9 match)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-71)
  #:export (mpd-output
            mpd-output?
            mpd-output-name
            mpd-output-type
            mpd-output-enabled?
            mpd-output-format
            mpd-output-tags?
            mpd-output-always-on?
            mpd-output-mixer-type
            mpd-output-replay-gain-handler
            mpd-output-extra-options

            mpd-plugin
            mpd-plugin?
            mpd-plugin-plugin
            mpd-plugin-name
            mpd-plugin-enabled?
            mpd-plugin-extra-options

            mpd-partition
            mpd-partition?
            mpd-partition-name
            mpd-partition-extra-options

            mpd-configuration
            mpd-configuration?
            mpd-configuration-package
            mpd-configuration-user
            mpd-configuration-group
            mpd-configuration-shepherd-requirement
            mpd-configuration-log-file
            mpd-configuration-log-level
            mpd-configuration-music-directory
            mpd-configuration-music-dir
            mpd-configuration-playlist-directory
            mpd-configuration-playlist-dir
            mpd-configuration-db-file
            mpd-configuration-state-file
            mpd-configuration-sticker-file
            mpd-configuration-default-port
            mpd-configuration-endpoints
            mpd-configuration-address
            mpd-configuration-database
            mpd-configuration-partitions
            mpd-configuration-neighbors
            mpd-configuration-inputs
            mpd-configuration-archive-plugins
            mpd-configuration-input-cache-size
            mpd-configuration-decoders
            mpd-configuration-resampler
            mpd-configuration-filters
            mpd-configuration-outputs
            mpd-configuration-playlist-plugins
            mpd-configuration-extra-options
            mpd-service-type))

;;; Commentary:
;;;
;;; Audio related services
;;;
;;; Code:

(define (uglify-field-name field-name)
  (let ((str (symbol->string field-name)))
    (string-join (string-split (if (string-suffix? "?" str)
                                   (string-drop-right str 1)
                                   str)
                               #\-) "_")))

(define list-of-string?
  (list-of string?))

(define list-of-symbol?
  (list-of symbol?))

(define (mpd-serialize-field field-name value)
  (let ((field (if (string? field-name) field-name
                   (uglify-field-name field-name)))
        (value (cond
                ((boolean? value) (if value "yes" "no"))
                ((string? value) value)
                (else (object->string value)))))
    #~(format #f "~a ~s~%" #$field #$value)))

(define (mpd-serialize-alist field-name value)
  #~(string-append #$@(generic-serialize-alist list mpd-serialize-field
                                               value)))

(define mpd-serialize-string mpd-serialize-field)
(define mpd-serialize-boolean mpd-serialize-field)

(define (mpd-serialize-list-of-string field-name value)
  #~(string-concatenate #$(map (cut mpd-serialize-string field-name <>) value)))

(define-maybe string (prefix mpd-))
(define-maybe list-of-string (prefix mpd-))
(define-maybe boolean (prefix mpd-))

;;; TODO: Procedures for deprecated fields, to be removed.

(define mpd-deprecated-fields '((music-dir . music-directory)
                                (playlist-dir . playlist-directory)
                                (address . endpoints)))

(define (port? value) (or (string? value) (integer? value)))

(define (mpd-serialize-deprecated-field field-name value)
  (if (maybe-value-set? value)
      (begin
        (warn-about-deprecation
         field-name #f
         #:replacement (assoc-ref mpd-deprecated-fields field-name))
        (match field-name
          ('playlist-dir (mpd-serialize-string "playlist_directory" value))
          ('music-dir (mpd-serialize-string "music_directory" value))
          ('address (mpd-serialize-string "bind_to_address" value))))
      ""))

(define (mpd-serialize-port field-name value)
  (when (string? value)
    (warning
     (G_ "string value for '~a' is deprecated, use integer instead~%")
     field-name))
  (mpd-serialize-field "port" value))

(define-maybe port (prefix mpd-))

;;;

;; Generic MPD plugin record, lists only the most prevalent fields.
(define-configuration mpd-plugin
  (plugin
   maybe-string
   "Plugin name.")

  (name
   maybe-string
   "Name.")

  (enabled?
   maybe-boolean
   "Whether the plugin is enabled/disabled.")

  (extra-options
   (alist '())
   "An association list of option symbols/strings to string values
to be appended to the plugin configuration. See
@uref{https://mpd.readthedocs.io/en/latest/plugins.html,MPD plugin reference}
for available options.")

  (prefix mpd-))

(define (mpd-serialize-mpd-plugin field-name value)
  #~(format #f "~a {~%~a}~%"
            '#$field-name
            #$(serialize-configuration value mpd-plugin-fields)))

(define (mpd-serialize-list-of-mpd-plugin field-name value)
  #~(string-append #$@(map (cut mpd-serialize-mpd-plugin field-name <>)
                           value)))

(define list-of-mpd-plugin? (list-of mpd-plugin?))

(define-maybe mpd-plugin (prefix mpd-))

(define-configuration mpd-partition
  (name
   string
   "Partition name.")

  (extra-options
   (alist '())
   "An association list of option symbols/strings to string values
to be appended to the partition configuration. See
@uref{https://mpd.readthedocs.io/en/latest/user.html#configuring-partitions,Configuring Partitions}
for available options.")

  (prefix mpd-))

(define (mpd-serialize-mpd-partition field-name value)
  #~(format #f "partition {~%~a}~%"
            #$(serialize-configuration value mpd-partition-fields)))

(define (mpd-serialize-list-of-mpd-partition field-name value)
  #~(string-append #$@(map (cut mpd-serialize-mpd-partition #f <>) value)))

(define list-of-mpd-partition?
  (list-of mpd-partition?))

(define-configuration mpd-output
  (name
   (string "MPD")
   "The name of the audio output.")

  (type
   (string "pulse")
   "The type of audio output.")

  (enabled?
   (boolean #t)
   "Specifies whether this audio output is enabled when MPD is started. By
default, all audio outputs are enabled. This is just the default
setting when there is no state file; with a state file, the previous
state is restored.")

  (format
   maybe-string
   "Force a specific audio format on output. See
@uref{https://mpd.readthedocs.io/en/latest/user.html#audio-output-format,Global Audio Format}
for a more detailed description.")

  (tags?
   (boolean #t)
   "If set to @code{#f}, then MPD will not send tags to this output. This
is only useful for output plugins that can receive tags, for example the
@code{httpd} output plugin.")

  (always-on?
   (boolean #f)
   "If set to @code{#t}, then MPD attempts to keep this audio output always
open. This may be useful for streaming servers, when you don’t want to
disconnect all listeners even when playback is accidentally stopped.")

  (mixer-type
   (string "none")
   "This field accepts a string that specifies which mixer should be used
for this audio output: the @code{hardware} mixer, the @code{software}
mixer, the @code{null} mixer (allows setting the volume, but with no
effect; this can be used as a trick to implement an external mixer
External Mixer) or no mixer (@code{none}).")

  (replay-gain-handler
   maybe-string
   "This field accepts a string that specifies how
@uref{https://mpd.readthedocs.io/en/latest/user.html#replay-gain,Replay Gain}
is to be applied. @code{software} uses an internal software volume control,
@code{mixer} uses the configured (hardware) mixer control and @code{none}
disables replay gain on this audio output.")

  (extra-options
   (alist '())
   "An association list of option symbols/strings to string values
to be appended to the audio output configuration.")

  (prefix mpd-))

(define (mpd-serialize-mpd-output field-name value)
  #~(format #f "audio_output {~%~a}~%"
            #$(serialize-configuration value mpd-output-fields)))

(define (mpd-serialize-list-of-mpd-plugin-or-output field-name value)
  (let ((plugins outputs (partition mpd-plugin? value)))
    #~(string-append #$@(map (cut mpd-serialize-mpd-plugin "audio_output" <>)
                             plugins)
                     #$@(map (cut mpd-serialize-mpd-output #f <>) outputs))))

(define list-of-mpd-plugin-or-output?
  (list-of (lambda (x)
             (or (mpd-output? x) (mpd-plugin? x)))))

(define-configuration mpd-configuration
  (package
   (file-like mpd)
   "The MPD package."
   empty-serializer)

  (user
   (string "mpd")
   "The user to run mpd as.")

  (group
   (string "mpd")
   "The group to run mpd as.")

  (shepherd-requirement
   (list-of-symbol '())
   "This is a list of symbols naming Shepherd services that this service
will depend on."
   empty-serializer)

  (log-file
   (maybe-string "/var/log/mpd/log")
   "The location of the log file. Set to @code{syslog} to use the
local syslog daemon or @code{%unset-value} to omit this directive
from the configuration file.")

  (log-level
   maybe-string
   "Supress any messages below this threshold.
Available values: @code{notice}, @code{info}, @code{verbose},
@code{warning} and @code{error}.")

  (music-directory
   maybe-string
   "The directory to scan for music files.")

  (music-dir ; TODO: deprecated, remove later
   maybe-string
   "The directory to scan for music files."
   mpd-serialize-deprecated-field)

  (playlist-directory
   maybe-string
   "The directory to store playlists.")

  (playlist-dir ; TODO: deprecated, remove later
   maybe-string
   "The directory to store playlists."
   mpd-serialize-deprecated-field)

  (db-file
   maybe-string
   "The location of the music database.")

  (state-file
   maybe-string
   "The location of the file that stores current MPD's state.")

  (sticker-file
   maybe-string
   "The location of the sticker database.")

  (default-port
   (maybe-port 6600)
   "The default port to run mpd on.")

  (endpoints
   maybe-list-of-string
   "The addresses that mpd will bind to. A port different from
@var{default-port} may be specified, e.g. @code{localhost:6602} and
IPv6 addresses must be enclosed in square brackets when a different
port is used.
To use a Unix domain socket, an absolute path or a path starting with @code{~}
can be specified here."
   (lambda (_ endpoints)
     (if (maybe-value-set? endpoints)
         (mpd-serialize-list-of-string "bind_to_address" endpoints)
         "")))

  (address ; TODO: deprecated, remove later
   maybe-string
   "The address that mpd will bind to.
To use a Unix domain socket, an absolute path can be specified here."
   mpd-serialize-deprecated-field)

  (database
   maybe-mpd-plugin
   "MPD database plugin configuration.")

  (partitions
   (list-of-mpd-partition '())
   "List of MPD \"partitions\".")

  (neighbors
   (list-of-mpd-plugin '())
   "List of MPD neighbor plugin configurations.")

  (inputs
   (list-of-mpd-plugin '())
   "List of MPD input plugin configurations."
   (lambda (_ x)
     (mpd-serialize-list-of-mpd-plugin "input" x)))

  (archive-plugins
   (list-of-mpd-plugin '())
   "List of MPD archive plugin configurations."
   (lambda (_ x)
     (mpd-serialize-list-of-mpd-plugin "archive_plugin" x)))

  (input-cache-size
   maybe-string
   "MPD input cache size."
   (lambda (_ x)
     (if (maybe-value-set? x)
         #~(string-append "\ninput_cache {\n"
                          #$(mpd-serialize-string "size" x)
                          "}\n") "")))

  (decoders
   (list-of-mpd-plugin '())
   "List of MPD decoder plugin configurations."
   (lambda (_ x)
     (mpd-serialize-list-of-mpd-plugin "decoder" x)))

  (resampler
   maybe-mpd-plugin
   "MPD resampler plugin configuration.")

  (filters
   (list-of-mpd-plugin '())
   "List of MPD filter plugin configurations."
   (lambda (_ x)
     (mpd-serialize-list-of-mpd-plugin "filter" x)))

  (outputs
   (list-of-mpd-plugin-or-output (list (mpd-output)))
   "The audio outputs that MPD can use.
By default this is a single output using pulseaudio.")

  (playlist-plugins
   (list-of-mpd-plugin '())
   "List of MPD playlist plugin configurations."
   (lambda (_ x)
     (mpd-serialize-list-of-mpd-plugin "playlist_plugin" x)))

  (extra-options
   (alist '())
   "An association list of option symbols/strings to string values to be
appended to the configuration.")

  (prefix mpd-))

(define (mpd-serialize-configuration configuration)
  (mixed-text-file
   "mpd.conf"
   (serialize-configuration configuration mpd-configuration-fields)))

(define (mpd-log-rotation config)
  (match-record config <mpd-configuration> (log-file)
    (log-rotation
     (files (list log-file))
     (post-rotate #~(begin
                      (use-modules (gnu services herd))
                      (with-shepherd-action 'mpd ('reopen) #f))))))

(define (mpd-shepherd-service config)
  (match-record config <mpd-configuration> (user package shepherd-requirement
                                            log-file playlist-directory
                                            db-file state-file sticker-file)
    (let* ((config-file (mpd-serialize-configuration config)))
      (shepherd-service
       (documentation "Run the MPD (Music Player Daemon)")
       (requirement `(user-processes loopback ,@shepherd-requirement))
       (provision '(mpd))
       (start #~(begin
                  (and=> #$(maybe-value log-file)
                         (compose mkdir-p dirname))

                  (let ((user (getpw #$user)))
                    (for-each
                     (lambda (x)
                       (when (and x (not (file-exists? x)))
                         (mkdir-p x)
                         (chown x (passwd:uid user) (passwd:gid user))))
                     (list #$(maybe-value playlist-directory)
                           (and=> #$(maybe-value db-file) dirname)
                           (and=> #$(maybe-value state-file) dirname)
                           (and=> #$(maybe-value sticker-file) dirname))))

                  (make-forkexec-constructor
                   (list #$(file-append package "/bin/mpd")
                         "--no-daemon"
                         #$config-file)
                   #:environment-variables
                   ;; Required to detect PulseAudio when run under a user account.
                   (list (string-append
                          "XDG_RUNTIME_DIR=/run/user/"
                          (number->string (passwd:uid (getpwnam #$user))))))))
       (stop  #~(make-kill-destructor))
       (actions
        (list (shepherd-configuration-action config-file)
              (shepherd-action
               (name 'reopen)
               (documentation "Re-open log files and flush caches.")
               (procedure
                #~(lambda (pid)
                    (if pid
                        (begin
                          (kill pid SIGHUP)
                          (format #t
                                  "Issued SIGHUP to Service MPD (PID ~a)."
                                  pid))
                        (format #t "Service MPD is not running.")))))))))))

(define (mpd-accounts config)
  (match-record config <mpd-configuration> (user group)
    (list (user-group
           (name group)
           (system? #t))
          (user-account
           (name user)
           (group group)
           (system? #t)
           (comment "Music Player Daemon (MPD) user")
           ;; MPD can use $HOME (or $XDG_CONFIG_HOME) to place its data
           (home-directory "/var/lib/mpd")
           (shell (file-append shadow "/sbin/nologin"))))))

(define mpd-service-type
  (service-type
   (name 'mpd)
   (description "Run the Music Player Daemon (MPD).")
   (extensions
    (list (service-extension shepherd-root-service-type
                             (compose list mpd-shepherd-service))
          (service-extension account-service-type
                             mpd-accounts)
          (service-extension rottlog-service-type
                             (compose list mpd-log-rotation))))
   (default-value (mpd-configuration))))