gnu: Add mpd service.

* doc/guix.texi: Add documentation.
* gnu/services/audio.scm (<mpd-configuration>): New record type.
  (mpd-service-type): New service type.
* gnu/tests/audio.scm: New file.
* gnu/local.mk: Add new files.

Signed-off-by: Christopher Baines <mail@cbaines.net>

doc/guix.texi

@@ -227,6 +227,7 @@ Services
 * Network File System::         NFS related services.
 * Continuous Integration::      The Cuirass service.
 * Power management Services::   The TLP tool.
+* Audio Services::              The MPD.
 * Miscellaneous Services::      Other services.
 
 Defining Services
@@ -9035,6 +9036,7 @@ declaration.
 * Network File System::         NFS related services.
 * Continuous Integration::      The Cuirass service.
 * Power management Services::   The TLP tool.
+* Audio Services::              The MPD.
 * Miscellaneous Services::      Other services.
 @end menu
 
@@ -15635,6 +15637,58 @@ Package object of thermald.
 @end table
 @end deftp
 
+@node Audio Services
+@subsubsection Audio Services
+
+The @code{(gnu services audio)} module provides a service to start MPD
+(the Music Player Daemon).
+
+@cindex mpd
+@subsubheading Music Player Daemon
+
+The Music Player Daemon (MPD) is a service that can play music while
+being controlled from the local machine or over the network by a variety
+of clients.
+
+The following example shows how one might run @code{mpd} as user
+@code{"bob"} on port @code{6666}.  It uses pulseaudio for output.
+
+@example
+(service mpd-service-type
+         (mpd-configuration
+          (user "bob")
+          (port "6666")))
+@end example
+
+@defvr {Scheme Variable} mpd-service-type
+The service type for @command{mpd}
+@end defvr
+
+@deftp {Data Type} mpd-configuration
+Data type representing the configuration of @command{mpd}.
+
+@table @asis
+@item @code{user} (default: @code{"mpd"})
+The user to run mpd as.
+
+@item @code{music-dir} (default: @code{"~/Music"})
+The directory to scan for music files.
+
+@item @code{playlist-dir} (default: @code{"~/.mpd/playlists"})
+The directory to store playlists.
+
+@item @code{pid-file} (default: @code{"/var/run/mpd.pid"})
+The file mpd wil store its PID.  This must be an absolute path.
+
+@item @code{port} (default: @code{"6600"})
+The port to run mpd on.
+
+@item @code{address} (default: @code{"any"})
+The address that mpd will bind to.  To use a Unix domain socket,
+an absolute path can be specified here.
+
+@end table
+@end deftp
 
 @node Miscellaneous Services
 @subsubsection Miscellaneous Services

gnu/local.mk

@@ -426,6 +426,7 @@ GNU_SYSTEM_MODULES =				\
 						\
   %D%/services.scm				\
   %D%/services/admin.scm			\
+  %D%/services/audio.scm                        \
   %D%/services/avahi.scm			\
   %D%/services/base.scm				\
   %D%/services/configuration.scm		\
@@ -481,6 +482,7 @@ GNU_SYSTEM_MODULES =				\
 						\
   %D%/tests.scm					\
   %D%/tests/admin.scm				\
+  %D%/tests/audio.scm				\
   %D%/tests/base.scm				\
   %D%/tests/databases.scm			\
   %D%/tests/dict.scm				\

gnu/services/audio.scm

@@ -0,0 +1,86 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 Peter Mikkelsen <petermikkelsen10@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 audio)
+  #:use-module (guix gexp)
+  #:use-module (gnu services)
+  #:use-module (gnu services shepherd)
+  #:use-module (gnu packages mpd)
+  #:use-module (guix records)
+  #:use-module (ice-9 match)
+  #:export (mpd-configuration
+            mpd-configuration?
+            mpd-service-type))
+
+;;; Commentary:
+;;;
+;;; Audio related services
+;;;
+;;; Code:
+
+(define-record-type* <mpd-configuration>
+  mpd-configuration make-mpd-configuration
+  mpd-configuration?
+  (user         mpd-configuration-user
+                (default "mpd"))
+  (music-dir    mpd-configuration-music-dir
+                (default "~/Music"))
+  (playlist-dir mpd-configuration-playlist-dir
+                (default "~/.mpd/playlists"))
+  (port         mpd-configuration-port
+                (default "6600"))
+  (address      mpd-configuration-address
+                (default "any"))
+  (pid-file     mpd-configuration-pid-file
+                (default "/var/run/mpd.pid")))
+
+(define (mpd-config->file config)
+  (apply
+   mixed-text-file "mpd.conf"
+   "audio_output {\n"
+   "  type \"pulse\"\n"
+   "  name \"MPD\"\n"
+   "}\n"
+   (map (match-lambda
+          ((config-name config-val)
+           (string-append config-name " \"" (config-val config) "\"\n")))
+        `(("user" ,mpd-configuration-user)
+          ("music_directory" ,mpd-configuration-music-dir)
+          ("playlist_directory" ,mpd-configuration-playlist-dir)
+          ("port" ,mpd-configuration-port)
+          ("bind_to_address" ,mpd-configuration-address)
+          ("pid_file" ,mpd-configuration-pid-file)))))
+
+(define (mpd-service config)
+  (shepherd-service
+   (documentation "Run the MPD (Music Player Daemon)")
+   (provision '(mpd))
+   (start #~(make-forkexec-constructor
+             (list #$(file-append mpd "/bin/mpd")
+                   "--no-daemon"
+                   #$(mpd-config->file config))
+             #:pid-file #$(mpd-configuration-pid-file config)))
+   (stop  #~(make-kill-destructor))))
+
+(define mpd-service-type
+  (service-type
+   (name 'mpd)
+   (extensions
+    (list (service-extension shepherd-root-service-type
+                             (compose list mpd-service))))
+   (default-value (mpd-configuration))))

gnu/tests/audio.scm

@@ -0,0 +1,78 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 Peter Mikkelsen <petermikkelsen10@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 tests audio)
+  #:use-module (gnu tests)
+  #:use-module (gnu system)
+  #:use-module (gnu system vm)
+  #:use-module (gnu services)
+  #:use-module (gnu services audio)
+  #:use-module (gnu packages mpd)
+  #:use-module (guix gexp)
+  #:export (%test-mpd))
+
+(define %mpd-os
+  (simple-operating-system
+   (service mpd-service-type
+            (mpd-configuration
+             (user "root")))))
+
+(define (run-mpd-test)
+  "Run tests in %mpd-os, which has mpd running."
+  (define os
+    (marionette-operating-system
+     %mpd-os
+     #:imported-modules '((gnu services herd))))
+
+  (define vm
+    (virtual-machine os))
+
+  (define test
+    (with-imported-modules '((gnu build marionette))
+      #~(begin
+          (use-modules (srfi srfi-64)
+                       (gnu build marionette))
+          (define marionette
+            (make-marionette (list #$vm)))
+
+          (mkdir #$output)
+          (chdir #$output)
+
+          (test-begin "mpd")
+
+          (test-assert "service is running"
+            (marionette-eval
+             '(begin
+                (use-modules (gnu services herd))
+                (start-service 'mpd))
+             marionette))
+
+          (test-assert "mpc connect"
+            (marionette-eval
+             '(zero? (system #$(file-append mpd-mpc "/bin/mpc")))
+             marionette))
+
+          (test-end)
+          (exit (= (test-runner-fail-count (test-runner-current)) 0)))))
+  (gexp->derivation "mpd-test" test))
+
+(define %test-mpd
+  (system-test
+   (name "mpd")
+   (description "Test that the mpd can run and be connected to.")
+   (value (run-mpd-test))))