aboutsummaryrefslogtreecommitdiff
path: root/gnu/services/audio.scm
blob: 5d2cd56a17fd3f4a0951387899ad6806008cff47 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
;;; 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 © 2022⁠–⁠2023 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 (guix modules)
  #:use-module ((gnu services) #:hide (delete))
  #:use-module (gnu services admin)
  #: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 format)
  #: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

            mympd-service-type
            mympd-configuration
            mympd-configuration?
            mympd-configuration-package
            mympd-configuration-shepherd-requirement
            mympd-configuration-user
            mympd-configuration-group
            mympd-configuration-work-directory
            mympd-configuration-cache-directory
            mympd-configuration-acl
            mympd-configuration-covercache-ttl
            mympd-configuration-http?
            mympd-configuration-host
            mympd-configuration-port
            mympd-configuration-log-level
            mympd-configuration-log-to
            mympd-configuration-lualibs
            mympd-configuration-uri
            mympd-configuration-script-acl
            mympd-configuration-ssl?
            mympd-configuration-ssl-port
            mympd-configuration-ssl-cert
            mympd-configuration-ssl-key
            mympd-configuration-pin-hash
            mympd-configuration-save-caches?
            mympd-ip-acl
            mympd-ip-acl?
            mympd-ip-acl-allow
            mympd-ip-acl-deny))

;;; 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)
                               #\-) "_")))

;; Helpers for deprecated field types, to be removed later.
(define %lazy-group (make-symbol "%lazy-group"))

(define (set-user-group user group)
  (user-account
   (inherit user)
   (group (user-group-name group))))


;;;
;;; MPD
;;;

(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-strings field-name value)
  #~(string-append #$@(map (cut mpd-serialize-string field-name <>) value)))

(define (mpd-serialize-user-account field-name value)
  (mpd-serialize-string field-name (user-account-name value)))

(define (mpd-serialize-user-group field-name value)
  (mpd-serialize-string field-name (user-group-name value)))

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

(define %mpd-user
  (user-account
   (name "mpd")
   ;; XXX: This is a place-holder to be lazily substituted in (…-accounts)
   ;; with the value from the 'group' field of <mpd-configuration>.
   (group %lazy-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-group
  (user-group
   (name "mpd")
   (system? #t)))

;;; 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-))

;;; Procedures for unsupported value types, to be removed.

(define (mpd-user-sanitizer value)
  (cond ((user-account? value) value)
        ((string? value)
         (warning (G_ "string value for 'user' is deprecated, use \
user-account instead~%"))
         (user-account
          (inherit %mpd-user)
          (name value)))
        (else
         (configuration-field-error #f 'user value))))

(define (mpd-group-sanitizer value)
  (cond ((user-group? value) value)
        ((string? value)
         (warning (G_ "string value for 'group' is deprecated, use \
user-group instead~%"))
         (user-group
          (inherit %mpd-group)
          (name value)))
        (else
         (configuration-field-error #f 'group value))))

(define (mpd-log-file-sanitizer value)
  ;; XXX: While leaving the 'sys_log' option out of the mpd.conf file is
  ;; supposed to cause logging to happen via systemd (elogind provides a
  ;; compatible interface), this doesn't work (nothing gets logged); use
  ;; syslog instead.
  (let ((value (maybe-value value "syslog")))
    (if (string? value)
        value
        (configuration-field-error #f 'log-file value))))

;;;

;; 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
   maybe-string
   "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}).  When left unspecified, a @code{hardware} mixer is used
for devices that support it."
   (sanitizer
    (lambda (x)  ; TODO: deprecated, remove me later.
      (cond
       ((eq? %unset-value x)
        x)
       ((symbol? x)
        (warning (G_ "symbol value for 'mixer-type' is deprecated, \
use string instead~%"))
        (symbol->string x))
       ((string? x) x)
       (else
        (configuration-field-error #f 'mixer-type x))))))

  (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
   (user-account %mpd-user)
   "The user to run mpd as."
   (sanitizer mpd-user-sanitizer))

  (group
   (user-group %mpd-group)
   "The group to run mpd as."
   (sanitizer mpd-group-sanitizer))

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

  (environment-variables
   (list-of-strings '("PULSE_CLIENTCONFIG=/etc/pulse/client.conf"
                      "PULSE_CONFIG=/etc/pulse/daemon.conf"))
   "A list of strings specifying environment variables."
   empty-serializer)

  (log-file
   maybe-string
   "The location of the log file.  Unless specified, logs are sent to the
local syslog daemon.  Alternatively, a log file name can be specified, for
example @file{/var/log/mpd.log}."
   (sanitizer mpd-log-file-sanitizer))

  (log-level
   maybe-string
   "Supress any messages below this threshold.
The available values, in decreasing order of verbosity, are: @code{verbose},
@code{info}, @code{notice}, @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."
   (serializer 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."
   (serializer mpd-serialize-deprecated-field))

  (db-file
   maybe-string
   "The location of the music database.  When left unspecified,
@file{~/.cache/db} is used.")

  (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-strings
   "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."
   (serializer
    (lambda (_ endpoints)
      (if (maybe-value-set? endpoints)
          (mpd-serialize-list-of-strings "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."
   (serializer 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."
   (serializer (lambda (_ x)
                 (mpd-serialize-list-of-mpd-plugin "input" x))))

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

  (auto-update?
   maybe-boolean
   "Whether to automatically update the music database when files are changed
in the @var{music-directory}.")

  (input-cache-size
   maybe-string
   "MPD input cache size."
   (serializer (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."
   (serializer (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."
   (serializer (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."
   (serializer (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)
    (if (string=? "syslog" log-file)
        '()                             ;nothing to do
        (list (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
          environment-variables)
    (let ((config-file (mpd-serialize-configuration config))
          (username (user-account-name user)))
      (shepherd-service
       (documentation "Run the MPD (Music Player Daemon)")
       (requirement `(user-processes loopback
                                     ,@(if (string=? "syslog" log-file)
                                           '(syslogd)
                                           '())
                                     ,@shepherd-requirement))
       (provision '(mpd))
       (start
        (with-imported-modules (source-module-closure
                                '((gnu build activation)))
          #~(begin
              (use-modules (gnu build activation))

              (let ((home #$(user-account-home-directory user)))
                (let ((user (getpw #$username))
                      (default-cache-dir (string-append home "/.cache")))

                  (define (init-directory directory)
                    (unless (file-exists? directory)
                      (mkdir-p/perms directory user #o755)))

                  ;; Define a cache location that can be automatically used
                  ;; for the database file, in case it hasn't been explicitly
                  ;; specified.
                  (for-each
                   init-directory
                   (cons default-cache-dir
                         '#$(map dirname
                                 ;; XXX: Delete the potential "syslog"
                                 ;; log-file value, which is not a directory.
                                 (delete "syslog"
                                         (filter-map maybe-value
                                                     (list db-file
                                                           log-file
                                                           state-file
                                                           sticker-file)))))))

                (make-forkexec-constructor
                 (list #$(file-append package "/bin/mpd") "--no-daemon"
                       #$config-file)
                 #:environment-variables
                 ;; Set HOME so MPD can infer default paths, such as
                 ;; for the database file.
                 (cons (string-append "HOME=" home)
                       '#$environment-variables))))))
       (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)
    ;; TODO: Deprecation code, to be removed.
    (let ((user (if (eq? (user-account-group user) %lazy-group)
                    (set-user-group user group)
                    user)))
      (list user group))))

(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 mpd-log-rotation)))
   (default-value (mpd-configuration))))


;;;
;;; myMPD
;;;

(define (string-or-symbol? x)
  (or (symbol? x) (string? x)))

(define-configuration/no-serialization mympd-ip-acl
  (allow
   (list-of-strings '())
   "Allowed IP addresses.")

  (deny
   (list-of-strings '())
   "Disallowed IP addresses."))

(define-maybe/no-serialization integer)
(define-maybe/no-serialization mympd-ip-acl)

(define %mympd-user
  (user-account
   (name "mympd")
   ;; XXX: This is a place-holder to be lazily substituted in 'mympd-accounts'
   ;; with the value from the 'group' field of <mympd-configuration>.
   (group %lazy-group)
   (system? #t)
   (comment "myMPD user")
   (home-directory "/var/empty")
   (shell (file-append shadow "/sbin/nologin"))))

(define %mympd-group
  (user-group
   (name "mympd")
   (system? #t)))

;;; TODO: Procedures for unsupported value types, to be removed.
(define (mympd-user-sanitizer value)
  (cond ((user-account? value) value)
        ((string? value)
         (warning (G_ "string value for 'user' is not supported, use \
user-account instead~%"))
         (user-account
          (inherit %mympd-user)
          (name value)))
        (else
         (configuration-field-error #f 'user value))))

(define (mympd-group-sanitizer value)
  (cond ((user-group? value) value)
        ((string? value)
         (warning (G_ "string value for 'group' is not supported, use \
user-group instead~%"))
         (user-group
          (inherit %mympd-group)
          (name value)))
        (else
         (configuration-field-error #f 'group value))))

(define (mympd-log-to-sanitizer value)
  (match value
    ('syslog
     (warning (G_ "syslog symbol value for 'log-to' is deprecated~%"))
     %unset-value)
    ((or %unset-value (? string?))
     value)
    (_ (configuration-field-error #f 'log-to value))))

;; XXX: The serialization procedures are insufficient since we require
;; access to multiple fields at once.
;; Fields marked with empty-serializer are never serialized and are
;; used for command-line arguments or by the service definition.
(define-configuration/no-serialization mympd-configuration
  (package
    (file-like mympd)
    "The package object of the myMPD server."
    empty-serializer)

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

  (user
   (user-account %mympd-user)
   "Owner of the @command{mympd} process."
   (sanitizer mympd-user-sanitizer)
   empty-serializer)

  (group
   (user-group %mympd-group)
   "Owner group of the @command{mympd} process."
   (sanitizer mympd-group-sanitizer)
   empty-serializer)

  (work-directory
   (string "/var/lib/mympd")
   "Where myMPD will store its data."
   empty-serializer)

  (cache-directory
   (string "/var/cache/mympd")
   "Where myMPD will store its cache."
   empty-serializer)

  (acl
   maybe-mympd-ip-acl
   "ACL to access the myMPD webserver.")

  (covercache-ttl
   (maybe-integer 31)
   "How long to keep cached covers, @code{0} disables cover caching.")

  (http?
   (boolean #t)
   "HTTP support.")

  (host
   (string "[::]")
   "Host name to listen on.")

  (port
   (maybe-port 80)
   "HTTP port to listen on.")

  (log-level
   (integer 5)
   "How much detail to include in logs, possible values: @code{0} to @code{7}.")

  (log-to
   maybe-string
   "Where to send logs.  Unless specified, the service logs to the local
syslog service under the @samp{daemon} facility.  Alternatively, a log file
name can be specified, for example @file{/var/log/mympd.log}."
   (sanitizer mympd-log-to-sanitizer)
   empty-serializer)

  (lualibs
   (maybe-string "all")
   "See
@url{https://jcorporation.github.io/myMPD/scripting/#lua-standard-libraries}.")

  (uri
   maybe-string
   "Override URI to myMPD.
See @url{https://github.com/jcorporation/myMPD/issues/950}.")

  (script-acl
   (maybe-mympd-ip-acl (mympd-ip-acl
                        (allow '("127.0.0.1"))))
   "ACL to access the myMPD script backend.")

  (ssl?
   (boolean #f)
   "SSL/TLS support.")

  (ssl-port
   (maybe-port 443)
   "Port to listen for HTTPS.")

  (ssl-cert
   maybe-string
   "Path to PEM encoded X.509 SSL/TLS certificate (public key).")

  (ssl-key
   maybe-string
   "Path to PEM encoded SSL/TLS private key.")

  (pin-hash
   maybe-string
   "SHA-256 hashed pin used by myMPD to control settings access by
prompting a pin from the user.")

  (save-caches?
   maybe-boolean
   "Whether to preserve caches between service restarts."))

(define (mympd-serialize-configuration config)
  (define serialize-value
    (match-lambda
      ((? boolean? val) (if val "true" "false"))
      ((? integer? val) (number->string val))
      ((? mympd-ip-acl? val) (ip-acl-serialize-configuration val))
      ((? string? val) val)))

  (define (ip-acl-serialize-configuration config)
    (define (serialize-list-of-strings prefix lst)
      (map (cut format #f "~a~a" prefix <>) lst))
    (string-join
     (append
      (serialize-list-of-strings "+" (mympd-ip-acl-allow config))
      (serialize-list-of-strings "-" (mympd-ip-acl-deny config))) ","))

  ;; myMPD configuration fields are serialized as individual files under
  ;; <work-directory>/config/.
  (match-record config <mympd-configuration> (work-directory acl
                                              covercache-ttl http? host port
                                              log-level lualibs uri script-acl
                                              ssl? ssl-port ssl-cert ssl-key
                                              pin-hash save-caches?)
    (define (serialize-field filename value)
      (when (maybe-value-set? value)
        (list (format #f "~a/config/~a" work-directory filename)
              (mixed-text-file filename (serialize-value value)))))

    (let ((filename-to-field `(("acl" . ,acl)
                               ("covercache_keep_days" . ,covercache-ttl)
                               ("http"                 . ,http?)
                               ("http_host"            . ,host)
                               ("http_port"            . ,port)
                               ("loglevel"             . ,log-level)
                               ("lualibs"              . ,lualibs)
                               ("mympd_uri"            . ,uri)
                               ("scriptacl"            . ,script-acl)
                               ("ssl"                  . ,ssl?)
                               ("ssl_port"             . ,ssl-port)
                               ("ssl_cert"             . ,ssl-cert)
                               ("ssl_key"              . ,ssl-key)
                               ("pin_hash"             . ,pin-hash)
                               ("save_caches"          . ,save-caches?))))
      (filter list?
              (generic-serialize-alist list serialize-field
                                       filename-to-field)))))

(define (mympd-shepherd-service config)
  (match-record config <mympd-configuration>
    (package shepherd-requirement user work-directory cache-directory
             log-level log-to)
    (shepherd-service
     (documentation "Run the myMPD daemon.")
     (requirement `(loopback user-processes
                             ,@(if (maybe-value-set? log-to)
                                   '()
                                   '(syslogd))
                             ,@shepherd-requirement))
     (provision '(mympd))
     (start
      (let ((username (user-account-name user)))
        (with-imported-modules (source-module-closure
                                '((gnu build activation)))
          #~(begin
              (use-modules (gnu build activation))

              (let ((user (getpw #$username)))

                (define (init-directory directory)
                  (unless (file-exists? directory)
                    (mkdir-p/perms directory user #o755)))

                (for-each init-directory
                          '#$(map dirname (filter-map maybe-value
                                                      (list log-to
                                                            work-directory
                                                            cache-directory)))))

              (make-forkexec-constructor
               `(#$(file-append package "/bin/mympd")
                 "--user" #$username
                 #$@(if (eq? log-to 'syslog) '("--syslog") '())
                 "--workdir" #$work-directory
                 "--cachedir" #$cache-directory)
               #:environment-variables
               (list #$(format #f "MYMPD_LOGLEVEL=~a" log-level))
               #:log-file #$(maybe-value log-to)))))))))

(define (mympd-accounts config)
  (match-record config <mympd-configuration> (user group)
    ;; TODO: Deprecation code, to be removed.
    (let ((user (if (eq? (user-account-group user) %lazy-group)
                    (set-user-group user group)
                    user)))
      (list user group))))

(define (mympd-log-rotation config)
  (match-record config <mympd-configuration>
    (log-to)
    (if (maybe-value-set? log-to)
        (list (log-rotation
               (files (list log-to))))
        '())))

(define mympd-service-type
  (service-type
   (name 'mympd)
   (extensions
    (list  (service-extension shepherd-root-service-type
                              (compose list mympd-shepherd-service))
           (service-extension account-service-type
                              mympd-accounts)
           (service-extension special-files-service-type
                              mympd-serialize-configuration)
           (service-extension rottlog-service-type
                              mympd-log-rotation)))
   (description "Run myMPD, a frontend for MPD. (Music Player Daemon)")
   (default-value (mympd-configuration))))