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[emms-help] MusicPD support enhanced

From: Michael Olson
Subject: [emms-help] MusicPD support enhanced
Date: Sat, 31 Dec 2005 03:43:03 -0500
User-agent: Gnus/5.110004 (No Gnus v0.4) Emacs/22.0.50 (gnu/linux)

I finally got around to working on those MusicPD wishlist items, after
waiting impatiently for a 300+ song playlist to load.  I've sent the
patch to forcer.  Just in case the patch gets mangled in transit,
here's the complete file.

I've tested it fairly thoroughly.

The most significant changes include:
 - Doesn't rely on the mpc binary.
 - Uses a network process to pass commands to the MusicPD daemon.
 - The above yields a massive speed increase.
 - Add a function for getting track info.
 - Add several options, including one that causes an error to be shown
   when adding a file to the MusicPD playlist fails.

;; emms-player-mpd.el --- MusicPD support for EMMS

;; Copyright (C) 2005  Free Software Foundation, Inc.

;; Author: Michael Olson (mwolson AT gnu DOT org)

;; This file is not part of GNU Emacs.

;; This 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 2, or (at your option) any later
;; version.
;; This 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 Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;;; Benefits

;; MusicPD features crossfade, very little skipping, minor CPU usage,
;; many clients, many supported output formats, fast manipulation via
;; network processes, and good abstraction of client and server.

;;; MusicPD setup

;; You'll need to have both mpc and mpd installed.  The website is at
;; http://musicpd.org/.  Debian packages are available.  I recommend
;; getting the latest development version; see
;; http://mpd.wikicities.com/wiki/Subversion for nightly Debian
;; packages and the svn repo.
;; Copy the example configuration for mpd into ~/.mpdconf and edit it
;; to your needs.  Use your top level music directory for
;; music_directory.  If your playlists use absolute file names, be
;; certain that music_directory has the leading directory part.
;; Before you try to play anything, but after setting up the above,
;; run `mkdir ~/.mpd && mpd --create-db' to create MusicPD's track
;; database.
;; Check to see if mpd is running.  It must be running as a daemon for
;; you to be able to play anything.  Launch it by executing "mpd".  It
;; can be killed later with "mpd --kill" (or just "killall mpd" if
;; you're not using the latest development version).

;;; EMMS setup

;; Add "emms-player-mpd" to the top of `emms-player-list'.  If you use
;; absolute file names in your m3u playlists (which is most likely),
;; make sure you set `emms-player-mpd-music-directory' to the value of
;; "music_directory" from your MusicPD config.

;; To get track info from MusicPD, do the following.

;; (add-to-list 'emms-info-functions 'emms-info-mpd)

;;; TODO

;; If you try to play individual songs, the tracks will not advance.
;; I recommend playing playlists instead.  This should be addresed
;; eventually, though, perhaps with a timer watching the mpd process.
;; It might also be good to "sync" the mpd playlist with the emms one.
;; Currently we just clear the mpd playlist, add the track, and play,
;; for each track.  Not the best approach, unless your track is a
;; playlist in itself, in which case all tracks from the playlist are
;; added immediately after clearing the mpd playlist.

(require 'emms-player-simple)

(defun emms-player-mpd-get-supported-regexp ()
  "Returns a regexp of file extensions that MusicPD supports,
or nil if we cannot figure it out."
  (let ((out (split-string (shell-command-to-string "mpd --version")
    ;; Get last non-empty line
    (while (car out)
      (when (not (string= (car out) ""))
        (setq supported (car out)))
      (setq out (cdr out)))
    ;; Create regexp
    (when (and (stringp supported)
               (not (string= supported "")))
      (concat "\\`http://\\|\\.\\(m3u\\|pls\\|"
              (mapconcat 'identity (delq nil (split-string supported))

(defvar emms-player-mpd-supported-regexp
  ;; Use a sane default, just in case
  (or (emms-player-mpd-get-supported-regexp)
  "Formats supported by MusicPD Client.")

(defcustom emms-player-mpd-music-directory nil
  "The value of 'music_directory' in your MusicPD configuration file.
You need this if your playlists use absolute file names, otherwise
leave it set to nil."
  ;; The :format part ensures that entering directories happens on the
  ;; next line, where there is more space to work with
  :type '(choice :format "%{%t%}:\n   %[Value Menu%] %v"
                 (const nil)
  :group 'emms-player-mpd)

(defcustom emms-player-mpd-connect-function
  (if (and (fboundp 'open-network-stream-nowait)
           ;; CVS Emacs claims to define open-network-stream-nowait on
           ;; windows, however, it does, in fact, not work.
           (not (memq system-type '(windows-nt cygwin ms-dos darwin))))
  "Function used to initiate the connection to MusicPD.
It should take same arguments as `open-network-stream' does.

This will usually be auto-detected correctly."
  :type 'function
  :group 'emms-player-mpd)

(defcustom emms-player-mpd-server-name "localhost"
  "The MusicPD server that we should connect to."
  :type 'string
  :group 'emms-player-mpd)

(defcustom emms-player-mpd-server-port "6600"
  "The port of the MusicPD server that we should connect to."
  :type '(choice number string)
  :group 'emms-player-mpd)

(defcustom emms-player-mpd-timeout 10
  "The maximum acceptable delay (in seconds) while waiting for a
response from the MusicPD server."
  :type 'integer
  :group 'emms-player-mpd)

(defcustom emms-player-mpd-verbose nil
  "Whether to provide notifications for server connection events
and errors."
  :type 'boolean
  :group 'emms-player-mpd)

(define-emms-simple-player mpd '(file url playlist)
  emms-player-mpd-supported-regexp "mpd")

(emms-player-set emms-player-mpd

(emms-player-set emms-player-mpd

(emms-player-set emms-player-mpd

;;; Dealing with the MusicPD network process

(defvar emms-player-mpd-process nil)
(defvar emms-player-mpd-returned-data nil)

(defun emms-player-mpd-sentinel (proc str)
  "The process sentinel for MusicPD."
  (let ((status (process-status proc)))
    (cond ((memq status '(exit signal closed))
           (when emms-player-mpd-verbose
             (message "Closed MusicPD process"))
           (setq emms-player-mpd-process nil))
          ((memq status '(run listen open))
           (when emms-player-mpd-verbose
             (message "MusicPD process started successfully"))))))

(defun emms-player-mpd-filter (proc string)
  "The process filter for MusicPD."
  (setq emms-player-mpd-returned-data string))

(defun emms-player-mpd-ensure-process ()
  "Make sure that a MusicPD process is currently active."
  (unless (and emms-player-mpd-process
               (processp emms-player-mpd-process)
               (memq (process-status emms-player-mpd-process) '(run open)))
    (setq emms-player-mpd-process
          (funcall emms-player-mpd-connect-function "mpd"
    (set-process-sentinel emms-player-mpd-process
    (set-process-filter emms-player-mpd-process

(defun emms-player-mpd-send (command)
  "Send the given COMMAND to the MusicPD server."
  (unless (string= (substring command -1) "\n")
    (setq command (concat command "\n")))
  (process-send-string emms-player-mpd-process command)

(defun emms-player-mpd-send-and-wait (command)
  "Send the given COMMAND to the MusicPD server and await a response,
which is returned."
  (setq emms-player-mpd-returned-data nil)
  (emms-player-mpd-send command)
  (accept-process-output emms-player-mpd-process emms-player-mpd-timeout)

;;; Helper functions

(defun emms-player-mpd-parse-response (response)
  "Convert the given MusicPD response into a list.
The car of the list is special:
If an error has occurred, it will contain a cons cell whose car is
an error number and whose cdr is the corresponding message.
Otherwise, it will be nil."
  (when (stringp response)
      (let* ((data (split-string response "\n"))
             (cruft (last data 3))
             (status (if (string= (cadr cruft) "")
                         (car cruft)
                       (cadr cruft))))
        (setcdr cruft nil)
        (when (string-match "^OK MPD " (car data))
          (setq data (cdr data)))
        (if (string-match "^ACK \\[\\([0-9]+\\)@[0-9]+\\] \\(.+\\)" status)
            (cons (cons (match-string 1 status)
                        (match-string 2 status))
          (cons nil data))))))

(defun emms-player-mpd-get-alist (info)
  "Turn the given parsed INFO from MusicPD into an alist.
The format of the alist is (name . value)."
  (when (and info
             (null (car info))          ; no error has occurred
             (cdr info))                ; data exists
    (let (alist)
      (dolist (line (cdr info))
        (string-match "\\`\\([^:]+\\):\\s-*\\(.+\\)" line)
        (let ((name (match-string 1 line))
              (value (match-string 2 line)))
          (when (and name value)
            (setq name (downcase name))
            (add-to-list 'alist (cons name value) t))))

(defun emms-player-mpd-get-filename (file)
  "Turn FILE into something that MusicPD can understand.
This usually means removing a prefix."
  (if (or (null emms-player-mpd-music-directory)
          (not (eq (aref file 0) ?/))
          (string-match "\\`http://"; file))
    (file-relative-name file emms-player-mpd-music-directory)))

;;; MusicPD commands

(defun emms-player-mpd-clear ()
  "Clear the playlist."
  (emms-player-mpd-send "clear"))

(defun emms-player-mpd-add (file)
  "Add FILE to the current MusicPD playlist.
If we do not succeed in adding the file, return the string from
the process, nil otherwise."
  (setq file (emms-player-mpd-get-filename file))
  (let ((output (emms-player-mpd-parse-response
                 (emms-player-mpd-send-and-wait (concat "add " file)))))
    (when (car output)
      (when emms-player-mpd-verbose
        (message "MusicPD error: %s: %s" file (cdar output)))
      (cdar output))))

(defun emms-player-mpd-load (playlist)
  "Load contents of PLAYLIST into MusicPD by adding each line.
This handles both m3u and pls type playlists."
  ;; This allows us to keep playlists anywhere and not worry about
  ;; having to mangle their names.  Also, mpd can't handle pls
  ;; playlists by itself.
  (let ((pls-p (if (string-match "\\.pls\\'" playlist)
    (mapc #'(lambda (file)
              (when pls-p
                (if (string-match "\\`File[0-9]*=\\(.*\\)\\'" file)
                    (setq file (match-string 1 file))
                  (setq file "")))
              (unless (or (string= file "")
                          (string-match "\\`#" file))
                (emms-player-mpd-add file)))
          (split-string (with-temp-buffer
                          (insert-file-contents playlist)

(defun emms-player-mpd-play ()
  "Play whatever is in the current MusicPD playlist."
  (emms-player-mpd-send "play"))

(defun emms-player-mpd-start (track)
  "Starts a process playing TRACK."
  (let ((name (emms-track-get track 'name)))
    ;; If it's a playlist, we have to `load' rather than `add' it
    (if (string-match "\\.\\(m3u\\|pls\\)\\'" name)
        (emms-player-mpd-load name)
      (emms-player-mpd-add name)))
  ;; Now that we've added/loaded the file/playlist, play it

(defun emms-player-mpd-stop ()
  "Stop the currently playing song."
  (emms-player-mpd-send "stop"))

(defun emms-player-mpd-pause ()
  "Pause the currently playing song."
  (emms-player-mpd-send "pause"))

(defun emms-player-mpd-seek (sec)
  "Seek backward or forward by SEC seconds, depending on sign of SEC."
  (emms-player-mpd-send (format "seek %s%d"
                                (if (> sec 0) "+" "")

;; Not currently used by the API (to my knowledge), but I make use of
;; these to advance my playlists.

(defun emms-player-mpd-next ()
  "Move forward by one track in MusicPD's internal playlist."
  (emms-player-mpd-send "next"))

(defun emms-player-mpd-previous ()
  "Move backward by one track in MusicPD's internal playlist."
  (emms-player-mpd-send "previous"))

;;; Track info

(defun emms-info-mpd (track &optional info)
  "Add track information to TRACK.
This is a useful addition to `emms-info-functions'.
If INFO is specified, use that instead of acquiring the necessary
info from MusicPD."
  (let (file)
    (unless info
      (when (and (eq 'file (emms-track-type track))
                 (setq file (emms-player-mpd-get-filename
                             (emms-track-name track)))
                 (string-match emms-player-mpd-supported-regexp file))
        (setq info (emms-player-mpd-get-alist
                      (concat "find filename " file)))))))
    (when info
      (dolist (data info)
        (let ((name (car data))
              (value (cdr data)))
          (setq name (cond ((string= name "artist") 'info-artist)
                           ((string= name "title") 'info-title)
                           ((string= name "album") 'info-album)
                           ((string= name "track") 'info-tracknumber)
                           ((string= name "date") 'info-year)
                           ((string= name "genre") 'info-genre)
                           ((string= name "time")
                            (setq value (string-to-number value))
                           (t nil)))
          (when name
            (emms-track-set track name value)))))))

(defun emms-player-mpd-show (&optional insertp)
  "Describe the current EMMS track in the minibuffer.
If INSERTP is non-nil, insert the description into the current buffer instead.
This function uses `emms-show-format' to format the current track.
It differs from `emms-show' in that it asks MusicPD for the current track,
rather than EMMS."
  (interactive "P")
  (let* ((info (emms-player-mpd-get-alist
                 (emms-player-mpd-send-and-wait "currentsong"))))
         (track (emms-dictionary '*track*))
         desc string)
    (when info
      (emms-track-set track 'type 'file)
      (emms-track-set track 'name (cdr (assoc "file" info)))
      (emms-info-mpd track info)
      (setq desc (emms-track-description track)))
    (setq string (if desc
                     (format emms-show-format desc)
                   "Nothing playing right now"))
    (if insertp
        (insert string)
      (message "%s" string))))

(provide 'emms-player-mpd)

;;; emms-player-mpd.el ends here

Michael Olson -- FSF Associate Member #652 -- http://www.mwolson.org/
Interests: manga, Debian, XHTML, wiki, Emacs Lisp
  /` |\ | | | IRC: mwolson on freenode.net: #hcoop, #muse, #PurdueLUG
 |_] | \| |_| Jabber: mwolson_at_hcoop.net

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