Silent gap for Strawberry audio player (alpha).

#!/usr/bin/env bash

# https://forum.strawberrymusicplayer.org/topic/3417/optional-gap-between-each-song-playback
#
# Poor man's custom gap for the Strawberry audio player via "Stop after this track" feature.
# Use case: Introduce a silent period after each track.

###################################### IMPORTANT ################################################
#                                                                                               #
#                  Close Strawberry first and make sure the process doesn't exist.              #
#                       Otherwise you may backup a corrupted database.                          #
#                                                                                               #
#    Backup the database:                                                                       #
#  echo cp ~/.local/share/strawberry/strawberry/strawberry.db{,__$(date +'%Y-%m-%d_%H:%M')__OK} #
#  ls -l ~/.local/share/strawberry/strawberry/                                                  #
#                                                                                               #
#    Install the latest version of Strawberry (1.2.4 as of now) from                            #
#   https://github.com/strawberrymusicplayer/strawberry/releases                                #
#                                                                                               #
#################################################################################################


# On the sunny side:
#   After running the script, every finished track will be followed by the chosen period of
# silent time, and then the next track will be played. During the gap, the player is stopped.
# Double clicks anywhere on the playlist work normally while playing or in Pause.
# The previous attempt (a different approach using Previous and pausing there, with an older
# Strawberry) lead to freezes of the player, other programs and the sound system. Never happened
# with this one, but be cautious.

# Limitations/nuisances:
#   The script uses D-Bus MPRIS interface, which doesn't account for the end of a track nor can
# it detect how Play, Stop and other actions were initiated. There is no way to differentiate
# between mouse clicks, commands or actions automatically performed by the player.
#   So, if the user clicks on Stop, the information received by the script will be the same as
# that of "Stop after this track", and it will start the countdowm of the silent period. Use
# pause instead to stop the audio temporarily, or interrupt the script.
#
#   The OSD/notification system of Strawberry is not controllable externally, aside from the two
# actions assignable to keyboard shortcuts. If it is active, it will notify the stop of every track.
# And in any case, the album cover pane will disappear when the player is stopped, as usual.

#   This alpha is to test and decide if the benefit of the general idea outweights its disadvantages.
# Several things are on the to-do list and may be achieved or not depending on availability of wisdom
# and possible comments: better argument handling, change of track during silence, start/end from a
# desktop icon, time units for the gap (minutes, currently only seconds are used), alternatives for
# the dbus tools, user input at runtime, custom layout of the metadata shown in the terminal,
# image-to-ascii for the album cover -kidding-, etc.

# Tested only for the general case of a regular static playlist.

##### User config.

gap_secs_default="30"           # The gap: seconds to wait before playing the next track.
show_countdown="yes"            # A little feedback in the terminal; not necessary.
countdown_step="0.2"            # "Faster seconds" for the first tests. Set to 1 when done.

#############################################################################

short="${0##*\/}"
_debug_=":"


_help () {
    echo "Usage: $short [-h|--help] [-nc] [N]"
    echo "Gap maker for Strawberry. Stops it for N seconds after each track and plays the next one."
    echo "        N  :    Seconds. Default: $gap_secs_default"
    echo "       -nc :    Don't show countdown."
#    echo "  --verbose:    "
    echo "       -h  :    This help."
    echo ""
    echo "  Example: ./$short -nc 35"
    echo "  Quit: Control-C                                       $short v0.1-alpha - \"Gapper's Delight.\""
    }


_args () {
    while : ; do
        case "$1" in
                     "--debug") _debug_="echo "  ; shift ;;
                 "-h"|"--help") _help ; exit ;;
        "-nc"|"--no-countdown") show_countdown="no" ; shift ;;
                   "--verbose") _debug_="echo " ; shift ;;
                            "") gap_secs="$gap_secs_default" ; break ;;
                             *) [[ "$1" =~ ^[0-9]+ ]] && gap_secs="$1" || \
                                    echo "Ignored parameter: $1" >&2
                                    break ;;
        esac
    done
    }


_checkTools () {
    for tool in gdbus dbus-monitor; do
        which "$tool" >/dev/null 2>&1 || {
            echo "$tool not found."
            missing="yes" ; }
    done
    [[ "$missing" == "yes" ]] && {
        echo "Can't find the above program(s). Exiting..."
        exit 1
        }
    }


args=( "$@" )
_args "${args[@]}"


_playerStatus () {
    player_status="$(gdbus call -e  --dest org.mpris.MediaPlayer2.strawberry --object-path /org/mpris/MediaPlayer2 --method org.freedesktop.DBus.Properties.Get org.mpris.MediaPlayer2.Player PlaybackStatus)"
    }


_metadataAlt () {
    metadata="$(gdbus call -e  --dest org.mpris.MediaPlayer2.strawberry --object-path /org/mpris/MediaPlayer2 --method org.freedesktop.DBus.Properties.Get org.mpris.MediaPlayer2.Player Metadata)"

    # xesam's quoting is worth it
    mod1="${metadata#????}"
    mod1="${mod1%????}"$'\n'
    mod1="${mod1//, \'mpris:/$'\n'}"
    mod1="${mod1//, \'xesam:/$'\n'}"
    mod1="${mod1/>, \'year\': </>$'\n'year\': <}"
    mod1="${mod1//\': <[/=}"
    mod1="${mod1//\': </=}"
    mod1="${mod1//\]>$'\n'/$'\n'}"
    mod1="${mod1/length=int64 /length=}"
    mod1="${mod1/trackid=objectpath \'/trackid=\'}"
    mod1="${mod1//>$'\n'/$'\n'}"
    mod1="${mod1/\{sv\} \{$'\n'/}"
    mod1="${mod1%$'\n'}"

    while read -r -u 8 line ; do
        eval "$line"
    done 8<<<"$mod1"

    art_url="$artUrl"
    duration="${length%???}"
    playlist_pos="${trackid##*\/}"
    album_artist="$albumArtist"
    birth="${contentCreated/T/ }"
    last_used="${lastUsed/T/ }"
    track_number="$trackNumber"
    use_count="$useCount"
    }


_printMetadata () {
    echo "    playlist_pos:  $(( playlist_pos + 1 ))"

    echo "    artist:        $artist"
    echo "    title:         $title"
    echo "    duration:      $duration"
    echo "    album:         $album"
    echo "    year:          $year"
    echo "    track_number:  $track_number"
    echo "    album_artist:  $album_artist"
    echo "    genre:         $genre"
    echo "    composer:      $composer"
    echo "    comment:       $comment"

    echo "    bitrate:       $bitrate"
    echo "    url:           $url"
    echo "    art_url:       $art_url"
    echo "    birth:         $birth"
    echo "    last_used:     $last_used"
    echo "    use_count:     $use_count"
    }


_gap () {
    unset cdi_length
    countdown="$gap_secs"
    [[ "$show_countdown" != "yes" ]] && {
        echo -n "Waiting... "
        sleep "$gap_secs" ; } || {
                cd0_length=$(( 13 + ${#countdown} ))
            echo -n "  Countdown: $countdown "
            ((countdown--))
            for ((i=countdown; i>=0; i--)); do
                sleep "$countdown_step"
                [[ "$show_countdown" == "yes" ]] && echo -n "$i "
                cdi_length="$(( cdi_length + ${#i} + 1 ))"
            done
    len="$(( cd0_length + cdi_length ))"
    echo -ne "\r"
    printf "%${len}s"
    echo -ne "\r"
     }
    }

############################################################### end functions

date -u

_checkTools

_metadataAlt

[[ "$_debug_" == ":" ]] || _printMetadata

st="strawberry"


coproc dbus_monitor {
    dbus-monitor --monitor --session \
        "type='signal',interface='org.freedesktop.DBus.Properties',member='PropertiesChanged',path='/org/mpris/MediaPlayer2'" | \
            grep --line-buffered --no-group-separator -A 1 '         string "PlaybackStatus"'
    }

coproc_pid="$dbus_monitor_PID"

$_debug_ "File descriptor is ${dbus_monitor[1]} -- \$dbus_monitor_PID is $dbus_monitor_PID  --  \$\$ is $$  "
$_debug_ "playlist_pos is $(( playlist_pos + 1 ))"

[[ -n "$title" ]] && echo "Títle:    $title"

while read -r line; do
    $_debug_
    $_debug_ ">> $line"
    case "$line" in
                     'string "PlaybackStatus"') : ;;
       'variant             string "Paused"'  ) $_debug_ $'\x0a'"PAUSED"
                                                paused="yes" ;;
       'variant             string "Playing"' ) $_debug_ $'\x0a'"PLAYING"
                                                _metadataAlt
                                                [[ "$_debug_" == ":" ]] || _printMetadata
                                                [[ "$paused" != "yes" ]] && {
                                                    echo "Title:    $title" ; }
                                                paused="no"
                                                $_debug_ "PLAYING NUM $(( playlist_pos + 1 ))"
                                                $st -q
                                                $_debug_ "requested STOP-after"  ;;
       'variant             string "Stopped"')  $_debug_ $'\x0a'"STOPPED (waiting)"
                                                $_debug_ "Waiting $gap_secs"
                                                _metadataAlt
                                                [[ "$_debug_" == ":" ]] || _printMetadata
                                                _gap
                                                $st -k $(( playlist_pos + 1 )) ;;
                                             *) $_debug_ "Stray line: --$line--" ;;

    esac
done <&"${dbus_monitor[0]}"


wait "${dbus_monitor[1]}"




exit
#############################################################################
exit


# Better safe than sorry: backup the database!