src/bin/volume

#!/bin/sh

argv0="$0"

# ADDING A NEW SOUND SERVER/CLIENT/WHATEVERIDK
# `volume a` and `volume s` are the system dependent functions.

# `volume a $2` must set the volume to $2, an integer value. This should be a
# percentage, 100% being the loudest possible volume that can be output by
# hardware without quality loss. Percentages above 100% will be allowable in
# software if using percentage units. If percentage units are implausible to
# implement, system units are okay (e.g. 0-$arbitrary scale versus 0-100).

# `volume s` must output the current volume in integer form in whatever units
# are being used by `volume a` on the given system.

VOLUME_TMP_FILE="$HOME/.volume-previous"

system_determine(){
	if [ "$(uname)" = NetBSD ]; then
		printf "NetBSD\n"
	elif command -v pactl >/dev/null 2>&1; then
		printf "PulseAudio\n"
	fi
}

unknown_system(){
	printf "%s: Unknown system.\n" "$argv0" 1>&2
	exit 1
}

usage(){
	printf "\
Usage: %b {function} (operand)\n" "$argv0"
	printf "\
Functions:
	'+'      - shortcut to \"relative \$2\"
	'-'      - shortcut to \"relative -\$2\"
	absolute - change sound output to absolute unit
	debug    - show debugging information
	help,''  - print this help output
	mute     - toggle mute/unmute
	relative - change sound output relative to current status
	status   - print current sound output in system unit \
"
	printf "\
The options are matched with [char]*. So \"%b help\"
works the same as \"%b h\".

" "$argv0" "$argv0"
	exit 1
}

# $1 becomes 'help' if previously empty
[ -n "$1" ] \
	&& argv1="$1" \
	|| argv1=help

case "$argv1" in
#
# SYSTEM DEPENDENT
#
a*) [ -n "$2" ] || usage
	case "$(system_determine)" in
	NetBSD)
		# NetBSD 9.2 STABLE 2021-07
		audioctl -w play.gain=$2 >/dev/null
		;;
	PulseAudio)
		# pactl 15.0 compiled+linked with libpulse 15.0.0
		pactl set-sink-volume @DEFAULT_SINK@ $2%
		;;
	*)	unknown_system ;;
	esac; exit 0 ;;

s*) [ -z "$2" ] || usage
	case "$(system_determine)" in
	NetBSD) # hacky
		audioctl -a \
			| grep "play\.gain" \
			| cut -d '=' -f 2
		;;
	PulseAudio)
		# really hacky, gets the job done
		# gets the volume % of Lchan specifically
		pactl get-sink-volume @DEFAULT_SINK@ \
			| sed q \
			| cut -d '/' -f 2 \
			| xargs echo \
			| sed s/'%'//
		;;
	*)	unknown_system ;;
	esac; exit 0 ;;

#
# SYSTEM independent
#
+) "$argv0" r  "$2" ;;
-) "$argv0" r -"$2" ;;

d*)
	printf '$0: %s\nAudio system detected: %s\n' \
		"$argv0" \
		"$(system_determine)"
	exit 0 ;;

m*) [ -z "$2" ] || usage
	# restore previous volume if there is one
	if [ -e "$VOLUME_TMP_FILE" ]; then
		xargs "$argv0" a <"$VOLUME_TMP_FILE" \
			&& rm "$VOLUME_TMP_FILE" \
			&& printf "Unmuted.\n" \
			&& exit 0 \
			|| printf "Error restoring previous volume.\n" \
				1>&2 \
			&& exit 1
	fi

	# otherwise, make new file with previous volume

	# dd used rather than shell redirect so it's easy to determine
	# whether or not the file write worked
	if ! printf "%b" "$("$argv0" s)" \
				| dd of="$VOLUME_TMP_FILE" 2>/dev/null
	then
		printf "Error writing to file.\n" 1>&2
		exit 1
	fi

	# and then of course mute
	"$argv0" a 0
	printf "Muted.\n"

	exit 0 ;;

r*)
	! newval=$(printf "%s %s + p\n" $("$argv0"s) "$2" | dc) \
		&& printf "%b: Error finding new value for volume.\n" "$argv0" \
		&& exit 1
	"$argv0" a "$newval"
	exit $? ;;

*)	usage ;;
esac