#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  volume ACTION
		  volume -h
	EOF
}

help() {
	cat <<-'EOF'


		Options:
		  -h, --help    show this message

		  ACTION        one of:
		                - up
		                - down
		                - toggle
		                - rotate


		Manage the audio output.


		Examples:

		  Increase the volume:

		    $ volume up


		  Toggle mute/unmute in the current audio output:

		    $ volume toggle


		  Change the audio output:

		    $ volume rotate
	EOF
}

for flag in "$@"; do
	case "$flag" in
		(--)
			break
			;;
		(--help)
			usage
			help
			exit
			;;
		(*)
			;;
	esac
done

while getopts 'h' flag; do
	case "$flag" in
		(h)
			usage
			help
			exit
			;;
		(*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))
ACTION="${1:-}"

eval "$(assert-arg -- "$ACTION" 'ACTION')"



case "$ACTION" in
	up)
		pactl set-sink-volume @DEFAULT_SINK@ +10%
		;;
	down)
		pactl set-sink-volume @DEFAULT_SINK@ -10%
		;;
	toggle)
		pactl set-sink-mute @DEFAULT_SINK@ toggle
		;;
	rotate)
		pacmd set-default-sink "$(
			pacmd list-sinks |
				grep index |
				grep -v 'index: 0$' |
				awk '
					{
						n = $(NF)
						sinks[i++] = n
						last = n
						if ($1 == "*") {
							curr = n
						}
					}
					END {
						print curr == last ? sinks[0] : sinks[i - 1]
					}'
		)"
		;;
	*)
		printf 'Bad ACTION: %s.\n\n' "$ACTION" >&2
		usage >&2
		exit 2
		;;
esac