mpv-song-description

#!/usr/bin/env bash
# print a description of the song, like
# title - artist (album)
#
# this uses the 'title', 'artist' and 'album' metadata keys
# as set by MPV, it handles parsing data from ID3 / metadata
#
# if the MPV_DESC_RAW environment variable is set, prints the raw JSON metadata
# if MPV_DESC_SKIP_ALBUM is set, doesn't include the album
#
# Exits unsuccessfully if nothing is playing or it couldn't find
# any of the expected keys on the parsed metadata

set -o pipefail

IFS=$'\n'

declare -a playing

if ! playing=($(mpv-currently-playing --socket)); then
	echo 'No mpv instances which are currently playing media...' >&2
	exit 1
fi

# reset IFS -- acts as normal
# https://unix.stackexchange.com/questions/26784/understanding-ifs
unset IFS

declare metadata

metadata="$(mpv-get-property "${playing[-1]}" 'metadata')"
[[ -n "$MPV_DESC_RAW" ]] && {
	printf '%s\n' "${metadata}"
	exit 0
}

declare TITLE ARTIST ALBUM DESCRIPTION

fetch_attr_or_empty() {
	# jq the key out default to empty space, remove newlines and spaces from end of field
	jq --arg FIELD "$1" '.[$FIELD]//""' -r <<<"${metadata}" | sed -e 's/\n/ /g; s/\s*$//g'
}

TITLE="$(fetch_attr_or_empty title)"
ARTIST="$(fetch_attr_or_empty artist)"
[[ -z "$MPV_DESC_SKIP_ALBUM" ]] && ALBUM="$(fetch_attr_or_empty album)"

DESCRIPTION=''
[[ -n "$TITLE" ]] && DESCRIPTION="${TITLE}"
[[ -n "$ARTIST" ]] && DESCRIPTION="${DESCRIPTION} - ${ARTIST}"
[[ -n "$ALBUM" && -z "${MPV_DESC_SKIP_ALBUM}" ]] && DESCRIPTION="${DESCRIPTION} (${ALBUM})"

if [[ -z "${DESCRIPTION}" ]]; then
	echo 'No data extracted from metadata' 1>&2
	exit 1
fi

printf '%s\n' "${DESCRIPTION}"