env/bin/invidious.sh

#!/bin/sh
# invidious
# Written in 2019 by Leslie
# Modified in 2019 by Lucas
# CC0 1.0 Universal/Public domain - No rights reserved
#
# To the extent possible under law, the author(s) have dedicated all
# copyright and related and neighboring rights to this software to the
# public domain worldwide. This software is distributed without any
# warranty. You should have received a copy of the CC0 Public Domain
# Dedication along with this software. If not, see
# <http://creativecommons.org/publicdomain/zero/1.0/>.

usage()
{
	printf "Usage: %s url\n" "${0##*/}" >&2
	exit 1
}

err()
{
	printf "%s: %s\n" "${0##*/}" "$*" >&2
	exit 1
}

[ $# -eq 1 ] || usage

case $1 in
"https://invidio.us/watch?v="*)
	;;
*)	err "Not an invidio.us url."
	;;
esac

video_id=
for param in $(printf "%s\n" "${1##*"?"}" | tr "&" "\n"); do
	k=${param%%=*}
	[ "$k" = v ] || continue

	v=${param#*=}
	if [ ${#v} -ne 11 ]; then
		printf  "%s: \"%s\": not a video ID." "${0##*/}" "$v" >&2
		continue
	fi
	video_id=$v
	break
done

[ -n "$video_id" ] || err "no video ID in URL."

dl_option=$(ftp -o - "$1" 2>/dev/null | grep -F "<option value='{" |
    head -n 1 | cut -d "\"" -f 8)

printf "https://invidio.us/latest_version?id=%s&itag=%s\n" \
    "$video_id" "$dl_option"