Make m3u playlist of a Youtube Playlist (youtube-dl & jq must be installed)

make_m3u_youtube_playlist.sh

#!/usr/bin/env bash

# $ ./make_m3u_youtube_playlist.sh [-d OUTPUT-DIR] URL [URL ...]

if ! which jq &>/dev/null || ! which youtube-dl &>/dev/null; then
	echo "'youtube-dl' and 'jq' must be installed in \$PATH, exiting." 1>&2
	exit 1
fi

declare log_file="$HOME/.make_m3u_youtube_playlist.log"
declare prefix_id='https://www.youtube.com/watch?v='
declare prefix_pls='https://www.youtube.com/playlist?list='
declare pls_url
declare pls_re='^https?://www\.youtube\.com/(watch|playlist)\?.*?list=([^&]+)'
declare pls_n
declare pls_json
declare pls_u
declare pls_ids
declare pls_titles
declare -i replace_tmp=0
declare -a pls_i_arr=()
declare -a pls_t_arr=()
declare top_str='#EXTM3U'$'\n'
declare str
declare file_name
declare desired_filename
declare -i pls_len=0
declare output_dir="$PWD" # where to write the m3u file
declare json_re='\{.+\}'
declare -a args=()

function log_echo ()
{
	echo "${*}" 1>&2
	echo "${*}" >> "$log_file"
	return $?
}

while getopts ":d:" options ; do
	case "$options" in
		d)	output_dir="$(sed -r 's#/+$##' <<< "$OPTARG")";; # override directory
		*)	log_echo "Not a valid option, exiting:" "${*}"
			exit 1;;
	esac
done
args+=("${@:OPTIND}")

# enable support for multiple playlists at once
for i in "${!args[@]}" ; do

	[[ ${args[i]} = '' ]] && continue
	pls_url="${args[i]}"
	# reset loop variables
	replace_tmp=0
	pls_len=0
	file_name=''
	str="$top_str"
	pls_i_arr=()
	pls_t_arr=()

	if [[ ! $pls_url =~ $pls_re ]] ; then
		log_echo "No valid playlist url given, exiting:" "$pls_url"
		exit 1
	fi
	pls_url="${BASH_REMATCH[2]}"
	pls_u="$(
		# Get the playlist's owner / username - lazy way
		curl -s -L -A "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:51.0) Gecko/20100101 Firefox/51.0" "${prefix_pls}${pls_url}" \
			| grep -oP 'channel-title.+?<a [^>]+>[^<]+</a>' \
			| sed -r 's#.+>([^<]+)</a>#\1#'
	)"
	if [[ $pls_u = '' ]]; then
		log_echo "No user found, exiting:" "$pls_u"
		exit 1
	fi
	pls_json="$(youtube-dl --ignore-config --flat-playlist --dump-single-json "${prefix_pls}${pls_url}")"
	if [[ $? -ne 0 || ! "$pls_json" =~ $json_re ]] ; then
		log_echo "Not a playlist or youtube-dl returned an error, exiting:" "$pls_json"
		exit 1
	fi
	# verify it's valid json first
	if ! jq . <<< "$pls_json" &>/dev/null; then
		log_echo "jq could not parse string, exiting:" "$pls_json"
		exit 1
	fi
	pls_ids="$(jq -rM '.entries[].id' <<< "$pls_json")" || exit 3
	pls_titles="$(jq -rM '.entries[].title' <<< "$pls_json")" || exit 4
	pls_n="$(jq -rM '.title' <<< "$pls_json")" || exit 5
	if [[ $pls_n = '' ]] ; then
		# Allow empty name
		pls_n="Untitled"
	fi
	pls_len=$(wc -l <<< "$pls_ids")
	if [[ $pls_len -eq 0 ]] ; then
		# Don't write empty playlists
		log_echo "No videos in playlist, exiting:" "$pls_len"
		exit 1
	fi
	# Turn lines into arrays
	while read -r LINE; do
		[[ $LINE = '' ]] && continue
		# Full url
		pls_i_arr+=("${prefix_id}${LINE}")
	done <<< "$pls_ids"
	while read -r LINE; do
		[[ $LINE = '' ]] && continue
		pls_t_arr+=("$LINE")
	done <<< "$pls_titles"
	# Build m3u string
	# https://en.wikipedia.org/wiki/M3U
	# Playlist will be missing the length property but it should work (does in mpv)
	for x in "${!pls_i_arr[@]}" ; do
		[[ ${pls_i_arr[x]} = '' ]] && continue
		# #EXTM3U
		# #EXTINF:,User - Title - YT-PL-ID i/size
		# https://www.youtube.com/watch?v=AAAAAAAAAAA
		#
		str="${str}#EXTINF:,$pls_u - $pls_n - ${pls_t_arr[x]} - $pls_url $((x+1))/$pls_len"$'\n'"${pls_i_arr[x]}"$'\n'$'\n'
	done
	desired_filename="$output_dir/$pls_u - $pls_n ($pls_len).m3u"
	file_name="$desired_filename"
	if [[ -e $file_name ]] ; then
		log_echo "creating tmp file and backing up existing file:" "$file_name"
		file_name="$(mktemp -p "$output_dir")"
		replace_tmp=1
	fi
	echo -n "$str" > "$file_name"
	if [[ $replace_tmp -eq 1 ]] ; then
		# depend on mv's backup functionallity to create a bak file
		mv -v --backup=t "$file_name" "$desired_filename" | tee -a "$log_file" 1>&2
		file_name="$desired_filename"
	fi
	if [[ $? -ne 0 || ! -f "$file_name" ]] ; then
		log_echo "$file_name"
		notify-send -i 'error' "M3U playlist" "Failed to create playlist"
	else
		echo "$file_name"
		notify-send -i 'gtk-ok' "M3U playlist created" "$(basename "$file_name" .m3u)"
	fi

done
exit $?