#!/bin/sh
#
# Copyright (C) 2020 Matteo Savatteri and Matteo Zeccoli Marazzini.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

# Global Variables
PROGRAM_NAME="vaporget"
PROGRAM_VERSION="0.1-alpha"
PROGRAM_UPSTREAM="https://lcm.mi.infn.it/gogs/matteozeccolimarazzini/vaporget.git"
AUTHOR_NAME="Matteo Savatteri and Matteo Zeccoli Marazzini"
CMDLINE="$@"
MODE="play"
USAGE="Usage: $PROGRAM_NAME [-Vh] [-pd | -m MPV_OPTION,...]"

HELP_TEXT="$USAGE
Get and play music from the Vaporwave Library Project.
Play music with mpv(1) if none of -pd is specified.

  -p			only print selected URLs to standard output
  -d			donwload selected songs in current working directory
  -m MPV_OPTION,...	pass options to mpv(1) (incompatible with -pd)
  -V			output version information and exit
  -h			display this extremely helpful text and exit

Exit Status:
  0	if OK,
  1	some errors occurred."

VERSION_INFOTEXT="$PROGRAM_NAME $PROGRAM_VERSION
git upstream $PROGRAM_UPSTREAM
Copyright (C) 2020 $AUTHOR_NAME.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by $AUTHOR_NAME."

WEBSITE="https://vaporwave.ivan.moe/list/"

###############################################################################
# USEFUL FUNCTIONS                                                            #
###############################################################################

# Check options
# Arguments: none
# Analize ARGVs in this order of precedence:
# Look for -h; If found, return 2
# Look for incompatible options; if found, return 1
# Look for -V; if found, return 2
check_options()
{
	local OPTIONS_STRING=$(printf -- "$CMDLINE" | sed -e 's/ [^-]*//g' -e 's/-//g')

	if [ "${OPTIONS_STRING#*h}" != "$OPTIONS_STRING" ]
	then
		printf "$HELP_TEXT\n"
		return 2
	fi

	if [ "${OPTIONS_STRING#*m}" != "$OPTIONS_STRING" -a \( "${OPTIONS_STRING#*d}" != "$OPTIONS_STRING" -o "${OPTIONS_STRING#*p}" != "$OPTIONS_STRING" \) ]
	then
		printf "$PROGRAM_NAME: incompatible options -- m, pd\n$USAGE\n" >&2
		return 1
	fi

	if [ "${OPTIONS_STRING#*V}" != "$OPTIONS_STRING" ]
	then
		printf "$VERSION_INFOTEXT\n"
		return 2
	fi

	return 0
}

# Download the html list of artists and urls
# Arguments: $1 = music library website
# Write to standard output a file made like this:
# "[url]\n[artist]\noff\n"... (repeat for each artist)
# The "off" at the end is needed by dialog.
get_library()
{
	wget -qO- "$1" 2>/dev/null \
	| grep "^<a href" \
	| sed -e 's/<a href="//' \
	      -e 's/">/\n/' \
	      -e 's/&gt;<\/a>.*/\noff/' \
	      -e 's/\/<\/a>.*/\noff/'
}

# Let the user select the artists he likes using a dialog checklist
# Arguments: $1 = music library website
# Write to standard output a '\n' separated list of the url of the selected artists.
# If the user selects cancel or presses ESC, send a SIGTERM to the script and all its subprocesses.
select_artist_list()
{
	{ xargs -d '\n' dialog --title "VAPORGET" --no-tags --checklist "Please, select an artist:" 0 0 0 3>&1 1>&2 2>&3 3>&- || kill -TERM -$$; } \
	| sed -e 's/ /\n/g' -e '$a\' \
	| sed -e 's,^,'"$1"','
}

# Prepare a list of song urls
# Arguments: $1 = list of selected artist urls
# Write to standard output and error the urls of all the songs by the selected artists.
prepare_playlist()
{
	wget --spider -r -l inf --no-parent --no-directories $1 2>&1 \
	| grep --line-buffered '^--' \
	| stdbuf -oL cut -d' ' -f4 \
	| grep --line-buffered '\.\(flac\|mp3\|wav\)$' \
	| tee /dev/stderr
}

# Plays the playlist it recieves via standard input
play_music()
{
	mpv --no-video --playlist=- $MPV_CMDLINE
}

# TERM signal handler
handle_term()
{
	clear
	exit 0
}



###############################################################################
# MAIN SECTION                                                                #
###############################################################################

# Look for incompatible command line options
check_options
case $? in
	1)
		exit 1
	;;
	2)
		exit 0
	;;
esac

# Parse command line
while getopts pdm:Vh f; do
	case $f in
		p)
			MODE="playlist"
		;;
		d)
			MODE="download"
		;;
		m)
			MPV_CMDLINE=$(printf "${OPTARG}" | sed -e 's/[[:space:]]//g' -e 's/[^,]\{2,\}/--& /g' -e 's/\(^\|,\)[[:alnum:]]\($\|,\)/ -& /g' -e 's/,//g')
		;;
		\?)
			printf "${USAGE}\n" >&2 && exit 1
		;;
	esac
done
shift $(( $OPTIND - 1 ))

# Use our custom handler for the TERM signal
trap handle_term TERM

# Fetch the artist list from the website and let the user select from a menu
CHOICES=$(get_library "${WEBSITE}" | select_artist_list "${WEBSITE}")

clear
if [ -z "${CHOICES}" ]; then	# User didn't select any artist
	printf "Please, select at least one artist.\n" >&2
	exit 1
fi

# Play the music
case $MODE in
	"play")
		prepare_playlist "${CHOICES}" | play_music
	;;
	"playlist")
		prepare_playlist "${CHOICES}" 2>/dev/null
	;;
	"download")
		prepare_playlist "${CHOICES}" | wget -i -
	;;
esac