#! /bin/bash
#
# ptgdp - Play the Goddamned Playlist
# Copyright (C) 2019 Vintage Salt <rehashedsalt@cock.li>
#
# Distributed under terms of the MIT license.
#
set -e

# Import user-dirs.dirs
_xdguserdirs="${XDG_CONFIG_HOME:-$HOME/.config}/user-dirs.dirs"
[ -z "$XDG_MUSIC_DIR" ] && [ -r "$_xdguserdirs" ] && source "$_xdguserdirs"
unset _xdguserdirs
# Read-only set-once variables
declare -r _name="$(basename -- "$0")"
declare -r _musicdir="${XDG_MUSIC_DIR:-$HOME/Music}"
declare -r _ptgdpmusicdir="$_musicdir/PTGDP Songs"
declare -ra _supportedbackends=("mpd" "audacious")
# May-need-amended variables
declare _mpdroot="$_musicdir"
# Options
declare -A _config=(
	[backend]="mpd"
	[ytdl_args]="--geo-bypass"
)
declare _optconfigfile="${XDG_CONFIG_HOME:-$HOME/.config}/${_name}.conf"
declare -i _optautoplay=0
declare -i _optdlonly
declare -i _opthelp
declare -i _optmachinemode
declare -i _optverbose
# Working variables
declare -a _queue
declare -a _args
declare _return

# Helper functions
log() {
	# Print a line to the terminal if _optverbose is greater than $2
	# $2 defaults to 0
	# loglevel 0: Daily-use messages
	# loglevel 1: Detailed but not quite debugging
	# loglevel 2: Definitely debugging
	[ -z "$1" ] && return 1
	local -i outstream=1
	[ -n "$_optmachinemode" ] && outstream=2
	if (( _optverbose >= ${2:-0} )); then
		printf "%s\\n" "$1" >&"$outstream"
	fi
}
warn() {
	# Print a yellow line to the terminal, respecting _optverbose
	[ -z "$1" ] && return 1
	local -i outstream=1
	[ -n "$_optmachinemode" ] && outstream=2
	if (( _optverbose >= ${2:-0} )); then
		if [ -t "$outstream" ]; then
			printf "\\e[33m%s\\e[0m\\n" "$1" >&"$outstream"
		else
			printf "WARN: %s\\n" "$1" >&"$outstream"
		fi
	fi
}
error() {
	# Print a red line to the terminal, exit if $2 is specified
	[ -z "$1" ] && return 1
	if [ -t 2 ]; then
		printf "\\e[31m%s\\e[0m\\n" "$1" 1>&2
	else
		printf "ERROR: %s\\n" "$1" 1>&2
	fi
	[ -n "$2" ] && exit "${2:-1}"
}
has() {
	# Parse out all arguments and try to find them in path
	# If an argument cannot be found, set _return and fail
	for prog in "$@"; do
		if ! command -v "$prog" > /dev/null 2>&1; then
			_return="$prog"
			return 1
		fi
	done
	return 0
}
sanitize() {
	# Strip a line of special charactersj
	[ -z "$1" ] && return 1
	_return="${1//[^ a-zA-Z0-9\[\]|()_-:]/}"
}

# More complex helper functions
checksong() {
	# Check to see if a song exists in the cache
	[ -z "$1" ] && return 1
	# Very rudimentary implementation
	# TODO: Make this a lot more thorough, maybe ensure MIME is good
	sanitize "$1"
	for file in "$_ptgdpmusicdir/$_return"*; do
		if [ -f "$file" ]; then
			_return="$file"
			return 0
		fi
	done
	unset _return
	return 1
}
cachesong() {
	# Check to see if a song exists in the cache, downloading if not
	# Sets _returnstatus to either "dl", "cache", or "err"
	# Sets _return to the song filename
	[ -z "$1" ] && return 1
	sanitize "$1"
	filename="$_ptgdpmusicdir/$_return"
	if ! checksong "$_return"; then
		log "Downloading new song \"$1\"" 2
		local ytdllog
		if ytdllog=$(youtube-dl \
			--add-metadata \
			--audio-format "best" \
			--default-search "ytsearch" \
			--playlist-items 1 \
			"${_config[ytdl_args]}" \
			-x \
			-o "$filename.%(ext)s" \
			"$1")
		then
			# Sanitize removes all periods, so this is safe
			for file in "$filename".*; do
				if [ -f "$file" ]; then
					_return="$file"
				else
					error "Downloaded song \"$_return\" but could not find output file"
					log "$ytdllog" 2
					_returnstatus="err"
					return 1
				fi
			done
			_returnstatus="dl"
			log "Downloaded song to \"$_return\"" 2
			log "$ytdllog" 2
			return 0
		else
			log "$ytdllog" 2
			_returnstatus="err"
			return 1
		fi
	else
		_returnstatus="cache"
		return 0
	fi
}
queuesong() {
	# Add a song to _queue, downloading if necessary
	# Sets _return to one of: dl, cache, err
	[ -z "$1" ] && return 1
	cachesong "$1" || return 1
	case $_returnstatus in
		cache)
			log "Using cached song \"$1\"" 1
			log " $_return" 2
			;;
		*)
			log "Downloaded song \"$1\""
			log " $_return" 2
			;;
	esac
	_queue+=("$_return")
}
validateline() {
	# Takes a line and errors if it's just whitespace or a comment
	local linenows=${1//[[:space:]]}
	if ! [ "${1#\#}" = "$1" ] || [ -z "$linenows" ]; then
		return 1
	fi
	return 0
}

# Backend-specific functions
backend-validate() {
	# Ensure the backend is even proper
	# Returns 1 for missing dependencies
	# Everything after that is backend-specific. See below
	(
		for backend in ${_supportedbackends[@]}; do
			if [ "$backend" = "${_config[backend]}" ]; then
				return 0
			fi
		done
		return 1
	) || return $?
	# Backend-specific checks
	case ${_config[backend]} in
		audacious)
			has audacious audtool || return 1
			;;
		mpd)
			has mpd mpc || return 1
			pgrep mpd > /dev/null 2>&1 || return 2
			;;
	esac
	return 0
}
backend-enqueue() { # Enqueues a song
	# Note: mpd will assume you've updated the library since!
	[ -z "$1" ] && return 1
	case ${_config[backend]} in
		audacious)
			audtool --playlist-addurl "$1"
			return 0
			;;
		mpd)
			file=${1##$_mpdroot/}
			if ! mpc add "$file" > /dev/null 2>&1; then
				errorval="$?"
				error "Could not add file: \"$file\" ($errorval)"
			fi
			return 0
			;;
	esac
	return 1
}
backend-play() {
	# Plays a set up queue
	case ${_config[backend]} in
		audacious)
			audtool --playback-play
			;;
		mpd)
			if ! mpc play > /dev/null 2>&1; then
				error "Could not play queue ($?)"
				return 1
			fi
			return 0
			;;
	esac
	log "Started playback" 1
}
backend-execqueue() {
	# Executes a queue, enqueueing files and autoplaying if configured
	case ${_config[backend]} in
		audacious)
			if ! pgrep audacious > /dev/null 2>&1; then
				warn "Audacious is not running; songs will be downloaded but not enqueued"
			fi
			;;
		mpd)
			if ! mpc update --wait > /dev/null 2>&1; then
				error "Failed to update mpd library" 51
			fi
			;;
	esac
	for song in "${_queue[@]}"; do
		backend-enqueue "$song"
	done
	if [ "$_optautoplay" != "0" ]; then
		backend-play
	fi
}

# Core program functions
printhelp() {
	cat << EOF
Usage: $_name [OPTION]... [FILE]...
Use youtube-dl and a music player to queue up or download a number of songs
given plaintext files with only search queries

  -c [FILE]		Load the given file in place of the usual config file
  -d			Download songs but don't queue them up
  -h			Print this help text
  -m			Machine-processible mode. Output all log text to STDERR
			and print only the final list of songs to STDOUT,
			separated by newlines.
  -p			Play the queue after it's built
  -v			Print more status messages. Stacks

Copyright (c) 2019 rehashedsalt@cock.li
Licensed under the MIT license
EOF
}
playlist() {
	[ -z "$1" ] && return 1
	[ -e "$1" ] || error "Playlist \"$1\" does not exist" 60
	[ -r "$1" ] || error "Playlist \"$1\" could not be read" 61
	local -i dlcache=0
	local -i dlsuccess=0
	local -i dlerr=0
	local -i goodlines=0
	local -i totallines=0
	while read line; do
		totallines+=1
		if validateline "$line"; then
			goodlines+=1
			queuesong "$line" || error "Failed to enqueue song: \"$line\""
			case $_returnstatus in
				dl)
					dlsuccess+=1
					;;
				cache)
					dlcache+=1
					;;
				err)
					dlerr+=1
					;;
			esac
		else
			continue
		fi
	done < "$1"
	if [ -n "$_optmachinemode" ]; then
		for file in "${_queue[@]}"; do
			printf "$file\\n"
		done
	elif [ -z "$_optdlonly" ]; then
		backend-execqueue
	fi
	log "Finished: $dlcache cached, $dlsuccess downloaded, $dlerr failed"
	log "Playlist has $totallines total lines, $goodlines of them songs" 1
}

# Main
main() {
	# Getopts before anything else
	while getopts ":c:dhmpv" opt; do
		case $opt in
			c)
				_optconfigfile="$OPTARG"
				;;
			d)
				_optdlonly=1
				;;
			h)
				_opthelp=1
				;;
			m)
				_optmachinemode=1
				;;
			p)
				_optautoplay=1
				;;
			v)
				_optverbose+=1
				;;
			:)
				error "Option requires argument: -$OPTARG" 2
				;;
			*)
				error "Invalid option: -$OPTARG" 2
				;;
		esac
	done
	# Parse out a config file if it exists
	if [ -f "$_optconfigfile" ]; then
		log "Loading config file" 2
		while read line; do
			# If the line has an equals sign and isn't a comment
			if [ "$line" != "${line#*=}" ] && validateline "$line"; then
				local varname="${line%=*}"
				local value="${line#*=}"
				_config[$varname]="$value"
				log "Setting $varname to $value" 2
			fi
		done < "$_optconfigfile"
	else
		warn "Could not find configuration file" 2
	fi
	# Store arguments
	shift $((OPTIND - 1))
	for arg in "$@"; do
		_args+=("$arg")
	done
	# Validate critical options
	(
		for backend in ${_supportedbackends[@]}; do
			if [ "$backend" = "${_config[backend]}" ]; then
				return 0
			fi
		done
		return 1
	) || error "Unsupported backend: ${_config[backend]}" 50
	if [ -z "$_optmachinemode" ] && ! backend-validate; then
		errorcode=$?
		case $errorcode in
			1)
				error "Missing dependency for backend ${_config[backend]}: $_return" 50
				;;
			*)
				error "Backend error: $errorcode: $_return" 50
				;;
		esac
	fi

	# Pre-really-do-stuff hooks like help text
	[ -n "$_opthelp" ] && printhelp && exit 0

	# Do the do
	log "Validating dependencies" 2
	if ! has youtube-dl pgrep; then
		error "Failed to find program: $_return" 1
	fi
	if [ -n "${_args[*]}" ]; then
		# Files specified on the command line have priority
		for arg in "${_args[@]}"; do
			playlist "$arg"
		done
	elif ! [ -t 0 ]; then
		# If there are none of those, read from STDIN
		playlist "/dev/stdin"
	else
		warn "Nothing to do"
		exit 0
	fi
}

main "$@"