#!/usr/bin/env sh

get_time(){
	echo "$*" | sed "s/[ \t].*//"
}

get_title(){
	echo "$*" | cut -d ' ' -f 2-
}

reverse_word_order(){
	local result=
	for word in $@; do
		result="$word $result"
	done
	echo "$result" 
}

# bc is mandatory: arythmetic operations are very limited in ash.
get_seconds(){
	number_position=0
	value=0

	values=$(echo "$*" | sed 's/:/\
/g' | sed "s/^0//")
	for i in $(reverse_word_order $values); do
		case $number_position in
			0) value=$(echo "$value +         $i " | bc);;
			1) value=$(echo "$value + (60   * $i)" | bc);;
			2) value=$(echo "$value + (3600 * $i)" | bc);;
			*) echo "invalid timecode $*"; exit 1;;
		esac

		number_position=$((number_position+1))
	done

	echo $value
}

# Get a more usable time representation for the beginning and the end of songs.
get_values(){

	audio_file="$1"
	time_file="$2"

	track_number=1

	while read X; do

		if [ $track_number -ne 1 ]; then
			to_unformatted=$(get_time $X)
			to_s=$(get_seconds $to_unformatted)
			echo "$from_s	$to_s	$title"
		fi

		from_unformatted=$(get_time $X)
		from_s=$(get_seconds $from_unformatted)
		title=$(get_title $X)

		if [ "$NONUMBER" = "" ]; then
			track_n=$track_number
			if [ $track_number -lt 10 ]; then
				track_n="0$track_number"
			fi
			title="${track_n}${SEPARATOR}${title}"
		fi

		track_number=$(echo $track_number + 1 | bc)
	done < "${time_file}"

	echo "$from_s	$eof_marker	$title"
}

run_ffmpeg(){
	file=$1
	from=$2
	duration=$3
	final_title=$4

	LOG_LEVEL="-loglevel error"
	FROM="-ss $from"
	if [ "$duration" = "" ]; then
		DURATION=""
	else
		DURATION="-t $duration"
	fi
	INPUT_FILE="-i $file"
	OUTPUT_FILE="$final_title"

	case "v$VERBOSITY" in
		v0)
			;;
		v1)
			echo "extracting '$final_title'"
			;;
		v2)
			echo "ffmpeg $LOG_LEVEL $FROM $DURATION $INPUT_FILE '$OUTPUT_FILE'"
			;;
		*)
			echo "verbosity is not set properly" >&2
			exit 1
			;;
	esac

	if [ "$SIMULATION" = "" ]; then
		$(< /dev/null ffmpeg $LOG_LEVEL $FROM $DURATION $INPUT_FILE "$OUTPUT_FILE")
	fi
}

rip(){
	track_start_s=0
	track_end_s=0

	audio_file="$1"
	time_file="$2"

	get_values "$audio_file" "$time_file" | while read LINE; do
		track_start_s=$(echo $LINE | cut -d ' ' -f 1)
		track_end_s=$(echo $LINE | cut -d ' ' -f 2)
		track_title=$(echo $LINE | cut -d ' ' -f 3-)
		if [ "$track_end_s" != "$eof_marker" ]; then
			track_duration=$(echo "$track_end_s - $track_start_s" | bc)
		else
			track_duration=""
		fi

		run_ffmpeg "${audio_file}" "${track_start_s}" "${track_duration}" "${track_title}.${FORMAT}"
	done
}

usage(){
	echo "usage: $0 command"
	echo "command: show <single-file-playlist> <song-list>"
	echo "command: rip  <single-file-playlist> <song-list>"
	echo
	echo "song-list line format example: 1:30 My second track of the playlist"
	echo "show output format: start end title"
	echo
	echo "envvar: SIMULATION, if non empty, do not invoke ffmpeg"
	echo "envvar: NONUMBER, if non empty, do not write song number"
	echo "envvar: FORMAT [mp3,ogg,opus,…], see the ffmpeg documentation"
	echo "envvar: SEPARATOR [separator] (default: ' - '), write song number, with this separator"
	echo "        example with SEPARATOR='_': song names will be 01_song.opus 02_song.opus…"
	echo "envvar: VERBOSITY [0-3] (default: 1)"
	echo "        VERBOSITY 0: no output exept errors from ffmpeg"
	echo "        VERBOSITY 1: simple indications on the current track being extracted"
	echo "        VERBOSITY 2: print actual ffmpeg commands the script currently runs"
}

if [ $# -lt 1 ]; then
	usage
	exit 0
fi

command=$1
shift

if [ "$FORMAT" = "" ]; then
	echo "default FORMAT: opus"
	FORMAT="opus"
fi

if [ "$VERBOSITY" = "" ]; then
	echo "default VERBOSITY: 1"
	VERBOSITY=1
fi

# Assume that there should be a separator.
if [ "$SEPARATOR" = "" ]; then
	echo "default SEPARATOR: ' - '"
	SEPARATOR=" - "
fi

if [ "$SIMULATION" != "" ]; then
	echo "SIMULATION envvar is set: this is a simulation."
fi

# soxi provides the total length of the music file.
#which soxi 2>/dev/null
#total_length=$(soxi -D "${audio_file}" | sed "s/\..*//") # integer values only
eof_marker="END_OF_FILE"

case "x-${command}" in
	x-show)

		# Takes the audio file in first parameter
		if [ $# -ne 2 ]; then
			echo "Usage: $0 show music-file time-stamps-file" >&2
			exit 1
		fi

		get_values "$1" "$2"
		;;

	x-rip)

		# Takes the audio file in first parameter
		if [ $# -ne 2 ]; then
			echo "Usage: $0 show music-file time-stamps-file" >&2
			exit 1
		fi

		rip "$1" "$2"
		;;

	*)
		usage 1>&2
		exit 1
esac