#!/bin/sh
# See LICENSE file for copyright and license details.

set -e

usage () {
	printf 'usage %s: [-Dry] in-file [out-file]\n' "$0" >&2
	exit 1
}

recursive=no
delete_in_file=no
ffmpeg_flag_y=
status=0

while getopts Dry flag; do
	case "$flag" in
	D)
		delete_in_file=yes;;
	r)
		recursive=yes;;
	y)
		ffmpeg_flag_y=-y;;
	?)
		usage;;
	esac
done
shift $(( ${OPTIND} - 1 ))

if test ! $# = 1 && test ! $# = 2; then
	usage
fi

in_file="$1"
if test -z "${in_file}"; then
	usage
fi

out_file=""
if test $# = 2; then
	out_file="$2"
	if test -z "${out_file}"; then
		usage
	fi
	if test "${out_file}" = -; then
		printf '%s: - is not supported for out-file\n' "$0" >&2
		exit 1
	fi
else
	if test "${in_file}" = -; then
		printf '%s: out-file must be specified if in-file is -\n' "$0" >&2
		exit 1
	fi
fi

getext () {
	probed_file="$1"
	if test ! "${probed_file}" = -; then
		probed_file="file:${probed_file}"
	fi
	ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -of default=noprint_wrappers=1:nokey=1 -- "${probed_file}"
}

removeext () {
	printf '%s\0' "$1" | tr '\0\n' '\n\0' | sed 's/\.[^.]*$//' | tr '\0' '\n'
}

extract () {
	printf '\033[1m%s\033[m\n' "Extracting audio track from ${1}" >&2
	printf '\033[1m%s\033[m\n' "and storing as ${2}" >&2
	in_file_prefixed="${1}"
	if test ! "${in_file_prefixed}" = -; then
		in_file_prefixed="file:${in_file_prefixed}"
	fi
	if ffmpeg -i "${in_file_prefixed}" -vn -acodec copy ${ffmpeg_flag_y} -- "file:${2}"; then
		if test ${delete_in_file} = yes; then
			unlink -- "${1}"
		fi
	fi
}

if test ${recursive} = no || test ! -d "${in_file}"; then
	if test -z "${out_file}"; then
		out_file="$(removeext "${in_file}").$(getext "${in_file}")"
	fi
	extract "${in_file}" "${out_file}"
	exit $?
fi

recursive () {
	for in_file in "${1}/"*; do
		out_file="$2/$(basename -- "${in_file}")"
		if test -d "${in_file}"; then
			mkdir -p -- "${out_file}"
			recursive "${in_file}" "${out_file}"
		else
			out_file="$(removeext "${out_file}").$(getext "${in_file}")"
			if ! extract "${in_file}" "${out_file}"; then
				status=1
			fi
		fi
	done
	if test ${delete_in_file} = yes; then
		rmdir -- "${1}" 2>/dev/null || :
	fi
}

if test -z "${out_file}"; then
	out_file="${in_file}"
else
	mkdir -p -- "${out_file}"
fi
recursive "${in_file}" "${out_file}"

exit $status