#!/bin/sh
file_extension=".srt"
season=1
episode=1

PROGNAME="$(basename "$0")"
USAGE="$( cat << EOF
usage: $PROGNAME [-h] [-s season] [-e episode] [-x extension] file1 [file2 ...]

rename files to s01e01.srt, s01e02.srt, etc.

options:
	-s    set season number (default: $season)
	-e    set episode number of first file (default: $episode)
	-x    set file extension for output files (default: $file_extension)
	-h    show help

example:
	subrename -x .ja.srt *.srt
EOF
)"
usage() {
	echo "$USAGE"
	exit 0
}
stupid() {
	echo "use $PROGNAME -h for help"
	exit 1
}

ARGC=0
while getopts e:s:x:h OPT; do
	[ $OPTIND -gt $ARGC ] && ARGC=$OPTIND
	case "$OPT" in
		e) episode="$OPTARG" ;;
		h) usage ;;
		s) season="$OPTARG" ;;
		x) file_extension="$OPTARG" ;;
		\?|*) stupid ;;
	esac
done
shift "$(( $OPTIND - 1 ))"

if [ $# -eq 0 ] ; then
	echo "error: no files provided"
	stupid
fi

for file in "$@" ; do
	new_filename="$(printf 's%02de%02d%s\n' "$season" "$episode" "$file_extension")"
	mv --verbose "$file" "$new_filename"
	episode=$(( $episode + 1 ))
done