#!/bin/bash
# Author:		smirky@smirky.net
# Created on:		09.06.2017
# Last modifier:	smirky@smirky.net
# Last modified:	23.03.2018

# Some 'sane' defaults
unset verbose
unset restore
unset music_dir
old_state_file=''
version="20180323"

print_version() {
	printf "Version: %s\\n" "${version}"
}

print_usage() {
	printf "Usage: %s -d DIRECTORY [-r STATE_FILE] [-V]\\n" "${0}"
}

print_help() {
	print_usage
	printf "Rename all mp3 files in a directory with ability to restore.

	-d, --directory DIRECTORY	specify the work path
	-r, --restore STATE_FILE	restore a previous state of file names
	-V, --verbose			output verbose details while running
	-h, --help			display this help and exit
	-v, --version			output version information and exit\\n"
}

vprintf() {
	if [ "${verbose}" ]; then
		printf "%s\\n" "$@"
	fi
}

OPTS=$(getopt -o d:r:Vhv --long directory:,restore:,verbose,help,version -n 'parse-options' -- "$@")

while true; do
	case "$1" in
		-v | --version ) print_version && exit;;
		-h | --help ) print_help && exit;;
		-V | --verbose ) verbose=true; shift;;
		-r | --restore ) restore=true && old_state_file="$2"; shift 2;;
		-d | --directory ) music_dir="$2"; shift 2;;
		-- ) shift; break;;
		* ) print_usage; exit;;
	esac
	if [ "$1" == "" ]; then
		break
	fi
done
if [ -z "${music_dir}" ]; then
	print_usage
	exit 1
fi

if [ ! -d "${music_dir}" ]; then
	printf "%s doesn't exist!\\n" "${music_dir}"
	exit 1
fi

if [ ! -w "${music_dir}" ]; then
	printf "No permissions to write in %s !\\n" "${music_dir}"
	exit 1
fi

state_dir="${music_dir}/_STATES_"
if [ ! -d "${state_dir}" ]; then
	vprintf "Creating: ${state_dir}"
	mkdir "${state_dir}"
fi

new_state_file="${state_dir}/$(date +'%Y.%m.%d_%H:%M:%S')"
vprintf "Generating state file: ${new_state_file}"
touch "${new_state_file}"

if [ $restore ]; then
	if [ ! -f "${old_state_file}" ]; then
		printf "No such STATE_FILE: %s !\\n" "${old_state_file}"
		rm "${new_state_file}"
		exit 1
	fi
	IFS=$'\t'
	while read -r old current
	do
		vprintf "mv \"${music_dir}/${current}\" \"${music_dir}/${old}\""
		mv "${music_dir}/${current}" "${music_dir}/${old}"
		printf "%s\\t%s\\n" "${old}" "${current}" >> "${new_state_file}"
	done < "${old_state_file}"
	exit
fi

vprintf "Generating mp3 file list..."
cd "${music_dir}" || return
IFS=$'\n'
list=$(find . -type f -iname "*.mp3" -printf '%P\n')
cd - 1>/dev/null || return

for i in ${list} ; do
	new_name="$(head -c 500 /dev/urandom | tr -dc 'a-zA-Z0-9_-' | fold -w 30 | head -n 1).mp3"
	vprintf "mv \"${music_dir}/$i\" \"${music_dir}/${new_name}\""
	mv "${music_dir}/${i}" "${music_dir}/${new_name}"
	printf "%s\\t%s\\n" "${i}" "${new_name}" >> "${new_state_file}"
done
vprintf "Done!"