#!/bin/sh
#
# xzize, Copyright © 2010 Matteo Cypriani
#
# This program is free software. It comes without any warranty, to
# the extent permitted by applicable law. You can redistribute it
# and/or modify it under the terms of the Do What The Fuck You Want
# To Public License, Version 2, as published by Sam Hocevar. See
# http://sam.zoy.org/wtfpl/COPYING for more details.
#
# This script recompresses to xz (with maximum compression level) a
# GZip (.gz), BZip2 (.bz2), LZMA (.lzma), and Lempel-Ziv (.Z)
# compressed file. The original file is keeped.
# If the file extension does not correspond to a known compression
# format, the file is compressed to xz. In that case, the original
# file is removed.


set -u


test_extension()
{
	local - FILE EXTENSION BASE
	FILE="$1"
	EXTENSION="$2"
	BASE="`basename "$FILE" ."$EXTENSION"`"
	if [ "$BASE" != "$FILE" ] ; then
		DEST="$BASE".xz
		return 0
	fi
	DEST="$FILE"
	return 1
}


do_recompress()
{
	if [ -e "$DEST" ] ; then
		echo "Skipping source file « $SOURCE »: destination file « $DEST » already exists!" >&2
		return 0
	fi
	echo "Recompressing « $SOURCE » to  « $DEST »…"
	$ACTION -c "$SOURCE" | xz -9 >"$DEST"
	return $?
}


## Verify number of arguments ##

if [ $# -lt 1 ] ; then
	echo "$0 requires at least one argument!" >&2
	exit 2
fi


## Process files ##

for SOURCE in "$@" ; do
	# Regular file?
	if [ ! -f "$SOURCE" ] ; then
		echo "Skipping source file « $SOURCE »: is not a regular file!" >&2
		continue
	fi

	# GZip
	test_extension "$SOURCE" gz
	if [ "$DEST" != "$SOURCE" ] ; then
		ACTION=gunzip
		do_recompress
		continue
	fi

	# BZip2
	test_extension "$SOURCE" bz2
	if [ "$DEST" != "$SOURCE" ] ; then
		ACTION=bunzip2
		do_recompress
		continue
	fi

	# LZMA
	test_extension "$SOURCE" lzma
	if [ "$DEST" != "$SOURCE" ] ; then
		ACTION=unlzma
		do_recompress
		continue
	fi

	# Compress
	test_extension "$SOURCE" Z
	if [ "$DEST" != "$SOURCE" ] ; then
		ACTION=uncompress
		do_recompress
		continue
	fi

	# XZ
	if test_extension "$SOURCE" xz ; then
		echo "Skipping source file « $DEST »: has already .xz suffix!" >&2
		continue
	fi

	# Uncompressed file: fall back to simple compression
	echo "Compressing « $SOURCE » to xz…"
	xz -9 "$SOURCE"

done