#!/bin/bash

# Archive/Backup file(s)
#
# This program copies the named file(s) to an archive directory. Version numbers
# are appended to archived files, beginning with version 000. The lastest
# version of a file is linked to a file with its same name -- the name without
# the version number.
#
# A log file named LOG is kept of all the files archived. It has the file's original path,
# the date it was archived, and it has a comment that is asked for from the user if it
# is not specified on the command line.
#
# This version tries to save files in a common archive shared by a login group
# located in /var/archive. If the directory /var/archive/GROUP_NAME does not exist,
# the archive is located in the user's home directory.
#
# Copyright 1989-2019, Mack Pexton (mack@mackpexton.com)
# License: https://opensource.org/licenses/mit-license.php

USAGE="Usage: ${0##*/} [ -a ] [ -l ] [ -ccomment ] [ file_name ... ]"

GROUP_ARCHIVE=/var/archive/$(id -gn)	# group archive directory path
USER_ARCHIVE=~/archive			# personal archive directory path

if [ -d "$GROUP_ARCHIVE" ]
then
	archive_dir="$GROUP_ARCHIVE"
else
	archive_dir="$USER_ARCHIVE"
fi

log="$archive_dir/LOG"
user="${REMOTE_USER:-$(id -un)}"	# used to brand comments in log file

if [ ! -d "$archive_dir" ]
then
	# Initialize archive.
	mkdir -m771 "$archive_dir" || exit 1
	> "$log"
	chmod 666 "$log"
fi

for arg
do
	case "$arg" in
	-a)	echo "$archive_dir" ;;
	-c*)	comment=${arg#-c} ;;		# like: -c"This is a Comment"
	-l)	cat "$log" ;;
	-*)	echo "$USAGE" 1>&2; exit 1 ;;
	*)
		# Argument is a file name.
		if [ -d "$arg" ]
		then
			# Do nothing for directories
			echo "$arg is a directory. Only regular files can be archived."
		elif [ -e "$arg" ]
		then
			# Get user comment to record in log file.
			if [ -z "$comment" ]
			then
				echo -n "Comment: "
				read comment
			fi

			file_name="${arg##*/}"

			# Determine source file's absolute path.
			src="$arg";
			if [ ${arg:0:1} != '/' ]
			then
				src="$(pwd)/$src"
			fi

			(
				cd "${archive_dir}"

				# Find next available version number for archive file.
				# 0 fill the number to 3 places.
				typeset v=0
				while vv=$(echo $v | sed -e 's/^/000/' -e 's/.*\(...\)$/\1/')
				      test -a "${file_name}.${vv}"
				do	
					v=$[ v+1 ]
				done
				
				archive_file="${file_name}.${vv}"

				# Copy file to archive file.
				cp --preserve -- "$src" "${archive_file}"

				# Link last archive version to archive file name (w/o version).
				if [ -a "${file_name}" ]
				then
					rm -f -- "${file_name}"
				fi
				ln -s -- "${archive_file}" "${file_name}"

				# Make archive file readonly.
				chmod a-w -- "${archive_file}"

				# Write archive details to log file.
				echo >> $log \
"$archive_file	$(date +"%m/%d/%y %H:%M")	$user	$src
     $comment"
			)
		else
			echo "File $arg not found." 1>&2
		fi
		;;
	esac
done