#!/bin/bash

# Copyright 2013  Norman Carver  <carver@cs.siu.edu>
#
# Bash shell script to compare two files, one local and the second remote,
# using sdiff to determine whether they are identical or they differ.
#
# Syntax:
# sdiff-remote [(-q | -d | -v)] [-f] LOCAL_FILE_PATH ( [USERNAME@]HOSTNAME:REMOTE_FILE_PATH | [USERNAME@]HOSTNAME: )
#
# Output can be controlled with -q, -d, or -v options:
#   default -- print same/difference message
#   -q -- quiet, suppress all output
#   -d -- if different, sdiff only differences
#   -v -- if different, sdiff entire files
#
# -f (fast) option causes files to be compared by size only, use for large files.
# Default is to compare files using checksums.
#
# Exit status is success if files match, failure if they differ.
#
# Example calls:
#   sdiff-remote Documents/instructions.text carver@remhost.example:/backup/files/diff.txt
#   sdiff-remote Documents/instructions.text carver@remhost.example:Documents/instructions.text
#   sdiff-remote Documents/instructions.text carver@remhost.example:
#   sdiff-remote Documents/instructions.text remhost.example:
#
# Requires: rsync (local machine)
#           ssh (local machine)
#           SSH server running on remote machine
#
# Version history:
#   1.0  (07/28/2013) Initial public release


# Copyright 2013  Norman Carver  <carver@cs.siu.edu>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.

# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.


function print_usage()
{
    echo "Usage: sdiff-remote [(-q | -d | -v)] [-f] LOCAL_FILE_PATH ( [USERNAME@]HOSTNAME:REMOTE_FILE_PATH | [USERNAME@]HOSTNAME: )"
    echo "(-q for quiet/no output, -d for sdiff differences, -v for verbose sdiff, -f for fast check using only file size)"
}


# Check that number of arguments was valid:
if [[ $# -lt 2 ]]; then
    print_usage
    exit 1
fi

# Decode options:
quiet=false
diff=false
verbdiff=false
fast=false
while getopts ":dfqv" opt; do
    case $opt in
        d)
            diff=true ;;
        f)
            fast=true ;;
        q) 
            quiet=true ;;
        v) 
            verbdiff=true ;;
        \?)
            print_usage
            exit 1 ;;
    esac
done
shift $((OPTIND-1))

if $quiet && ( $diff || $verbdiff ); then
    print_usage
    exit 1
fi


# Decode arguments:
filelocal=$1
remotespec=$2


# Determine the remote host and file:
if [[ ! ("$remotespec" =~ .+:.*) ]]; then
    echo "No \"HOSTNAME:\""
    print_usage
    exit 1
fi

remotehost=${remotespec%%:*}

if [[ "$remotespec" =~ .+:$ ]]; then
    #Given hostname only for remote file spec:
    if [[ "$filelocal" =~ /.+ ]]; then
	# Absolute local path, so:
	fileremote=$filelocal
    else
	# Relative local path, so:
	fileremote=${PWD}/${filelocal}
    fi
else
    fileremote=${remotespec#*:}
fi


# Verify the file arguments:
error=false
if [[ ! -f "$filelocal" ]]; then
    echo "Invalid LOCAL_FILE_PATH: $filelocal"
    print_usage
    exit 1
fi

if ! ssh "${remotehost}" "ls \"${fileremote}\" &> /dev/null"; then
    echo "Invalid remote file: $remotehost:$fileremote"
    print_usage
    exit 1
fi

# Find out if the local and remote files differ:
if $fast; then
    rsyncoutput=$(rsync --dry-run --size-only --itemize-changes "${filelocal}" "${remotehost}:${fileremote}" 2> /dev/null)
else
    rsyncoutput=$(rsync --dry-run --checksum --itemize-changes "${filelocal}" "${remotehost}:${fileremote}" 2> /dev/null)
fi

if [[ $? != 0 ]]; then
    echo "rsync failed: \"${filelocal}\" vs. \"${remotehost}:${fileremote}\""
    exit 1
fi

if [[ -z "$rsyncoutput" ]]; then
    #The files are identical:
    if ! $quiet; then echo "The files are identical."; fi
    exit 0
else
    #The files differ:
    if ! $quiet; then echo "The files DIFFER!"; fi
    if $verbdiff; then
        echo
        ssh "${remotehost}" "cat ${fileremote}" | sdiff ${sdiffoptions} "${filelocal}" -
    elif $diff; then
        echo
        ssh "${remotehost}" "cat ${fileremote}" | sdiff --suppress-common-lines ${sdiffoptions} "${filelocal}" -
    fi
    exit 1
fi

# EOF