#! /bin/bash

 #

 set -e  # abort on errors

 shopt -s nullglob  # file globs that don't match expand

 		   # to nothing

 #

 # Check if $EDITOR is set, otherwise set to "vi".

 #

 : ${EDITOR:=vi}

 #

 # Check for -f option ()

 #

 if [ "$1" = -f ]; then

     retry_lock=1

     shift

 fi

 #

 # Detect the name of the file to edit

 #

 unset FILE

 if [ -n "$1" ]; then

     if [ -f "$1" ]; then

 	FILE=$1

     else

 	if [ -d "$1" ]; then

 	    cd $1

 	else

 	    FILE=$(package_name $1).changelog

 	fi

     fi

 fi

 if [ -z "$FILE" ]; then

     for f in *.changelog; do

 	if [ -n "$FILE" ]; then

 	    FILE=

 	    break

 	fi

 	FILE=$f

     done

 fi

 if [ -z "$FILE" ]; then

     for f in *.spec; do

 	if [ -n "$FILE" ]; then

 	    FILE=

 	    break

 	fi

 	FILE=$f

     done

     if [ -n "$FILE" ]; then

 	FILE=$(package_name $FILE).changelog

     fi

 fi

 if [ -z "$FILE" ]; then

     echo "usage: ${0##*/} [filename[.changelog]|path [file_with_comment]]"

     echo "If no <filename> is given, exactly one *.changelog or"

     echo "*.spec file has to be in the cwd or in <path>."

     echo

     exit 1

 fi

 user=`whoami`

 COMMENT_FILE=$2

 #

 # Create the lockfile and temporary file.

 #

 lockfile=.${FILE##*/}.lock

 if [ "${FILE/\//}" != "$FILE" ]; then

     lockfile=${FILE%/*}/.$lockfile

 fi

 if [ ! -w "$(dirname "$FILE")" ]; then

     echo "Write access to directory $(dirname "$FILE") required" >&2

     exit 1

 fi

 if [ -e "$FILE" -a ! -w "$FILE" ]; then

     echo "Write access to file $FILE required" >&2

     exit 1

 fi

 set -o noclobber

 while ! echo $$@$(hostname -f) 2> /dev/null > $lockfile; do

     if [ -z "$retry_lock" ]; then

 	echo "$lockfile: Lock by process $(cat $lockfile)" >&2

 	echo "Please remove stale lockfiles manually" >&2

 	exit 1

     fi

     echo "$lockfile: Waiting for process $(cat $lockfile) to release lock" >&2

     sleep 1

 done

 set +o noclobber

 tmpfile=$(mktemp /tmp/${0##*/}.XXXXXX)

 trap "rm -f $lockfile $tmpfile" EXIT

 #

 # Prepare the working copy and start the editor

 #

 {   timestamp=$(LC_ALL=POSIX TZ=Europe/Berlin date)

     echo "-------------------------------------------------------------------"

     echo "$timestamp - $user"

     echo

     if [ -z "$COMMENT_FILE" ]; then

 	echo "- "

     else

 	cat $COMMENT_FILE

     fi

     echo

     if [ -f "$FILE" ]; then

     	cat $FILE

     fi

 } >> $tmpfile \

 || exit 1

 if [ -z "$COMMENT_FILE" ]; then

     lines=1

     CHKSUM_BEFORE=$(md5sum $tmpfile | awk '{print $1}')

 else

     lines=$(wc -l $COMMENT_FILE | awk '{print $1}')

     CHKSUM_BEFORE=has_changed

 fi

 $EDITOR +$((3+lines)) $tmpfile

 if [ "$CHKSUM_BEFORE" = "$(md5sum $tmpfile | awk '{print $1}')" ]; then

     exit 1

 fi

 cat $tmpfile > $FILE