#! /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