#!/bin/ksh

PATCH=/usr/bin/patch
SED="/usr/bin/sed"
MESSAGE_FILE=/tmp/PaTcHrM_mEsSaGe_12001x

OLD_PATCH_SEPARATOR="___Old_File_Diff_Separator_aBcDeFgHiJkLmN___OjK___5924894_6548915___"
PATCH_SAVE_SUFFIX="pre${ACTIVE_PATCH}"

get_orig()
{
   cat $1 | \
      $SED -ne "1,/${OLD_PATCH_SEPARATOR}/{/${OLD_PATCH_SEPARATOR}/d;p;}"
}

get_diff()
{
   cat $1 | \
      $SED -ne "/${OLD_PATCH_SEPARATOR}/,\${/${OLD_PATCH_SEPARATOR}/d;p;}"
}

while read src dst ; do
   realdst="`echo $dst| /bin/sed -e 's/\.old_and_patch$//'`"
   if [ "$realdst" != "$dst" ]; then
      cp "${src}" "${dst}"
      if [ -f "${realdst}" ] ; then
	 get_diff $src | $PATCH -o /dev/null -R $realdst >/dev/null 2>&1
	 if [ "$?" = "0" ] ; then
	    get_diff $src | $PATCH -R $realdst >/dev/null 2>&1
	 else
	    get_orig $src > "$realdst.${PATCH_SAVE_SUFFIX}"
	    echo "  File $realdst has changed since installation of ${ACTIVE_PATCH}" >> "${MESSAGE_FILE}"
	    echo "  Copy of that file as found on the system prior to applying ${ACTIVE_PATCH}" >> "${MESSAGE_FILE}"
	    echo "  is stored in $realdst.${PATCH_SAVE_SUFFIX}" >> "${MESSAGE_FILE}"
	    echo "  Please, review those files to see whether you wish to undo any changes." >> "${MESSAGE_FILE}"
	    echo >> "${MESSAGE_FILE}"
	    if [ -f "${realdst}.rej" ] ; then
	       rm -f "${realdst}.rej"
	    fi
	 fi
      else
	 get_orig $src > $realdst
      fi
   fi
done

exit 0