##### http://autoconf-archive.cryp.to/ac_check_docbook_dtd.html
#
# SYNOPSIS
#
#   AC_CHECK_DOCBOOK_DTD([dtd-version])
#
# DESCRIPTION
#
#   Check for access to a docbook DTD of a particular revision. This
#   macro can be used for multiple versions within the same script.
#
#   Input:
#
#   $1 is the version of docbook to search for; default 'current'.
#
#   Output:
#
#   $HAVE_DOCBOOK_DTD_VERS will be set to 'yes' or 'no' depending on
#   the results of the test, where VERS is $1, with '_' substituted for
#   '.' $HAVE_DOCBOOK_DTD will also be set to the same value.
#
#   Example:
#
#    AC_CHECK_DOCBOOK_DTD(4.3)
#    if test "x$HAVE_DOCBOOK_DTD_4_3" = "xyes"; then
#    ...
#
# LAST MODIFICATION
#
#   2007-05-15
#
# COPYLEFT
#
#   Copyright (c) 2007 Zmanda Inc. <http://www.zmanda.com/>
#   Copyright (c) 2007 Dustin J. Mitchell <dustin@zmanda.com>
#
#   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 2 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, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
#   02111-1307, USA.
#
#   As a special exception, the respective Autoconf Macro's copyright
#   owner gives unlimited permission to copy, distribute and modify the
#   configure scripts that are the output of Autoconf when processing
#   the Macro. You need not follow the terms of the GNU General Public
#   License when using or distributing such scripts, even though
#   portions of the text of the Macro appear in them. The GNU General
#   Public License (GPL) does govern all other use of the material that
#   constitutes the Autoconf Macro.
#
#   This special exception to the GPL applies to versions of the
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#   may extend this special exception to the GPL to apply to your
#   modified version as well.

AC_DEFUN([AC_CHECK_DOCBOOK_DTD],
[
    AC_REQUIRE([AC_PROG_XSLTPROC])

    dnl define a temporary variable for the version, so this macro can be
    dnl used with multiple versions
    define([_VERS], $1)
    ifelse(_VERS, [], [define([_VERS], [current])])
    define([ac_cv_docbook_dtd_VERS], patsubst([ac_cv_docbook_dtd_]_VERS, [\.], [_]))
    define([HAVE_DOCBOOK_DTD_VERS], patsubst([HAVE_DOCBOOK_DTD_]_VERS, [\.], [_]))

    AC_CACHE_CHECK([for Docbook DTD version ]_VERS, [ac_cv_docbook_dtd_VERS],
    [
	ac_cv_docbook_dtd_VERS=no
	if test -n "$XSLTPROC"; then
	    MY_XSLTPROC_FLAGS=`echo "" $XSLTPROC_FLAGS|sed -e s/--novalid//g`
	    cat <<EOF >conftest.xml
<?xml version="1.0" encoding='ISO-8859-1'?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V[]_VERS//EN" "http://www.oasis-open.org/docbook/xml/_VERS/docbookx.dtd">
<book id="empty">
</book>
EOF
	    echo "Trying '$XSLTPROC $MY_XSLTPROC_FLAGS conftest.xml'" >&AS_MESSAGE_LOG_FD
	    $XSLTPROC $MY_XSLTPROC_FLAGS conftest.xml >conftest.out 2>&1
	    if test "$?" = 0; then
		# failing to load the DTD is just a warning, so check for it in the output.
		if grep 'warning: failed to load external entity' conftest_out >/dev/null 2>&1; then
		    : # no good..
		else
		    ac_cv_docbook_dtd_VERS=yes
		fi
	    fi
	    cat conftest.out >&AS_MESSAGE_LOG_FD

	    rm -f conftest.xml conftest.out
	fi
    ])

    HAVE_DOCBOOK_DTD_VERS="$ac_cv_docbook_dtd_VERS"
    HAVE_DOCBOOK_DTD=HAVE_DOCBOOK_DTD_VERS
    undefine([_VERS])
])