# Selima Website Content Management System
# XHTML.pm: The subroutine to return application/xhtml+xml on supported browsers and text/html othersise.

#  Copyright (c) 2004-2018 imacat.
#
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.

# Author: imacat <imacat@mail.imacat.idv.tw>
# First written: 2004-12-26

package Selima::XHTML;
use 5.008;
use strict;
use warnings;
use base qw(Exporter);
use vars qw(@EXPORT @EXPORT_OK);
BEGIN {
@EXPORT = qw(xhtml_content_type);
@EXPORT_OK = @EXPORT;
# Prototype declaration
sub xhtml_content_type();
}

use Selima::DataVars qw($IS_MODPERL :env);

# xhtml_content_type: Check whether application/xhtml+xml or text/html
#   should be sent to the client
sub xhtml_content_type() {
    local ($_, %_);
    my ($r, $acpt, $ua);
    
    # Obtain the required parameters
    if ($IS_MODPERL) {
        $r = $IS_MP2? Apache2::RequestUtil->request:
            Apache->request;
        $acpt = $r->headers_in->get("Accept");
        $ua = $r->headers_in->get("User-Agent");
    } else {
        $acpt = exists $ENV{"HTTP_ACCEPT"}? $ENV{"HTTP_ACCEPT"}: undef;
        $ua = exists $ENV{"HTTP_USER_AGENT"}? $ENV{"HTTP_USER_AGENT"}: undef;
    }
    
    # Browsers that claim to support application/xhtml+xml explicitly
    return "application/xhtml+xml"
        if defined $acpt && $acpt =~ /\bapplication\/xhtml\+xml\b/;
    # Browsers that are known to support application/xhtml+xml
    return "application/xhtml+xml"
        if defined $ua && $ua =~ /^W3C_Validator\//;
    # Else, we assume that application/xhtml+xml is not supported
    return "text/html";
}

return 1;