<?php
/**
 * Metadata.php -- provides DublinCore and CreativeCommons metadata
 * Copyright 2004, Evan Prodromou <evan@wikitravel.org>.
 *
 *  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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 *
 * @author Evan Prodromou <evan@wikitravel.org>
 */

/**
 * TODO: Perhaps make this file into a Metadata class, with static methods (declared 
 * as private where indicated), to move these functions out of the global namespace?
 */
define('RDF_TYPE_PREFS', "application/rdf+xml,text/xml;q=0.7,application/xml;q=0.5,text/rdf;q=0.1");

function wfDublinCoreRdf($article) {

	$url = dcReallyFullUrl($article->mTitle);

	if (rdfSetup()) {
		dcPrologue($url);
		dcBasics($article);
		dcEpilogue();
	}
}

function wfCreativeCommonsRdf($article) {

	if (rdfSetup()) {
		global $wgRightsUrl;

		$url = dcReallyFullUrl($article->mTitle);

		ccPrologue();
		ccSubPrologue('Work', $url);
		dcBasics($article);
		if (isset($wgRightsUrl)) {
			$url = htmlspecialchars( $wgRightsUrl );
			print "    <cc:license rdf:resource=\"$url\" />\n";
		}

		ccSubEpilogue('Work');

		if (isset($wgRightsUrl)) {
			$terms = ccGetTerms($wgRightsUrl);
			if ($terms) {
				ccSubPrologue('License', $wgRightsUrl);
				ccLicense($terms);
				ccSubEpilogue('License');
			}
		}
	}

	ccEpilogue();
}

/**
 * @private
 */
function rdfSetup() {
	global $wgOut, $_SERVER;

	$httpaccept = isset($_SERVER['HTTP_ACCEPT']) ? $_SERVER['HTTP_ACCEPT'] : null;

	$rdftype = wfNegotiateType(wfAcceptToPrefs($httpaccept), wfAcceptToPrefs(RDF_TYPE_PREFS));

	if (!$rdftype) {
		wfHttpError(406, "Not Acceptable", wfMsg("notacceptable"));
		return false;
	} else {
		$wgOut->disable();
		header( "Content-type: {$rdftype}; charset=utf-8" );
		$wgOut->sendCacheControl();
		return true;
	}
}

/**
 * @private
 */
function dcPrologue($url) {
	global $wgOutputEncoding;

	$url = htmlspecialchars( $url );
	print "<" . "?xml version=\"1.0\" encoding=\"{$wgOutputEncoding}\" ?" . ">

																			  <!DOCTYPE rdf:RDF PUBLIC \"-//DUBLIN CORE//DCMES DTD 2002/07/31//EN\" \"http://dublincore.org/documents/2002/07/31/dcmes-xml/dcmes-xml-dtd.dtd\">

																			  <rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\"
																			  xmlns:dc=\"http://purl.org/dc/elements/1.1/\">
																			  <rdf:Description rdf:about=\"$url\">
																			  ";
}

/**
 * @private
 */
function dcEpilogue() {
	print "
			</rdf:Description>
			</rdf:RDF>
			";
}

/**
 * @private
 */
function dcBasics($article) {
	global $wgContLanguageCode, $wgSitename;

	dcElement('title', $article->mTitle->getText());
	dcPageOrString('publisher', wfMsg('aboutpage'), $wgSitename);
	dcElement('language', $wgContLanguageCode);
	dcElement('type', 'Text');
	dcElement('format', 'text/html');
	dcElement('identifier', dcReallyFullUrl($article->mTitle));
	dcElement('date', dcDate($article->getTimestamp()));

	$last_editor = $article->getUser();

	if ($last_editor == 0) {
		dcPerson('creator', 0);
	} else {
		dcPerson('creator', $last_editor, $article->getUserText(),
				 User::whoIsReal($last_editor));
	}

	$contributors = $article->getContributors();

	foreach ($contributors as $user_parts) {
		dcPerson('contributor', $user_parts[0], $user_parts[1], $user_parts[2]);
	}

	dcRights();
}

/**
 * @private
 */
function ccPrologue() {
	global $wgOutputEncoding;

	echo "<" . "?xml version='1.0'  encoding='{$wgOutputEncoding}' ?" . ">

																		  <rdf:RDF xmlns:cc=\"http://web.resource.org/cc/\"
																		  xmlns:dc=\"http://purl.org/dc/elements/1.1/\"
																		  xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\">
																		  ";
}

/**
 * @private
 */
function ccSubPrologue($type, $url) {
	$url = htmlspecialchars( $url );
	echo "  <cc:{$type} rdf:about=\"{$url}\">\n";
}

/**
 * @private
 */
function ccSubEpilogue($type) {
	echo "  </cc:{$type}>\n";
}

/**
 * @private
 */
function ccLicense($terms) {

	foreach ($terms as $term) {
		switch ($term) {
		 case 're':
			ccTerm('permits', 'Reproduction'); break;
		 case 'di':
			ccTerm('permits', 'Distribution'); break;
		 case 'de':
			ccTerm('permits', 'DerivativeWorks'); break;
		 case 'nc':
			ccTerm('prohibits', 'CommercialUse'); break;
		 case 'no':
			ccTerm('requires', 'Notice'); break;
		 case 'by':
			ccTerm('requires', 'Attribution'); break;
		 case 'sa':
			ccTerm('requires', 'ShareAlike'); break;
		 case 'sc':
			ccTerm('requires', 'SourceCode'); break;
		}
	}
}

/**
 * @private
 */
function ccTerm($term, $name) {
	print "    <cc:{$term} rdf:resource=\"http://web.resource.org/cc/{$name}\" />\n";
}

/**
 * @private
 */
function ccEpilogue() {
	echo "</rdf:RDF>\n";
}

/**
 * @private
 */
function dcElement($name, $value) {
	$value = htmlspecialchars( $value );
	print "    <dc:{$name}>{$value}</dc:{$name}>\n";
}

/**
 * @private
 */
function dcDate($timestamp) {
	return substr($timestamp, 0, 4) . '-'
	  . substr($timestamp, 4, 2) . '-'
	  . substr($timestamp, 6, 2);
}

/**
 * @private
 */
function dcReallyFullUrl($title) {
	return $title->getFullURL();
}

/**
 * @private
 */
function dcPageOrString($name, $page, $str) {
	$nt = Title::newFromText($page);

	if (!$nt || $nt->getArticleID() == 0) {
		dcElement($name, $str);
	} else {
		dcPage($name, $nt);
	}
}

/**
 * @private
 */
function dcPage($name, $title) {
	dcUrl($name, dcReallyFullUrl($title));
}

/**
 * @private
 */
function dcUrl($name, $url) {
	$url = htmlspecialchars( $url );
	print "    <dc:{$name} rdf:resource=\"{$url}\" />\n";
}

/**
 * @private
 */
function dcPerson($name, $id, $user_name='', $user_real_name='') {
	global $wgContLang;

	if ($id == 0) {
		dcElement($name, wfMsg('anonymous'));
	} else if ( !empty($user_real_name) ) {
		dcElement($name, $user_real_name);
	} else {
		# XXX: This shouldn't happen.
		if( empty( $user_name ) ) {
			$user_name = User::whoIs($id);
		}
		dcPageOrString($name, $wgContLang->getNsText(NS_USER) . ':' . $user_name, wfMsg('siteuser', $user_name));
	}
}

/**
 * Takes an arg, for future enhancement with different rights for
 * different pages.
 * @private
 */
function dcRights() {

	global $wgRightsPage, $wgRightsUrl, $wgRightsText;

	if (isset($wgRightsPage) &&
		($nt = Title::newFromText($wgRightsPage))
		&& ($nt->getArticleID() != 0)) {
		dcPage('rights', $nt);
	} else if (isset($wgRightsUrl)) {
		dcUrl('rights', $wgRightsUrl);
	} else if (isset($wgRightsText)) {
		dcElement('rights', $wgRightsText);
	}
}

/**
 * @private
 */
function ccGetTerms($url) {
	global $wgLicenseTerms;

	if (isset($wgLicenseTerms)) {
		return $wgLicenseTerms;
	} else {
		$known = getKnownLicenses();
		if( isset( $known[$url] ) ) {
			return $known[$url];
		} else {
			return array();
		}
	}
}

/**
 * @private
 */
function getKnownLicenses() {

	$ccLicenses = array('by', 'by-nd', 'by-nd-nc', 'by-nc',
						'by-nc-sa', 'by-sa');
	$ccVersions = array('1.0', '2.0');
	$knownLicenses = array();

	foreach ($ccVersions as $version) {
		foreach ($ccLicenses as $license) {
			if( $version == '2.0' && substr( $license, 0, 2) != 'by' ) {
				# 2.0 dropped the non-attribs licenses
				continue;
			}
			$lurl = "http://creativecommons.org/licenses/{$license}/{$version}/";
			$knownLicenses[$lurl] = explode('-', $license);
			$knownLicenses[$lurl][] = 're';
			$knownLicenses[$lurl][] = 'di';
			$knownLicenses[$lurl][] = 'no';
			if (!in_array('nd', $knownLicenses[$lurl])) {
				$knownLicenses[$lurl][] = 'de';
			}
		}
	}

	/* Handle the GPL and LGPL, too. */

	$knownLicenses['http://creativecommons.org/licenses/GPL/2.0/'] =
	  array('de', 're', 'di', 'no', 'sa', 'sc');
	$knownLicenses['http://creativecommons.org/licenses/LGPL/2.1/'] =
	  array('de', 're', 'di', 'no', 'sa', 'sc');
	$knownLicenses['http://www.gnu.org/copyleft/fdl.html'] =
	  array('de', 're', 'di', 'no', 'sa', 'sc');

	return $knownLicenses;
}