<?php
/*
 * Copyright 2007 Reini Urban
 *
 * This file is part of PhpWiki.
 *
 * PhpWiki 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.
 *
 * PhpWiki 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 PhpWiki; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/**
 * Ad-hoc support for an RDF-Triple search in our link database.
 *
 * This iterator will work with any WikiDB_backend
 * which has a working get_links() method with want_relation support.
 * Currently we iterate over all pages, check for all matching links.
 * As optimization a backend could iterate over the linktable instead
 * and check the matching page there. There are most likely less links
 * than pages and links are smaller than pages.
 *
 * This is mostly here for testing, very slow.
 *
 * @author Reini Urban
 * @see WikiDB_backend::link_search
 */

class WikiDB_backend_dumb_LinkSearchIter
extends WikiDB_backend_iterator
{
    function WikiDB_backend_dumb_LinkSearchIter(&$backend, &$pageiter, $search, $linktype,
                        $relation=false, $options=array())
    {
        $this->_backend  = &$backend;
        $this->_pages    = $pageiter;
        $this->search    = $search;   // search the linkvalue. it should be the value or pagename
        $this->relation  = $relation; // limit the search to this linkname
        $this->linktype  = $linktype;
    $this->_reverse  = false;
    $this->_want_relations = true;
    $this->sortby  = isset($options['sortby'])  ? $options['sortby']  : '';
    $this->limit   = isset($options['limit'])   ? $options['limit']   : '';
    $this->exclude = isset($options['exclude']) ? $options['exclude'] : '';
    $this->_field = 'pagename'; // the name of the linkvalue field to apply the search
    $this->_dbi =& $GLOBALS['request']->_dbi;
    if ($linktype == 'relation') {
        $this->_want_relations = true;
        $this->_field = 'linkrelation';
    }
    if ($linktype == 'attribute') {
        $this->_want_relations = true;
        $this->_field = 'attribute';
    }
    if ($linktype == 'linkfrom') {
        $this->_reverse = true;
    }
    $this->_page = false;
    }

    // iterate a nested page-links loop. there will be multiple results per page.
    // we must keep the page iter internally.
    function next() {
        while (1) {
        if (!isset($this->_links) or count($this->_links) == 0) {
        $page = $this->_next_page(); // initialize all links of this page
        if (!$page) return false;
        } else {
            $page = $this->_page;
        }
        // iterate the links. the links are pushed into the handy triple by _get_links
        while ($link = array_shift($this->_links)) {
        // unmatching relations are already filtered out
        if ($this->search->match($link['linkvalue'])) { //pagename or attr-value
            if ($link['linkname'])
            return array('pagename' => $page,
                     'linkname' => $link['linkname'],
                     'linkvalue'=> $link['linkvalue']);
            else
            return array('pagename' => $page,
                     'linkvalue'=> $link['linkvalue']);
        }
        }
        // no links on this page anymore.
        }
    }

    // initialize the links also
    function _next_page() {
    unset($this->_links);
    if (!($next = $this->_pages->next()))
        return false;
    $this->_page = $next['pagename'];
    while(!($this->_links = $this->_get_links($this->_page))) {
        if (!($next = $this->_pages->next()))
            return false;
        $this->_page = $next['pagename'];
    }
    return $this->_page;
    }

    // get the links of each page in advance
    function _get_links($pagename) {
    $links = array();
    if ($this->linktype == 'attribute') {
        $page = $this->_dbi->getPage($pagename);
        $attribs = $page->get('attributes');
        if ($attribs) {
          foreach ($attribs as $attribute => $value) {
          if ($this->relation and !$this->relation->match($attribute)) continue;
          // The logical operator and unit unification (not yet) is encoded into
          // a seperate search object.
          if (!$this->search->match($value)) continue;
          $links[] = array('pagename'  => $pagename,
                   'linkname'  => $attribute,
                   'linkvalue' => $value);
          }
        }
        unset($attribs);
    } else {
        $link_iter = $this->_backend->get_links($pagename, $this->_reverse, true,
                            $this->sortby, $this->limit,
                            $this->exclude, $this->_want_relations);
        // we already stepped through all links. make use of that.
        if ($this->_want_relations
            and isset($link_iter->_options['found_relations'])
        and $link_iter->_options['found_relations'] == 0)
        {
        $link_iter->free();
        return $links;
        }
        while ($link = $link_iter->next()) {
            if (empty($link[$this->_field])) continue;
        if ($this->_want_relations and $this->relation
            and !$this->relation->match($link['linkrelation'])) continue;
        // check hash values, with/out want_relations
        $links[] = array('pagename'  => $pagename,
                         'linkname'  => $this->_want_relations ? $link['linkrelation'] : '',
                 'linkvalue' => $link['pagename']);
        }
        $link_iter->free();
    }
    return $links;
    }

    function free() {
    $this->_page = false;
    unset($this->_links);
        $this->_pages->free();
    }
}

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