<?php
  require_once("$CFG->dirroot/search/Zend/Search/Lucene.php");

  class SearchResult {
    public  $url,
            $title,            
            $doctype,
            $author,
            $score,
            $number;
  } //SearchResult


  //split this into Cache class and extend to SearchCache?
  class SearchCache {
    private $mode,
            $valid;
                
    public function __construct($mode='session') {
      $accepted_modes = array('session');
      
      if (in_array($mode, $accepted_modes)) {
        $this->mode = $mode;
      } else {
        $this->mode = 'session';
      } //else
      
      $this->valid = true;
    } //constructor
    
    public function can_cache() {
      return $this->valid;
    } //can_cache
    
    public function cache($id=false, $object=false) {
      //see if there was a previous query
      $last_term = $this->fetch('search_last_term');
      
      //if this query is different from the last, clear out the last one
      if ($id != false and $last_term != $id) {
        $this->clear($last_term);
      } //if
      
      //store the new query if id and object are passed in
      if ($object and $id) {
        $this->store('search_last_term', $id);
        $this->store($id, $object);
        return true;
      //otherwise return the stored results
      } else if ($id and $this->exists($id)) {        
        return $this->fetch($id);
      } //else
    } //cache
    
    private function exists($id) {
      switch ($this->mode) {
        case 'session' :
          return isset($_SESSION[$id]);
      } //switch
    } //exists
        
    private function clear($id) {
      switch ($this->mode) {
        case 'session' :
          unset($_SESSION[$id]);
          session_unregister($id);
          return;
      } //switch
    } //clear    
        
    private function fetch($id) {
      switch ($this->mode) {
        case 'session' :
          return ($this->exists($id)) ? unserialize($_SESSION[$id]) : false;
      } //switch
    } //fetch
    
    private function store($id, $object) {
      switch ($this->mode) {
        case 'session' :
          $_SESSION[$id] = serialize($object);
          return;
      } //switch
    } //store        
  } //SearchCache
  
  
  class SearchQuery {
    private $index,
            $term,
            $pagenumber,            
            $cache,
            $validquery,
            $validindex,            
            $results,
            $results_per_page;
    
    public function __construct($term='', $page=1, $results_per_page=10, $cache=false) {
      global $CFG;
      
      $this->term       = $term;
      $this->pagenumber = $page;
      $this->cache      = $cache;
      $this->validquery = true;
      $this->validindex = true;      
      $this->results_per_page = $results_per_page;      
      
      $index_path = SEARCH_INDEX_PATH;
      
      try {
        $this->index = new Zend_Search_Lucene($index_path, false);
      } catch(Exception $e) {    
        $this->validindex = false;        
        return;
      } //catch
            
      if (empty($this->term)) {
        $this->validquery = false;
      } else {
        $this->set_query($this->term);
      } //else      
    } //constructor
    
    public function set_query($term='') {            
      if (!empty($term)) {
        $this->term = $term;
      } //if
      
      if (empty($this->term)) {
        $this->validquery = false;
      } else {
        $this->validquery = true;
      } //else
      
      if ($this->validquery and $this->validindex) {
        $this->results = $this->get_results();
      } else {
        $this->results = array();
      } //else      
    } //set_query
    
    public function results() {
      if ($this->validquery and $this->validindex) {
        return $this->get_subset_results();
      } else {
        return array();
      } //else
    } //results
    
    private function get_subset_results() {
      if ($this->count() < $this->results_per_page) {
        $this->pagenumber = 1;
      } else if ($this->pagenumber > $this->total_pages()) {
        $this->pagenumber = $this->total_pages();
      } //if
    
      $start  = ($this->pagenumber - 1) * $this->results_per_page;
                     
      return array_slice($this->results, $start, $this->results_per_page);    
    } //get_results
    
    private function get_all_results() {
      global $USER;
      
      $resultdoc  = new SearchResult();
      $resultdocs = array();
      $i = 0;
      
      $term = strtolower($this->term);
      
      $hits = $this->index->find($term." title:".$term." author:".$term);
            
      foreach ($hits as $hit) {            
        //check permissions on each result
        if ($this->can_display($USER, $hit->id, $hit->doctype, $hit->course_id, $hit->group_id)) {
          $resultdoc->number  = $i;
          $resultdoc->url     = $hit->url;
          $resultdoc->title   = $hit->title;
          $resultdoc->score   = $hit->score;
          $resultdoc->doctype = $hit->doctype;
          $resultdoc->author  = $hit->author;
        
          //and store it
          $resultdocs[] = clone($resultdoc);
          
          $i++;
        } //if
      } //foreach
      
      return $resultdocs;
    } //get_all_results
              
    private function get_results() {
      $cache = new SearchCache();
      
      if ($this->cache and $cache->can_cache()) {        
        if (!($resultdocs = $cache->cache($this->term))) {
          $resultdocs = $this->get_all_results();
          //cache the results so we don't have to compute this on every page-load
          $cache->cache($this->term, $resultdocs);          
          //print "Using new results.";
        } else {            
          //There was something in the cache, so we're using that to save time
          //print "Using cached results.";
        } //else                
      } else {
        //no caching :(
        //print "Caching disabled!";
        $resultdocs = $this->get_all_results();
      } //else

      return $resultdocs;
    } //get_results  
    
    public function page_numbers() {
      $pages  = $this->total_pages();
      $query  = htmlentities($this->term);     
      $page   = $this->pagenumber;
      $next   = "Next";
      $back   = "Back";
      
      $ret = "<div align='center' id='search_page_links'>";    
      
      //Back is disabled if we're on page 1
      if ($page > 1) {
        $ret .= "<a href='query.php?query_string=$query&page=".($page-1)."'>< $back</a>&nbsp;";
      } else {
        $ret .= "< $back&nbsp;";
      } //else
      
      //don't <a href> the current page
      for ($i = 1; $i <= $pages; $i++) {
        if ($page == $i) {
          $ret .= "[$i]&nbsp;";
        } else {
          $ret .= "<a href='query.php?query_string=$query&page=$i'>$i</a>&nbsp;";
        } //else
      } //for
      
      //Next disabled if we're on the last page
      if ($page < $pages) {      
        $ret .= "<a href='query.php?query_string=$query&page=".($page+1)."'>$next ></a>&nbsp;";
      } else {
        $ret .= "$next >&nbsp;";
      } //else
      
      $ret .= "</div>";    
      
      //shorten really long page lists, to stop table distorting width-ways
      if (strlen($ret) > 70) {
        $start = 4;
        $end = $page - 5;     
        $ret = preg_replace("/<a\D+\d+\D+>$start<\/a>.*?<a\D+\d+\D+>$end<\/a>/", '...', $ret);
  
        $start = $page + 5;
        $end = $pages - 3;      
        $ret = preg_replace("/<a\D+\d+\D+>$start<\/a>.*?<a\D+\d+\D+>$end<\/a>/", '...', $ret);
      } //if
     
      return $ret;
    } //page_numbers    

    //can the user see this result?          
    private function can_display(&$user, $this_id, $doctype, $course_id, $group_id) {
      //this function should return true/false depending on
      //whether or not a user can see this resource
      //..
      //if one of you nice moodlers see this, feel free to
      //implement it for me .. :-P      
      return true;
    } //can_display
    
    public function count() {
      return count($this->results);
    } //count
    
    //this shouldn't be in this class
    //public function index_count() {
    //  return $this->index->count();
    //} //index_count    
    
    public function is_valid() {
      return ($this->validquery and $this->validindex);
    } //is_valid
    
    public function is_valid_query() {
      return $this->validquery;
    } //is_valid_query

    public function is_valid_index() {
      return $this->validindex;
    } //is_valid_index
    
    public function total_pages() {
      return ceil($this->count()/$this->results_per_page);
    } //pages    
    
    public function get_pagenumber() {
      return $this->pagenumber;
    } //get_pagenumber
    
    public function get_results_per_page() {
      return $this->results_per_page;
    } //get_results_per_page        
  } //SearchQuery

?>