<?php 
class SummaryHelper extends AppHelper {

  function excerpt($text, $words, $length=150, $prefix="...", $suffix = null, $options = array()) {

    // Set default score modifiers [tweak away...]
    $options = am(array(
      'exact_case_bonus'  => 2,
      'exact_word_bonus'  => 3,
      'abs_length_weight' => 0.0,
      'rel_length_weight' => 1.0,

      'debug' => true
    ), $options);

    // Null suffix defaults to same as prefix
    if (is_null($suffix)) {
      $suffix = $prefix;
    }

    // Not enough to work with?
    if (strlen($text) <= $length) {
      return $text;
    }

    // Just in case
    if (!is_array($words)) {
      $words = array($words);
    }

    // Build the event list
    // [also calculate maximum word length for relative weight bonus]
    $events = array();
    $maxWordLength = 0;

    foreach ($words as $word) {

      if (strlen($word) > $maxWordLength) {
        $maxWordLength = strlen($word);
      }

      $i = -1;
      while ( ($i = stripos($text, $word, $i+1)) !== false ) {

        // Basic score for a match is always 1
        $score = 1;

        // Apply modifiers
        if (substr($text, $i, strlen($word)) == $word) {
          // Case matches exactly
          $score += $options['exact_case_bonus'];
        }
        if ($options['abs_length_weight'] != 0.0) {
          // Absolute length weight (longer words count for more)
          $score += strlen($word) * $options['abs_length_weight'];
        }
        if ($options['rel_length_weight'] != 0.0) {
          // Relative length weight (longer words count for more)
          $score += strlen($word) / $maxWordLength * $options['rel_length_weight'];
        }
        if (preg_match('/\W/', substr($text, $i-1, 1))) {
          // The start of the word matches exactly
          $score += $options['exact_word_bonus'];
        }
        if (preg_match('/\W/', substr($text, $i+strlen($word), 1))) {
          // The end of the word matches exactly
          $score += $options['exact_word_bonus'];
        }

        // Push event occurs when the word comes into range
        $events[] = array(
          'type'  => 'push',
          'word'  => $word,
          'pos'   => max(0, $i + strlen($word) - $length),
          'score' => $score
        );
        // Pop event occurs when the word goes out of range
        $events[] = array(
          'type' => 'pop',
          'word' => $word,
          'pos'  => $i + 1,
          'score' => $score
        );
        // Bump event makes it more attractive for words to be in the
        // middle of the excerpt [@todo: this needs work]
        $events[] = array(
          'type' => 'bump',
          'word' => $word,
          'pos'  => max(0, $i + floor(strlen($word)/2) - floor($length/2)),
          'score' => 0.5
        );

      }
    }

    // If nothing is found then just truncate from the beginning
    if (empty($events)) {
      return substr($text, 0, $length) . $suffix;
    }

    // We want to handle each event in the order it occurs in
    // [i.e. we want an event queue]
    $events = sortByKey($events, 'pos');

    $scores = array();
    $score = 0;
    $current_words = array();

    // Process each event in turn
    foreach ($events as $idx => $event) {
      $thisPos = floor($event['pos']);

      $word = strtolower($event['word']);

      switch ($event['type']) {
      case 'push':
        if (empty($current_words[$word])) {
          // First occurence of a word gets full value
          $current_words[$word] = 1;
          $score += $event['score'];
        }
        else {
          // Subsequent occurrences mean less and less
          $current_words[$word]++;
          $score += $event['score'] / sizeof($current_words[$word]);
        }
        break;
      case 'pop':
        if (($current_words[$word])==1) {
          unset($current_words[$word]);
          $score -= ($event['score']);
        }
        else {
          $current_words[$word]--;
          $score -= $event['score'] / sizeof($current_words[$word]);
        }
        break;
      case 'bump':
        if (!empty($event['score'])) {
          $score += $event['score'];
        }
        break;
      default:
      }

      // Close enough for government work...
      $score = round($score, 2);

      // Store the position/score entry
      $scores[$thisPos] = $score;

      // For use with debugging
      $debugWords[$thisPos] = $current_words;

      // Remove score bump
      if ($event['type'] == 'bump') {
          $score -= $event['score'];
      }
    }

    // Calculate the best score
    // Yeah, could have done this in the main event loop
    // but it's better here
    $bestScore = 0;
    foreach ($scores as $pos => $score) {
        if ($score > $bestScore) {
          $bestScore = $score;
        }
    }


    if ($options['debug']) {
      // This is really quick, really tatty debug information
      // (but it works)
      echo "<table border>";
      echo "<caption>Events</caption>";
      echo "<tr><th>Pos</th><th>Type</th><th>Word</th><th>Score</th>";
      foreach ($events as $event) {
        echo "<tr>";
        echo "<td>{$event['pos']}</td><td>{$event['type']}</td><td>{$event['word']}</td><td>{$event['score']}</td>";
        echo "</tr>";
      }
      echo "</table>";

      echo "<table border>";
      echo "<caption>Positions and their scores</caption>";
      $idx = 0;
      foreach ($scores as $pos => $score) {
        $excerpt = substr($text, $pos, $length);
        $style = ($score == $bestScore) ? 'background: #ff7;' : '';

        //$score = floor($score + 0.5);

        echo "<tr>";
        echo "<th style=\"$style\">" . $idx . "</th>";
        echo "<td style=\"$style\">" . $pos . "</td>";
        echo "<td style=\"$style\"><div style=\"float: left; width: 2em; margin-right: 1em; text-align right; background: #ddd\">" . $score . "</div><code>" . str_repeat('*', $score) . "</code></td>";
        echo "<td style=\"$style\"><table border>";
        foreach ($debugWords[$pos] as $word => $count) {
          echo "<tr><td>$word</td><td>$count</td></tr>";
        }
        echo "</table></td>";
        echo "<td style=\"$style\">" . (preg_replace('/(' . implode('|', $words) . ')/i', '<b style="border: 1px solid red;">\1</b>', htmlentities($excerpt))) . "</td>";
        echo "</tr>";
        $idx++;
      }
      echo "</table>";
    }


    // Find all positions that correspond to the best score
    $positions = array();
    foreach ($scores as $pos => $score) {
      if ($score == $bestScore) {
        $positions[] = $pos;
      }
    }

    if (sizeof($positions) > 1) {
      // Scores are tied => do something clever to choose one
      // @todo: Actually do something clever here
      $pos = $positions[0];
    }
    else {
      $pos = $positions[0];
    }

    // Extract the excerpt from the position, (pre|ap)pend the (pre|suf)fix
    $excerpt = substr($text, $pos, $length);
    if ($pos > 0) {
      $excerpt = $prefix . $excerpt;
    }
    if ($pos + $length < strlen($text)) {
      $excerpt .= $suffix;
    }

    return $excerpt;
  }
}
?>