filter.module

<?php
// $Id$

define('FILTER_HTML_DONOTHING', 0);
define('FILTER_HTML_STRIP', 1);
define('FILTER_HTML_ESCAPE', 2);

define('FILTER_STYLE_ALLOW', 0);
define('FILTER_STYLE_STRIP', 1);

function filter_help($section = "admin/help#filter") {
  switch ($section) {
    case 'admin/system/modules#description':
      return t("Framework for handling filtering of content.");
    case 'admin/system/filters':
      return t("
<p>Filters fit between the raw text in a node and the HTML output. They allow you to replace text selectively. Uses include automatic conversion of emoticons into graphics and filtering HTML content from users' submissions.</p>
<p>If you notice some filters are causing conflicts in the output, you can <a href=\"%url\">rearrange them</a>.</p>", array("%url" => url("admin/system/filters/order")));
    case 'admin/system/filters/order':
      return t("
<p>Because of the flexible filtering system, you might encounter a situation where one filter prevents another from doing its job. For example: a word in an URL gets converted into a glossary term, before the URL can be converted in a clickable link. When this happens, you will need to rearrange the order in which filters get executed.</p>
<p>Filters are executed from top-to-bottom. You can use the weight column to rearrange them: heavier filters 'sink' to the bottom. Standard HTML filtering is always run first.</p>");
    case 'filter#long-tip':
    case 'filter#short-tip':
      switch (variable_get("filter_html", FILTER_HTML_DONOTHING)) {
        case 0:
          return t("All HTML tags allowed");
          break;
        case 1:
          if ($allowed_html = variable_get("allowed_html", "<a> <b> <dd> <dl> <dt> <i> <li> <ol> <u> <ul>")) {
            return t("Allowed HTML tags") .": ". htmlspecialchars($allowed_html);
          } else {
            return t("No HTML tags allowed");
          }
          break;
        case 2:
          return t("No HTML tags allowed");
          break;
      }
      break;
  }
}

/**
 * Implementation of hook_link().
 */
function filter_link($type) {
  if ($type == 'system') {
    menu('admin/system/filters', t('filters'), user_access('administer site configuration') ? 'filter_admin' : MENU_DENIED, 5);
    menu('admin/system/filters/order', t('ordering'), user_access('administer site configuration') ? 'filter_admin' : MENU_DENIED, 5);
    menu('filter/tips', t('compose tips'), 'filter_tips_long', 0, MENU_HIDE);
  }
}

function filter_admin_order() {
  $edit = $_POST["edit"];
  $op = $_POST["op"];
  if ($op == t("Save configuration")) {
    foreach ($edit as $module => $filter) {
      db_query("UPDATE {filters} SET weight = %d WHERE module = '%s'", $filter["weight"], $module);
    }
  }

  // Get list (with forced refresh)
  filter_refresh();
  $filters = filter_list();

  $header = array(t('name'), t('weight'));
  $rows = array();

  // Standard HTML filters are always run first, we add a dummy row to indicate this
  $rows[] = array(t("HTML filtering"), array("data" => t("locked")));

  foreach ($filters as $module => $filter) {
    $name = module_invoke($module, "filter", "name");
    $rows[] = array($name, array("data" => form_weight(NULL, $module ."][weight", $filter["weight"])));
  }

  $form  = theme("table", $header, $rows);
  $form .= form_submit(t("Save configuration"));
  $output = form($form);

  return $output;
}

function filter_admin_settings() {
  system_settings_save();

  filter_refresh();

  $form  = filter_default_settings();
  $form .= implode("\n", module_invoke_all("filter", "settings"));
  $output = system_settings_form($form);

  return $output;
}

function filter_admin() {
  switch (arg(3)) {
    case "order":
      $output = filter_admin_order();
      break;
    default:
      $output = filter_admin_settings();
      break;
  }
  print theme("page", $output);
}

function filter_refresh() {
  $modules = module_list();
  $filters = filter_list();

  // Update list in database
  db_query("DELETE FROM {filters}");
  foreach ($modules as $module) {
    if (module_hook($module, "filter")) {
      $weight = $filters[$module]["weight"];

      db_query("INSERT INTO {filters} (module, weight) VALUES ('%s', %d)", $module, $weight);
    }
  }

  filter_list(1);
}

function filter_list($force = 0) {
  static $filters;

  if (!is_array($filters) || $force) {
    $filters = array();
    $result = db_query("SELECT * FROM {filters} ORDER BY weight ASC");
    while ($filter = db_fetch_array($result)) {
      // Fail-safe in case a module was deleted/changed without disabling it
      if (module_hook($filter["module"], "filter")) {
        $filters[$filter["module"]] = $filter;
      }
    }
  }

  return $filters;
}

function check_output($text) {
  if (isset($text)) {
    // Filter content on output:
    $filters = filter_list();

    // Give filters the chance to escape HTML-like data such as code or formulas
    // (from this point on, the input can be treated as HTML)
    if (variable_get("filter_html", FILTER_HTML_DONOTHING) != FILTER_HTML_ESCAPE) {
      foreach ($filters as $module => $filter) {
        $text = module_invoke($module, "filter", "prepare", $text);
      }
    }

    // HTML handling is done before all regular filtering activities
    $text = filter_default($text);

    // Regular filtering
    foreach ($filters as $module => $filter) {
      $text = module_invoke($module, "filter", "process", $text);
    }

    /*
    ** If only inline elements are used and no block level elements, we
    ** replace all newlines with HTML line breaks.
    */
    if (strip_tags($text, '<a><br><span><bdo><map><object><img><tt><i><b><u><big><small><em><strong><dfn><code><q><samp><kbd><var><cite><abbr><acronym><sub><sup><input><select><textarea><label><button><ins><del><script>') == $text) {
      $text = nl2br($text);
    }
  }
  else {
    $text = message_na();
  }

  return $text;
}

function filter_default($text) {
  if (variable_get("filter_html", FILTER_HTML_DONOTHING) == FILTER_HTML_STRIP) {
    // Allow users to enter HTML, but filter it
    $text = strip_tags($text, variable_get("allowed_html", ""));
    if (variable_get("filter_style", FILTER_STYLE_STRIP)) {
      $text = preg_replace("/\Wstyle\s*=[^>]+?>/i", ">", $text);
    }
    $text = preg_replace("/\Won[a-z]+\s*=[^>]+?>/i", ">", $text);
  }

  if (variable_get("filter_html", FILTER_HTML_DONOTHING) == FILTER_HTML_ESCAPE) {
    // Escape HTML
    $text = htmlspecialchars($text);
  }

  return trim($text);
}

function filter_default_settings() {
  $group   = form_radios(t("Filter HTML tags"), "filter_html", variable_get("filter_html", FILTER_HTML_DONOTHING), array(FILTER_HTML_DONOTHING => t("Do not filter"), FILTER_HTML_STRIP => t("Strip tags"), FILTER_HTML_ESCAPE => t("Escape tags")), t("How to deal with HTML and PHP tags in user-contributed content. If set to \"Strip tags\", dangerous tags are removed (see below).  If set to \"Escape tags\", all HTML is escaped and presented as it was typed."));
  $group  .= form_textfield(t("Allowed HTML tags"), "allowed_html", variable_get("allowed_html", "<a> <b> <dd> <dl> <dt> <i> <li> <ol> <u> <ul>"), 64, 255, t("If \"Strip tags\" is selected, optionally specify tags which should not be stripped.  'ON*' attributes are always stripped."));
  $group  .= form_radios(t("HTML style attributes"), "filter_style", variable_get("filter_style", FILTER_STYLE_STRIP), array(FILTER_STYLE_ALLOW => t("Allowed"), FILTER_STYLE_STRIP => t("Removed")), t("If \"Strip tags\" is selected, you can choose whether 'STYLE' attributes are allowed or removed from input."));
  $output .= form_group(t("HTML filtering"), $group);

  return $output;
}

function filter_filter($op, $text = "") {
  switch ($op) {
    case "name":
      return t("Legacy filtering");
    case "process":
      if (variable_get("rewrite_old_urls", 0)) {
        $text = filter_old_urls($text);
      }
      return $text;
    case "settings":
      $group   = form_radios(t("Rewrite old URLs"), "rewrite_old_urls", variable_get("rewrite_old_urls", 0), array(t("Disabled"), t("Enabled")), t("The introduction of 'clean URLs' in Drupal 4.2.0 breaks internal URLs that date back from Drupal 4.1.0 and before.  If enabled, this filter will attempt to rewrite the old style URLs to avoid broken links.  If <code>mod_rewrite</code> is available on your system, use the rewrite rules in Drupal's <code>.htaccess</code> file instead as these will also correct external referrers."));
      $output .= form_group(t("Legacy filtering"), $group);
      return $output;
    default:
      return $text;
  }
}

function filter_old_urls($text) {
  global $base_url;

  $end = substr($base_url, 12);

  /*
  ** This is a *temporary* filter to rewrite old-style URLs to new-style
  ** URLs (clean URLs).  Currently, URLs are being rewritten dynamically
  ** (ie. "on output"), however when these rewrite rules have been tested
  ** enough, we will use them to permanently rewrite the links in node
  ** and comment bodies.
  */

  if (variable_get("clean_url", "0") == "0") {
    /*
    ** Relative URLs:
    */

    // rewrite 'node.php?id=<number>[&cid=<number>]' style URLs:
    $text = eregi_replace("\"(node)\.php\?id=([[:digit:]]+)(&cid=)?([[:digit:]]*)", "\"?q=\\1/view/\\2/\\4", $text);

    // rewrite 'module.php?mod=<name>{&<op>=<value>}' style URLs:
    $text = ereg_replace("\"module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))", "\"?q=\\2/\\4/\\6" , $text);
    $text = ereg_replace("\"module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))", "\"?q=\\2/\\4", $text);
    $text = ereg_replace("\"module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))", "\"?q=\\2", $text);

    /*
    ** Absolute URLs:
    */

    // rewrite 'node.php?id=<number>[&cid=<number>]' style URLs:
    $text = eregi_replace("$end/(node)\.php\?id=([[:digit:]]+)(&cid=)?([[:digit:]]*)", "$end/?q=\\1/view/\\2/\\4", $text);

    // rewrite 'module.php?mod=<name>{&<op>=<value>}' style URLs:
    $text = ereg_replace("$end/module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))", "$end/?q=\\2/\\4/\\6" , $text);
    $text = ereg_replace("$end/module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))", "$end/?q=\\2/\\4", $text);
    $text = ereg_replace("$end/module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))", "\"$end/?q=\\2", $text);
  }
  else {
    /*
    ** Relative URLs:
    */

    // rewrite 'node.php?id=<number>[&cid=<number>]' style URLs:
    $text = eregi_replace("\"(node)\.php\?id=([[:digit:]]+)(&cid=)?([[:digit:]]*)", "\"\\1/view/\\2/\\4", $text);

    // rewrite 'module.php?mod=<name>{&<op>=<value>}' style URLs:
    $text = ereg_replace("\"module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))", "\"\\2/\\4/\\6", $text);
    $text = ereg_replace("\"module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))", "\"\\2/\\4", $text);
    $text = ereg_replace("\"module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))", "\"\\2", $text);

    /*
    ** Absolute URLs:
    */

    // rewrite 'node.php?id=<number>[&cid=<number>]' style URLs:
    $text = eregi_replace("$end/(node)\.php\?id=([[:digit:]]+)(&cid=)?([[:digit:]]*)", "$end/\\1/view/\\2/\\4", $text);

    // rewrite 'module.php?mod=<name>{&<op>=<value>}' style URLs:
    $text = ereg_replace("$end/module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))", "$end/\\2/\\4/\\6", $text);
    $text = ereg_replace("$end/module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))(&?[[:alpha:]]+=([[:alnum:]]+))", "$end/\\2/\\4", $text);
    $text = ereg_replace("$end/module\.php\?(&?[[:alpha:]]+=([[:alnum:]]+))", "$end/\\2", $text);
  }

  return $text;
}

function filter_tips_long() {
  $tiplist = '';
  foreach (module_list() as $name) {
    if ($tip = module_invoke($name, 'help', 'filter#long-tip')) {
      $tiplist .= "<li id=\"filter-$name\">$tip</li>\n";
    }
  }
  $output = "<ul class=\"filter-tips-long\">\n$tiplist\n</ul>\n";
  print theme("page", $output, t('Compose Tips'));
}

function filter_tips_short() {
  $tiplist = '';
  foreach (module_list() as $name) {
    if ($tip = module_invoke($name, 'help', 'filter#short-tip')) {
      $tiplist .= "<li>$tip</li>\n";
    }
  }
  $tiplist .= '<li class="more-tips">' . l(t('More information on formatting options'), 'filter/tips') . '</li>';
  return "<ul class=\"filter-tips-short\">\n$tiplist\n</ul>\n";
}

?>