<?php
// $Id$

/**
 * @file
 * Allow editing of subsections.
 * Todo:
 *  - concurrent edits
 *    - try to circumvent node submission check
 *    - detect if section numbers changed
 *  - preview changes of diff module is broken
 *  - refactor duplicated code in 'section_edit_extract_section'
 *  - see how CCK behaves with this
 */

/**
 * Implementation of hook_nodeapi().
 */
function section_edit_nodeapi(&$node, $op) {
  global $_section_edit_current_section, $_section_edit_header, $_section_edit_nid;

  // Only apply changes if section editing is activated for this node type
  if (section_edit_activated($node->type) && section_edit_header_style($node->format)) {
    // Get section number from url
    $section = isset($_GET['section']) ? $_GET['section'] : NULL;

    switch ($op) {
      case 'presave':
        // Node is being submitted to database. Is only a section edited?
        if (!is_null($section)) {
          // Make sure two newlines are at the end of the body. This gives some space to the next header.
          $new_section_text = rtrim($node->body) ."\n\n";
          // Get original content from database
          $original_body = db_result(db_query('SELECT body FROM {node_revisions} WHERE vid = %d', $node->vid));
          // Extract the old section text from the original body
          list($section_header, $section_text) = section_edit_extract_section($original_body, $node->format, $section);
          // Replace the old section text with the new one
          $node->body = str_replace($section_text, $new_section_text, $original_body);
          // Set teaser from the whole node body. At the moment the teaser was generated only from the edited part
          $node->teaser = node_teaser($node->body, $node->format);
        }
        break;

      case 'prepare':
        // Node is being shown in edit form. Is only a section edited?
        if (!is_null($section)) {
          // Extract the section which is edited.
          list($section_header, $section_text) = section_edit_extract_section($node->body, $node->format, $section);
          // Was the section valid?
          if ($section_text) {
            // Replace the body which is being edited with the section text.
            $node->body = $section_text;
            // Set the global variable to the header. This is used to set the log message in hook_form_alter().
            $_section_edit_header = $section_header;
            
            $node->teaser = node_teaser($node->body, $node->format);
          }
        }
        break;

      case 'view':
        // Node is being shown as HTML. Is current user allowed to edit?
        if (node_access('update', $node)) {
          // Add css style sheet for edit links
          drupal_add_css(drupal_get_path('module', 'section_edit') .'/section_edit.css', 'module', 'all', FALSE);
          // Set the global variables which are used in the 'preg_replace_callback' callback.
          $_section_edit_current_section = 0;
          $_section_edit_nid = $node->nid;
          // Add edit links to all headers
          $node->content['body']['#value'] = preg_replace_callback('#<(h\d)(\s[^>]*)?>(.*?)</\1>#', 'section_edit_insert_link', $node->content['body']['#value']);
        }
        break;
    }
  }
}

/**
 * Callback of preg_replace_calback for inserting edit links in headers.
 */
function section_edit_insert_link($match) {
  global $_section_edit_current_section, $_section_edit_nid;

  // Construct edit link and append it to header
  $link = l('edit', "node/$_section_edit_nid/edit", array('attributes' => array('class' => 'section-edit'), 'query' => "section=$_section_edit_current_section"));
  $_section_edit_current_section++;
  return $link .' '. $match[0];
}

/**
 * Extract section from text
 *
 * @param $text
 *    text to extract section from
 * @param $format
 *    input format used
 * @param $nr
 *    the number of which section to extract. it is zero-based and the sections are numbered flat
 */
function section_edit_extract_section($text, $format, $nr) {
  switch (section_edit_header_style($format)) {
    case 'html':
      $match = preg_split('#(<h(\d)[^>]*>(.*?)</h\2>)#m', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
      if (count($match) > 0) {
        // Match 0 is before the first header
        unset($match[0]);
        // The match contains three parts of the regexp and the final text, split it in groups of four.
        $sections = array_chunk($match, 4);
        if (isset($sections[$nr])) {
          // match 0 is the header
          // match 1 is the header number (1-6)
          // match 2 is the text of the header
          // match 3 the splitted text
          $section_header = $sections[$nr][0];
          $section_depth = $sections[$nr][1];
          $section_text = $sections[$nr][0] . $sections[$nr][3];
          // Append the text of all subsections
          // The subsection have more equal signs (higher depth)
          $i = $nr + 1;
          while ($i < count($sections) && $sections[$i][1] > $section_depth) {
            $section_text .= $sections[$i][0] . $sections[$i][3];
            $i++;
          }
          return array(
            $section_header,
            $section_text
          );
        }
      }
      break;

    case 'mediawiki':
      // Split text at headers
      $match = preg_split('/^((={1,6})(.*?)\2(?:\s|$))/m', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
      if (count($match) > 0) {
        // Match 0 is before the first header
        unset($match[0]);
        // The match contains three parts of the regexp and the final text, split it in groups of four.
        $sections = array_chunk($match, 4);
        if (isset($sections[$nr])) {
          // match 0 is the header
          // match 1 is the string of equal signs
          // match 2 is the text of the header
          // match 3 the splitted text
          $section_header = $sections[$nr][0];
          $section_depth = strlen($sections[$nr][1]);
          $section_text = $sections[$nr][0] . $sections[$nr][3];
          // Append the text of all subsections
          // The subsection have more equal signs (higher depth)
          $i = $nr + 1;
          while ($i < count($sections) && strlen($sections[$i][1]) > $section_depth) {
            $section_text .= $sections[$i][0] . $sections[$i][3];
            $i++;
          }
          return array(
            $section_header,
            $section_text
          );
        }
      }
      break;

    case 'creole':
      // Split text at headers
      $match = preg_split('/^((={1,6}) *(.*?) *=*)$/m', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
      if (count($match) > 0) {
        // Match 0 is before the first header
        unset($match[0]);
        // The match contains three parts of the regexp and the final text, split it in groups of four.
        $sections = array_chunk($match, 4);
        if (isset($sections[$nr])) {
          // match 0 is the header
          // match 1 is the string of equal signs
          // match 2 is the text of the header
          // match 3 the splitted text
          $section_header = $sections[$nr][0];
          $section_depth = strlen($sections[$nr][1]);
          $section_text = $sections[$nr][0] . $sections[$nr][3];
          // Append the text of all subsections
          // The subsection have more equal signs (higher depth)
          $i = $nr + 1;
          while ($i < count($sections) && strlen($sections[$i][1]) > $section_depth) {
            $section_text .= $sections[$i][0] . $sections[$i][3];
            $i++;
          }
          return array(
            $section_header,
            $section_text
          );
        }
      }
      break;

    case 'dokuwiki':
      // Split text at headers
      $match = preg_split('/^(={2,6}) (.*?) \1$/m', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
      if (count($match) > 0) {
        // Match 0 is before the first header
        unset($match[0]);
        // The match contains three parts of the regexp and the final text, split it in groups of four.
        $sections = array_chunk($match, 4);
        if (isset($sections[$nr])) {
          // match 0 is the header
          // match 1 is the string of equal signs
          // match 2 is the text of the header
          // match 3 the splitted text
          $section_header = $sections[$nr][0];
          $section_depth = 6 - strlen($sections[$nr][1]);
          $section_text = $sections[$nr][0] . $sections[$nr][3];
          // Append the text of all subsections
          // The subsection have more equal signs (higher depth)
          $i = $nr + 1;
          while ($i < count($sections) && (6 - strlen($sections[$i][1])) > $section_depth) {
            $section_text .= $sections[$i][0] . $sections[$i][3];
            $i++;
          }
          return array(
            $section_header,
            $section_text
          );
        }
      }
      break;
  }
  return array(NULL, NULL);
}

/**
 * Implementation of hook_form_alter().
 */
function section_edit_form_alter(&$form, $form_state, $form_id) {
  global $_section_edit_header;
  if ($form_id == 'node_type_form' && isset($form['identity']['type']) && module_exists('comment')) {
    // Node type edit form: Add checkbox to activate per section editing
    $form['workflow']['section_edit'] = array(
      '#type' => 'checkbox',
      '#title' => t('Display edit links for single sections'),
      '#prefix' => '<strong>'. t('Section edit') .'</strong>',
      '#weight' => 5,
      '#default_value' => section_edit_activated($form['#node_type']->type),
    );
  }
  elseif (isset($form['type']) && $form['type']['#value'] .'_node_form' == $form_id) {
    // Node edit form: Set log message if only a section is edited.
    if ($_section_edit_header) {
      $form['log']['#default_value'] = $_section_edit_header;
    }
  }
  elseif ($form_id == 'filter_admin_configure') {
    // Filter configuration form: Add selection of header syntax type
    // The fourth path entry is the format id (admin/settings/filter/#nr/configure)
    $format_id = arg(3);
    $form['section_edit'] = array(
      '#type' => 'fieldset',
      '#title' => t('Section edit type'),
      '#weight' => -4,
      '#description' => t('Section editing must be activated per node type. The setting here will be ignored on node types where section edit is not active.')
    );
    $form['section_edit']["section_edit_header_style_$format_id"] = array(
      '#type' => 'radios',
      '#title' => 'Header style',
      '#options' => array(
        'off' => t('Off: No section edit links'),
        'html' => t('HTML: Use this for HTML or WYSIWYG formats.'),
        'mediawiki' => t('Mediawiki: Use this for Mediawiki format'),
        'dokuwiki' => t('Dokuwiki: Use this for DokuWiki format'),
        'creole' => t('Creole: Use this for Creole format'),
      ),
      '#default_value' => variable_get("section_edit_header_style_$format_id", 'off'),
      '#description' => t('Select the header style for this input format. The header style will be used to insert edit links for single sections.')
    );
  }
}

/*
 * Settings
 */

/**
 * Are section edit links activated for this node type?
 *
 * @param $node_type
 *   Node type string
 */
function section_edit_activated($node_type, $value = NULL) {
  if (is_null($value)) {
    return variable_get("section_edit_$node_type", FALSE);
  }
  variable_set("section_edit_$node_type", $value);
}

/**
 * Header style for a specific input format.
 *
 * @param $format
 *   The ID of the input format.
 */
function section_edit_header_style($format, $value = NULL) {
  if (is_null($value)) {
    return variable_get("section_edit_header_style_$format", 'html');
  }
  variable_set("section_edit_header_style_$format");
}