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<?php
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// $Id: collaborative_editor.module,v 0.10
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/**
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* @file
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* Collaborative Editor Module
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*
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* This module allows concurrent edition when content is created in Drupal
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*
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*
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* IMPORTANT: Read INSTALL.txt first
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*
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*
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*/
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/**
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* Implementation of hook_help().
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*/
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function collaborative_editor_help($section) {
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switch ($section) {
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case 'admin/modules#description':
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return('Allows concurrent edition when content is created');
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}
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}
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/**
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* Implementation of hook_perm().
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*/
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function collaborative_editor_perm() {
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return array('create content', 'edit own content');
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}
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/**
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* Implementation of hook_access().
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*/
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function collaborative_editor_access($op, $node) {
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global $user;
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if ($op == 'create') {
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return user_access('create content');
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}
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if ($op == 'update' || $op == 'delete') {
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if (user_access('create content') ) {
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return TRUE;
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}
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}
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}
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/**
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* Implementation of hook_menu
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*/
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function collaborative_editor_menu($may_cache) {
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$items = array();
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if ($may_cache) {
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/* only used to remove change the user status when they leave the document
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$items[] = array('path' => 'collaborative_editor/removeUserStatus',
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'title' => t('collaborative_editor'),
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'callback' => 'remove_user_status',
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'type' => MENU_CALLBACK,
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'access' => user_access('create content'));
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*/
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}
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else {
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// this path will be called in each async call
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$items[] = array('path' => 'collaborative_editor/'. arg(1) .'/getAsyncContent',
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'title' => t('collaborative_editor'),
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'callback' => 'collaborative_editor_async_content',
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'type' => MENU_CALLBACK,
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'access' => user_access('create content'));
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}
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return $items;
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}
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/**
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* Implementation of hook_form_alter
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*/
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function collaborative_editor_form_alter($form_id, &$form) {
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global $user;
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if (is_numeric(arg(1))) {
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$result = db_query('SELECT * FROM {ce_content} WHERE cid = %d',arg(1));
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// if we already have the ce content created already
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if (db_num_rows($result)) {
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$content_from_db = db_fetch_object($result);
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$init_content = $content_from_db->body;
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$revision = $content_from_db->rid;
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}
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else {
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$revision = 0;
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$init_content = '';
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}
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if (isset($form['type'])) {
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$path = drupal_get_path('module', 'collaborative_editor');
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// here we insert the js files we need
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drupal_add_js($path . '/drupal.collaborative_editor_ui.js');
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drupal_add_js($path . '/drupal.collaborative_editor.js');
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// this fieldset is used to insert ui elements via DOM
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$form['track'] = array(
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'#type' => 'fieldset',
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'#title' => t('Collaborative editor'),
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);
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$form['cid'] = array('#type' => 'hidden', '#default_value' => arg(1));
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// the initial revision id should be present in the initial form as well
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$form['rev'] = array('#type' => 'hidden', '#default_value' => $revision);
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$form['init'] = array('#type' => 'hidden', '#default_value' => $init_content);
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// this field is only to show the debug values
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$form['debug'] = array('#type' => 'textarea', '#title' => t('Debug'), '#rows' => 10);
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}
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}
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}
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// this function handles the use cases of each async call
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function collaborative_editor_async_content() {
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global $user;
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$cid = arg(1);
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// remove those user status whose users are not currently editing
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check_user_status();
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//This variable is used to store the revision id the server will send back to the client
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$return_rev = '';
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// get post params:
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$new_content = $_POST['diffText']; // the new content the user has added
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$client_rev = $_POST['clientRev']; // should be the same as the server give them last time
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$result = db_query("SELECT * FROM {ce_content} WHERE cid = %d", $cid);
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// if we already have the ce content created already
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if (db_num_rows($result)) {
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$content_from_db = db_fetch_object($result);
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$insert_start = $_POST['prefixLength']; // in what initial position has been added this content
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$replacement_length = $_POST['replacementLength']; // if there has been a replacement or content deleted, how long it is
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// this checks if the client has modified the content
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$is_diff = strlen($new_content) > 0 || $replacement_length != 0;
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// insert the values we upload into an array to send it later as pending changes for other users
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// The aim is to avoid other users work on outdated versions of the content
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// This changes will be applied to other users so that they can insert their content in the right place
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$pchanges = array();
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$pchanges['start'] = $insert_start;
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$pchanges['replacement'] = $replacement_length;
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$pchanges['content_length'] = strlen($new_content); // here we dont need to know the content, only its length
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// the revision id of the current content on the server. It changes everytime someone uploads new content
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$server_rev = $content_from_db->rid;
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}
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else {
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// if there is no ce content we create a new one
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db_query("INSERT INTO {ce_content} (cid,rid) VALUES (%d,'%s')",$cid,$client_rev);
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$server_rev = $client_rev;
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$new_doc = true;
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}
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/* implement use cases
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# case 1: client uploads diff. no changes in server
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# case 2: client checks but no diff to upload. no changes in server
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# case 3: client uploads diff. there are changes in server (modifications by others)
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# case 4: client checks but no diff to upload. there are changes in server (modifications by others)
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# case 5: client uploads diff but there is a collision
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# case 6: user still typing, whatever other cases are happening. If there are new changes from other users they will be updated when user stops typing
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*/
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if ($server_rev != $client_rev) { // if the revision in the server is different than ours means that somebody else has done changes in the document
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//we set the flag to know there has been changes from others
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$otherschange = 1;
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if ($is_diff) { // if we have done any changes
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// debug var
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$phase = "#3 - changes done. also changes from others";
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// first check if we have pending changes
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$result = db_query("SELECT pchange FROM {ce_pchanges} WHERE uid = %d AND cid = %d", $user->uid, $cid);
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// if so, we use them to know where we will have to insert our content
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while ($row = db_fetch_object($result)) {
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$offset = unserialize($row->pchange); // the values are extracted from the array
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$offset_start = $offset['start'];
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$offset_length = $offset['content_length'];
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$offset_content = $offset['replacement'];
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// Note: the more tests we do the more bugs we can find in the lines below of collision detection
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// Dont get confused with the bug # in IE which can make fail the following lines
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// Here we bother the others inserts happening before our caret position. We dont bother those after our caret position
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if ($offset_start <= $insert_start) {
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// check if there is collision with others' changes
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// This is true if our caret is in between others replacements or deletions
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if (($offset_start + $offset_content) > $insert_start) {
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$phase = "#5 - collision";
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$collision = true;
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}
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// update the caret position where we will insert content
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$insert_start += $offset_length - $offset_content;
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}
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// there is a second possible collision to check. Others' inserts happen after our caret position
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// This is true if we replace or delete where others' caret is
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elseif (($insert_start + $replacement_length) > $offset_start) {
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$phase = "#5 - collision";
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$collision = true;
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}
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}
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// if there's no collision we continue with the use case #3
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if (!$collision) {
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// everytime we store new content the revision id is updated
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$new_rev = rand(10000,99999);
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db_query("UPDATE {ce_content} SET rid = '%s' WHERE cid = %d", $new_rev, $cid);
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// put the changes to others' pending list
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// we take the active users from the ce_users table
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$result = db_query("SELECT uid FROM {ce_users} WHERE cid = %d", $cid);
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while ($row = db_fetch_object($result)) {
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if ($row->uid != $user->uid) {
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db_query("INSERT INTO {ce_pchanges} (cid,uid,pchange) VALUES ('%s',%d,'%s')",$cid,$row->uid,serialize($pchanges));
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}
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}
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// do the insert or replacement and update the database content
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$display = substr_replace($content_from_db->body, $new_content, $insert_start, $replacement_length); // ( mixed string, string replacement, int start [, int length] )
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db_query("UPDATE {ce_content} SET body = '%s' WHERE cid = %d", $display, $cid);
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// delete our pending changes
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delete_pending_changes(arg(1));
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$return_rev = $new_rev;
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}
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// here we handle the collision case. Since the last change is not valid we only return the server content as it is
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else {
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$display = $content_from_db->body;
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$return_rev = $server_rev;
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delete_pending_changes(arg(1));
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}
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}
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else {
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$phase = "#4 - no changes. but changes from others";
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// we return the content of the server
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$display = $content_from_db->body;
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$return_rev = $server_rev;
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delete_pending_changes(arg(1));
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}
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}
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// If we get this point is because the revision id in the server is the same as the revision we upload. Therefore there is
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// no change from others in the server content. Two use cases are possible here depending on whether we upload new content (case 1)
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// or not (case 2: periodic check -> when this case happens and we are editing alone the heartbeat refresh ought to be set
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// to 30 seconds or so)
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elseif ($is_diff && !$new_doc) { // #1
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$phase = "#1 - changes done. nobody else changes";
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// create a new revision since there is a new version of the content
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$new_rev = rand(10000,99999);
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db_query("UPDATE {ce_content} SET rid = '%s' WHERE cid = %d", $new_rev, $cid);
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// put the changes to others' pending list
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// we take the active users from the ce_users table
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$result = db_query("SELECT uid FROM {ce_users} WHERE cid = %d", $cid);
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while ($row = db_fetch_object($result)) {
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if ($row->uid != $user->uid) {
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db_query("INSERT INTO {ce_pchanges} (cid,uid,pchange) VALUES ('%s',%d,'%s')",$cid,$row->uid,serialize($pchanges));
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}
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}
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// do changes and update to db
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$display = substr_replace($content_from_db->body, $new_content, $insert_start, $replacement_length); // ( mixed string, string replacement, int start [, int length] )
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db_query("UPDATE {ce_content} SET body = '%s' WHERE cid = %d", $display, $cid);
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// delete our pending changes
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delete_pending_changes(arg(1));
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// the revision id returned will be the one we created before
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$return_rev = $new_rev;
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// set the flag since there are no changes from others
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$otherschange = 0;
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}
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else {
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// here we dont set the return_rev variable, so this will be blank in the returned hash. The uploaded_rev will be used in the client side instead
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// since there has been no change in the content the uploaded revision id by the client is valid
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$phase = "#2 - no movement";
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$display = $content_from_db->body; // Note: I have to test if I can avoid to send this back
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$otherschange = 0;
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}
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// set response . json object
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$display = rawurlencode($display); // we encode line breaks since so that json object doesnt show an error
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if ($collision) $collision = 1; // not possible send back boolean types ???
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// we store the current users in an array to show them in the list below the textarea
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$result = db_query("SELECT n.name FROM {users} n, {ce_users} c WHERE c.cid = %d AND c.uid = n.uid", $cid);
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$currentusers = array();
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while ($row = db_fetch_object($result)) {
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array_push($currentusers, "'".$row->name."'");
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}
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$sendusers = implode(",",$currentusers);
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// if the user is editing the content for the first time the user status is set
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$result = db_query('SELECT * FROM {ce_users} WHERE cid = %d AND uid = %d',arg(1),$user->uid);
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if (!db_num_rows($result)) {
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db_query("INSERT INTO {ce_users} (cid,uid) VALUES (%d,%d)",arg(1),$user->uid);
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}
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// if it is not the first time but still editing we update the checked field
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db_query("UPDATE {ce_users} SET checked = %d, refresh = %d WHERE uid = %d AND cid = %d", time(), 20, $user->uid, $cid);
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echo "{content: '$display',
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return_rev: '$return_rev',
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uploaded_rev: '$client_rev',
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phase: '$phase',
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otherschange: '$otherschange',
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collision: '$collision',
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currentusers: [ $sendusers ]
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}";
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}
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function check_user_status() {
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// remove those users who havent edited in the last 20 seconds
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$result = db_query('SELECT * FROM {ce_users} WHERE checked + %d < %d', 20, time());
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while ($row = db_fetch_object($result)) {
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remove_user_status($row->cid, $row->uid);
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}
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}
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function delete_pending_changes($cid) {
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global $user;
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db_query("DELETE FROM {ce_pchanges} WHERE uid = %d AND cid = %d", $user->uid, $cid);
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}
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function remove_user_status($cid, $uid) {
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global $user;
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db_query("DELETE FROM {ce_users} WHERE uid = %d AND cid = %d", $uid, $cid);
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db_query("DELETE FROM {ce_pchanges} WHERE uid = %d AND cid = %d", $uid, $cid);
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}
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?>
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