A generic module to store arbitrary entity locks in Contao.

• backend user support is not done, yet -> currently frontend handling only

• adds a lock entity for storing the current editor, lock time, locked entity, ...
• offers a rich model interface to easily handle creation, update and deletion of locks for any entity
• read the "Usage" chapter for more details on the functionality

The module is just a helper module for storing lock relevant information like the editor, the lock time, ...

The intended usage is as follows:

• Some kind of edit form is opened -> Hence the currently edited record (aka entity) should be locked from another concurrent editing.
• A lock is created in the moment of the form's loading.
• On submit of the form the lock is removed and a the user has to be redirected to some other page in order to prevent the form from locking the entity again as happened in the previous step.
• In case of deletion of the entity, of course, all linked locks are also removed.
• The developer can specify how long the lock interval is (in the global settings or overrride it in the module config using EntityLock::DEFAULT_PALETTE). After the age of a lock passed this interval it isn't active anymore (it times out).
• The developer can specify in a module's config whether any frontend user can delete active locks (e.g. if the lock is more a hint than a hard barrier)

A module developer using entity_lock can store a new lock, check for their existance in the appropriate places and could use heimrichhannot/contao-entity_cleaner in order to remove elapsed locks.

In addition you could use heimrichhannot/contao-frontendedit to build your frontend module, since it already supports entity_lock, i.e. new locks are created automatically in frontend.

Extend $GLOBALS['TL_CONFIG']['entityLockEntityTitleFields'] defined in config/config.php in order to define mapping for your custom entities. Otherwise auto completion will only use the id field.

Do the following in your frontend module (or use heimrichhannot/contao-frontendedit since it already does that for you):

1. Add the necessary fields to tl_module and check addEntityLock in the module config in Contao:

$GLOBALS['TL_DCA']['tl_module']['palettes']['my_module'] .= \HeimrichHannot\EntityLock\EntityLock::DEFAULT_PALETTE;

2. Check for existing locks and create one if necessary:

   if ($this->addEntityLock && EntityLockModel::isLocked('tl_calendar_events', $objEvent->id, $this))
   {
       // do something like display a message that the entity is locked (or check for lock removal being allowed -> see 4.)
   }
   else
   {
       EntityLockModel::create('tl_calendar_events', $objEvent->id, $this);
   }
   

3. Remove all locks linked to a certain entity after submission of the edit form and on deletion of the entity:

   EntityLockModel::deleteLocks('tl_calendar_events', $objEvent->id);
   

4. If a frontend user should be able to take over some other user's record (i.e. delete a lock), you can check for that in the module as follows:

   $strMessage = EntityLock::generateErrorMessage('tl_calendar_events', $objEvent->id, $this);
   
   if ($this->allowLockDeletion)
   {
       // generateUnlockForm() also does the actual deletion of the lock and the sending of a notification to the former editor
       $strUnlockForm = $this->generateUnlockForm($objItem, $objLock);
       $strMessage .= $strUnlockForm;
   }