drupal-civicrm/sites/all/modules/civicrm/Civi/API/Events.php

<?php
/*
 +--------------------------------------------------------------------+
 | CiviCRM version 4.7                                                |
 +--------------------------------------------------------------------+
 | Copyright CiviCRM LLC (c) 2004-2017                                |
 +--------------------------------------------------------------------+
 | This file is a part of CiviCRM.                                    |
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 | CiviCRM is free software; you can copy, modify, and distribute it  |
 | under the terms of the GNU Affero General Public License           |
 | Version 3, 19 November 2007 and the CiviCRM Licensing Exception.   |
 |                                                                    |
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 | See the GNU Affero General Public License for more details.        |
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 | with this program; if not, contact CiviCRM LLC                     |
 | at info[AT]civicrm[DOT]org. If you have questions about the        |
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 */
namespace Civi\API;

/**
 * The API kernel dispatches a series of events while processing each API request.
 * For a successful API request, the sequence is RESOLVE => AUTHORIZE => PREPARE => RESPOND.
 * If an exception arises in any stage, then the sequence is aborted and the EXCEPTION
 * event is dispatched.
 *
 * Event subscribers which are concerned about the order of execution should assign
 * a weight to their subscription (such as W_EARLY, W_MIDDLE, or W_LATE).
 * W_LATE).
 */
class Events {

  /**
   * Determine whether the API request is allowed for the current user.
   * For successful execution, at least one listener must invoke
   * $event->authorize().
   *
   * @see AuthorizeEvent
   */
  const AUTHORIZE = 'civi.api.authorize';

  /**
   * Determine which API provider executes the given request. For successful
   * execution, at least one listener must invoke
   * $event->setProvider($provider).
   *
   * @see ResolveEvent
   */
  const RESOLVE = 'civi.api.resolve';

  /**
   * Apply pre-execution logic
   *
   * @see PrepareEvent
   */
  const PREPARE = 'civi.api.prepare';

  /**
   * Apply post-execution logic
   *
   * @see RespondEvent
   */
  const RESPOND = 'civi.api.respond';

  /**
   * Handle any exceptions.
   *
   * @see ExceptionEvent
   */
  const EXCEPTION = 'civi.api.exception';

  /**
   * Weight - Early
   */
  const W_EARLY = 100;

  /**
   * Weight - Middle
   */
  const W_MIDDLE = 0;

  /**
   * Weight - Late
   */
  const W_LATE = -100;

  /**
   * @return array<string>
   */
  public static function allEvents() {
    return array(
      self::AUTHORIZE,
      self::EXCEPTION,
      self::PREPARE,
      self::RESOLVE,
      self::RESPOND,
    );
  }

  /**
   * @param \Civi\Core\Event\GenericHookEvent $e
   * @see \CRM_Utils_Hook::eventDefs
   */
  public static function hookEventDefs($e) {
    $e->inspector->addEventClass(self::AUTHORIZE, 'Civi\API\Event\AuthorizeEvent');
    $e->inspector->addEventClass(self::EXCEPTION, 'Civi\API\Event\ExceptionEvent');
    $e->inspector->addEventClass(self::PREPARE, 'Civi\API\Event\PrepareEvent');
    $e->inspector->addEventClass(self::RESOLVE, 'Civi\API\Event\ResolveEvent');
    $e->inspector->addEventClass(self::RESPOND, 'Civi\API\Event\RespondEvent');
  }

}