<?php defined("SYSPATH") or die("No direct script access.");
/**
 * Gallery - a web based photo album viewer and editor
 * Copyright (C) 2000-2009 Bharat Mediratta
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA  02110-1301, USA.
 */
/**
 * This abstract controller makes it easy to create a RESTful controller.  To use it, create a
 * subclass which defines the resource type and implements get/post/put/delete methods, like this:
 *
 * class Comment_Controller extends REST_Controller {
 *   protected $resource_type = "comment";  // this tells REST which model to use
 *
 *   public function _index() {
 *     // Handle GET request to /controller
 *   }
 *
 *   public function _show(ORM $comment) {
 *     // Handle GET request to /comments/{comment_id}
 *   }
 *
 *   public function _update(ORM $comment) {
 *     // Handle PUT request to /comments/{comment_id}
 *   }
 *
 *   public function _create(ORM $comment) {
 *     // Handle POST request to /comments
 *   }
 *
 *   public function _delete(ORM $comment) {
 *     // Handle DELETE request to /comments/{comments_id}
 *   }
 *
 *   public function _form_add($parameters) {
 *     // Handle GET request to /form/add/comments
 *     // Show a form for creating a new comment
 *   }
 *
 *   public function _form_edit(ORM $comment) {
 *     // Handle GET request to /form/edit/comments
 *     // Show a form for editing an existing comment
 *   }
 *
 * A request to http://example.com/gallery3/comments/3 will result in a call to
 * REST_Controller::__call(3) which will load up the comment associated with id 3.  If there's
 * no such comment, it returns a 404.  Otherwise, it will then delegate to
 * Comment_Controller::get() with the ORM instance as an argument.
 */
class REST_Controller extends Controller {
  protected $resource_type = null;

  public function __construct() {
    if ($this->resource_type == null) {
      throw new Exception("@todo ERROR_MISSING_RESOURCE_TYPE");
    }
    parent::__construct();
  }

  /**
   * Handle dispatching for all REST controllers.
   */
  public function __call($function, $args) {
    // If no parameter was provided after the controller name (eg "/albums") then $function will
    // be set to "index".  Otherwise, $function is the first parameter, and $args are all
    // subsequent parameters.
    $request_method = rest::request_method();
    if ($function == "index" && $request_method == "get") {
      return $this->_index();
    }

    $resource = ORM::factory($this->resource_type, (int)$function);
    if (!$resource->loaded && $request_method != "post") {
      return Kohana::show_404();
    }

    if ($request_method != "get") {
      access::verify_csrf();
    }

    switch ($request_method) {
    case "get":
      return $this->_show($resource);

    case "put":
      return $this->_update($resource);

    case "delete":
      return $this->_delete($resource);

    case "post":
      return $this->_create($resource);
    }
  }

  /* We're editing an existing item, load it from the database. */
  public function form_edit($resource_id) {
    if ($this->resource_type == null) {
      throw new Exception("@todo ERROR_MISSING_RESOURCE_TYPE");
    }

    // @todo this needs security checks
    $resource = ORM::factory($this->resource_type, $resource_id);
    if (!$resource->loaded) {
      return Kohana::show_404();
    }

    return $this->_form_edit($resource);
  }

  /* We're adding a new item, pass along any additional parameters. */
  public function form_add($parameters) {
    return $this->_form_add($parameters);
  }

  /**
   * Perform a GET request on the controller root
   * (e.g. http://www.example.com/gallery3/comments)
   */
  public function _index() {
    throw new Exception("@todo _create NOT IMPLEMENTED");
  }

  /**
   * Perform a POST request on this resource
   * @param ORM $resource the instance of this resource type
   */
  public function _create($resource) {
    throw new Exception("@todo _create NOT IMPLEMENTED");
  }

  /**
   * Perform a GET request on this resource
   * @param ORM $resource the instance of this resource type
   */
  public function _show($resource) {
    throw new Exception("@todo _show NOT IMPLEMENTED");
  }

  /**
   * Perform a PUT request on this resource
   * @param ORM $resource the instance of this resource type
   */
  public function _update($resource) {
    throw new Exception("@todo _update NOT IMPLEMENTED");
  }

  /**
   * Perform a DELETE request on this resource
   * @param ORM $resource the instance of this resource type
   */
  public function _delete($resource) {
    throw new Exception("@todo _delete NOT IMPLEMENTED");
  }

  /**
   * Present a form for adding a new resource
   * @param string part of the URI after the controller name
   */
  public function _form_add($parameter) {
    throw new Exception("@todo _form_add NOT IMPLEMENTED");
  }

  /**
   * Present a form for editing an existing resource
   * @param ORM $resource the resource container for instances of this resource type
   */
  public function _form_edit($resource) {
    throw new Exception("@todo _form_edit NOT IMPLEMENTED");
  }
}