/*
Wotonomy: OpenStep design patterns for pure Java applications.
Copyright (C) 2000 Blacksmith, Inc.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library 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
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see http://www.gnu.org
*/

package net.wotonomy.web;

import java.io.Serializable;

import net.wotonomy.foundation.NSDictionary;

/**
 * This class represents a static or dynamic portion of the content returned to
 * a request. Each request walks a tree of WOElements to generate a response.
 *
 * @author michael@mpowers.net
 * @author $Author: cgruber $
 * @version $Revision: 905 $
 */
public abstract class WOElement implements WOActionResults, Serializable {
	private static final long serialVersionUID = 3854088436393061500L;
	NSDictionary associations;

	/**
	 * Default constructor. Performs necessary initialization.
	 */
	public WOElement() {
	}

	/**
	 * This method is called to retrieve user-entered data from the request.
	 * WOElements should retrieve data from the request based on their elementID and
	 * set values in the context's current WOComponent, typically those values that
	 * are associated with the element in the binding. This implementation does
	 * nothing.
	 */
	public void takeValuesFromRequest(WORequest aRequest, WOContext aContext) {
		// does nothing
	}

	/**
	 * This method is called on all objects and elements of the application until a
	 * non-null value is returned. WOElements should first check to see if they are
	 * the target of an action by checking the WOContext's senderID to see if it
	 * matches this element's elementID. If this element is the target, it should
	 * perform an appropriate action on the context's current WOComponent, usually
	 * the action specified in the binding, and return the result of that action.
	 * This implementation returns null.
	 */
	public WOActionResults invokeAction(WORequest aRequest, WOContext aContext) {
		return null;
	}

	/**
	 * This method is called on all elements of the content tree to build a response
	 * to a user request. The message should be forwarded to any child elements so
	 * that the entire tree is traversed. This implementation does nothing.
	 */
	public void appendToResponse(WOResponse aResponse, WOContext aContext) {
		// does nothing
	}

	/**
	 * Package access only. Called to initialize the component with the proper
	 * context before the start of the request-response cycle. If the context has a
	 * current component, that component becomes this component's parent.
	 */
	void ensureAwakeInContext(WOContext aContext) {
		// does nothing
	}

}