/* Copyright (C) 2005 Tresys Technology, LLC

 * License: refer to COPYING file for license information.

 * Authors: Spencer Shimko <sshimko@tresys.com>

 * 

 * PolicyElement.java: The reference policy base class		

 * Version: @version@ 

 */

package policy;

import java.util.Map;

import java.util.TreeMap;

/**

 * Reference policy elements have certain similarties which

 * should be inherited from a base class.  This includes a name

 * attribute that will be used for hashing, sorting, and converting

 * to a string.  

 * 

 * @see Layer

 * @see Module

 * @see Interface

 * @see Parameter

 */

public abstract class PolicyElement {

	/** the string identifying the element */

	public final String Name;

	/** the parent component */

	public final PolicyElement Parent;

	/** the attributes of this element */

	private final Map<String,String> attributes;

	public String PCDATA;

	/**

	 * Default constructor assigns name.

	 * 

	 * @param _name		The name of the element.

	 * @param _Parent 	The reference to the parent element.

	 */

	public PolicyElement(String _name, PolicyElement _Parent){

		Name = _name;

		Parent = _Parent;

		attributes = new TreeMap<String,String>();

	}

	/**

	 * Add attribute to policy element.

	 * 

	 * @param aName		String to identify attribute

	 * @param aString 	Value of attribute identified by string aName

	 * @return 			true when attribute added to element,

	 * 					false when attribute already defined for element 

	 */

	public boolean AddAttribute(String aName, String aString){

		if (attributes.containsKey(aName)){

			return false;

		}

		attributes.put(aName,aString);

		return true;

	}

	/**

	 * Get attribute from policy element.

	 * 

	 * @param aName		String to identify attribute

	 * @return 			String value associated with named attribute

	 * 					or null if no attribute defined

	 * 					for aName. 

	 */

	public String GetAttribute(String aName){

		return attributes.get(aName);

	}

	/**

	 * Overridden equals method

	 * 

	 * @param obj	Object for comparison

	 */

	@Override public boolean equals(Object obj){

		return obj.toString().equals(this.Name);

	}

	/**

	 * Return a hashcode for the element. Currently implemented as a 

	 * call to the String hashCode() method.

	 * 

	 * @return integer hashCode of this instance assuring two objects that

	 * 		   are == will return same hashcode.

	 */

	@Override public int hashCode() {

		return this.toString().hashCode();

	}

	/**

	 * Overridden toString() method.

	 * 

	 * @return String representation of instance (it's name).

	 */

	@Override public String toString(){

			return Name;

	}		

	/**

	 * Since Component might be used as a key in some type of sort Compare

	 * is implemented.

	 * 

	 * @return	0 if this==that, <0 if this<that, >0 if this>that

	 * @see String.compareTo

	 */

	public int compareTo(Layer that){

		return Name.compareTo(that.Name);

	}

}