SecCondition.java

package de.persosim.simulator.seccondition;

import java.util.Collection;
import java.util.Collections;

import de.persosim.simulator.secstatus.SecMechanism;
import de.persosim.simulator.secstatus.SecStatus;

/**
 * Describes a SecurityCondition to be checked against given
 * {@link SecMechanism} obtained from {@link SecStatus}.
 * 
 * The check itself is implemented within this interface and may rely on all
 * data provided by required {@link SecMechanism}s.
 * 
 * @author amay
 * 
 */
public interface SecCondition {
	
	/**
	 * Implements a {@link SecCondition} where the condition check always returns true.
	 */
	public static final SecCondition ALLOWED = new SecCondition() {

		@Override
		public boolean check(Collection<SecMechanism> mechanisms) {
			return true;
		}

		@Override
		public Collection<Class<? extends SecMechanism>> getNeededMechanisms() {
			return Collections.emptySet();
		}
		
	};

	/**
	 * Implements a {@link SecCondition} where the condition check always returns false.
	 */
	public static final SecCondition DENIED = new SecCondition() {

		@Override
		public boolean check(Collection<SecMechanism> mechanisms) {
			return false;
		}

		@Override
		public Collection<Class<? extends SecMechanism>> getNeededMechanisms() {
			return Collections.emptySet();
		}
		
	};

	/**
	 * Perform the condition check.
	 * 
	 * As the calling entity requires the result of this check it is safe to
	 * rely on it to provide correct mechanisms as input for the check. This
	 * means that any {@link SecCondition} can expect to receive correct
	 * {@link SecMechanism} objects. However there is no guarantee to the number
	 * and type of received mechanisms. A condition may receive the exact number
	 * and type of requested mechanisms but it may also receive fewer ore more
	 * mechanisms. Hence any condition must deal with any number and type of
	 * conditions received.
	 * 
	 * @param mechanisms
	 *            SecMechanisms required by this SecCondition as input to the
	 *            verification. This Collection needs to be consistent with the
	 *            template returned by {@link #getNeededMechanisms()}.
	 * 
	 * @return true if the condition is fulfilled by the provided SecMechanisms,
	 *         false otherwise
	 */
	boolean check(Collection<SecMechanism> mechanisms);

	/**
	 * This method provides a List of required {@link SecMechanism}s that the
	 * caller of {@link #check(Collection)} needs to query from the
	 * {@link SecStatus} and provide as parameter.
	 * 
	 * The returned Object might be immutable (e.g. immutable empty Collection)
	 * and thus must not be modified by the caller.
	 * 
	 * @return Collection of required {@link SecMechanism}s
	 */
	Collection<Class<? extends SecMechanism>> getNeededMechanisms();
}