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package org.drools.runtime.rule;

import java.util.Collection;

import org.drools.KnowledgeBaseConfiguration;
import org.drools.runtime.ObjectFilter;
import org.drools.time.SessionClock;

/**
 * The WorkingMemory is a super-interface for all StatefulKnowledgeSessions.
 * Although, users are encouraged to use StatefulKnowledgeSession or KnowledgeRuntime
 * interface instead of WorkingMemory interface, specially because of the dispose() method
 * that is only available in the StatefulKnowledgeSession interface.  
 * 
 * @see org.drools.runtime.StatefulKnowledgeSession 
 */
public interface WorkingMemory
    extends
    WorkingMemoryEntryPoint {

    /**
     * Request the engine to stop firing rules. If the engine is currently firing a rule, it will
     * finish executing this rule's consequence before stopping.
     * This method will not remove active activations from the Agenda.
     * In case the application later wants to continue firing rules from the point where it stopped,
     * it should just call org.drools.runtime.StatefulKnowledgeSession.fireAllRules() or 
     * org.drools.runtime.StatefulKnowledgeSession.fireUntilHalt() again.
     */
    void halt();

    /**
     * Returns the session clock instance assigned to this session
     * @return
     */
    public SessionClock getSessionClock();

    /**
     * Returns the fact handle associated with the given object. It is important to note that this 
     * method behaves in accordance with the configured assert behaviour for this knowledge base
     * (either IDENTITY or EQUALITY).
     *  
     * @param object 
     *               the fact for which the fact handle will be returned.
     * 
     * @return the fact handle for the given object, or null in case no fact handle was found for the
     *         given object.
     *         
     * @see KnowledgeBaseConfiguration
     */
    FactHandle getFactHandle(Object object);

    /**
     * Returns the object associated with the given FactHandle.
     * 
     * @param factHandle
     * @return
     */
    Object getObject(FactHandle factHandle);

    /**
     * Returns all facts from the current session.
     * 
     * @return
     */
    Collection< ? > getObjects();

    /**
     * Returns all facts from the current session that are accepted by the given ObjectFilter.
     * 
     * @param filter the filter to be applied to the returned collection of facts.
     *  
     * @return
     */
    Collection< ? > getObjects(ObjectFilter filter);

    /**
     * Returns all FactHandles from the current session.
     * 
     * @return
     */
    Collection< ? extends FactHandle> getFactHandles();

    /**
     * Returns all FactHandles from the current session for which the facts are accepted by 
     * the given filter.
     * 
     * @param filter the filter to be applied to the returned collection of FactHandles.
     * 
     * @return
     */
    Collection< ? extends FactHandle> getFactHandles(ObjectFilter filter);

    /**
     * Returns a reference to this session's Agenda.
     * 
     * @return
     */
    Agenda getAgenda();

    /**
     * Returns the WorkingMemoryEntryPoint instance associated with the given name.
     * 
     * @param name
     * @return
     */
    WorkingMemoryEntryPoint getWorkingMemoryEntryPoint(String name);
}