/*
 ***************************************************************************************
 *  Copyright (C) 2006 EsperTech, Inc. All rights reserved.                            *
 *  http://www.espertech.com/esper                                                     *
 *  http://www.espertech.com                                                           *
 *  ---------------------------------------------------------------------------------- *
 *  The software in this package is published under the terms of the GPL license       *
 *  a copy of which has been included with this distribution in the license.txt file.  *
 ***************************************************************************************
 */
package com.espertech.esper.epl.variable;

import com.espertech.esper.client.EventType;
import com.espertech.esper.collection.Pair;
import com.espertech.esper.core.service.StatementExtensionSvcContext;

import java.util.Set;

/**
 * Interface for a plug-in to {@link VariableService} to handle variable persistent state.
 */
public interface VariableStateHandler {
    /**
     * Returns the current variable state plus Boolean.TRUE if there is a current state since the variable
     * may have the value of null; returns Boolean.FALSE and null if there is no current state
     *
     * @param variableName        variable name
     * @param variableNumber      number of the variable
     * @param type                type of the variable
     * @param eventType           event type or null if not a variable that represents an event
     * @param statementExtContext for caches etc.
     * @param agentInstanceId     agent instance id
     * @param isConstant          indicator for constant
     * @return indicator whether the variable is known and it's state, or whether it doesn't have state (false)
     */
    public Pair<Boolean, Object> getHasState(String variableName, int variableNumber, int agentInstanceId, Class type, EventType eventType, StatementExtensionSvcContext statementExtContext, boolean isConstant);

    /**
     * Sets the new variable value
     *
     * @param variableName    name of the variable
     * @param variableNumber  number of the variable
     * @param agentInstanceId agent instance id
     * @param newValue        new variable value, null values allowed
     */
    public void setState(String variableName, int variableNumber, int agentInstanceId, Object newValue);

    public void removeState(String variableName, int variableNumber, int agentInstanceId);

    public void removeVariable(String name, Set<Integer> cps);
}