/**************************************************************************************
 * Copyright (C) 2008 EsperTech, Inc. All rights reserved.                            *
 * http://esper.codehaus.org                                                          *
 * 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.view.std;

import com.espertech.esper.client.EventType;
import com.espertech.esper.core.context.util.AgentInstanceViewFactoryChainContext;
import com.espertech.esper.core.service.StatementContext;
import com.espertech.esper.epl.expression.ExprNode;
import com.espertech.esper.view.*;

import java.util.List;

/**
 * Factory for {@link com.espertech.esper.view.std.FirstElementView} instances.
 */
public class FirstElementViewFactory implements AsymetricDataWindowViewFactory
{
    private EventType eventType;

    public void setViewParameters(ViewFactoryContext viewFactoryContext, List<ExprNode> expressionParameters) throws ViewParameterException
    {
        List<Object> viewParameters = ViewFactorySupport.validateAndEvaluate("'First element' view", viewFactoryContext.getStatementContext(), expressionParameters);
        String errorMessage = "'First element' view does not take any parameters";
        if (!viewParameters.isEmpty())
        {
            throw new ViewParameterException(errorMessage);
        }
    }

    public void attach(EventType parentEventType, StatementContext statementContext, ViewFactory optionalParentFactory, List<ViewFactory> parentViewFactories) throws ViewParameterException
    {
        this.eventType = parentEventType;
    }

    public View makeView(AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext)
    {
        return new FirstElementView();
    }

    public EventType getEventType()
    {
        return eventType;
    }

    public boolean canReuse(View view)
    {
        if (!(view instanceof FirstElementView))
        {
            return false;
        }
        return true;
    }
}