/*
 ***************************************************************************************
 *  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.view;

import com.espertech.esper.client.EventBean;
import com.espertech.esper.epl.expression.core.ExprEvaluator;
import com.espertech.esper.epl.expression.core.ExprEvaluatorContext;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Iterator for reading and filtering a source event iterator.
 */
public class FilterExprViewIterator implements Iterator<EventBean> {
    private final Iterator<EventBean> sourceIterator;
    private final ExprEvaluator filter;
    private final ExprEvaluatorContext exprEvaluatorContext;
    private final EventBean[] evalEventArr;

    private EventBean nextResult;

    /**
     * Ctor.
     *
     * @param sourceIterator       is the iterator supplying events to filter out.
     * @param filter               is the filter expression
     * @param exprEvaluatorContext context for expression evalauation
     */
    public FilterExprViewIterator(Iterator<EventBean> sourceIterator, ExprEvaluator filter, ExprEvaluatorContext exprEvaluatorContext) {
        this.sourceIterator = sourceIterator;
        this.filter = filter;
        this.exprEvaluatorContext = exprEvaluatorContext;
        evalEventArr = new EventBean[1];
    }

    public boolean hasNext() {
        if (nextResult != null) {
            return true;
        }
        findNext();
        if (nextResult != null) {
            return true;
        }
        return false;
    }

    public EventBean next() {
        if (nextResult != null) {
            EventBean result = nextResult;
            nextResult = null;
            return result;
        }
        findNext();
        if (nextResult != null) {
            EventBean result = nextResult;
            nextResult = null;
            return result;
        }
        throw new NoSuchElementException();
    }

    private void findNext() {
        while (sourceIterator.hasNext()) {
            EventBean candidate = sourceIterator.next();
            evalEventArr[0] = candidate;

            Boolean pass = (Boolean) filter.evaluate(evalEventArr, true, exprEvaluatorContext);
            if ((pass != null) && pass) {
                nextResult = candidate;
                break;
            }
        }
    }

    public void remove() {
        throw new UnsupportedOperationException();
    }
}