/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators;

import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.POStatus;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.Result;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.ComparisonOperator;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhyPlanVisitor;
import org.apache.pig.impl.plan.NodeIdGenerator;
import org.apache.pig.impl.plan.OperatorKey;
import org.apache.pig.impl.plan.VisitorException;

public class POLimit extends PhysicalOperator {
	   /**
     * 
     */
    private static final long serialVersionUID = 1L;

    transient private Log log = LogFactory.getLog(getClass());

    // Counts for outputs processed
    private long soFar = 0;
    
    // Number of limited outputs
    long mLimit;

    public POLimit(OperatorKey k) {
        this(k, -1, null);
    }

    public POLimit(OperatorKey k, int rp) {
        this(k, rp, null);
    }

    public POLimit(OperatorKey k, List<PhysicalOperator> inputs) {
        this(k, -1, inputs);
    }

    public POLimit(OperatorKey k, int rp, List<PhysicalOperator> inputs) {
        super(k, rp, inputs);
    }
    
    public void setLimit(long limit)
    {
    	mLimit = limit;
    }
    
    public long getLimit()
    {
    	return mLimit;
    }

    /**
     * Counts the number of tuples processed into static variable soFar, if the number of tuples processed reach the 
     * limit, return EOP; Otherwise, return the tuple 
     */
    @Override
    public Result getNext(Tuple t) throws ExecException {
        Result res = null;
        Result inp = null;
        while (true) {
            inp = processInput();
            if (inp.returnStatus == POStatus.STATUS_EOP
                    || inp.returnStatus == POStatus.STATUS_ERR)
                break;
            
            if (soFar>=mLimit)
            	inp.returnStatus = POStatus.STATUS_EOP;
            
            soFar++;
            break;
        }

        return inp;
    }

    @Override
    public String name() {
        return getAliasString() + "Limit - " + mKey.toString();
    }

    @Override
    public boolean supportsMultipleInputs() {
        return false;
    }

    @Override
    public boolean supportsMultipleOutputs() {
        return false;
    }

    @Override
    public void visit(PhyPlanVisitor v) throws VisitorException {
        v.visitLimit(this);
    }

    @Override
    public void reset() {
        soFar = 0;
    }

    @Override
    public POLimit clone() throws CloneNotSupportedException {
        POLimit newLimit = new POLimit(new OperatorKey(this.mKey.scope,
            NodeIdGenerator.getGenerator().getNextNodeId(this.mKey.scope)),
            this.requestedParallelism, this.inputs);
        newLimit.mLimit = this.mLimit;
        newLimit.setAlias(alias);
        return newLimit;
    }
}