/*
 * Copyright 2009-2013 by The Regents of the University of California
 * Licensed 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 from
 * 
 *     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 edu.uci.ics.hivesterix.optimizer.rules;

import org.apache.commons.lang3.mutable.Mutable;

import edu.uci.ics.hivesterix.logical.plan.HiveOperatorAnnotations;
import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.IOptimizationContext;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.IPhysicalOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalOperatorTag;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.OperatorAnnotations;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.PhysicalOperatorTag;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.ExchangeOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.operators.physical.OneToOneExchangePOperator;
import edu.uci.ics.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;

public class LocalGroupByRule implements IAlgebraicRewriteRule {

    @Override
    public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context) throws AlgebricksException {
        return false;
    }

    @Override
    public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
            throws AlgebricksException {
        AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue();
        if (op.getOperatorTag() != LogicalOperatorTag.GROUP) {
            return false;
        }
        Boolean localGby = (Boolean) op.getAnnotations().get(HiveOperatorAnnotations.LOCAL_GROUP_BY);
        if (localGby != null && localGby.equals(Boolean.TRUE)) {
            Boolean hashGby = (Boolean) op.getAnnotations().get(OperatorAnnotations.USE_HASH_GROUP_BY);
            Boolean externalGby = (Boolean) op.getAnnotations().get(OperatorAnnotations.USE_EXTERNAL_GROUP_BY);
            if ((hashGby != null && (hashGby.equals(Boolean.TRUE)) || (externalGby != null && externalGby
                    .equals(Boolean.TRUE)))) {
                reviseExchange(op);
            } else {
                ILogicalOperator child = op.getInputs().get(0).getValue();
                AbstractLogicalOperator childOp = (AbstractLogicalOperator) child;
                while (child.getInputs().size() > 0) {
                    if (childOp.getOperatorTag() == LogicalOperatorTag.ORDER)
                        break;
                    else {
                        child = child.getInputs().get(0).getValue();
                        childOp = (AbstractLogicalOperator) child;
                    }
                }
                if (childOp.getOperatorTag() == LogicalOperatorTag.ORDER)
                    reviseExchange(childOp);
            }
            return true;
        }
        return false;
    }

    private void reviseExchange(AbstractLogicalOperator op) {
        ExchangeOperator exchange = (ExchangeOperator) op.getInputs().get(0).getValue();
        IPhysicalOperator physicalOp = exchange.getPhysicalOperator();
        if (physicalOp.getOperatorTag() == PhysicalOperatorTag.HASH_PARTITION_EXCHANGE) {
            exchange.setPhysicalOperator(new OneToOneExchangePOperator());
        }
    }

}