/*
 * 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.newplan.logical.rules;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.pig.FuncSpec;
import org.apache.pig.impl.builtin.IdentityColumn;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.impl.util.Pair;
import org.apache.pig.newplan.Operator;
import org.apache.pig.newplan.OperatorPlan;
import org.apache.pig.newplan.OperatorSubPlan;
import org.apache.pig.newplan.logical.expression.LogicalExpression;
import org.apache.pig.newplan.logical.expression.LogicalExpressionPlan;
import org.apache.pig.newplan.logical.expression.ProjectExpression;
import org.apache.pig.newplan.logical.expression.UserFuncExpression;
import org.apache.pig.newplan.logical.relational.LOCross;
import org.apache.pig.newplan.logical.relational.LOForEach;
import org.apache.pig.newplan.logical.relational.LOGenerate;
import org.apache.pig.newplan.logical.relational.LOInnerLoad;
import org.apache.pig.newplan.logical.relational.LOJoin;
import org.apache.pig.newplan.logical.relational.LOSort;
import org.apache.pig.newplan.logical.relational.LogicalPlan;
import org.apache.pig.newplan.logical.relational.LogicalRelationalOperator;
import org.apache.pig.newplan.logical.relational.LogicalSchema;
import org.apache.pig.newplan.logical.rules.PushDownForEachFlatten.PushDownForEachFlattenTransformer;
import org.apache.pig.newplan.optimizer.Rule;
import org.apache.pig.newplan.optimizer.Transformer;

/*
 * This rule rewrite duplicate column projection into Identity UDF.
 * So that we can generate different uid for each column
 */
public class DuplicateForEachColumnRewrite extends Rule {

    public DuplicateForEachColumnRewrite(String n) {
        super(n, true);
    }

    @Override
    protected OperatorPlan buildPattern() {
        LogicalPlan plan = new LogicalPlan();
        LogicalRelationalOperator foreach = new LOForEach(plan);
        plan.add( foreach );
        return plan;
    }

    @Override
    public Transformer getNewTransformer() {
        return new DuplicateForEachColumnRewriteTransformer();
    }

    class DuplicateForEachColumnRewriteTransformer extends Transformer {
        private List<LogicalExpressionPlan> expPlansToInsertIdentity = new ArrayList<LogicalExpressionPlan>();
        
        @Override
        public boolean check(OperatorPlan matched) throws FrontendException {
            
            LOForEach foreach = (LOForEach)matched.getSources().get(0);
            LOGenerate gen = (LOGenerate)foreach.getInnerPlan().getSinks().get(0);
            
            List<LogicalExpressionPlan> expPlans = gen.getOutputPlans();
            
            List<Long> uidSeen = new ArrayList<Long>();
            
            for (LogicalExpressionPlan expPlan : expPlans) {
                LogicalExpression exp = (LogicalExpression)expPlan.getSources().get(0);
                if (exp.getFieldSchema()!=null) {
                    long uid = exp.getFieldSchema().uid;
                    if (uidSeen.contains(uid)) {
                        expPlansToInsertIdentity.add(expPlan);
                    }
                    else {
                        uidSeen.add(uid);
                    }
                }
            }
            
            if (expPlansToInsertIdentity.isEmpty())
                return false;
            
            return true;
        } 
        
        @Override
        public OperatorPlan reportChanges() {
            return currentPlan;
        }

        @Override
        public void transform(OperatorPlan matched) throws FrontendException {
            for (LogicalExpressionPlan expPlan : expPlansToInsertIdentity) {
                LogicalExpression oldRoot = (LogicalExpression)expPlan.getSources().get(0);
                UserFuncExpression userFuncExpression = new UserFuncExpression(expPlan, new FuncSpec(IdentityColumn.class.getName()));
                expPlan.connect(userFuncExpression, oldRoot);
            }
            expPlansToInsertIdentity.clear();
        }
    }
}