/**
 * 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.tajo.engine.planner.logical.join;

import com.google.common.collect.Sets;
import org.apache.tajo.catalog.CatalogUtil;
import org.apache.tajo.catalog.Column;
import org.apache.tajo.engine.eval.AlgebraicUtil;
import org.apache.tajo.engine.eval.EvalNode;
import org.apache.tajo.engine.eval.EvalTreeUtil;
import org.apache.tajo.engine.planner.LogicalPlan;
import org.apache.tajo.engine.planner.NamedExprsManager;
import org.apache.tajo.engine.planner.PlannerUtil;
import org.apache.tajo.engine.planner.PlanningException;
import org.apache.tajo.engine.planner.graph.SimpleUndirectedGraph;
import org.apache.tajo.engine.planner.logical.JoinNode;

import java.util.Collection;
import java.util.Set;

public class JoinGraph extends SimpleUndirectedGraph<String, JoinEdge> {

  private String [] guessRelationsFromJoinQual(LogicalPlan.QueryBlock block, EvalNode joinCondition)
      throws PlanningException {

    // Note that we can guarantee that each join qual used here is a singleton.
    // This is because we use dissect a join qual into conjunctive normal forms.
    // In other words, each join qual has a form 'col1 = col2'.
    Column leftExpr = EvalTreeUtil.findAllColumnRefs(joinCondition.getLeftExpr()).get(0);
    Column rightExpr = EvalTreeUtil.findAllColumnRefs(joinCondition.getRightExpr()).get(0);

    // 0 - left table, 1 - right table
    String [] relationNames = new String[2];

    NamedExprsManager namedExprsMgr = block.getNamedExprsManager();
    if (leftExpr.hasQualifier()) {
      relationNames[0] = leftExpr.getQualifier();
    } else {
      if (namedExprsMgr.isAliasedName(leftExpr.getSimpleName())) {
        String columnName = namedExprsMgr.getOriginalName(leftExpr.getSimpleName());
        String qualifier = CatalogUtil.extractQualifier(columnName);
        relationNames[0] = qualifier;
      } else {
        throw new PlanningException("Cannot expect a referenced relation: " + leftExpr);
      }
    }

    if (rightExpr.hasQualifier()) {
      relationNames[1] = rightExpr.getQualifier();
    } else {
      if (namedExprsMgr.isAliasedName(rightExpr.getSimpleName())) {
        String columnName = namedExprsMgr.getOriginalName(rightExpr.getSimpleName());
        String qualifier = CatalogUtil.extractQualifier(columnName);
        relationNames[1] = qualifier;
      } else {
        throw new PlanningException("Cannot expect a referenced relation: " + rightExpr);
      }
    }

    return relationNames;
  }
  public Collection<EvalNode> addJoin(LogicalPlan plan, LogicalPlan.QueryBlock block,
                                      JoinNode joinNode) throws PlanningException {
    Set<EvalNode> cnf = Sets.newHashSet(AlgebraicUtil.toConjunctiveNormalFormArray(joinNode.getJoinQual()));
    Set<EvalNode> nonJoinQuals = Sets.newHashSet();
    for (EvalNode singleQual : cnf) {
      if (EvalTreeUtil.isJoinQual(singleQual, true)) {

        String [] relations = guessRelationsFromJoinQual(block, singleQual);
        String leftExprRelName = relations[0];
        String rightExprRelName = relations[1];

        Collection<String> leftLineage = PlannerUtil.getRelationLineageWithinQueryBlock(plan, joinNode.getLeftChild());

        boolean isLeftExprForLeftTable = leftLineage.contains(leftExprRelName);
        JoinEdge edge;
        edge = getEdge(leftExprRelName, rightExprRelName);

        if (edge != null) {
          edge.addJoinQual(singleQual);
        } else {
          if (isLeftExprForLeftTable) {
            edge = new JoinEdge(joinNode.getJoinType(),
                block.getRelation(leftExprRelName), block.getRelation(rightExprRelName), singleQual);
            addEdge(leftExprRelName, rightExprRelName, edge);
          } else {
            edge = new JoinEdge(joinNode.getJoinType(),
                block.getRelation(rightExprRelName), block.getRelation(leftExprRelName), singleQual);
            addEdge(rightExprRelName, leftExprRelName, edge);
          }
        }
      } else {
        nonJoinQuals.add(singleQual);
      }
    }
    cnf.retainAll(nonJoinQuals);
    return cnf;
  }
}