/*
 * 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.eigenbase.rel;

import java.util.*;

import org.eigenbase.relopt.*;
import org.eigenbase.reltype.*;
import org.eigenbase.sql.SqlKind;

import net.hydromatic.linq4j.Ord;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

/**
 * <code>SetOpRel</code> is an abstract base for relational set operators such
 * as UNION, MINUS (aka EXCEPT), and INTERSECT.
 */
public abstract class SetOpRel extends AbstractRelNode {
  //~ Instance fields --------------------------------------------------------

  protected ImmutableList<RelNode> inputs;
  public final SqlKind kind;
  public final boolean all;

  //~ Constructors -----------------------------------------------------------

  /**
   * Creates a SetOpRel.
   */
  protected SetOpRel(
      RelOptCluster cluster,
      RelTraitSet traits,
      List<RelNode> inputs,
      SqlKind kind,
      boolean all) {
    super(cluster, traits);
    Preconditions.checkArgument(kind == SqlKind.UNION
        || kind == SqlKind.INTERSECT
        || kind == SqlKind.EXCEPT);
    this.kind = kind;
    this.inputs = ImmutableList.copyOf(inputs);
    this.all = all;
  }

  /**
   * Creates a SetOpRel by parsing serialized output.
   */
  protected SetOpRel(RelInput input) {
    this(input.getCluster(), input.getTraitSet(), input.getInputs(),
        SqlKind.UNION, input.getBoolean("all"));
  }

  //~ Methods ----------------------------------------------------------------

  public abstract SetOpRel copy(
      RelTraitSet traitSet,
      List<RelNode> inputs,
      boolean all);

  @Override
  public SetOpRel copy(
      RelTraitSet traitSet,
      List<RelNode> inputs) {
    return copy(traitSet, inputs, all);
  }

  @Override
  public void replaceInput(int ordinalInParent, RelNode p) {
    final List<RelNode> newInputs = new ArrayList<RelNode>(inputs);
    newInputs.set(ordinalInParent, p);
    inputs = ImmutableList.copyOf(newInputs);
    recomputeDigest();
  }

  @Override
  public boolean isKey(BitSet columns) {
    // If not ALL then the rows are distinct.
    // Therefore the set of all columns is a key.
    return !all && columns.nextClearBit(0) >= getRowType().getFieldCount();
  }

  @Override
  public List<RelNode> getInputs() {
    return inputs;
  }

  @Override
  public RelWriter explainTerms(RelWriter pw) {
    super.explainTerms(pw);
    for (Ord<RelNode> ord : Ord.zip(inputs)) {
      pw.input("input#" + ord.i, ord.e);
    }
    return pw.item("all", all);
  }

  @Override
  protected RelDataType deriveRowType() {
    return getCluster().getTypeFactory().leastRestrictive(
        new AbstractList<RelDataType>() {
          @Override
          public RelDataType get(int index) {
            return inputs.get(index).getRowType();
          }

          @Override
          public int size() {
            return inputs.size();
          }
        });
  }

  /**
   * Returns whether all the inputs of this set operator have the same row
   * type as its output row.
   *
   * @param compareNames whether or not column names are important in the
   *                     homogeneity comparison
   */
  public boolean isHomogeneous(boolean compareNames) {
    RelDataType unionType = getRowType();
    for (RelNode input : getInputs()) {
      if (!RelOptUtil.areRowTypesEqual(
          input.getRowType(), unionType, compareNames)) {
        return false;
      }
    }
    return true;
  }

  /**
   * Returns whether all the inputs of this set operator have the same row
   * type as its output row. Equivalent to {@link #isHomogeneous(boolean)
   * isHomogeneous(true)}.
   */
  public boolean isHomogeneous() {
    return isHomogeneous(true);
  }
}

// End SetOpRel.java