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Calcite APIs for LINQ (Language-Integrated Query) in Java
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/*
 * 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.calcite.linq4j.tree;

import java.util.List;
import java.util.Objects;

/**
 * Represents an expression that has a conditional operator.
 *
 * With an odd number of expressions
 * {c0, e0, c1, e1, ..., c_n-1, e_n-1, e_n}
 * represents "if (c0) e0 else if (c1) e1 ... else e_n";
 * with an even number of expressions
 * {c0, e0, c1, e1, ..., c_n-1, e_n-1}
 * represents
 * "if (c0) e0 else if (c1) e1 ... else if (c_n-1) e_n-1".
 * 
 */
public class ConditionalStatement extends Statement {
  public final List expressionList;

  public ConditionalStatement(List expressionList) {
    super(ExpressionType.Conditional, Void.TYPE);
    assert expressionList != null : "expressionList should not be null";
    this.expressionList = expressionList;
  }

  @Override public Statement accept(Shuttle shuttle) {
    shuttle = shuttle.preVisit(this);
    List list = Expressions.acceptNodes(expressionList, shuttle);
    return shuttle.visit(this, list);
  }

  public  R accept(Visitor visitor) {
    return visitor.visit(this);
  }

  @Override void accept0(ExpressionWriter writer) {
    for (int i = 0; i < expressionList.size() - 1; i += 2) {
      if (i > 0) {
        writer.backUp();
        writer.append(" else ");
      }
      writer.append("if (")
          .append(expressionList.get(i))
          .append(") ")
          .append(Blocks.toBlock(expressionList.get(i + 1)));
    }
    if (expressionList.size() % 2 == 1) {
      writer.backUp();
      writer.append(" else ")
          .append(Blocks.toBlock(last(expressionList)));
    }
  }

  private static  E last(List collection) {
    return collection.get(collection.size() - 1);
  }

  @Override public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    if (!super.equals(o)) {
      return false;
    }

    ConditionalStatement that = (ConditionalStatement) o;

    if (!expressionList.equals(that.expressionList)) {
      return false;
    }

    return true;
  }

  @Override public int hashCode() {
    return Objects.hash(nodeType, type, expressionList);
  }
}

// End ConditionalStatement.java