/*
 * 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.phoenix.expression;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.List;
import org.apache.hadoop.io.WritableUtils;
import org.apache.phoenix.expression.visitor.ExpressionVisitor;

import org.apache.phoenix.thirdparty.com.google.common.collect.ImmutableList;

/**
 * Base class for expressions which have a single child expression
 * @since 0.1
 */
public abstract class BaseSingleExpression extends BaseExpression {

  protected List<Expression> children;

  public BaseSingleExpression() {
  }

  public BaseSingleExpression(Expression expression) {
    this(ImmutableList.of(expression));
  }

  public BaseSingleExpression(List<Expression> children) {
    this.children = children;
  }

  @Override
  public List<Expression> getChildren() {
    return children;
  }

  @Override
  public void readFields(DataInput input) throws IOException {
    Expression expression = ExpressionType.values()[WritableUtils.readVInt(input)].newInstance();
    expression.readFields(input);
    children = ImmutableList.of(expression);
  }

  @Override
  public void write(DataOutput output) throws IOException {
    WritableUtils.writeVInt(output, ExpressionType.valueOf(children.get(0)).ordinal());
    children.get(0).write(output);
  }

  @Override
  public boolean isNullable() {
    return children.get(0).isNullable();
  }

  @Override
  public void reset() {
    children.get(0).reset();
  }

  @Override
  public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + children.get(0).hashCode();
    return result;
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj) return true;
    if (obj == null) return false;
    if (getClass() != obj.getClass()) return false;
    BaseSingleExpression other = (BaseSingleExpression) obj;
    if (!children.get(0).equals(other.children.get(0))) return false;
    return true;
  }

  @Override
  public <T> T accept(ExpressionVisitor<T> visitor) {
    List<T> l = acceptChildren(visitor, null);
    if (l.isEmpty()) {
      return visitor.defaultReturn(this, l);
    }
    return l.get(0);
  }

  public Expression getChild() {
    return children.get(0);
  }

  @Override
  public boolean requiresFinalEvaluation() {
    return children.get(0).requiresFinalEvaluation();
  }

  @Override
  public Determinism getDeterminism() {
    return children.get(0).getDeterminism();
  }

  @Override
  public boolean isCloneExpression() {
    return children.get(0).isCloneExpression();
  }
}
