// Copyright (C) 2009 The Android Open Source Project
//
// Licensed 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 com.google.gerrit.server.query;

import com.google.gwtorm.server.OrmException;

import java.util.Collection;
import java.util.Collections;
import java.util.List;

/**
 * Holds another predicate in a named variable.
 *
 * @see QueryRewriter
 */
public class VariablePredicate<T> extends Predicate<T> {
  private final String name;
  private final Predicate<T> that;

  protected VariablePredicate(final String name, final Predicate<T> that) {
    this.name = name;
    this.that = that;
  }

  public String getName() {
    return name;
  }

  @Override
  public final List<Predicate<T>> getChildren() {
    return Collections.singletonList(that);
  }

  @Override
  public final int getChildCount() {
    return 1;
  }

  @Override
  public final Predicate<T> getChild(final int i) {
    if (i != 0) {
      throw new ArrayIndexOutOfBoundsException(i);
    }
    return that;
  }

  @Override
  public Predicate<T> copy(final Collection<? extends Predicate<T>> children) {
    if (children.size() != 1) {
      throw new IllegalArgumentException("Expected exactly one child");
    }
    return new VariablePredicate<>(getName(), children.iterator().next());
  }

  @Override
  public boolean match(final T object) throws OrmException {
    return that.match(object);
  }

  @Override
  public int getCost() {
    return that.getCost();
  }

  @Override
  public int hashCode() {
    return getName().hashCode() * 31 + that.hashCode();
  }

  @Override
  public boolean equals(final Object other) {
    if (other == null) {
      return false;
    }
    if (getClass() == other.getClass()) {
      final VariablePredicate<?> v = (VariablePredicate<?>) other;
      return getName().equals(v.getName())
          && getChildren().equals(v.getChildren());
    }
    return false;
  }

  @Override
  public final String toString() {
    return getName() + "=(" + that.toString() + ")";
  }
}