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Java idiomatic client for Google Cloud Firestore.

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/*
 * Copyright 2017 Google LLC
 *
 * 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.cloud.firestore.collection;

import com.google.api.core.InternalApi;

// Note: This package is copied from https://github.com/firebase/firebase-admin-java/tree/master/
// src/main/java/com/google/firebase/database/collection
@InternalApi
public class LLRBBlackValueNode extends LLRBValueNode {

  /**
   * Only memoize size on black nodes, not on red nodes. This saves memory while guaranteeing that
   * size will still have an amortized constant runtime. The first time size() may have to traverse
   * the entire tree. However, the red black tree algorithm guarantees that every red node has two
   * black children. So future invocations of the size() function will have to go at most 2 levels
   * deep if the child is a red node.
   *
   * Needs to be mutable because left node can be updated via setLeft.
   */
  private int size = -1;

  LLRBBlackValueNode(K key, V value, LLRBNode left, LLRBNode right) {
    super(key, value, left, right);
  }

  @Override
  protected Color getColor() {
    return Color.BLACK;
  }

  @Override
  public boolean isRed() {
    return false;
  }

  @Override
  public int size() {
    if (size == -1) {
      size = getLeft().size() + 1 + getRight().size();
    }
    return size;
  }

  @Override
  void setLeft(LLRBNode left) {
    if (size != -1) {
      // Modifying left node after invoking size
      throw new IllegalStateException("Can't set left after using size");
    }
    super.setLeft(left);
  }

  @Override
  protected LLRBValueNode copy(K key, V value, LLRBNode left, LLRBNode right) {
    K newKey = key == null ? this.getKey() : key;
    V newValue = value == null ? this.getValue() : value;
    LLRBNode newLeft = left == null ? this.getLeft() : left;
    LLRBNode newRight = right == null ? this.getRight() : right;
    return new LLRBBlackValueNode<>(newKey, newValue, newLeft, newRight);
  }
}