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/*
 * Copyright (C) 2018 The Guava Authors
 *
 * 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.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.errorprone.annotations.concurrent.LazyInit;
import com.google.j2objc.annotations.RetainedWith;
import com.google.j2objc.annotations.WeakOuter;
import java.util.Map;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of ImmutableBiMap backed by a pair of JDK HashMaps, which have smartness
 * protecting against hash flooding.
 */
@GwtCompatible(emulated = true)
final class JdkBackedImmutableBiMap extends ImmutableBiMap {
  @VisibleForTesting
  static  ImmutableBiMap create(int n, Entry[] entryArray) {
    Map forwardDelegate = Maps.newHashMapWithExpectedSize(n);
    Map backwardDelegate = Maps.newHashMapWithExpectedSize(n);
    for (int i = 0; i < n; i++) {
      Entry e = RegularImmutableMap.makeImmutable(entryArray[i]);
      entryArray[i] = e;
      V oldValue = forwardDelegate.putIfAbsent(e.getKey(), e.getValue());
      if (oldValue != null) {
        throw conflictException("key", e.getKey() + "=" + oldValue, entryArray[i]);
      }
      K oldKey = backwardDelegate.putIfAbsent(e.getValue(), e.getKey());
      if (oldKey != null) {
        throw conflictException("value", oldKey + "=" + e.getValue(), entryArray[i]);
      }
    }
    ImmutableList> entryList = ImmutableList.asImmutableList(entryArray, n);
    return new JdkBackedImmutableBiMap<>(entryList, forwardDelegate, backwardDelegate);
  }

  private final transient ImmutableList> entries;
  private final Map forwardDelegate;
  private final Map backwardDelegate;

  private JdkBackedImmutableBiMap(
      ImmutableList> entries, Map forwardDelegate, Map backwardDelegate) {
    this.entries = entries;
    this.forwardDelegate = forwardDelegate;
    this.backwardDelegate = backwardDelegate;
  }

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

  @LazyInit @RetainedWith private transient JdkBackedImmutableBiMap inverse;

  @Override
  public ImmutableBiMap inverse() {
    JdkBackedImmutableBiMap result = inverse;
    if (result == null) {
      inverse =
          result =
              new JdkBackedImmutableBiMap(
                  new InverseEntries(), backwardDelegate, forwardDelegate);
      result.inverse = this;
    }
    return result;
  }

  @WeakOuter
  private final class InverseEntries extends ImmutableList> {
    @Override
    public Entry get(int index) {
      Entry entry = entries.get(index);
      return Maps.immutableEntry(entry.getValue(), entry.getKey());
    }

    @Override
    boolean isPartialView() {
      return false;
    }

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

  @Override
  public V get(@Nullable Object key) {
    return forwardDelegate.get(key);
  }

  @Override
  ImmutableSet> createEntrySet() {
    return new ImmutableMapEntrySet.RegularEntrySet(this, entries);
  }

  @Override
  ImmutableSet createKeySet() {
    return new ImmutableMapKeySet(this);
  }

  @Override
  boolean isPartialView() {
    return false;
  }
}