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/*
 * ProGuardCORE -- library to process Java bytecode.
 *
 * Copyright (c) 2002-2022 Guardsquare NV
 *
 * 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 proguard.analysis.cpa.defaults;

import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import java.util.function.BiFunction;
import java.util.function.Function;
import proguard.analysis.cpa.util.TriFunction;

/**
 * This {@link LimitedHashMap} is a {@link HashMap} which limits its content based on the function
 * {@code removeElement}. {@code removeElement} determines whether the map limit is reached. If it
 * returns an empty value, the map behaves as usual. Otherwise, the returned key is removed from the
 * map.
 *
 * @author Dmitry Ivanov
 */
public class LimitedHashMap extends HashMap {

  protected TriFunction, K, V, Optional> removeElement;

  /**
   * Create an empty limited hash map.
   *
   * @param removeElement determines whether the map limit is reached if it returns an empty value,
   *     the map behaves as usual otherwise, the returned key is removed from the map
   */
  public LimitedHashMap(TriFunction, K, V, Optional> removeElement) {
    this.removeElement = removeElement;
  }

  /**
   * Create an empty limited map with reserved initial capacity.
   *
   * @param initialCapacity the initial capacity of the hash table
   * @param removeElement determines whether the map limit is reached if it returns an empty value,
   *     the map behaves as usual otherwise, the returned key is removed from the map
   */
  public LimitedHashMap(
      int initialCapacity, TriFunction, K, V, Optional> removeElement) {
    super(initialCapacity);
    this.removeElement = removeElement;
  }

  /**
   * Create a limited map from another map and a tripredicate.
   *
   * @param m map which elements are used for initialization
   * @param removeElement determines whether the map limit is reached if it returns an empty value,
   *     the map behaves as usual otherwise, the returned key is removed from the map
   */
  public LimitedHashMap(
      Map m,
      TriFunction, K, V, Optional> removeElement) {
    super(m);
    this.removeElement = removeElement;
  }

  // implementations for HashMap

  @Override
  public V put(K key, V value) {
    V oldValue = super.put(key, value);
    removeElement.apply(this, key, value).ifPresent(this::remove);
    return oldValue;
  }

  @Override
  public void putAll(Map m) {
    m.entrySet().forEach((e -> put(e.getKey(), e.getValue())));
  }

  @Override
  public V putIfAbsent(K key, V value) {
    V oldValue = super.putIfAbsent(key, value);
    if (oldValue == null) {
      Optional.ofNullable(get(key))
          .flatMap(v -> removeElement.apply(this, key, v))
          .ifPresent(this::remove);
    }
    return oldValue;
  }

  @Override
  public V computeIfAbsent(K key, Function mappingFunction) {
    V oldValue = get(key);
    V newValue = super.computeIfAbsent(key, mappingFunction);
    if (oldValue == null) {
      Optional.ofNullable(newValue)
          .flatMap(v -> removeElement.apply(this, key, v))
          .ifPresent(this::remove);
    }
    return newValue;
  }

  @Override
  public V compute(K key, BiFunction remappingFunction) {
    V newValue = super.compute(key, remappingFunction);
    Optional.ofNullable(newValue)
        .flatMap(v -> removeElement.apply(this, key, v))
        .ifPresent(this::remove);
    return newValue;
  }

  @Override
  public V merge(K key, V value, BiFunction remappingFunction) {
    V newValue = super.merge(key, value, remappingFunction);
    Optional.ofNullable(newValue)
        .flatMap(v -> removeElement.apply(this, key, v))
        .ifPresent(this::remove);
    return newValue;
  }
}