/*
    * 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.commons.collections4.bloomfilter;
  
  import java.util.Arrays;
  import java.util.NoSuchElementException;
  import java.util.Objects;
  import java.util.function.IntPredicate;
  import java.util.function.LongPredicate;
  import java.util.function.Predicate;
  
  /**
   * Layered Bloom filters are described in Zhiwang, Cen; Jungang, Xu; Jian, Sun (2010), "A multi-layer Bloom filter for duplicated URL detection", Proc. 3rd
   * International Conference on Advanced Computer Theory and Engineering (ICACTE 2010), vol. 1, pp. V1-586-V1-591, doi:10.1109/ICACTE.2010.5578947, ISBN
   * 978-1-4244-6539-2, S2CID 3108985
   * <p>
   * In short, Layered Bloom filter contains several bloom filters arranged in layers.
   * </p>
   * <ul>
   * <li>When membership in the filter is checked each layer in turn is checked and if a match is found {@code true} is returned.</li>
   * <li>When merging each bloom filter is merged into the newest filter in the list of layers.</li>
   * <li>When questions of cardinality are asked the cardinality of the union of the enclosed Bloom filters is used.</li>
   * </ul>
   * <p>
   * The net result is that the layered Bloom filter can be populated with more items than the Shape would indicate and yet still return a false positive rate in
   * line with the Shape and not the over population.
   * </p>
   * <p>
   * This implementation uses a LayerManager to handle the manipulation of the layers.
   * </p>
   * <ul>
   * <li>Level 0 is the oldest layer and the highest level is the newest.</li>
   * <li>There is always at least one enclosed filter.</li>
   * <li>The newest filter is the {@code target} into which merges are performed.
   * <li>Whenever the target is retrieved, or a {@code merge} operation is performed the code checks if any older layers should be removed, and if so removes
   * them. It also checks it a new layer should be added, and if so adds it and sets the {@code target} before the operation.</li>
   * </ul>
   *
   * @param <T> The type of Bloom Filter that is used for the layers.
   * @since 4.5.0-M2
   */
  public class LayeredBloomFilter<T extends BloomFilter<T>> implements BloomFilter<LayeredBloomFilter<T>>, BloomFilterExtractor {
  
      /**
       * A class used to locate matching filters across all the layers.
       */
      private class Finder implements Predicate<BloomFilter> {
          int[] result = new int[layerManager.getDepth()];
          int bfIdx;
          int resultIdx;
          BloomFilter<?> bf;
  
          Finder(final BloomFilter<?> bf) {
              this.bf = bf;
          }
  
          int[] getResult() {
              return Arrays.copyOf(result, resultIdx);
          }
  
          @Override
          public boolean test(final BloomFilter x) {
              if (x.contains(bf)) {
                  result[resultIdx++] = bfIdx;
              }
              bfIdx++;
              return true;
          }
      }
  
      private final Shape shape;
  
      private final LayerManager<T> layerManager;
  
      /**
       * Constructs a new instance.
       *
       * @param shape        the Shape of the enclosed Bloom filters
       * @param layerManager the LayerManager to manage the layers.
       */
      public LayeredBloomFilter(final Shape shape, final LayerManager<T> layerManager) {
          this.shape = shape;
          this.layerManager = layerManager;
      }
  
     @Override
     public int cardinality() {
         return SetOperations.cardinality(this);
     }
 
     @Override
     public int characteristics() {
         return 0;
     }
 
     /**
      * Forces the execution of the cleanup Consumer that was provided when the associated LayerManager was built.
      *
      * @see LayerManager.Builder#setCleanup(java.util.function.Consumer)
      */
     public void cleanup() {
         layerManager.cleanup();
     }
 
     @Override
     public final void clear() {
         layerManager.clear();
     }
 
     @Override
     public boolean contains(final BitMapExtractor bitMapExtractor) {
         return contains(createFilter(bitMapExtractor));
     }
 
     /**
      * Returns {@code true} if this any layer contained by this filter contains the specified filter.
      * <p>
      * If the {@code other} is a BloomFilterExtractor each filter within the {@code other} is checked to see if it exits within this filter.
      * </p>
      *
      * @param other the other Bloom filter
      * @return {@code true} if this filter contains the other filter.
      */
     @Override
     public boolean contains(final BloomFilter other) {
         return other instanceof BloomFilterExtractor ? contains((BloomFilterExtractor) other) : !processBloomFilters(x -> !x.contains(other));
     }
 
     /**
      * Returns {@code true} if each filter within the {@code bloomFilterExtractor} exits within this filter.
      *
      * @param bloomFilterExtractor the BloomFilterExtractor that provides the filters to check for.
      * @return {@code true} if this filter contains all of the filters contained in the {@code bloomFilterExtractor}.
      */
     public boolean contains(final BloomFilterExtractor bloomFilterExtractor) {
         final boolean[] result = { true };
         // return false when we have found a match to short circuit checks
         return bloomFilterExtractor.processBloomFilters(x -> {
             result[0] &= contains(x);
             return result[0];
         });
     }
 
     @Override
     public boolean contains(final Hasher hasher) {
         return contains(createFilter(hasher));
     }
 
     @Override
     public boolean contains(final IndexExtractor indexExtractor) {
         return contains(createFilter(indexExtractor));
     }
 
     /**
      * Creates a new instance of this {@link LayeredBloomFilter} with the same properties as the current one.
      *
      * @return a copy of this {@link LayeredBloomFilter}.
      */
     @Override
     public LayeredBloomFilter<T> copy() {
         return new LayeredBloomFilter<>(shape, layerManager.copy());
     }
 
     /**
      * Creates a Bloom filter from a BitMapExtractor.
      *
      * @param bitMapExtractor the BitMapExtractor to create the filter from.
      * @return the BloomFilter.
      */
     private SimpleBloomFilter createFilter(final BitMapExtractor bitMapExtractor) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(bitMapExtractor);
         return bf;
     }
 
     /**
      * Creates a Bloom filter from a Hasher.
      *
      * @param hasher the hasher to create the filter from.
      * @return the BloomFilter.
      */
     private SimpleBloomFilter createFilter(final Hasher hasher) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(hasher);
         return bf;
     }
 
     /**
      * Creates a Bloom filter from an IndexExtractor.
      *
      * @param indexExtractor the IndexExtractor to create the filter from.
      * @return the BloomFilter.
      */
     private SimpleBloomFilter createFilter(final IndexExtractor indexExtractor) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(indexExtractor);
         return bf;
     }
 
     @Override
     public int estimateN() {
         return flatten().estimateN();
     }
 
     @Override
     public int estimateUnion(final BloomFilter other) {
         Objects.requireNonNull(other, "other");
         final BloomFilter cpy = this.flatten();
         cpy.merge(other);
         return cpy.estimateN();
     }
 
     /**
      * Finds the layers in which the BitMapExtractor is found.
      *
      * @param bitMapExtractor the BitMapExtractor to search for.
      * @return an array of layer indices in which the Bloom filter is found.
      */
     public int[] find(final BitMapExtractor bitMapExtractor) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(bitMapExtractor);
         return find(bf);
     }
 
     /**
      * Finds the layers in which the Bloom filter is found.
      *
      * @param bf the Bloom filter to search for.
      * @return an array of layer indices in which the Bloom filter is found.
      */
     public int[] find(final BloomFilter bf) {
         final Finder finder = new Finder(bf);
         processBloomFilters(finder);
         return finder.getResult();
     }
 
     /**
      * Finds the layers in which the Hasher is found.
      *
      * @param hasher the Hasher to search for.
      * @return an array of layer indices in which the Bloom filter is found.
      */
     public int[] find(final Hasher hasher) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(hasher);
         return find(bf);
     }
 
     /**
      * Finds the layers in which the IndexExtractor is found.
      *
      * @param indexExtractor the Index extractor to search for.
      * @return an array of layer indices in which the Bloom filter is found.
      */
     public int[] find(final IndexExtractor indexExtractor) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(indexExtractor);
         return find(bf);
     }
 
     /**
      * Create a standard (non-layered) Bloom filter by merging all of the layers. If the filter is empty this method will return an empty Bloom filter.
      *
      * @return the merged bloom filter.
      */
     @Override
     public SimpleBloomFilter flatten() {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         processBloomFilters(bf::merge);
         return bf;
     }
 
     /**
      * Gets the Bloom filter at the specified depth
      *
      * @param depth the depth of the filter to return.
      * @return the Bloom filter at the specified depth.
      * @throws NoSuchElementException if depth is not in the range [0,getDepth())
      */
     public T get(final int depth) {
         return layerManager.get(depth);
     }
 
     /**
      * Gets the depth of the deepest layer. The minimum value returned by this method is 1.
      *
      * @return the depth of the deepest layer.
      */
     public final int getDepth() {
         return layerManager.getDepth();
     }
 
     @Override
     public final Shape getShape() {
         return shape;
     }
 
     @Override
     public boolean isEmpty() {
         return processBloomFilters(BloomFilter::isEmpty);
     }
 
     @Override
     public boolean merge(final BitMapExtractor bitMapExtractor) {
         return layerManager.getTarget().merge(bitMapExtractor);
     }
 
     @Override
     public boolean merge(final BloomFilter bf) {
         return layerManager.getTarget().merge(bf);
     }
 
     @Override
     public boolean merge(final IndexExtractor indexExtractor) {
         return layerManager.getTarget().merge(indexExtractor);
     }
 
     /**
      * Forces and advance to the next layer. This method will clean-up the current layers and generate a new filter layer. In most cases is it unnecessary to
      * call this method directly.
      *
      * @see LayerManager.Builder#setCleanup(java.util.function.Consumer)
      * @see LayerManager.Builder#setExtendCheck(Predicate)
      */
     public void next() {
         layerManager.next();
     }
 
     @Override
     public boolean processBitMaps(final LongPredicate predicate) {
         return flatten().processBitMaps(predicate);
     }
 
     /**
      * Processes the Bloom filters in depth order with the most recent filters first. Each filter is passed to the predicate in turn. The function exits on the
      * first {@code false} returned by the predicate.
      *
      * @param bloomFilterPredicate the predicate to execute.
      * @return {@code true} if all filters passed the predicate, {@code false} otherwise.
      */
     @Override
     public final boolean processBloomFilters(final Predicate<BloomFilter> bloomFilterPredicate) {
         return layerManager.processBloomFilters(bloomFilterPredicate);
     }
 
     @Override
     public boolean processIndices(final IntPredicate predicate) {
         return processBloomFilters(bf -> bf.processIndices(predicate));
     }
 
 }