/*
    * 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.eclipse.aether.util.graph.version;
  
  import java.util.Arrays;
  import java.util.Collection;
  
  import org.eclipse.aether.RepositoryException;
  import org.eclipse.aether.collection.DependencyCollectionContext;
  import org.eclipse.aether.collection.VersionFilter;
  
  /**
   * A version filter that combines multiple version filters into a chain where each filter gets invoked one after the
   * other, thereby accumulating their filtering effects.
   */
  public final class ChainedVersionFilter implements VersionFilter {
  
      private final VersionFilter[] filters;
  
      private int hashCode;
  
      /**
       * Chains the specified version filters.
       *
       * @param filter1 The first version filter, may be {@code null}.
       * @param filter2 The second version filter, may be {@code null}.
       * @return The chained version filter or {@code null} if both input filters are {@code null}.
       */
      public static VersionFilter newInstance(VersionFilter filter1, VersionFilter filter2) {
          if (filter1 == null) {
              return filter2;
          }
          if (filter2 == null) {
              return filter1;
          }
          return new ChainedVersionFilter(new VersionFilter[] {filter1, filter2});
      }
  
      /**
       * Chains the specified version filters.
       *
       * @param filters The version filters to chain, must not be {@code null} or contain {@code null}.
       * @return The chained version filter or {@code null} if the input array is empty.
       */
      public static VersionFilter newInstance(VersionFilter... filters) {
          if (filters.length <= 1) {
              if (filters.length <= 0) {
                  return null;
              }
              return filters[0];
          }
          return new ChainedVersionFilter(filters.clone());
      }
  
      /**
       * Chains the specified version filters.
       *
       * @param filters The version filters to chain, must not be {@code null} or contain {@code null}.
       * @return The chained version filter or {@code null} if the input collection is empty.
       */
      public static VersionFilter newInstance(Collection<? extends VersionFilter> filters) {
          if (filters.size() <= 1) {
              if (filters.isEmpty()) {
                  return null;
              }
              return filters.iterator().next();
          }
          return new ChainedVersionFilter(filters.toArray(new VersionFilter[0]));
      }
  
      private ChainedVersionFilter(VersionFilter[] filters) {
          this.filters = filters;
      }
  
      @Override
      public void filterVersions(VersionFilterContext context) throws RepositoryException {
          for (int i = 0, n = filters.length; i < n && context.getCount() > 0; i++) {
              filters[i].filterVersions(context);
          }
      }
  
      @Override
      public VersionFilter deriveChildFilter(DependencyCollectionContext context) {
         VersionFilter[] children = null;
         int removed = 0;
         for (int i = 0, n = filters.length; i < n; i++) {
             VersionFilter child = filters[i].deriveChildFilter(context);
             if (children != null) {
                 children[i - removed] = child;
             } else if (child != filters[i]) {
                 children = new VersionFilter[filters.length];
                 System.arraycopy(filters, 0, children, 0, i);
                 children[i - removed] = child;
             }
             if (child == null) {
                 removed++;
             }
         }
         if (children == null) {
             return this;
         }
         if (removed > 0) {
             int count = filters.length - removed;
             if (count <= 0) {
                 return null;
             }
             if (count == 1) {
                 return children[0];
             }
             VersionFilter[] tmp = new VersionFilter[count];
             System.arraycopy(children, 0, tmp, 0, count);
             children = tmp;
         }
         return new ChainedVersionFilter(children);
     }
 
     @Override
     public boolean equals(Object obj) {
         if (this == obj) {
             return true;
         } else if (null == obj || !getClass().equals(obj.getClass())) {
             return false;
         }
 
         ChainedVersionFilter that = (ChainedVersionFilter) obj;
         return Arrays.equals(filters, that.filters);
     }
 
     @Override
     public int hashCode() {
         if (hashCode == 0) {
             int hash = getClass().hashCode();
             hash = hash * 31 + Arrays.hashCode(filters);
             hashCode = hash;
         }
         return hashCode;
     }
 }