package org.eclipse.aether.util.graph.version;
   
   /*
    * 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.
   */
  
  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[filters.size()] ) );
      }
  
      private ChainedVersionFilter( VersionFilter[] filters )
     {
         this.filters = filters;
     }
 
     public void filterVersions( VersionFilterContext context )
         throws RepositoryException
     {
         for ( int i = 0, n = filters.length; i < n && context.getCount() > 0; i++ )
         {
             filters[i].filterVersions( context );
         }
     }
 
     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;
     }
 
 }