package org.eclipse.aether.util.graph.selector;
   
   /*
    * 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 java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashSet;
  import java.util.Set;
  
  import org.eclipse.aether.collection.DependencyCollectionContext;
  import org.eclipse.aether.collection.DependencySelector;
  import org.eclipse.aether.graph.Dependency;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A dependency selector that combines zero or more other selectors using a logical {@code AND}. The resulting selector
   * selects a given dependency if and only if all constituent selectors do so.
   */
  public final class AndDependencySelector
      implements DependencySelector
  {
  
      private final Set<? extends DependencySelector> selectors;
  
      private int hashCode;
  
      /**
       * Creates a new selector from the specified selectors. Prefer
       * {@link #newInstance(DependencySelector, DependencySelector)} if any of the input selectors might be {@code null}.
       * 
       * @param selectors The selectors to combine, may be {@code null} but must not contain {@code null} elements.
       */
      public AndDependencySelector( DependencySelector... selectors )
      {
          if ( selectors != null && selectors.length > 0 )
          {
              this.selectors = new LinkedHashSet<>( Arrays.asList( selectors ) );
          }
          else
          {
              this.selectors = Collections.emptySet();
          }
      }
  
      /**
       * Creates a new selector from the specified selectors.
       * 
       * @param selectors The selectors to combine, may be {@code null} but must not contain {@code null} elements.
       */
      public AndDependencySelector( Collection<? extends DependencySelector> selectors )
      {
          if ( selectors != null && !selectors.isEmpty() )
          {
              this.selectors = new LinkedHashSet<>( selectors );
          }
          else
          {
              this.selectors = Collections.emptySet();
          }
      }
  
      private AndDependencySelector( Set<DependencySelector> selectors )
      {
          if ( selectors != null && !selectors.isEmpty() )
          {
              this.selectors = selectors;
          }
          else
          {
              this.selectors = Collections.emptySet();
          }
      }
  
      /**
       * Creates a new selector from the specified selectors.
       * 
       * @param selector1 The first selector to combine, may be {@code null}.
       * @param selector2 The second selector to combine, may be {@code null}.
       * @return The combined selector or {@code null} if both selectors were {@code null}.
      */
     public static DependencySelector newInstance( DependencySelector selector1, DependencySelector selector2 )
     {
         if ( selector1 == null )
         {
             return selector2;
         }
         else if ( selector2 == null || selector2.equals( selector1 ) )
         {
             return selector1;
         }
         return new AndDependencySelector( selector1, selector2 );
     }
 
     public boolean selectDependency( Dependency dependency )
     {
         requireNonNull( dependency, "dependency cannot be null" );
         for ( DependencySelector selector : selectors )
         {
             if ( !selector.selectDependency( dependency ) )
             {
                 return false;
             }
         }
         return true;
     }
 
     public DependencySelector deriveChildSelector( DependencyCollectionContext context )
     {
         requireNonNull( context, "context cannot be null" );
         int seen = 0;
         Set<DependencySelector> childSelectors = null;
 
         for ( DependencySelector selector : selectors )
         {
             DependencySelector childSelector = selector.deriveChildSelector( context );
             if ( childSelectors != null )
             {
                 if ( childSelector != null )
                 {
                     childSelectors.add( childSelector );
                 }
             }
             else if ( selector != childSelector )
             {
                 childSelectors = new LinkedHashSet<>();
                 if ( seen > 0 )
                 {
                     for ( DependencySelector s : selectors )
                     {
                         if ( childSelectors.size() >= seen )
                         {
                             break;
                         }
                         childSelectors.add( s );
                     }
                 }
                 if ( childSelector != null )
                 {
                     childSelectors.add( childSelector );
                 }
             }
             else
             {
                 seen++;
             }
         }
 
         if ( childSelectors == null )
         {
             return this;
         }
         if ( childSelectors.size() <= 1 )
         {
             if ( childSelectors.isEmpty() )
             {
                 return null;
             }
             return childSelectors.iterator().next();
         }
         return new AndDependencySelector( childSelectors );
     }
 
     @Override
     public boolean equals( Object obj )
     {
         if ( this == obj )
         {
             return true;
         }
         else if ( null == obj || !getClass().equals( obj.getClass() ) )
         {
             return false;
         }
 
         AndDependencySelector that = (AndDependencySelector) obj;
         return selectors.equals( that.selectors );
     }
 
     @Override
     public int hashCode()
     {
         if ( hashCode == 0 )
         {
             int hash = 17;
             hash = hash * 31 + selectors.hashCode();
             hashCode = hash;
         }
         return hashCode;
     }
 
     @Override
     public String toString()
     {
         StringBuilder builder = new StringBuilder().append( this.getClass().getSimpleName() ).append( '(' );
         Iterator<? extends DependencySelector> iterator = this.selectors.iterator();
         while ( iterator.hasNext() )
         {
             final DependencySelector selector = iterator.next();
             builder.append( selector.toString() );
             if ( iterator.hasNext() ) // not last
             {
                 builder.append( " && " );
             }
         }
         return builder.append( ')' ).toString();
     }
 
 }