/*
    * 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.selector;
  
  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();
     }
 }