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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.eclipse.aether.util.graph.version;
20  
21  import java.util.Arrays;
22  import java.util.Collection;
23  
24  import org.eclipse.aether.RepositoryException;
25  import org.eclipse.aether.collection.DependencyCollectionContext;
26  import org.eclipse.aether.collection.VersionFilter;
27  
28  /**
29   * A version filter that combines multiple version filters into a chain where each filter gets invoked one after the
30   * other, thereby accumulating their filtering effects.
31   */
32  public final class ChainedVersionFilter implements VersionFilter {
33  
34      private final VersionFilter[] filters;
35  
36      private int hashCode;
37  
38      /**
39       * Chains the specified version filters.
40       *
41       * @param filter1 The first version filter, may be {@code null}.
42       * @param filter2 The second version filter, may be {@code null}.
43       * @return The chained version filter or {@code null} if both input filters are {@code null}.
44       */
45      public static VersionFilter newInstance(VersionFilter filter1, VersionFilter filter2) {
46          if (filter1 == null) {
47              return filter2;
48          }
49          if (filter2 == null) {
50              return filter1;
51          }
52          return new ChainedVersionFilter(new VersionFilter[] {filter1, filter2});
53      }
54  
55      /**
56       * Chains the specified version filters.
57       *
58       * @param filters The version filters to chain, must not be {@code null} or contain {@code null}.
59       * @return The chained version filter or {@code null} if the input array is empty.
60       */
61      public static VersionFilter newInstance(VersionFilter... filters) {
62          if (filters.length <= 1) {
63              if (filters.length <= 0) {
64                  return null;
65              }
66              return filters[0];
67          }
68          return new ChainedVersionFilter(filters.clone());
69      }
70  
71      /**
72       * Chains the specified version filters.
73       *
74       * @param filters The version filters to chain, must not be {@code null} or contain {@code null}.
75       * @return The chained version filter or {@code null} if the input collection is empty.
76       */
77      public static VersionFilter newInstance(Collection<? extends VersionFilter> filters) {
78          if (filters.size() <= 1) {
79              if (filters.isEmpty()) {
80                  return null;
81              }
82              return filters.iterator().next();
83          }
84          return new ChainedVersionFilter(filters.toArray(new VersionFilter[0]));
85      }
86  
87      private ChainedVersionFilter(VersionFilter[] filters) {
88          this.filters = filters;
89      }
90  
91      public void filterVersions(VersionFilterContext context) throws RepositoryException {
92          for (int i = 0, n = filters.length; i < n && context.getCount() > 0; i++) {
93              filters[i].filterVersions(context);
94          }
95      }
96  
97      public VersionFilter deriveChildFilter(DependencyCollectionContext context) {
98          VersionFilter[] children = null;
99          int removed = 0;
100         for (int i = 0, n = filters.length; i < n; i++) {
101             VersionFilter child = filters[i].deriveChildFilter(context);
102             if (children != null) {
103                 children[i - removed] = child;
104             } else if (child != filters[i]) {
105                 children = new VersionFilter[filters.length];
106                 System.arraycopy(filters, 0, children, 0, i);
107                 children[i - removed] = child;
108             }
109             if (child == null) {
110                 removed++;
111             }
112         }
113         if (children == null) {
114             return this;
115         }
116         if (removed > 0) {
117             int count = filters.length - removed;
118             if (count <= 0) {
119                 return null;
120             }
121             if (count == 1) {
122                 return children[0];
123             }
124             VersionFilter[] tmp = new VersionFilter[count];
125             System.arraycopy(children, 0, tmp, 0, count);
126             children = tmp;
127         }
128         return new ChainedVersionFilter(children);
129     }
130 
131     @Override
132     public boolean equals(Object obj) {
133         if (this == obj) {
134             return true;
135         } else if (null == obj || !getClass().equals(obj.getClass())) {
136             return false;
137         }
138 
139         ChainedVersionFilter that = (ChainedVersionFilter) obj;
140         return Arrays.equals(filters, that.filters);
141     }
142 
143     @Override
144     public int hashCode() {
145         if (hashCode == 0) {
146             int hash = getClass().hashCode();
147             hash = hash * 31 + Arrays.hashCode(filters);
148             hashCode = hash;
149         }
150         return hashCode;
151     }
152 }