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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.text.similarity;
19  
20  import java.util.Objects;
21  
22  /**
23   * An ordered input of elements used to compute a similarity score.
24   * <p>
25   * You can implement a SimilarityInput on a domain object instead of CharSequence where implementing CharSequence does not make sense.
26   * </p>
27   *
28   * @param <E> the type of elements in this input.
29   * @since 1.13.0
30   */
31  public interface SimilarityInput<E> {
32  
33      /**
34       * Creates a new input for a {@link CharSequence}.
35       *
36       * @param cs input character sequence.
37       * @return a new input.
38       */
39      static SimilarityInput<Character> input(final CharSequence cs) {
40          return new SimilarityCharacterInput(cs);
41      }
42  
43      /**
44       * Creates a new input for a {@link CharSequence} or {@link SimilarityInput}.
45       *
46       * @param <T> The type of similarity score unit.
47       * @param input character sequence or similarity input.
48       * @return a new input.
49       * @throws IllegalArgumentException when the input type is neither {@link CharSequence} or {@link SimilarityInput}.
50       */
51      @SuppressWarnings("unchecked")
52      static <T> SimilarityInput<T> input(final Object input) {
53          if (input instanceof SimilarityInput) {
54              return (SimilarityInput<T>) input;
55          }
56          if (input instanceof CharSequence) {
57              return (SimilarityInput<T>) input((CharSequence) input);
58          }
59          throw new IllegalArgumentException(Objects.requireNonNull(input, "input").getClass().getName());
60      }
61  
62      /**
63       * Gets the element in the input at the given 0-based index.
64       *
65       * @param index a 0-based index.
66       * @return the element in the input at the given 0-based index.
67       */
68      E at(int index);
69  
70      /**
71       * Gets the length of the input.
72       *
73       * @return the length of the input.
74       */
75      int length();
76  
77  }