001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.text.similarity;
019
020import java.util.Objects;
021
022/**
023 * An ordered input of elements used to compute a similarity score.
024 * <p>
025 * You can implement a SimilarityInput on a domain object instead of CharSequence where implementing CharSequence does not make sense.
026 * </p>
027 *
028 * @param <E> the type of elements in this input.
029 * @since 1.13.0
030 */
031public interface SimilarityInput<E> {
032
033    /**
034     * Creates a new input for a {@link CharSequence}.
035     *
036     * @param cs input character sequence.
037     * @return a new input.
038     */
039    static SimilarityInput<Character> input(final CharSequence cs) {
040        return new SimilarityCharacterInput(cs);
041    }
042
043    /**
044     * Creates a new input for a {@link CharSequence} or {@link SimilarityInput}.
045     *
046     * @param <T> The type of similarity score unit.
047     * @param input character sequence or similarity input.
048     * @return a new input.
049     * @throws IllegalArgumentException when the input type is neither {@link CharSequence} or {@link SimilarityInput}.
050     */
051    @SuppressWarnings("unchecked")
052    static <T> SimilarityInput<T> input(final Object input) {
053        if (input instanceof SimilarityInput) {
054            return (SimilarityInput<T>) input;
055        }
056        if (input instanceof CharSequence) {
057            return (SimilarityInput<T>) input((CharSequence) input);
058        }
059        throw new IllegalArgumentException(Objects.requireNonNull(input, "input").getClass().getName());
060    }
061
062    /**
063     * Gets the element in the input at the given 0-based index.
064     *
065     * @param index a 0-based index.
066     * @return the element in the input at the given 0-based index.
067     */
068    E at(int index);
069
070    /**
071     * Gets the length of the input.
072     *
073     * @return the length of the input.
074     */
075    int length();
076
077}