/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.apache.lucene.search.postingshighlight;

import org.elasticsearch.search.fetch.subphase.highlight.HighlightUtils;
import org.elasticsearch.test.ESTestCase;

import java.text.BreakIterator;
import java.text.CharacterIterator;
import java.text.StringCharacterIterator;
import java.util.Locale;

import static org.hamcrest.CoreMatchers.equalTo;

public class CustomSeparatorBreakIteratorTests extends ESTestCase {
    public void testBreakOnCustomSeparator() throws Exception {
        Character separator = randomSeparator();
        BreakIterator bi = new CustomSeparatorBreakIterator(separator);
        String source = "this" + separator + "is" + separator + "the" + separator + "first" + separator + "sentence";
        bi.setText(source);
        assertThat(bi.current(), equalTo(0));
        assertThat(bi.first(), equalTo(0));
        assertThat(source.substring(bi.current(), bi.next()), equalTo("this" + separator));
        assertThat(source.substring(bi.current(), bi.next()), equalTo("is" + separator));
        assertThat(source.substring(bi.current(), bi.next()), equalTo("the" + separator));
        assertThat(source.substring(bi.current(), bi.next()), equalTo("first" + separator));
        assertThat(source.substring(bi.current(), bi.next()), equalTo("sentence"));
        assertThat(bi.next(), equalTo(BreakIterator.DONE));

        assertThat(bi.last(), equalTo(source.length()));
        int current = bi.current();
        assertThat(source.substring(bi.previous(), current), equalTo("sentence"));
        current = bi.current();
        assertThat(source.substring(bi.previous(), current), equalTo("first" + separator));
        current = bi.current();
        assertThat(source.substring(bi.previous(), current), equalTo("the" + separator));
        current = bi.current();
        assertThat(source.substring(bi.previous(), current), equalTo("is" + separator));
        current = bi.current();
        assertThat(source.substring(bi.previous(), current), equalTo("this" + separator));
        assertThat(bi.previous(), equalTo(BreakIterator.DONE));
        assertThat(bi.current(), equalTo(0));

        assertThat(source.substring(0, bi.following(9)), equalTo("this" + separator + "is" + separator + "the" + separator));

        assertThat(source.substring(0, bi.preceding(9)), equalTo("this" + separator + "is" + separator));

        assertThat(bi.first(), equalTo(0));
        assertThat(source.substring(0, bi.next(3)), equalTo("this" + separator + "is" + separator + "the" + separator));
    }

    public void testSingleSentences() throws Exception {
        BreakIterator expected = BreakIterator.getSentenceInstance(Locale.ROOT);
        BreakIterator actual = new CustomSeparatorBreakIterator(randomSeparator());
        assertSameBreaks("a", expected, actual);
        assertSameBreaks("ab", expected, actual);
        assertSameBreaks("abc", expected, actual);
        assertSameBreaks("", expected, actual);
    }

    public void testSliceEnd() throws Exception {
        BreakIterator expected = BreakIterator.getSentenceInstance(Locale.ROOT);
        BreakIterator actual = new CustomSeparatorBreakIterator(randomSeparator());
        assertSameBreaks("a000", 0, 1, expected, actual);
        assertSameBreaks("ab000", 0, 1, expected, actual);
        assertSameBreaks("abc000", 0, 1, expected, actual);
        assertSameBreaks("000", 0, 0, expected, actual);
    }

    public void testSliceStart() throws Exception {
        BreakIterator expected = BreakIterator.getSentenceInstance(Locale.ROOT);
        BreakIterator actual = new CustomSeparatorBreakIterator(randomSeparator());
        assertSameBreaks("000a", 3, 1, expected, actual);
        assertSameBreaks("000ab", 3, 2, expected, actual);
        assertSameBreaks("000abc", 3, 3, expected, actual);
        assertSameBreaks("000", 3, 0, expected, actual);
    }

    public void testSliceMiddle() throws Exception {
        BreakIterator expected = BreakIterator.getSentenceInstance(Locale.ROOT);
        BreakIterator actual = new CustomSeparatorBreakIterator(randomSeparator());
        assertSameBreaks("000a000", 3, 1, expected, actual);
        assertSameBreaks("000ab000", 3, 2, expected, actual);
        assertSameBreaks("000abc000", 3, 3, expected, actual);
        assertSameBreaks("000000", 3, 0, expected, actual);
    }

    /** the current position must be ignored, initial position is always first() */
    public void testFirstPosition() throws Exception {
        BreakIterator expected = BreakIterator.getSentenceInstance(Locale.ROOT);
        BreakIterator actual = new CustomSeparatorBreakIterator(randomSeparator());
        assertSameBreaks("000ab000", 3, 2, 4, expected, actual);
    }

    private static char randomSeparator() {
        return randomFrom(' ', HighlightUtils.NULL_SEPARATOR, HighlightUtils.PARAGRAPH_SEPARATOR);
    }

    private static void assertSameBreaks(String text, BreakIterator expected, BreakIterator actual) {
        assertSameBreaks(new StringCharacterIterator(text),
                new StringCharacterIterator(text),
                expected,
                actual);
    }

    private static void assertSameBreaks(String text, int offset, int length, BreakIterator expected, BreakIterator actual) {
        assertSameBreaks(text, offset, length, offset, expected, actual);
    }

    private static void assertSameBreaks(String text, int offset, int length, int current, BreakIterator expected, BreakIterator actual) {
        assertSameBreaks(new StringCharacterIterator(text, offset, offset + length, current),
                new StringCharacterIterator(text, offset, offset + length, current),
                expected,
                actual);
    }

    /** Asserts that two breakiterators break the text the same way */
    private static void assertSameBreaks(CharacterIterator one, CharacterIterator two, BreakIterator expected, BreakIterator actual) {
        expected.setText(one);
        actual.setText(two);

        assertEquals(expected.current(), actual.current());

        // next()
        int v = expected.current();
        while (v != BreakIterator.DONE) {
            assertEquals(v = expected.next(), actual.next());
            assertEquals(expected.current(), actual.current());
        }

        // first()
        assertEquals(expected.first(), actual.first());
        assertEquals(expected.current(), actual.current());
        // last()
        assertEquals(expected.last(), actual.last());
        assertEquals(expected.current(), actual.current());

        // previous()
        v = expected.current();
        while (v != BreakIterator.DONE) {
            assertEquals(v = expected.previous(), actual.previous());
            assertEquals(expected.current(), actual.current());
        }

        // following()
        for (int i = one.getBeginIndex(); i <= one.getEndIndex(); i++) {
            expected.first();
            actual.first();
            assertEquals(expected.following(i), actual.following(i));
            assertEquals(expected.current(), actual.current());
        }

        // preceding()
        for (int i = one.getBeginIndex(); i <= one.getEndIndex(); i++) {
            expected.last();
            actual.last();
            assertEquals(expected.preceding(i), actual.preceding(i));
            assertEquals(expected.current(), actual.current());
        }
    }
}
