/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.analysis.common;

import org.apache.lucene.analysis.CharacterUtils;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.util.CharTokenizer;

import java.io.IOException;

@Deprecated
class XLowerCaseTokenizer extends Tokenizer {

    private int offset = 0, bufferIndex = 0, dataLen = 0, finalOffset = 0;

    private static final int IO_BUFFER_SIZE = 4096;

    private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
    private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);

    private final CharacterUtils.CharacterBuffer ioBuffer = CharacterUtils.newCharacterBuffer(IO_BUFFER_SIZE);

    @Override
    public final boolean incrementToken() throws IOException {
        clearAttributes();
        int length = 0;
        int start = -1; // this variable is always initialized
        int end = -1;
        char[] buffer = termAtt.buffer();
        while (true) {
            if (bufferIndex >= dataLen) {
                offset += dataLen;
                CharacterUtils.fill(ioBuffer, input); // read supplementary char aware with CharacterUtils
                if (ioBuffer.getLength() == 0) {
                    dataLen = 0; // so next offset += dataLen won't decrement offset
                    if (length > 0) {
                        break;
                    } else {
                        finalOffset = correctOffset(offset);
                        return false;
                    }
                }
                dataLen = ioBuffer.getLength();
                bufferIndex = 0;
            }
            // use CharacterUtils here to support < 3.1 UTF-16 code unit behavior if the char based methods are gone
            final int c = Character.codePointAt(ioBuffer.getBuffer(), bufferIndex, ioBuffer.getLength());
            final int charCount = Character.charCount(c);
            bufferIndex += charCount;

            if (Character.isLetter(c)) {               // if it's a token char
                if (length == 0) {                // start of token
                    assert start == -1;
                    start = offset + bufferIndex - charCount;
                    end = start;
                } else if (length >= buffer.length - 1) { // check if a supplementary could run out of bounds
                    buffer = termAtt.resizeBuffer(2 + length); // make sure a supplementary fits in the buffer
                }
                end += charCount;
                length += Character.toChars(Character.toLowerCase(c), buffer, length); // buffer it, normalized
                int maxTokenLen = CharTokenizer.DEFAULT_MAX_WORD_LEN;
                if (length >= maxTokenLen) { // buffer overflow! make sure to check for >= surrogate pair could break == test
                    break;
                }
            } else if (length > 0) {           // at non-Letter w/ chars
                break;                           // return 'em
            }
        }

        termAtt.setLength(length);
        assert start != -1;
        offsetAtt.setOffset(correctOffset(start), finalOffset = correctOffset(end));
        return true;

    }

    @Override
    public final void end() throws IOException {
        super.end();
        // set final offset
        offsetAtt.setOffset(finalOffset, finalOffset);
    }

    @Override
    public void reset() throws IOException {
        super.reset();
        bufferIndex = 0;
        offset = 0;
        dataLen = 0;
        finalOffset = 0;
        ioBuffer.reset(); // make sure to reset the IO buffer!!
    }

}