content: /*
   * Copyright 2025 the original author or authors.
   *
   * Licensed 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
   *
   *      https://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 com.alibaba.cloud.ai.studio.core.rag.splitter;
  
  import org.springframework.ai.transformer.splitter.TextSplitter;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * A text splitter that splits text based on a regular expression pattern. It supports
   * overlapping segments to maintain context between splits.
   *
   * @since 1.0.0.3
   */
  public class RegexTextSplitter extends TextSplitter {
  
  	/** The compiled regular expression pattern used for splitting */
  	private final Pattern pattern;
  
  	/** The number of characters to overlap between consecutive segments */
  	private final int overlapSize;
  
  	/**
  	 * Creates a new RegexTextSplitter with the specified regex pattern and overlap size.
  	 * @param regex The regular expression pattern to split the text
  	 * @param overlapSize The number of characters to overlap between segments
  	 */
  	public RegexTextSplitter(String regex, int overlapSize) {
  		this.pattern = Pattern.compile(regex);
  		this.overlapSize = overlapSize;
  	}
  
  	/**
  	 * Splits the input text into segments based on the regex pattern. Each segment
  	 * includes an overlap with the previous segment to maintain context.
  	 * @param text The text to split
  	 * @return List of text segments
  	 */
  	@Override
  	protected List<String> splitText(String text) {
  		List<String> segments = new ArrayList<>();
  		Matcher matcher = pattern.matcher(text);
  
  		int lastEnd = 0;
  		while (matcher.find()) {
  			int start = matcher.start();
  			int end = matcher.end();
  
  			int overlapStart = Math.max(0, start - overlapSize);
  			if (lastEnd == 0) {
  				segments.add(text.substring(0, end));
  			}
  			else {
  				segments.add(text.substring(overlapStart, end));
  			}
  
  			lastEnd = end;
  		}
  
  		if (lastEnd < text.length()) {
  			int overlapStart = Math.max(0, lastEnd - overlapSize);
  			segments.add(text.substring(overlapStart));
  		}
  
  		return segments;
  	}
  
  }
  