MarkdownIndexGenerator.java

import java.io.IOException;
import java.nio.file.*;
import java.util.*;
import java.util.regex.*;
import java.util.stream.Collectors;

public class MarkdownIndexGenerator {

 private static final Pattern FILE_PATTERN = Pattern.compile("^(\\d+)(?:_(\\d+))?");

 public static void main(String[] args) {
 String projectFolder = Paths.get("classNotes").toAbsolutePath().toString();
 generateIndex(Paths.get(projectFolder));
 }

 private static void generateIndex(Path rootFolder) {
 StringBuilder indexContent = new StringBuilder("# ClassNotes Index\n\n");

 try {
 // Collect all markdown files and convert their index (1_1 -> 1.1)
 List<FileWithIndex> filesWithIndex = Files.walk(rootFolder)
 .filter(Files::isRegularFile)
 .filter(file -> file.toString().endsWith(".md") && !file.getFileName().toString().equals("index.md"))
 .map(file -> new FileWithIndex(file, convertFileNameToSortableIndex(file.getFileName().toString())))
 .sorted(Comparator.comparing(FileWithIndex::getIndex))
 .collect(Collectors.toList());

 // Generate the index file content
 for (FileWithIndex fileWithIndex : filesWithIndex) {
 Path file = fileWithIndex.getFile();
 Path relativePath = rootFolder.relativize(file);
 String linkPath = "classNotes/" + relativePath.toString().replace("\\", "/");
 indexContent.append("## ").append(file.getFileName()).append("\n\n");

 List<Heading> headings = extractHeadings(Files.readString(file));
 for (Heading heading : headings) {
 String link = generateLink(linkPath, heading.title);
 String indent = " ".repeat(heading.level - 1);
 indexContent.append(indent).append("- ").append(link).append("\n");
 }
 indexContent.append("\n");
 }

 // Write to index.md
 Path indexFilePath = Paths.get("index.md");
 Files.writeString(indexFilePath, indexContent.toString(), StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);

 System.out.println("Index generated at: " + indexFilePath.toAbsolutePath());

 } catch (IOException e) {
 System.err.println("Error processing files: " + e.getMessage());
 }
 }

 private static String convertFileNameToSortableIndex(String fileName) {
 // Match patterns like 1_1, 2_10, etc. and convert to sortable format
 Matcher matcher = FILE_PATTERN.matcher(fileName);
 if (matcher.find()) {
 String part1 = matcher.group(1);
 String part2 = matcher.group(2);
 return part2 != null ? String.format("%03d.%02d", Integer.parseInt(part1), Integer.parseInt(part2)) : String.format("%03d", Integer.parseInt(part1));
 }
 return fileName; // Return as-is if no match
 }

 private static List<Heading> extractHeadings(String fileContent) {
 List<Heading> headings = new ArrayList<>();
 String[] lines = fileContent.split("\n");

 for (String line : lines) {
 Matcher matcher = Pattern.compile("^(#{1,6})\\s+(.*)").matcher(line);
 if (matcher.find()) {
 int level = matcher.group(1).length();
 String title = matcher.group(2).trim();
 headings.add(new Heading(level, title));
 }
 }
 return headings;
 }

 private static String generateLink(String filename, String title) {
 String anchor = title.toLowerCase()
 .replaceAll("[^a-z0-9\\- ]", "")
 .replace(" ", "-");
 filename = filename.replace(" ", "%20");
 return "[" + title + "](" + filename + "#" + anchor + ")";
 }

 private static class Heading {
 int level;
 String title;

 Heading(int level, String title) {
 this.level = level;
 this.title = title;
 }
 }

 private static class FileWithIndex {
 Path file;
 String index;

 FileWithIndex(Path file, String index) {
 this.file = file;
 this.index = index;
 }

 public Path getFile() {
 return file;
 }

 public String getIndex() {
 return index;
 }
 }
}