sidebarsPapers.js

import fs from 'fs';
import path from 'path';

/**
 * Recursively counts Markdown (.md) files in a directory and its subdirectories.
 * Excludes hidden entries (names starting with '.') and '_category_.json'.
 *
 * @param {string} directoryPath Absolute path to the target directory.
 * @return {number} Total count of Markdown files.
 */
function countMarkdownFiles(directoryPath) {
  let total = 0;
  const entries = fs.readdirSync(directoryPath);

  for (const entry of entries) {
    if (entry.startsWith('.') || entry === '_category_.json') {
      continue;
    }
    const entryPath = path.join(directoryPath, entry);
    const stats = fs.statSync(entryPath);

    if (stats.isDirectory()) {
      total += countMarkdownFiles(entryPath);
    } else if (stats.isFile() && entry.endsWith('.md')) {
      total++;
    }
  }

  return total;
}

/**
 * Encodes a relative POSIX path into a URL-friendly slug.
 *
 * @param {string} relativePath Relative POSIX path segments separated by '/'.
 * @return {string} URL-encoded slug.
 */
function toSlug(relativePath) {
  return relativePath
    .replace(/\\/g, "/")
    .split('/')
    .map(segment => encodeURIComponent(segment))
    .join('/');
}

/**
 * Retrieves visible subdirectories of a directory, excluding hidden ones.
 *
 * @param {string} directoryPath Absolute path to the parent directory.
 * @return {string[]} Alphabetically sorted list of visible subdirectory names.
 */
function getVisibleSubDirs(directoryPath) {
  return fs
    .readdirSync(directoryPath)
    .filter(name => {
      const subPath = path.join(directoryPath, name);
      return !name.startsWith('.') && fs.statSync(subPath).isDirectory();
    })
    .sort((a, b) => {
      // 檢查是否含有 _category_.json
      const aHasCategory = fs.existsSync(path.join(directoryPath, a, '_category_.json'));
      const bHasCategory = fs.existsSync(path.join(directoryPath, b, '_category_.json'));

      // 含有 _category_.json 的資料夾排在前面
      if (aHasCategory && !bHasCategory) return -1;
      if (bHasCategory && !aHasCategory) return 1;

      // 同類型的按字母順序排列
      return a.localeCompare(b);
    });
}

/**
 * Builds a Docusaurus sidebar category item for a directory containing '_category_.json'.
 * Subdirectories are listed first, followed by the current directory's markdown items.
 *
 * @param {string} absoluteDirPath Absolute path to the category directory.
 * @param {string} relativeDirPath Relative POSIX path from the 'papers' base directory.
 * @return {import('@docusaurus/plugin-content-docs').SidebarItem} Sidebar category item.
 * @throws {Error} If the '_category_.json' file cannot be parsed.
 */
function buildCategoryItem(absoluteDirPath, relativeDirPath) {
  const metaFilePath = path.join(absoluteDirPath, '_category_.json');
  let metadata;

  try {
    metadata = JSON.parse(fs.readFileSync(metaFilePath, 'utf8'));
  } catch (err) {
    throw new Error(`Failed to parse ${metaFilePath}: ${err.message}`);
  }

  const baseLabel = metadata.label || path.basename(absoluteDirPath);
  const itemCount = countMarkdownFiles(absoluteDirPath);
  const label = `${baseLabel} (${itemCount})`;

  const defaultSlug = `/category/${toSlug(relativeDirPath)}`;
  const link = {
    type: 'generated-index',
    slug: metadata.link?.slug || defaultSlug,
    title: metadata.link?.title || baseLabel,
    ...metadata.link,
  };

  const hasOwnMd = fs
    .readdirSync(absoluteDirPath)
    .some(file => file.endsWith('.md'));

  const items = [
    // 1. 子資料夾項目（含 _category_.json 的目錄遞迴呼叫）
    ...getVisibleSubDirs(absoluteDirPath).map(subDir => {
      const subAbsPath = path.join(absoluteDirPath, subDir);
      const subRelPath = path.posix.join(relativeDirPath, subDir);
      return fs.existsSync(path.join(subAbsPath, '_category_.json'))
        ? buildCategoryItem(subAbsPath, subRelPath)
        : { type: 'autogenerated', dirName: subRelPath };
    }),
    // 2. 本層 Markdown 自動產生項目（若存在 .md 檔）
    ...(hasOwnMd ? [{ type: 'autogenerated', dirName: relativeDirPath }] : []),
  ];

  return { type: 'category', label, link, items };
}

/**
 * Generates the Docusaurus sidebar configuration for the 'papers' directory.
 *
 * @return {{papersSidebar: import('@docusaurus/plugin-content-docs').SidebarItem[]}}
 *   Sidebar configuration object.
 */
function generateSidebarConfig() {
  const baseDir = path.join(__dirname, 'papers');
  const sidebarItems = ['intro'];

  const subDirs = getVisibleSubDirs(baseDir);

  // 優先處理有 _category_.json 的子目錄
  for (const dirName of subDirs) {
    const absDirPath = path.join(baseDir, dirName);
    const catConfigPath = path.join(absDirPath, '_category_.json');

    if (fs.existsSync(catConfigPath)) {
      sidebarItems.push(buildCategoryItem(absDirPath, dirName));
    }
  }

  // 再處理純自動產生的子目錄
  for (const dirName of subDirs) {
    const absDirPath = path.join(baseDir, dirName);
    const catConfigPath = path.join(absDirPath, '_category_.json');

    if (!fs.existsSync(catConfigPath)) {
      sidebarItems.push({ type: 'autogenerated', dirName });
    }
  }

  // 統計所有筆記數量
  const totalNotes = countMarkdownFiles(baseDir);
  sidebarItems.push({
    type: 'link',
    label: `All Notes: ${totalNotes} entries`,
    href: '/papers/intro',
  });

  return { papersSidebar: sidebarItems };
}

export default generateSidebarConfig();