export function createExcerpt()

in packages/docusaurus-utils/src/markdownUtils.ts [54:130]

• 52 lines of code
• 13 McCabe index (conditional complexity)

export function createExcerpt(fileString: string): string | undefined {
  const fileLines = fileString
    .trimStart()
    // Remove Markdown alternate title
    .replace(/^[^\n]*\n[=]+/g, '')
    .split('\n');
  let inCode = false;
  let inImport = false;
  let lastCodeFence = '';

  for (const fileLine of fileLines) {
    if (fileLine === '' && inImport) {
      inImport = false;
    }
    // Skip empty line.
    if (!fileLine.trim()) {
      continue;
    }

    // Skip import/export declaration.
    if ((/^(?:import|export)\s.*/.test(fileLine) || inImport) && !inCode) {
      inImport = true;
      continue;
    }

    // Skip code block line.
    if (fileLine.trim().startsWith('```')) {
      const codeFence = fileLine.trim().match(/^`+/)![0]!;
      if (!inCode) {
        inCode = true;
        lastCodeFence = codeFence;
        // If we are in a ````-fenced block, all ``` would be plain text instead
        // of fences
      } else if (codeFence.length >= lastCodeFence.length) {
        inCode = false;
      }
      continue;
    } else if (inCode) {
      continue;
    }

    const cleanedLine = fileLine
      // Remove HTML tags.
      .replace(/<[^>]*>/g, '')
      // Remove Title headers
      .replace(/^#[^#]+#?/gm, '')
      // Remove Markdown + ATX-style headers
      .replace(/^#{1,6}\s*(?<text>[^#]*)\s*#{0,6}/gm, '$1')
      // Remove emphasis.
      .replace(/(?<opening>[*_]{1,3})(?<text>.*?)\1/g, '$2')
      // Remove strikethroughs.
      .replace(/~~(?<text>\S.*\S)~~/g, '$1')
      // Remove images.
      .replace(/!\[(?<alt>.*?)\][[(].*?[\])]/g, '$1')
      // Remove footnotes.
      .replace(/\[\^.+?\](?:: .*$)?/g, '')
      // Remove inline links.
      .replace(/\[(?<alt>.*?)\][[(].*?[\])]/g, '$1')
      // Remove inline code.
      .replace(/`(?<text>.+?)`/g, '$1')
      // Remove blockquotes.
      .replace(/^\s{0,3}>\s?/g, '')
      // Remove admonition definition.
      .replace(/:::.*/, '')
      // Remove Emoji names within colons include preceding whitespace.
      .replace(/\s?:(?:::|[^:\n])+:/g, '')
      // Remove custom Markdown heading id.
      .replace(/\{#*[\w-]+\}/, '')
      .trim();

    if (cleanedLine) {
      return cleanedLine;
    }
  }

  return undefined;
}