mermaid-js / mermaid / 4608236643

import { DiagramDb } from './types';

// The "* as yaml" part is necessary for tree-shaking

import * as yaml from 'js-yaml';

// Match Jekyll-style front matter blocks (https://jekyllrb.com/docs/front-matter/).

// Based on regex used by Jekyll: https://github.com/jekyll/jekyll/blob/6dd3cc21c40b98054851846425af06c64f9fb466/lib/jekyll/document.rb#L10

// Note that JS doesn't support the "\A" anchor, which means we can't use

// multiline mode.

// Relevant YAML spec: https://yaml.org/spec/1.2.2/#914-explicit-documents

export const frontMatterRegex = /^-{3}\s*[\n\r](.*?)[\n\r]-{3}\s*[\n\r]+/s;

type FrontMatterMetadata = {

  title?: string;

  // Allows custom display modes. Currently used for compact mode in gantt charts.

  displayMode?: string;

};

/**

 * Extract and parse frontmatter from text, if present, and sets appropriate

 * properties in the provided db.

 * @param text - The text that may have a YAML frontmatter.

 * @param db - Diagram database, could be of any diagram.

 * @returns text with frontmatter stripped out

 */

export function extractFrontMatter(text: string, db: DiagramDb): string {

  const matches = text.match(frontMatterRegex);

  if (matches) {

    const parsed: FrontMatterMetadata = yaml.load(matches[1], {

      // To keep things simple, only allow strings, arrays, and plain objects.

      // https://www.yaml.org/spec/1.2/spec.html#id2802346

      schema: yaml.FAILSAFE_SCHEMA,

    }) as FrontMatterMetadata;

    if (parsed?.title) {

      db.setDiagramTitle?.(parsed.title);

    }

    return text.slice(matches[0].length);

  } else {

    return text;

  }

}