index.ts

import deepmerge from 'deepmerge';
import Metalsmith from 'metalsmith';
import readingTime, { Options as ReadingTimeOptions } from 'reading-time';

export interface Options {
  pattern?: string;
  stripHtml?: boolean;
  replacements?: [string | RegExp, string][];
  readingTime?: ReadingTimeOptions;
}

export default (options: Options = {}): Metalsmith.Plugin => {
  const defaultedOptions = deepmerge(
    {
      pattern: '**/*',
      stripHtml: true,
      replacements: [],
      readingTime: {},
    } satisfies Options,
    options || {},
  );

  return (files, metalsmith, done) => {
    const debug = metalsmith.debug('metalsmith-reading time');
    debug('running with options: %O', defaultedOptions);

    // For each file that matches the given pattern
    metalsmith.match(defaultedOptions.pattern, Object.keys(files)).forEach((filename) => {
      debug('processing file: %s', filename);

      let contents = files[filename].contents.toString();

      if (defaultedOptions.stripHtml) {
        contents = contents
          // XML
          .replace(/<\?xml[^>]+\?>/gs, ' ') // namespaces
          .replace(/<!--.*?-->/gs, ' ') // comments
          // HTML
          .replace(/<[a-zA-Z0-9]+[^>]*>/gs, ' ') // start tag
          .replace(/<\/[a-zA-Z0-9]+>/gs, ' ') // end tag
          .trim();
      }

      if (defaultedOptions.replacements && defaultedOptions.replacements.length) {
        defaultedOptions.replacements.forEach((replacement) => {
          let pattern = replacement[0];
          if (typeof pattern === 'string') {
            const matches = pattern.match(/^\/(.+)\/([a-z]*)/);
            if (matches) {
              pattern = new RegExp(matches[1], matches[2]);
            }
          }

          contents = contents.replace(pattern, replacement[1]);
        });
      }

      files[filename].readingTime = readingTime(contents, defaultedOptions.readingTime).text;
    });

    done();
  };
};