logos.js

var path = require('path');
var fs = require('fs');
var crypto = require('crypto');

var readmeFile = fs.readFileSync(path.resolve(__dirname, 'README.md'));
var metasPattern = /(^<(?:link|meta).+>$)/mig;
var metas = readmeFile.toString().match(metasPattern);

/**
 * @typedef ?Config 
 * 
 * @prop title {String}
 * @prop url {String}
 */
var config = null;

function metasFilesFilter(input) {
  const regExp = /property="og:(?!image)/;
  return !regExp.test(input);
}

function getMetas(processFilename) {
  function processor(meta) {
    return meta.replace(/((?:href|content)=")([^"#]+)(")/, function (match, prefix, file, suffix) {
      return prefix +  processFilename(file) + suffix;
    });
  }

  function filterOGPropsOut(input) {
    const regExp = /property="og:/;
    return !regExp.test(input);
  }

  if (!config) {
    let _metas = metas.filter(filterOGPropsOut);
    return processFilename ?
      _metas.map(processor) :
      _metas;
  } else {
    return processFilename ?
      metas.map(meta => metasFilesFilter(meta) ? processor(meta) : meta) :
      metas;
  }
}

function getFiles(product) {
  if (typeof product !== 'string') {
    throw new Error('Product directory name is required as argument');
  }

  function resolve(file) {
    return path.resolve(__dirname, product, file);
  }

  var files = [];

  getMetas(function(file) {
    files.push(resolve(file));
  });

  return files;
}
/**
 * @param {String} folderName containing files
 * @param {Boolean|Function} [hash] function or MD5 hash of file contents if `true`
 * @param {Function} [processFilename] function to pass to `getMetas` internal call
 */
function getInfo(folderName, hash, processFilename) {
  /**
   * @param {string} fileWithPath
   */
  var defaultHashGenerator = function(fileWithPath) {
    var md5sum = crypto.createHash('md5');
    md5sum.update(fs.readFileSync(fileWithPath));
    return md5sum.digest('hex');
  };

  const processMeta = function(meta) {
    var item = {meta: meta};
    var fileName = meta.replace(/^.*((?:href|content)=")([^"#]+)(").*$/, '\$2');

    if (fileName !== meta) {
      var fileWithPath = path.resolve(__dirname, folderName, fileName);
      item.file = fileWithPath;

      if (hash) {
        item.hash = typeof hash === 'function' ?
          hash(fileWithPath) :
          defaultHashGenerator(fileWithPath);
        
        item.meta = item.meta.replace(/((?:href|content)=")([^"#]+)(")/, function (match, prefix, file, suffix) {
          return prefix + file + '?' + item.hash + suffix;
        });
      }
    }

    return item;
  };

  return getMetas(processFilename)
    .filter(metasFilesFilter)
    .map(processMeta);
}

function configure(configuration) {
  if (!configuration || !configuration.url || !configuration.title) {
    throw new Error('Both `url` and `title` parameters are required');
  }

  metas = metas.map(meta => meta
    .replace('%website_title%', configuration.title)
    .replace('%website_url%', configuration.url));

  return config = Object.assign(config || {}, configuration);
}

module.exports = {
  getMetas: getMetas,
  getFiles: getFiles,
  getInfo: getInfo,
  configure: configure
};