react-native-devtools-frontend/front_end/sdk/CSSPropertyParser.js

// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

const globalValues = new Set(['inherit', 'initial', 'unset']);

const tagRegexp = /[\x20-\x7E]{4}/;
const numRegexp = /[+-]?(?:\d*\.)?\d+(?:[eE]\d+)?/;
const fontVariationSettingsRegexp =
    new RegExp(`(?:'(${tagRegexp.source})')|(?:"(${tagRegexp.source})")\\s+(${numRegexp.source})`);

/**
 * Extracts information about font variation settings assuming
 * value is valid according to the spec: https://drafts.csswg.org/css-fonts-4/#font-variation-settings-def
 *
 * @param {string} value A valid CSS font-variation-settings property value
 * @return {!Array<!{tag:string, value:number}>}
 */
export function parseFontVariationSettings(value) {
  if (globalValues.has(value.trim()) || value.trim() === 'normal') {
    return [];
  }
  const results = [];
  for (const setting of splitByComma(stripComments(value))) {
    const match = setting.match(fontVariationSettingsRegexp);
    if (match) {
      results.push({
        tag: match[1] || match[2],    // Tag name match.
        value: parseFloat(match[3]),  // Tag value.
      });
    }
  }
  return results;
}

// "str" or 'str'
const fontFamilyRegexp = /^"(.+)"|'(.+)'$/;

/**
 * Extracts font families assuming the value is valid according to
 * the spec: https://drafts.csswg.org/css-fonts-4/#font-family-prop
 *
 * @param {string} value A valid CSS font-family property value
 * @return {!Array<string>}
 */
export function parseFontFamily(value) {
  if (globalValues.has(value.trim())) {
    return [];
  }
  const results = [];
  for (const family of splitByComma(stripComments(value))) {
    const match = family.match(fontFamilyRegexp);
    if (match) {
      // Either the 1st or 2nd group matches if the value is in quotes
      results.push(match[1] || match[2]);
    } else {
      // Value without without quotes.
      results.push(family);
    }
  }
  return results;
}

/**
 * Splits a list of values by comma and trims parts
 * @param {string} value
 * @return {!Array<string>}
 */
export function splitByComma(value) {
  return value.split(',').map(part => part.trim());
}

/**
 * @param {string} value
 * @return {string}
 */
export function stripComments(value) {
  return value.replaceAll(/(\/\*(?:.|\s)*?\*\/)/g, '');
}