JohnCashmore/node-fonts-used

/**
   * @enum {number}
   */
  var states = {
    VARIATION: 1,
    LINE_HEIGHT: 2,
    FONT_FAMILY: 3
  };

  /**
   * @param {string} input
   * @return {Object}
   */
  function parse(input) {
    var state = states.VARIATION,
        buffer = '',
        result = {
          'font-family': []
        };

    for (var c, i = 0; c = input.charAt(i); i += 1) {
      if (state === states.FONT_FAMILY && (c === '"' || c === "'")) {
        var index = i + 1;

        // consume the entire string
        do {
          index = input.indexOf(c, index) + 1;
          if (!index) {
            // If a string is not closed by a ' or " return null.
            // TODO: Check to see if this is correct.
            return null;
          }
        } while (input.charAt(index - 2) === '\\');

        result['font-family'].push(input.slice(i + 1, index - 1).replace(/\\('|")/g, "$1"));

        i = index - 1;
        buffer = '';
      } else if (state === states.FONT_FAMILY && c === ',') {
        if (!/^\s*$/.test(buffer)) {
          result['font-family'].push(buffer.replace(/^\s+|\s+$/, '').replace(/\s+/g, ' '));
          buffer = '';
        }
      } else if (state === states.VARIATION && (c === ' ' || c === '/')) {
        if (/^((xx|x)-large|(xx|s)-small|small|large|medium)$/.test(buffer) ||
            /^(larg|small)er$/.test(buffer) ||
            /^(\+|-)?([0-9]*\.)?[0-9]+(em|ex|ch|rem|vh|vw|vmin|vmax|px|mm|cm|in|pt|pc|%)$/.test(buffer)) {
          state = c === '/' ? states.LINE_HEIGHT : states.FONT_FAMILY;
          result['font-size'] = buffer;
        } else if (/^(italic|oblique)$/.test(buffer)) {
          result['font-style'] = buffer;
        } else if (/^small-caps$/.test(buffer)) {
          result['font-variant'] = buffer;
        } else if (/^(bold(er)?|lighter|[1-9]00)$/.test(buffer)) {
          result['font-weight'] = buffer;
        } else if (/^((ultra|extra|semi)-)?(condensed|expanded)$/.test(buffer)) {
          result['font-stretch'] = buffer;
        }
        buffer = '';
      } else if (state === states.LINE_HEIGHT && c === ' ') {
        if (/^(\+|-)?([0-9]*\.)?[0-9]+(em|ex|ch|rem|vh|vw|vmin|vmax|px|mm|cm|in|pt|pc|%)?$/.test(buffer)) {
          result['line-height'] = buffer;
        }
        state = states.FONT_FAMILY;
        buffer = '';
      } else {
        buffer += c;
      }
    }

    if (state === states.FONT_FAMILY && !/^\s*$/.test(buffer)) {
      result['font-family'].push(buffer.replace(/^\s+|\s+$/, '').replace(/\s+/g, ' '));
    }

    if (result['font-size'] && result['font-family'].length) {
      return result;
    } else {
      return null;
    }
  }

module.exports = parse;