function caseFoldCharset()

in content/resources/js/prettify.js [276:346]
63 lines of code
16 McCabe index (conditional complexity)

    function caseFoldCharset(charSet) {
      var charsetParts = charSet.substring(1, charSet.length - 1).match(
          new RegExp(
              '\\\\u[0-9A-Fa-f]{4}'
              + '|\\\\x[0-9A-Fa-f]{2}'
              + '|\\\\[0-3][0-7]{0,2}'
              + '|\\\\[0-7]{1,2}'
              + '|\\\\[\\s\\S]'
              + '|-'
              + '|[^-\\\\]',
              'g'));
      var groups = [];
      var ranges = [];
      var inverse = charsetParts[0] === '^';
      for (var i = inverse ? 1 : 0, n = charsetParts.length; i < n; ++i) {
        var p = charsetParts[i];
        if (/\\[bdsw]/i.test(p)) {  // Don't muck with named groups.
          groups.push(p);
        } else {
          var start = decodeEscape(p);
          var end;
          if (i + 2 < n && '-' === charsetParts[i + 1]) {
            end = decodeEscape(charsetParts[i + 2]);
            i += 2;
          } else {
            end = start;
          }
          ranges.push([start, end]);
          // If the range might intersect letters, then expand it.
          // This case handling is too simplistic.
          // It does not deal with non-latin case folding.
          // It works for latin source code identifiers though.
          if (!(end < 65 || start > 122)) {
            if (!(end < 65 || start > 90)) {
              ranges.push([Math.max(65, start) | 32, Math.min(end, 90) | 32]);
            }
            if (!(end < 97 || start > 122)) {
              ranges.push([Math.max(97, start) & ~32, Math.min(end, 122) & ~32]);
            }
          }
        }
      }

      // [[1, 10], [3, 4], [8, 12], [14, 14], [16, 16], [17, 17]]
      // -> [[1, 12], [14, 14], [16, 17]]
      ranges.sort(function (a, b) { return (a[0] - b[0]) || (b[1]  - a[1]); });
      var consolidatedRanges = [];
      var lastRange = [NaN, NaN];
      for (var i = 0; i < ranges.length; ++i) {
        var range = ranges[i];
        if (range[0] <= lastRange[1] + 1) {
          lastRange[1] = Math.max(lastRange[1], range[1]);
        } else {
          consolidatedRanges.push(lastRange = range);
        }
      }

      var out = ['['];
      if (inverse) { out.push('^'); }
      out.push.apply(out, groups);
      for (var i = 0; i < consolidatedRanges.length; ++i) {
        var range = consolidatedRanges[i];
        out.push(encodeEscape(range[0]));
        if (range[1] > range[0]) {
          if (range[1] + 1 > range[0]) { out.push('-'); }
          out.push(encodeEscape(range[1]));
        }
      }
      out.push(']');
      return out.join('');
    }