function computePlusOneIndentLevel(line, tabSize) {
        var indent = 0;
        var i = 0;
        var len = line.length;
        while (i < len) {
            var chCode = line.charCodeAt(i);
            if (chCode === 32 /* Space */) {
                indent++;
            }
            else if (chCode === 9 /* Tab */) {
                indent = indent - indent % tabSize + tabSize;
            }
            else {
                break;
            }
            i++;
        }
        if (i === len) {
            return 0; // line only consists of whitespace
        }
        return indent + 1;
    }
Returns:
 - 0 => the line consists of whitespace
 - otherwise => the indent level is returned value - 1