Json parse_json()

in GomokuServer/GomokuServer/json11.cpp [644:728]
67 lines of code
25 McCabe index (conditional complexity)

    Json parse_json(int depth) {
        if (depth > max_depth) {
            return fail("exceeded maximum nesting depth");
        }

        char ch = get_next_token();
        if (failed)
            return Json();

        if (ch == '-' || (ch >= '0' && ch <= '9')) {
            i--;
            return parse_number();
        }

        if (ch == 't')
            return expect("true", true);

        if (ch == 'f')
            return expect("false", false);

        if (ch == 'n')
            return expect("null", Json());

        if (ch == '"')
            return parse_string();

        if (ch == '{') {
            map<string, Json> data;
            ch = get_next_token();
            if (ch == '}')
                return data;

            while (1) {
                if (ch != '"')
                    return fail("expected '\"' in object, got " + esc(ch));

                string key = parse_string();
                if (failed)
                    return Json();

                ch = get_next_token();
                if (ch != ':')
                    return fail("expected ':' in object, got " + esc(ch));

                data[std::move(key)] = parse_json(depth + 1);
                if (failed)
                    return Json();

                ch = get_next_token();
                if (ch == '}')
                    break;
                if (ch != ',')
                    return fail("expected ',' in object, got " + esc(ch));

                ch = get_next_token();
            }
            return data;
        }

        if (ch == '[') {
            vector<Json> data;
            ch = get_next_token();
            if (ch == ']')
                return data;

            while (1) {
                i--;
                data.push_back(parse_json(depth + 1));
                if (failed)
                    return Json();

                ch = get_next_token();
                if (ch == ']')
                    break;
                if (ch != ',')
                    return fail("expected ',' in list, got " + esc(ch));

                ch = get_next_token();
                (void)ch;
            }
            return data;
        }

        return fail("expected value, got " + esc(ch));
    }