Bowling Game: State Machine: Std::Variant: Step 29

To get the perfect game test to pass we need to add a couple of states, the WaitingForFirstRollWith3Bonuses and LastFrameWith2Bonuses states, like so:

        struct WaitingForFirstRollWith2Bonuses
        {
            State Update(int pins, int& score, int& frame) const
            {
                score += pins*2;
                if (pins == 10) {
                    ++frame;
                    return WaitingForFirstRollWith3Bonuses{};
                }
                return WaitingForSecondRollWith1Bonus{pins};
            }
        };
        struct WaitingForFirstRollWith3Bonuses
        {
            State Update(int pins, int& score, int& frame) const
            {
                score += pins*3;
                if (pins == 10) {
                    ++frame;
                    if (frame == 10)
                        return LastFrameWith2Bonuses{};
                    return WaitingForFirstRollWith3Bonuses{};
                }
                return WaitingForSecondRollWith1Bonus{pins};
            }
        };
        struct LastFrameWith1Bonus
        {
            State Update(int pins, int& score, int& /*frame*/) const
            {
                score += pins;
                return GameOver{};
            }
        };
        struct LastFrameWith2Bonuses
        {
            State Update(int pins, int& score, int& /*frame*/) const
            {
                score += pins*2;
                if (pins == 10)
                    return LastFrameWith1Bonus{};
                return GameOver{};
            }
        };

Now, I see if (pins == 10) multiple times in the code, and that could be replaced with a well-named method in an extracted base class. Let’s do that refactoring and then click next.