Create BallState class and use this to store ball state

[MathewMacDougall]

Description of the task

Create a BallState class to store all existing ball state at a single point in time, and have the Ball class store a buffer of BallState in order to preserver history.

Outline the task in more detail

Currently, we store the history of the ball state by maintaining a buffer of previous positions, velocities, timestamps, etc. Maintaining a buffer for each member variable is cumbersome, and opens us up for mistakes since we don't have guarantees that the buffers will all be the same length. (So for example you can't loop over one buffer and access data in another buffer at the same index, because one might be longer than the other).

Therefore, we think it's better to separate the "state" of the ball, and the class that stores state.

A new BallState class should be created, that represents a ball's state at a single point in time / aka a single timestamp. This new class will not have any buffers, but will still have the same member variables like position, 'velocity', 'timestamp'.

The current Ball class should then store a single buffer of BallStates in order to store history. The Ball class should still expose the same interface for getting the current data. Eg. ball.position(), ball.velocity() should still exist.

The only function related to the ball's "state history" should be "getBallStateHistory" which returns the values in the buffer.

There should be very few places, if any, that currently use the Ball's getPreviousPositions() functions. This should make changing the classes relatively safe since they expose the same interface.

Tests will need to be updated. Most existing Ball tests would just become BallState tests now. The new Ball class would need tests to make sure it returns the correct position, velocity values (ie. making sure we're returning from the right end of the buffer), and that the history it returns is expected.

Acceptance criteria

• [ ] ICreate a new BallState class
• [ ] Implement the BallState class
• [ ] Update unit tests for the BallState class
• [ ] Update the Ball class to use BallState
• [ ] Update unit tests for the new Ball class

[garethellis0]

@jared-paul - this is finished right? Please close if so, or leave a comment with remaining work to do if there is any.

[garethellis0]

@jared-paul ?

[jared-paul]

Yep this is finished, sorry about that