Resolves #73

[RickFqt]

Resolves #73. When complete, this pull request should have:

• [x] Implementation of ProtossState, TerranState, and ZergState classes.
• [x] Implementation of unit tests for these classes.

[RickFqt]

@alvarofpp For the implementation of TerranState class, I used Simple64GridState class from the original sc2 state classes from urnai as a base. It basically stores information from the player (number of units, barracks and minerals, for example), and also builds a 4x4 grid that stores the location of enemy units. Do you think there is a better choice? I considered choosing UnitStackingState as a base since it is pretty well commented, but it seemed to me that it is too specific for a general purpose class.

Also, I implemented the methods get_my_units_amount and get_units_by_type at the end of the file. Is that right?

[alvarofpp]

@RickFqt Please mark as solved the modifications that you have already solved.

[RickFqt]

Many parts of the code have "magic numbers" (values without an explicit definition). I listed a few in the review, but I think you should create a file with constants to map them all.

Should this new file be on the path sc2/states/ as well?

[alvarofpp]

Should this new file be on the path sc2/states/ as well?

I don't think so. Constants are generally used in many parts of the project, so it is recommended to apply them to a single file or use Enum to give them more context.

[RickFqt]

I don't think so. Constants are generally used in many parts of the project, so it is recommended to apply them to a single file or use Enum to give them more context.

In that case, is the path urnai/constants.py a good choice? On the previous version, it was located on urnai/utils/constants.py, but I think we are not using utils anymore, right?

[alvarofpp]

In that case, is the path urnai/constants.py a good choice?

Yes.