My JavaScript / TypeScript bot for the Halite 2 programming challenge.

I did not work on it for more than a few weeks and it did not reach a high rank. Still, there are a few interesting things in this repo, namely the typings I created and the quite nice integration of halite tooling.

typings/halite.d.ts defines TypeScript typings for the halite JavaScript library. They define the basic data types of the game objects, such as Planet, Ship, Point, GameMap, etc. But they also define "virtual" types, such as OwnPlanet, PlayerId, EnemyPlayerId, EnemyShip, etc.

Those allow for smart type checking that e.g. catches attempting to dock a ship without checking that it can dock that specific planet (Dockable), or attempting to command an enemy ship.

They also provide type inference, e.g. GameMap.myShips is of type OwnShip[], OwnShip.ownerId is of type number & OwnPlayerId, Planet.isOwnedByMe() is of type this is OwnPlanet<Turn>, OwnPlanet.isOwnedByMe() is of type true, GameMap.shipById(EnemyShipId) is of type EnemyShip while GameMap.shipById(number) is of type Ship | undefined, etc.

The Turn type variable that is present on many types ensures that game objects are not saved outside of the strategy function and later reused in an unsafe way, because the capture cannot escape the strategy function. Of course, all these type checks could be annulled by using unsafe things like the any type.

Check out the typings file for more, and try to introduce some errors related to these types on purpose and see if TypeScript catches them :) There is also src/guards.ts, which implements some type guards that are "missing" in the standard halite library, namely findPlanetById and shipBelongsToPlayer with lots of overloads.

First, run yarn to install the dependencies. These are some of the scripts defined in the package.json:

• yarn all - run all checks and build
• yarn lint - lint the code
• yarn typecheck - typecheck using TSC
• yarn test - run tests (interactive)
• yarn build - bundle the code (dist folder)
• yarn start - let 4 instances of the bot (from dist folder) play against each other
• yarn view replays/xyz - view a replay
• yarn run versions - build the git revisions specified on the lines of versions.txt and let them compete until interrupted