# Module 12 reference engine (TypeScript)

The course's own engine as of the end of Module 12: Module 11's engine (Part I's card engine, Part II's grid engine with conditions, and SpellGrid joining them), with combat and the end of a turn in Part I. Every test from Modules 1–11 still passes. Module 11's reference was the starting point, so a diff between the two shows what this module adds. `course/11-conditions/reference/ts/README.md` and the READMEs it points to describe everything else.

- `cards/` and `levels/` (at the package root; not in this directory): staged by `tools/verify-references.mjs` as for Module 11, plus `course/12-combat/cards/` (`Test Bell`).
- Part I (`src/engine/`):
  - `combat.ts` (new): `attackError(world, attacker, defender)`, the legality rules (a minion in play attacks an enemy character in play, with more than 0 Attack, and a Taunt minion if the defender's side has one), and `TAUNT`.
  - `card.ts`: `Card.keywords`, compiled from keyword clauses. `"endOfTurn"` now fires.
  - `event.ts`: `{ type: "TurnEnded", player }`, which end of turn triggers answer. The course's log doesn't show it.
  - `queue.ts`: the `damage` action carries `hits`, each a target, an amount and a `Priority` (`hits(targets, amount)` builds the usual one-amount list). `react` takes the priority of each event's entries and sorts its Queue by priority, highest first, keeping the order it was filled in within one priority. The `attack` action builds one Damage action: the attacker's Attack to the defender at priority `DEFENDER`, and the defender's Attack (if more than 0) to the attacker at `NORMAL`. The `endTurn` action records `TurnEnded` and resolves the triggers that answer it.
- `src/harness.ts`: `orderAttack(attacker, defender)` (throws an `Error` with the reason if the attack is illegal), `canAttack(attacker, defender): string | null` and `endTurn(player)` on `Game`.
- Part II, Part III and `src/cli.ts`: unchanged from Module 11. SpellGrid doesn't attack. `tools/diff-tracks.mjs` uses this module's CLIs by default.

Run it with the module's tests: `node tools/verify-references.mjs 12` from the course repository.