Add scripted trainer battle foundation and native move AI

tests/trainer-battle.test.ts

@@ -0,0 +1,151 @@
+import { beforeAll, describe, expect, it } from "vitest";
+import { existsSync, readFileSync } from "node:fs";
+import { CrystalAssets } from "../src/game/rom/assets";
+import { TrainerData } from "../src/game/rom/trainers";
+import {
+  Battle,
+  UnsupportedBattle,
+  type BattleInput,
+  type BattleOptions,
+} from "../src/game/battle/battle";
+import { generatePartyMon } from "../src/game/party/pokemon";
+import { defaultTextContext } from "../src/game/scripts/text";
+
+const romPath =
+  process.env.CRYSTAL_ROM_PATH ??
+  "Pokemon - Crystal Version (UE) (V1.1) [C][!].gbc";
+describe.skipIf(!existsSync(romPath))("single-Pokémon trainer battles", () => {
+  let assets: CrystalAssets, trainers: TrainerData;
+  beforeAll(() => {
+    assets = new CrystalAssets(new Uint8Array(readFileSync(romPath)));
+    trainers = new TrainerData(assets.reader);
+  });
+  const setup = (level = 15) => {
+    const trainer = trainers.trainer(22, 1); // Youngster Joey, level 4 Rattata.
+    const mon = generatePartyMon(assets.pokemon, {
+      species: 155,
+      level,
+      item: 0,
+      otId: 1234,
+      ot: "CHRIS",
+      dvs: 0x823b,
+      caughtData: 0,
+    });
+    let seed = 1;
+    const options: BattleOptions = {
+      data: assets.pokemon,
+      party: [mon],
+      playerId: 1234,
+      playerName: "CHRIS",
+      timeOfDay: 1,
+      pokedex: { seen: new Set(), caught: new Set() },
+      random: () => {
+        seed = (seed * 1103515245 + 12345) >>> 0;
+        return (seed >>> 16) & 255;
+      },
+      text: () => defaultTextContext("CHRIS"),
+      trainer: {
+        name: trainer.name,
+        className: trainer.className,
+        party: trainers.createParty(trainer),
+        aiFlags: trainer.attributes.aiMoveFlags,
+        reward: trainer.reward,
+      },
+    };
+    return { mon, options };
+  };
+  const finish = (battle: Battle, runFirst = false) => {
+    const gen = battle.run();
+    const texts: string[] = [];
+    let input: BattleInput,
+      triedRun = false;
+    for (let guard = 0; guard < 2000; guard++) {
+      const next = gen.next(input);
+      if (next.done)
+        return { ...next.value, texts: texts.join(" ").replace(/\n/g, " ") };
+      const effect = next.value;
+      input = undefined;
+      if (effect.kind === "text") texts.push(effect.text);
+      if (effect.kind === "action") {
+        input =
+          runFirst && !triedRun
+            ? { action: "run" }
+            : { action: "fight", move: 0 };
+        triedRun = true;
+      }
+      if (effect.kind === "yesno") input = 0;
+      if (effect.kind === "forget") input = 4;
+    }
+    throw new Error("Battle did not finish.");
+  };
+  it("announces the trainer, refuses escape without spending a turn, and awards trainer experience and money", () => {
+    const direct = setup(),
+      escape = setup();
+    const before = direct.mon.exp;
+    const won = finish(new Battle(direct.options));
+    const escaped = finish(new Battle(escape.options), true);
+    expect(won.result).toBe(0);
+    expect(won.prizeMoney).toBe(64);
+    expect(won.texts).toContain("YOUNGSTER JOEY wants to battle!");
+    expect(won.texts).toContain("sent out RATTATA!");
+    expect(won.texts).toContain("was defeated!");
+    expect(won.texts).toContain("CHRIS got ¥64");
+    expect(escaped.texts).toContain("trainer battle");
+    expect(escape.mon).toEqual(direct.mon);
+    expect(direct.mon.exp - before).toBe(48); // floor(57 * 4 / 7), then 1.5x.
+    expect(direct.options.pokedex.seen.has(19)).toBe(true);
+  });
+  it("doubles prize money when the active Pokémon holds an Amulet Coin", () => {
+    const { mon, options } = setup();
+    mon.item = 0x5b;
+    const result = finish(new Battle(options));
+    expect(result.prizeMoney).toBe(128);
+    expect(result.texts).toContain("CHRIS got ¥128");
+  });
+  it("scores exhausted trainer moves before the menu, then uses Struggle", () => {
+    const { options } = setup();
+    options.trainer!.party[0].pp.fill(0);
+    let draws = 0;
+    options.random = () => { draws++; return 0; };
+    const battle = new Battle(options), run = battle.run();
+    for (let guard = 0; guard < 20; guard++) {
+      const next = run.next();
+      if (!next.done && next.value.kind === "action") break;
+    }
+    expect(draws).toBeGreaterThan(0);
+    // The AI selected a normal move despite exhausted PP; ParseEnemyAction
+    // replaces it before the first attack, as the cartridge does.
+    expect(battle.enemy.curMove).toBe(33);
+    run.next({ action: "fight", move: 0 });
+    expect(battle.enemy.curMove).toBe(165);
+  });
+  it("loses without receiving prize money", () => {
+    const { mon, options } = setup(2);
+    mon.hp = 1;
+    const lost = finish(new Battle(options));
+    expect(lost.result).toBe(1);
+    expect(lost.prizeMoney).toBeUndefined();
+    expect(mon.hp).toBe(0);
+  });
+  it("heals the party after a CANLOSE victory", () => {
+    const { mon, options } = setup();
+    options.canLose = true;
+    mon.hp--;
+    finish(new Battle(options));
+    expect(mon.hp).toBe(mon.stats[0]);
+    expect(mon.status).toBe(0);
+    expect(mon.pp[0]).toBe(assets.pokemon.move(mon.moves[0]).pp);
+  });
+  it("refuses unported party switching and AI before mutating the party or Pokédex", () => {
+    for (const kind of ["party", "ai"] as const) {
+      const { options } = setup();
+      if (kind === "party")
+        options.trainer!.party.push(structuredClone(options.trainer!.party[0]));
+      else options.trainer!.aiFlags |= 1 << 4;
+      const before = structuredClone(options.party);
+      expect(() => new Battle(options).run().next()).toThrow(UnsupportedBattle);
+      expect(options.party).toEqual(before);
+      expect(options.pokedex.seen.size).toBe(0);
+    }
+  });
+});