Crystal/tests/trainer-battle.test.ts

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 { C } from "../src/game/battle/constants";
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))("trainer battles", () => {
  let assets: CrystalAssets, trainers: TrainerData;
  beforeAll(() => {
    assets = new CrystalAssets(new Uint8Array(readFileSync(romPath)));
    trainers = new TrainerData(assets.reader);
  });
  const setup = (level = 15, [classId, id] = [22, 1], species = 155) => {
    // Youngster Joey, level 4 Rattata, unless another trainer is named.
    const trainer = trainers.trainer(classId, id);
    const mon = generatePartyMon(assets.pokemon, {
      species,
      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,
        switchFlags: trainer.attributes.aiItemSwitchFlags,
        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("uses the native damage estimate for Aggressive move scoring", () => {
    const { options } = setup();
    const enemy = options.trainer!.party[0];
    enemy.moves = [33, 98, 0, 0]; // Tackle, Quick Attack
    enemy.pp = enemy.moves.map((move) => move ? assets.pokemon.move(move).pp : 0);
    options.trainer!.aiFlags = 1 << 6;
    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(battle.enemy.curMove).toBe(98);
  });
  it("lets a leftover critical-hit flag alter the AI damage estimate", () => {
    const { options } = setup();
    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;
    }
    const internals = battle as unknown as {
      criticalHit: number;
      enemyAIDamage(move: number): number;
    };
    const plain = internals.enemyAIDamage(33); // Tackle
    battle.player.screens = 1 << C.SCREENS_REFLECT;
    const screened = internals.enemyAIDamage(33);
    // CheckDamageStatsCritical: equal stages select unboosted stats, which
    // ignore Reflect; DamageCalc then doubles the estimate.
    internals.criticalHit = 1;
    const critical = internals.enemyAIDamage(33);
    // Rattata L4 (Atk 10) Tackle into Cyndaquil (Def 18, 36 under Reflect).
    expect([plain, screened, critical]).toEqual([4, 3, 6]);
  });
  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);
  });
  /** Run to the first battle menu; the battle's internals for AI checks. */
  const atMenu = (battle: Battle) => {
    const run = battle.run();
    for (let guard = 0; guard < 20; guard++) {
      const next = run.next();
      if (!next.done && next.value.kind === "action") break;
    }
    return {
      run,
      internals: battle as unknown as {
        curOTMon: number;
        playerUsedMoves: number[];
        findMonInOTPartyToSwitchIntoBattle(): number;
        checkAbleToSwitch(): number;
        aiSwitchOrTryItem(): Generator<{ kind: string; text?: string }, boolean>;
      },
    };
  };
  it("sends out a trainer's next Pokémon with no random draw when a candidate is unthreatened", () => {
    // Totodile's Water type is neutral against Bug Catcher Don's Caterpie.
    const { options } = setup(15, [36, 1], 158);
    const battle = new Battle(options),
      { internals } = atMenu(battle);
    options.trainer!.party[0].hp = 0;
    options.random = () => {
      throw new Error("Unexpected random draw");
    };
    expect(internals.findMonInOTPartyToSwitchIntoBattle()).toBe(1);
  });
  it("draws BattleRandom & 7 when the player's types threaten every candidate", () => {
    // Cyndaquil's Fire type is super effective against the other Caterpie.
    const { options } = setup(15, [36, 1], 155);
    const battle = new Battle(options),
      { internals } = atMenu(battle);
    options.trainer!.party[0].hp = 0;
    const draws = [0x0d, 0x08, 0x02, 0x09];
    options.random = () => draws.shift()!;
    // 5 and 0 (the fainted current Pokémon) and 2 (past the party) retry.
    expect(internals.findMonInOTPartyToSwitchIntoBattle()).toBe(1);
    expect(draws).toEqual([]);
  });
  it("switches out under SWITCH_SOMETIMES using the enemy move type for every matchup", () => {
    const { options } = setup(15, [22, 2]); // Youngster Mikey: Pidgey, Rattata
    const battle = new Battle(options),
      { internals } = atMenu(battle);
    const WATER = 0x15, GROUND = 0x04, GRASS = 0x16;
    // CheckTypeMatchup reads the enemy's move type (here Grass), so it is
    // super effective against the enemy's Water type and the player's Water/Ground.
    battle.player.mon.types = [WATER, GROUND];
    battle.enemy.mon.types = [WATER, WATER];
    battle.enemy.move = { ...battle.enemy.move, type: GRASS };
    const rattata = options.trainer!.party[1];
    // FindEnemyMonsWithAtLeastQuarterMaxHP's rotation: 16 HP gives 4, never
    // above the maximum, while 1 HP gives $200.
    rattata.hp = 16;
    expect(internals.checkAbleToSwitch()).toBe(0);
    rattata.hp = 1;
    expect(internals.checkAbleToSwitch()).toBe(0x11);

    battle.enemy.mon.hp = 3;
    battle.enemy.mon.status = 1 << 3; // poisoned
    const draws = [49];
    options.random = () => draws.shift()!;
    const texts: string[] = [];
    const run = internals.aiSwitchOrTryItem();
    let next = run.next();
    for (; !next.done; next = run.next()) if (next.value.text) texts.push(next.value.text);
    expect(next.value).toBe(true);
    expect(texts.join(" ").replace(/\n/g, " ")).toMatch(/withdrew PIDGEY.*sent out RATTATA/);
    expect(internals.curOTMon).toBe(1);
    expect(battle.enemy.mon.hp).toBe(1);
    // AI_Switch keeps the withdrawn Pokémon's HP and status in the party.
    expect(options.trainer!.party[0]).toMatchObject({ hp: 3, status: 1 << 3 });
  });
  it("records the player's used moves for the switch AI", () => {
    const { options } = setup(15, [22, 2]);
    const battle = new Battle(options),
      { run, internals } = atMenu(battle);
    expect(internals.playerUsedMoves).toEqual([0, 0, 0, 0]);
    run.next({ action: "fight", move: 0 });
    expect(internals.playerUsedMoves).toEqual([options.party[0].moves[0], 0, 0, 0]);
  });
  it("refuses the untranslated Smart AI and empty parties before mutating the party or Pokédex", () => {
    for (const kind of ["empty", "ai"] as const) {
      const { options } = setup();
      if (kind === "empty") options.trainer!.party = [];
      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);
    }
  });
});