Crystal/tests/capture.test.ts

import { beforeAll, describe, expect, it } from "vitest";
import { existsSync, readFileSync } from "node:fs";
import { CrystalAssets } from "../src/game/rom/assets";
import {
  Battle,
  UnsupportedBattle,
  catchRate,
  type BattleInput,
  type BattleOptions,
  type BattleOutcome,
} from "../src/game/battle/battle";
import { C } from "../src/game/battle/constants";
import { generatePartyMon, validPartyMon, type PartyMon } from "../src/game/party/pokemon";
import type { Bag } from "../src/game/party/bag";
import { defaultTextContext } from "../src/game/scripts/text";

const romPath =
  process.env.CRYSTAL_ROM_PATH ?? "Pokemon - Crystal Version (UE) (V1.1) [C][!].gbc";

describe("catch rate formula", () => {
  const none = { effect: 0, parameter: 0 };
  const rate = (input: Partial<Parameters<typeof catchRate>[0]>) =>
    catchRate({ rate: 255, ball: C.POKE_BALL, hp: 20, maxHp: 20, status: 0, held: none, ...input });

  it("follows PokeBallEffect's HP term and ball multipliers", () => {
    expect(rate({})).toBe(85); // 255 * (60 - 40) / 60
    expect(rate({ hp: 1 })).toBe(246); // 255 * 58 / 60
    expect(rate({ rate: 45, ball: C.GREAT_BALL, hp: 10 })).toBe(44); // 67 * 40 / 60
    expect(rate({ rate: 200, ball: C.ULTRA_BALL })).toBe(85); // doubled, capped at 255
    expect(rate({ rate: 1 })).toBe(1); // a zero quotient becomes 1
    // Above 255 (3 * max HP), both terms are divided by four; a zero HP
    // byte becomes 1.
    expect(rate({ hp: 1, maxHp: 100 })).toBe(251); // 255 * (75 - 1) / 75
  });

  it("keeps the original status, held-item and high-HP bugs", () => {
    expect(rate({ status: 1 })).toBe(95); // sleep: +10
    expect(rate({ status: 1 << C.FRZ })).toBe(95);
    for (const status of [1 << 3, 1 << 4, 1 << 6]) expect(rate({ status })).toBe(85); // PSN/BRN/PAR
    expect(rate({ held: { effect: C.HELD_CATCH_CHANCE, parameter: 5 } })).toBe(90);
    // Max HP 400: the low bytes wrap, so a full-HP Pokémon gets 67, not 85.
    expect(rate({ hp: 400, maxHp: 400 })).toBe(67);
    // These maximum HP values divide by zero in the original.
    for (const maxHp of [342, 683]) expect(rate({ hp: maxHp, maxHp })).toBeUndefined();
  });
});

describe.skipIf(!existsSync(romPath))("capture with the local ROM", () => {
  let data: CrystalAssets["pokemon"];
  beforeAll(() => {
    data = new CrystalAssets(new Uint8Array(readFileSync(romPath))).pokemon;
  });
  const RATTATA = 19,
    CYNDAQUIL = 155,
    TACKLE = 33;
  const starter = (): PartyMon => {
    const mon = generatePartyMon(data, {
      species: CYNDAQUIL, level: 5, item: 0, otId: 1234, ot: "CHRIS", dvs: 0x823b, caughtData: 0,
    });
    mon.moves = [TACKLE, 0, 0, 0];
    mon.pp = [35, 0, 0, 0];
    return mon;
  };
  const setup = (options: Partial<BattleOptions> & { seed?: number } = {}) => {
    let seed = options.seed ?? 1,
      draws = 0;
    const bag: Bag = options.bag ?? { items: [], balls: [{ item: C.POKE_BALL, quantity: 5 }], keyItems: [] };
    const pokedex = { seen: new Set<number>(), caught: new Set<number>() };
    const party = options.party ?? [starter()];
    const battle = new Battle({
      data,
      party,
      pokedex,
      playerId: 1234,
      playerName: "CHRIS",
      timeOfDay: 1,
      random: () => {
        draws++;
        seed = (seed * 1103515245 + 12345) >>> 0;
        return (seed >>> 16) & 255;
      },
      wild: { species: RATTATA, level: 3 },
      text: () => defaultTextContext("CHRIS"),
      bag,
      hasPokedex: true,
      caughtData: (level) => 0x4000 | (level << 8) | 1,
      ...options,
    });
    return { battle, bag, pokedex, party, draws: () => draws };
  };
  /** Run a battle: `actions` answer the battle menu, `answers` the Yes/No
   * and naming prompts. Returns the texts and the outcome. */
  const play = (
    battle: Battle,
    actions: BattleInput[],
    answers: BattleInput[] = [],
    until?: () => boolean,
  ) => {
    const run = battle.run();
    const texts: string[] = [];
    let input: BattleInput;
    for (let guard = 0; guard < 2000; guard++) {
      const next = run.next(input);
      input = undefined;
      if (next.done) return { texts, outcome: next.value as BattleOutcome };
      const effect = next.value;
      if (effect.kind === "text") texts.push(effect.text.replace(/\n/g, " "));
      else if (effect.kind === "action") {
        if (until?.() || !actions.length) return { texts, outcome: undefined };
        input = actions.shift();
      } else if (effect.kind === "yesno" || effect.kind === "name") input = answers.shift();
      else if (effect.kind === "forget") input = 4;
    }
    throw new Error("The battle did not finish.");
  };
  const ball = (slot = 0) => ({ action: "item" as const, item: C.POKE_BALL, slot });

  it("catches a wild Pokémon into the party with its original moves, PP and current HP", () => {
    // Weaken it first so the seeded throws succeed.
    for (let seed = 1; seed < 50; seed++) {
      const { battle, bag, pokedex, party } = setup({ seed });
      const { texts, outcome } = play(
        battle,
        [{ action: "fight", move: 0 }, ball(), ball(), ball(), ball(), ball()],
        [1, "RATTY"],
      );
      if (!outcome || party.length !== 2) continue;
      expect(outcome.result).toBe(C.WIN);
      expect(texts).toContain("CHRIS used the POKé BALL.");
      expect(texts.some((text) => text.startsWith("Gotcha! RATTATA was caught!"))).toBe(true);
      expect(texts).toContain("RATTATA's data was newly added to the #DEX.".replace("#", "POKé"));
      expect(texts).toContain("Give a nickname to RATTATA?");
      const caught = party[1];
      const enemy = battle.enemy.mon;
      expect(caught).toMatchObject({
        species: RATTATA,
        nickname: "RATTY",
        level: 3,
        otId: 1234,
        ot: "CHRIS",
        dvs: enemy.dvs,
        hp: enemy.hp,
        status: enemy.status,
        item: enemy.item,
        happiness: C.BASE_HAPPINESS,
        caughtData: 0x4000 | (3 << 8) | 1,
        exp: data.expAtLevel(data.baseData(RATTATA).growthRate, 3),
        statExp: [0, 0, 0, 0, 0],
      });
      expect(caught.hp).toBeLessThan(caught.stats[0]);
      // wWildMonMoves and wWildMonPP: the moves it appeared with, less the
      // PP it spent in the battle (DoTurn consumes wWildMonPP too).
      const full = caught.moves.map((move) => (move ? data.move(move).pp : 0));
      expect(caught.pp).toEqual(enemy.pp);
      expect(caught.pp.reduce((a, b) => a + b, 0)).toBeLessThan(full.reduce((a, b) => a + b, 0));
      expect(validPartyMon(data, caught)).toBe(true);
      expect(pokedex.caught.has(RATTATA)).toBe(true);
      const thrown = texts.filter((text) => text === "CHRIS used the POKé BALL.").length;
      expect(bag.balls).toEqual(thrown === 5 ? [] : [{ item: C.POKE_BALL, quantity: 5 - thrown }]);
      return;
    }
    throw new Error("No seed caught the Pokémon.");
  });

  it("uses the turn when the Pokémon breaks free, with the wobble message", () => {
    const messages = [
      "Oh no! The POKéMON broke free!",
      "Aww! It appeared to be caught!",
      "Aargh! Almost had it!",
      "Shoot! It was so close too!",
    ];
    const seen = new Set<string>();
    for (let seed = 1; seed < 200 && seen.size < 4; seed++) {
      const { battle, bag, party } = setup({ seed });
      const { texts } = play(battle, [ball()], [], () => bag.balls[0]?.quantity === 4);
      if (party.length !== 1) continue;
      const failure = messages.find((message) => texts.includes(message));
      expect(failure, texts.join(" | ")).toBeDefined();
      seen.add(failure!);
      // The wild Pokémon then moves, and the ball is gone.
      expect(texts.some((text) => text.startsWith("Enemy RATTATA used")), texts.join(" | ")).toBe(true);
      expect(bag.balls).toEqual([{ item: C.POKE_BALL, quantity: 4 }]);
    }
    expect(seen.size).toBe(4);
  });

  it("catches with a Master Ball without drawing a catch or wobble random", () => {
    const { battle, bag, party, draws } = setup({
      bag: { items: [], balls: [{ item: C.MASTER_BALL, quantity: 1 }], keyItems: [] },
    });
    let before = 0;
    const run = battle.run();
    let input: BattleInput;
    for (let guard = 0; guard < 100; guard++) {
      const next = run.next(input);
      input = undefined;
      if (next.done) break;
      if (next.value.kind === "action") {
        before = draws();
        input = { action: "item", item: C.MASTER_BALL, slot: 0 };
      } else if (next.value.kind === "yesno") input = 0;
    }
    // Only LoadEnemyMon's wild item roll (one or two draws) remains.
    expect(draws() - before).toBeGreaterThanOrEqual(1);
    expect(draws() - before).toBeLessThanOrEqual(2);
    expect(party).toHaveLength(2);
    expect(party[1].nickname).toBe("RATTATA");
    expect(bag.balls).toEqual([]);
  });

  it("keeps the species name for a blank nickname and skips the Pokédex text without a Pokédex", () => {
    const { battle, party } = setup({
      hasPokedex: false,
      bag: { items: [], balls: [{ item: C.MASTER_BALL, quantity: 1 }], keyItems: [] },
    });
    const { texts } = play(battle, [{ action: "item", item: C.MASTER_BALL, slot: 0 }], [1, "   "]);
    expect(party[1].nickname).toBe("RATTATA");
    expect(texts.join(" ")).not.toContain("newly added");
  });

  it("ignores a slot that does not hold the ball", () => {
    const { battle, bag } = setup();
    const { outcome } = play(battle, [{ action: "item", item: C.GREAT_BALL, slot: 0 }, { action: "run" }]);
    expect(outcome).toBeDefined();
    expect(bag.balls).toEqual([{ item: C.POKE_BALL, quantity: 5 }]);
  });

  it("refuses to send a Pokémon to the PC with a full party", () => {
    const { battle } = setup({ party: Array.from({ length: 6 }, starter) });
    expect(() => play(battle, [ball()])).toThrow(UnsupportedBattle);
  });

  it("blocks balls in trainer battles and still uses the ball and turn", () => {
    const joey = generatePartyMon(data, {
      species: RATTATA, level: 2, item: 0, otId: 0, ot: "JOEY", dvs: 0x9888, caughtData: 0,
    });
    const { battle, bag, party } = setup({
      trainer: {
        name: "JOEY", className: "YOUNGSTER", party: [joey], aiFlags: 0, switchFlags: 0, reward: 10,
      },
    });
    const { texts } = play(battle, [ball()], [], () => bag.balls[0]?.quantity === 4);
    expect(texts).toContain("The trainer blocked the BALL!");
    expect(texts).toContain("Don't be a thief!");
    expect(texts.join(" ")).not.toContain("used the POKé BALL");
    expect(texts.some((text) => text.includes("RATTATA used"))).toBe(true);
    expect(bag.balls).toEqual([{ item: C.POKE_BALL, quantity: 4 }]);
    expect(party).toHaveLength(1);
  });

  it("runs the Dude's tutorial without touching the player's party or pack", () => {
    const { battle, bag, party, pokedex } = setup({ tutorial: true, bag: undefined });
    const { texts, outcome } = play(battle, []);
    expect(outcome?.result).toBe(C.WIN);
    expect(texts).toEqual([
      "Wild RATTATA appeared!",
      "DUDE used the POKé BALL.",
      "Gotcha! RATTATA was caught!",
    ]);
    expect(party).toHaveLength(1);
    expect(bag.balls).toEqual([{ item: C.POKE_BALL, quantity: 5 }]);
    expect(pokedex.seen.has(RATTATA)).toBe(true);
    expect(pokedex.caught.has(RATTATA)).toBe(false);
    expect(battle.player.mon).toBeUndefined();
  });
});