Crystal/tests/battle-switch.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 } from "../src/game/battle/battle";
import { C } from "../src/game/battle/constants";
import type { PartyMon } from "../src/game/party/pokemon";
import { battleOptions, partyMon, playBattle } from "./battle-driver";

const romPath =
  process.env.CRYSTAL_ROM_PATH ??
  "Pokemon - Crystal Version (UE) (V1.1) [C][!].gbc";
const PIDGEY = 16,
  RATTATA = 19,
  CYNDAQUIL = 155,
  TOTODILE = 158;

describe.skipIf(!existsSync(romPath))("switching Pokémon in battle", () => {
  let assets: CrystalAssets, trainers: TrainerData;
  beforeAll(() => {
    assets = new CrystalAssets(new Uint8Array(readFileSync(romPath)));
    trainers = new TrainerData(assets.reader);
  });
  const mon = (species: number, level: number) =>
    partyMon(assets, species, level);
  const options = (
    party: PartyMon[],
    enemy: Parameters<typeof battleOptions>[3],
    seed = 1,
  ) => battleOptions(assets, trainers, party, enemy, { seed });
  const play = playBattle;

  it("switches from the PKMN menu: the enemy still attacks and both share the experience", () => {
    const first = mon(CYNDAQUIL, 10),
      second = mon(TOTODILE, 10);
    const battle = new Battle(
      options([first, second], { wild: { species: PIDGEY, level: 3 } }),
    );
    const { texts, prompts } = play(battle, {
      action: [{ action: "pkmn" }],
      party: [0, 1],
    });
    expect(prompts[1]).toEqual({
      kind: "party",
      text: "Choose a POKéMON.",
      menu: true,
      cancel: true,
    });
    const switched = texts.indexOf("CYNDAQUIL is already out.");
    expect(switched).toBeGreaterThan(0);
    // The enemy's HP is untouched, so the withdrawal is "that's enough".
    expect(texts.slice(switched + 1, switched + 4)).toEqual([
      "CYNDAQUIL, that's enough! Come back!",
      "Go! TOTODILE!",
      expect.stringMatching(/^Enemy PIDGEY used /),
    ]);
    expect(battle.curBattleMon).toBe(1);
    expect(battle.lastPlayerMon).toBe(0);
    // Base experience 55 × level 3 ÷ 7 = 23, halved for two participants.
    expect(texts).toContain("CYNDAQUIL gained 11 EXP. Points!");
    expect(texts).toContain("TOTODILE gained 11 EXP. Points!");
  });

  it("goes back to the battle menu when the party menu is cancelled", () => {
    const battle = new Battle(
      options([mon(CYNDAQUIL, 10), mon(TOTODILE, 10)], {
        wild: { species: PIDGEY, level: 3 },
      }),
    );
    const { prompts, texts } = play(battle, {
      action: [{ action: "pkmn" }],
      party: [-1],
    });
    expect(prompts.slice(0, 3).map((prompt) => prompt.kind)).toEqual([
      "action",
      "party",
      "action",
    ]);
    expect(texts).toContain("CYNDAQUIL gained 23 EXP. Points!");
    expect(battle.curBattleMon).toBe(0);
  });

  it("measures the withdrawal against the enemy's HP when the Pokémon went out", () => {
    const battle = new Battle(
      options(
        [mon(CYNDAQUIL, 12), mon(TOTODILE, 10)],
        { wild: { species: RATTATA, level: 12 } },
        3,
      ),
    );
    // Tackle once, then switch: the lost HP picks the text.
    const { texts } = play(battle, {
      action: [{ action: "fight", move: 0 }, { action: "pkmn" }],
      party: [1],
    });
    const withdrawal = texts.find((text) => text.startsWith("CYNDAQUIL, "))!;
    expect([
      "CYNDAQUIL, come back!",
      "CYNDAQUIL, OK! Come back!",
      "CYNDAQUIL, good! Come back!",
    ]).toContain(withdrawal);
  });

  it("asks for the next Pokémon after a faint and refuses a fainted choice", () => {
    const first = mon(CYNDAQUIL, 5),
      second = mon(TOTODILE, 10),
      fainted = mon(PIDGEY, 5);
    first.hp = 1;
    fainted.hp = 0;
    const battle = new Battle(
      options(
        [first, fainted, second],
        { wild: { species: RATTATA, level: 8 } },
        5,
      ),
    );
    const { texts, prompts } = play(battle, { party: [1, 2] });
    expect(texts).toContain("CYNDAQUIL fainted!");
    expect(texts).toContain("Use next POKéMON?");
    const forced = prompts.find((prompt) => prompt.kind === "party");
    expect(forced).toEqual({
      kind: "party",
      text: "Which POKéMON?",
      menu: false,
      cancel: false,
    });
    expect(texts).toContain("There's no will to battle!");
    const sentOut = texts.findIndex((text) => text.endsWith("TOTODILE!"));
    expect(texts[sentOut]).toMatch(
      /^(Go!|Do it!|Go for it,|Your foe's weak! Get'm,) TOTODILE!$/,
    );
    expect(battle.curBattleMon).toBe(2);
    // The fainted Pokémon did not share the experience.
    expect(first.exp).toBe(assets.pokemon.expAtLevel(3, 5));
  });

  it("keeps asking for a Pokémon when the forced party menu is cancelled", () => {
    const first = mon(CYNDAQUIL, 5);
    first.hp = 1;
    const battle = new Battle(
      options(
        [first, mon(TOTODILE, 10)],
        { wild: { species: RATTATA, level: 8 } },
        5,
      ),
    );
    const { prompts } = play(battle, { party: [-1, -1, 1] });
    expect(prompts.filter((prompt) => prompt.kind === "party")).toHaveLength(3);
    expect(battle.curBattleMon).toBe(1);
  });

  it("runs after declining the next Pokémon, with the first party Pokémon's Speed", () => {
    const first = mon(CYNDAQUIL, 5);
    first.hp = 1;
    const battle = new Battle(
      options(
        [first, mon(TOTODILE, 10)],
        { wild: { species: RATTATA, level: 8 } },
        5,
      ),
    );
    // The party's stored Speed, not the fainted battle Pokémon's, decides.
    first.stats[3] = 999;
    const { texts, result } = play(battle, { yesno: [0] });
    expect(texts.slice(-2)).toEqual(["Use next POKéMON?", "Got away safely!"]);
    expect(result).toBe(C.DRAW);
  });

  it("offers a switch in Shift mode when a trainer sends out the next Pokémon", () => {
    // Youngster Mikey: Pidgey, then Rattata.
    const first = mon(CYNDAQUIL, 15),
      second = mon(TOTODILE, 15);
    const battle = new Battle(options([first, second], { trainer: [22, 2] }));
    const { texts } = play(battle, { yesno: [1], party: [1] });
    const offer = texts.indexOf("YOUNGSTER MIKEY is about to use RATTATA.");
    expect(offer).toBeGreaterThan(0);
    expect(texts.slice(offer + 1, offer + 5)).toEqual([
      "Will CHRIS change POKéMON?",
      "YOUNGSTER MIKEY sent out RATTATA!",
      expect.stringMatching(/^CYNDAQUIL, /),
      "Go! TOTODILE!",
    ]);
    expect(texts).toContain("YOUNGSTER MIKEY was defeated!");
  });

  it("keeps the Pokémon in when the offer is declined", () => {
    const battle = new Battle(
      options([mon(CYNDAQUIL, 15), mon(TOTODILE, 15)], { trainer: [22, 2] }),
    );
    const { texts } = play(battle, { yesno: [0] });
    const offer = texts.findIndex((text) => text.includes("Will CHRIS change"));
    expect(texts[offer + 1]).toBe("YOUNGSTER MIKEY sent out RATTATA!");
    expect(texts.some((text) => text.startsWith("CYNDAQUIL, "))).toBe(false);
    expect(battle.curBattleMon).toBe(0);
  });

  it("sends out both sides without an offer after a double faint", () => {
    // Struggle's recoil faints the attacker as the trainer's Pidgey faints.
    const first = mon(CYNDAQUIL, 15);
    first.hp = 1;
    first.pp = [0, 0, 0, 0];
    const battle = new Battle(
      options([first, mon(TOTODILE, 15)], { trainer: [22, 2] }),
    );
    const { texts, prompts } = play(battle, { party: [1] });
    const fainted = texts.indexOf("Enemy PIDGEY fainted!");
    expect(fainted).toBeGreaterThan(0);
    // The fainted Pokémon is no longer a participant, so nobody gains
    // experience for the Pidgey.
    expect(texts.slice(fainted, fainted + 4)).toEqual([
      "Enemy PIDGEY fainted!",
      "CYNDAQUIL fainted!",
      "Go! TOTODILE!",
      "YOUNGSTER MIKEY sent out RATTATA!",
    ]);
    expect(texts.some((text) => text.includes("change POKéMON"))).toBe(false);
    expect(prompts.find((prompt) => prompt.kind === "party")).toMatchObject({
      cancel: false,
    });
    expect(texts).toContain("YOUNGSTER MIKEY was defeated!");
  });
});