import { beforeAll, describe, expect, it } from "vitest";
import { existsSync, readFileSync } from "node:fs";
import { CrystalAssets } from "../src/game/rom/assets";
import { Battle, type BattleEffect, type BattleMon, type BattleTrainer } from "../src/game/battle/battle";
import { C } from "../src/game/battle/constants";
import { partyMon } from "./battle-driver";
import { defaultTextContext } from "../src/game/scripts/text";

const romPath =
  process.env.CRYSTAL_ROM_PATH ??
  "Pokemon - Crystal Version (UE) (V1.1) [C][!].gbc";
const RATTATA = 19,
  PIDGEY = 16;
// TrainerClassAttributes AI_ITEM_SWITCH bits (constants/trainer_data_constants.asm).
const SWITCH_SOMETIMES = 1 << 2,
  ALWAYS_USE = 1 << 4,
  UNKNOWN_USE = 1 << 5,
  CONTEXT_USE = 1 << 6;

describe.skipIf(!existsSync(romPath))("trainer item AI (AI_TryItem)", () => {
  let assets: CrystalAssets;
  beforeAll(() => {
    assets = new CrystalAssets(new Uint8Array(readFileSync(romPath)));
  });

  const enemyMon = (
    level: number,
    hp: number,
    maxHp: number,
    status = 0,
  ): BattleMon => ({
    species: RATTATA,
    item: 0,
    moves: [33, 0, 0, 0],
    pp: [35, 0, 0, 0],
    dvs: 0,
    happiness: 70,
    level,
    status,
    hp,
    maxHp,
    stats: [30, 30, 30, 30, 30],
    types: [0, 0],
    nickname: "RATTATA",
  });
  const makeTrainer = (
    overrides: Partial<BattleTrainer> = {},
    levels: number[] = [30],
  ): BattleTrainer => ({
    name: "",
    className: "CLAIR",
    party: levels.map((level) => partyMon(assets, RATTATA, level)),
    aiFlags: 0,
    switchFlags: CONTEXT_USE | SWITCH_SOMETIMES,
    items: [0, 0],
    baseReward: 25,
    reward: 100,
    ...overrides,
  });
  /** Builds a Battle with the enemy's battle Pokémon and curOTMon set
   * directly (as the reference specs do), skipping the opening send-out,
   * and exposes the private AI_TryItem for direct calls. */
  const rig = (
    trainer: BattleTrainer,
    enemy: BattleMon,
    { curOTMon = 0, random = () => 0 }: { curOTMon?: number; random?: () => number } = {},
  ) => {
    const battle = new Battle({
      data: assets.pokemon,
      party: [partyMon(assets, PIDGEY, 10)],
      pokedex: { seen: new Set(), caught: new Set() },
      playerId: 1234,
      playerName: "CHRIS",
      timeOfDay: 1,
      random,
      trainer,
      text: () => defaultTextContext("CHRIS"),
    });
    battle.turn = 1;
    battle.curOTMon = curOTMon;
    battle.enemy.mon = enemy;
    const internal = battle as unknown as {
      aiTryItem(): Generator<BattleEffect, boolean, unknown>;
      aiSwitchOrTryItem(): Generator<BattleEffect, boolean, unknown>;
    };
    return { battle, internal };
  };
  const run = (gen: Generator<BattleEffect, boolean, unknown>) => {
    const texts: string[] = [];
    let step = gen.next();
    while (!step.done) {
      if (step.value.kind === "text") texts.push(step.value.text.replace(/\n/g, " "));
      step = gen.next();
    }
    return { used: step.value, texts };
  };

  it("does nothing with no items held", () => {
    const trainer = makeTrainer({ items: [0, 0] });
    const enemy = enemyMon(30, 10, 100, 1 << C.FRZ);
    const { internal } = rig(trainer, enemy);
    const { used, texts } = run(internal.aiTryItem());
    expect(used).toBe(false);
    expect(texts).toEqual([]);
    expect(enemy.status).toBe(1 << C.FRZ);
  });

  it.each(["mean-look", "wrap"])("a trainer blocked from switching by %s can still heal", (trap) => {
    const trainer = makeTrainer({ items: [C.POTION, 0] });
    const enemy = enemyMon(30, 10, 100);
    const { battle, internal } = rig(trainer, enemy, {
      random: () => { throw new Error("Trapped trainers must skip the switch roll"); },
    });
    if (trap === "mean-look") battle.player.set(5, C.SUBSTATUS_CANT_RUN);
    else battle.enemy.wrapCount = 2;
    expect(run(internal.aiSwitchOrTryItem()).used).toBe(true);
    expect(enemy.hp).toBe(30);
    expect(trainer.items).toEqual([0, 0]);
  });

  it.each([
    [C.POTION, 20],
    [C.SUPER_POTION, 50],
    [C.HYPER_POTION, 200],
  ])("item %i heals %i HP, clamped to the maximum, and is consumed", (item, amount) => {
    const trainer = makeTrainer({ items: [item, 0] });
    const enemy = enemyMon(30, 10, 100);
    const { internal } = rig(trainer, enemy);
    const { used, texts } = run(internal.aiTryItem());
    expect(used).toBe(true);
    expect(enemy.hp).toBe(Math.min(10 + amount, 100));
    expect(trainer.items).toEqual([0, 0]);
    expect(texts).toEqual([expect.stringMatching(/^CLAIR used .* on RATTATA!$/)]);
  });

  it("Max Potion and Full Restore fill to the maximum HP", () => {
    for (const item of [C.MAX_POTION, C.FULL_RESTORE]) {
      const trainer = makeTrainer({ items: [item, 0] });
      const enemy = enemyMon(30, 1, 100);
      const { internal } = rig(trainer, enemy);
      const { used } = run(internal.aiTryItem());
      expect(used).toBe(true);
      expect(enemy.hp).toBe(100);
    }
  });

  it("Full Restore clears confusion, but Full Heal keeps it (a kept bug)", () => {
    for (const [item, staysConfused] of [[C.FULL_RESTORE, false], [C.FULL_HEAL, true]] as const) {
      const trainer = makeTrainer({ items: [item, 0] });
      const enemy = enemyMon(30, item === C.FULL_HEAL ? 100 : 1, 100, 1 << C.FRZ);
      const { battle, internal } = rig(trainer, enemy);
      battle.enemy.set(3, C.SUBSTATUS_CONFUSED);
      const { used } = run(internal.aiTryItem());
      expect(used).toBe(true);
      expect(enemy.status).toBe(0);
      expect(battle.enemy.has(3, C.SUBSTATUS_CONFUSED)).toBe(staysConfused);
    }
  });

  it("Full Heal only cures Toxic, Freeze or Sleep under CONTEXT_USE, not plain status", () => {
    const trainer = makeTrainer({ items: [C.FULL_HEAL, 0] });
    const enemy = enemyMon(30, 100, 100, 1 << C.PAR);
    const { internal } = rig(trainer, enemy);
    const { used } = run(internal.aiTryItem());
    expect(used).toBe(false);
    expect(enemy.status).toBe(1 << C.PAR);
  });

  it("X Accuracy, Guard Spec and Dire Hit set their SubStatus4 flag", () => {
    const cases = [
      [C.X_ACCURACY, C.SUBSTATUS_X_ACCURACY],
      [C.GUARD_SPEC, C.SUBSTATUS_MIST],
      [C.DIRE_HIT, C.SUBSTATUS_FOCUS_ENERGY],
    ] as const;
    for (const [item, bit] of cases) {
      const trainer = makeTrainer({ items: [item, 0], switchFlags: CONTEXT_USE });
      const enemy = enemyMon(30, 100, 100);
      // .XItem's first-turn-out gate (`cp 128; jp c, DontUse`) declines
      // below 128, so a high roll is the one that lets CONTEXT_USE through.
      const { battle, internal } = rig(trainer, enemy, { random: () => 254 });
      const { used } = run(internal.aiTryItem());
      expect(used).toBe(true);
      expect(battle.enemy.has(4, bit)).toBe(true);
    }
  });

  it.each([
    [C.X_ATTACK, C.ATTACK],
    [C.X_DEFEND, C.DEFENSE],
    [C.X_SPEED, C.SPEED],
    [C.X_SPECIAL, C.SP_ATTACK],
  ])("item %i raises the matching stat", (item, stat) => {
    const trainer = makeTrainer({ items: [item, 0], switchFlags: CONTEXT_USE });
    const enemy = enemyMon(30, 100, 100);
    const { battle, internal } = rig(trainer, enemy, { random: () => 254 });
    const before = battle.enemy.levels[stat];
    const { used } = run(internal.aiTryItem());
    expect(used).toBe(true);
    expect(battle.enemy.levels[stat]).toBe(before + 1);
  });

  it("consumes whichever of the two slots the match came from", () => {
    // item2 (Hyper Potion) is tried before item1 (Potion) is ever reached,
    // since AI_Items lists Hyper Potion first.
    const trainer = makeTrainer({ items: [C.POTION, C.HYPER_POTION] });
    const enemy = enemyMon(30, 10, 100);
    const { internal } = rig(trainer, enemy);
    const { used } = run(internal.aiTryItem());
    expect(used).toBe(true);
    expect(enemy.hp).toBe(100); // Hyper Potion's 200 HP, clamped
    expect(trainer.items).toEqual([C.POTION, 0]);
  });

  it("BUG: a declined second item strands the first for the rest of that scan", () => {
    // Clair: FULL_HEAL, HYPER_POTION. Full HP declines Hyper Potion, after
    // which the scan can never see item1 (Full Heal) again this call, even
    // though a frozen status would otherwise ask for it.
    const stuck = makeTrainer({ items: [C.FULL_HEAL, C.HYPER_POTION] });
    const frozenStuck = enemyMon(30, 100, 100, 1 << C.FRZ);
    const { internal: stuckInternal } = rig(stuck, frozenStuck);
    const { used: stuckUsed } = run(stuckInternal.aiTryItem());
    expect(stuckUsed).toBe(false);
    expect(frozenStuck.status).toBe(1 << C.FRZ);
    expect(stuck.items).toEqual([C.FULL_HEAL, C.HYPER_POTION]);

    // The same Full Heal works fine once nothing else occupies the scan.
    const clear = makeTrainer({ items: [C.FULL_HEAL, 0] });
    const frozenClear = enemyMon(30, 100, 100, 1 << C.FRZ);
    const { internal: clearInternal } = rig(clear, frozenClear);
    const { used: clearUsed } = run(clearInternal.aiTryItem());
    expect(clearUsed).toBe(true);
    expect(frozenClear.status).toBe(0);
  });

  it("BUG: the stuck pointer can drift into the base reward and misread it as a third item", () => {
    // No real item1; item2 (Hyper Potion) is declined at full HP, which
    // strands the scan at item2. It then reaches Full Heal's table entry
    // with the stuck pointer one past item2, i.e. wEnemyTrainerBaseReward:
    // a base reward that happens to equal FULL_HEAL's id is misread as
    // that item and "used", simply zeroing the reward (docs/bugs_and_glitches.md
    // "AI might use its base reward value as an item"). No real trainer's
    // base reward aliases an item id, so this needs an explicit setup.
    const trainer = makeTrainer({ items: [0, C.HYPER_POTION], baseReward: C.FULL_HEAL });
    const enemy = enemyMon(30, 100, 100, 1 << C.FRZ);
    const { internal } = rig(trainer, enemy);
    const { used } = run(internal.aiTryItem());
    expect(used).toBe(true);
    expect(enemy.status).toBe(0);
    expect(trainer.baseReward).toBe(0);
    expect(trainer.items).toEqual([0, C.HYPER_POTION]);
  });

  it("only the trainer's highest-level Pokémon (ties included) may use an item", () => {
    const trainer = makeTrainer({ items: [C.FULL_HEAL, 0] }, [20, 30]);
    const enemy = enemyMon(20, 100, 100, 1 << C.FRZ);
    const { internal } = rig(trainer, enemy, { curOTMon: 0 });
    expect(run(internal.aiTryItem()).used).toBe(false);
    expect(enemy.status).toBe(1 << C.FRZ);

    // A tie at the trainer's highest level still counts.
    trainer.party[0].level = 30;
    const tied = enemyMon(30, 100, 100, 1 << C.FRZ);
    const { internal: tiedInternal } = rig(trainer, tied, { curOTMon: 0 });
    expect(run(tiedInternal.aiTryItem()).used).toBe(true);
    expect(tied.status).toBe(0);
  });

  it("HealItem's random gate: above a quarter but at or below half HP, under CONTEXT_USE", () => {
    const trainer = makeTrainer({ items: [C.POTION, 0] });
    const enemy = () => enemyMon(30, 30, 100); // 30% of max: below half, above a quarter
    for (const [roll, expected] of [[0, true], [254, false]] as const) {
      trainer.items = [C.POTION, 0];
      const mon = enemy();
      const { internal } = rig(trainer, mon, { random: () => roll });
      expect(run(internal.aiTryItem()).used).toBe(expected);
    }
  });

  it("HealItem's UNKNOWN_USE path (dead in this game, but ported)", () => {
    const trainer = makeTrainer({ items: [C.POTION, 0], switchFlags: UNKNOWN_USE });
    // At or below a quarter: a roll below 50/255 declines; otherwise uses.
    for (const [roll, expected] of [[0, false], [254, true]] as const) {
      const mon = enemyMon(30, 10, 100);
      const { internal } = rig(trainer, mon, { random: () => roll });
      expect(run(internal.aiTryItem()).used).toBe(expected);
    }
  });

  it("Status's ALWAYS_USE and plain-random paths (dead in this game, but ported)", () => {
    const always = makeTrainer({ items: [C.FULL_HEAL, 0], switchFlags: ALWAYS_USE });
    const alwaysMon = enemyMon(30, 100, 100, 1 << C.PAR);
    const { internal: alwaysInternal } = rig(always, alwaysMon);
    expect(run(alwaysInternal.aiTryItem()).used).toBe(true);

    const plain = makeTrainer({ items: [C.FULL_HEAL, 0], switchFlags: 0 });
    for (const [roll, expected] of [[0, true], [254, false]] as const) {
      plain.items = [C.FULL_HEAL, 0];
      const mon = enemyMon(30, 100, 100, 1 << C.PAR);
      const { internal } = rig(plain, mon, { random: () => roll });
      expect(run(internal.aiTryItem()).used).toBe(expected);
    }
  });

  it("XItem is more eager on the enemy's first turn out than later", () => {
    const trainer = makeTrainer({ items: [C.X_SPEED, 0], switchFlags: CONTEXT_USE });
    // First turn out (turnsTaken 0): the first random draw declines below
    // 128 (`cp 128; jp c, DontUse`); CONTEXT_USE then needs no second draw.
    {
      const mon = enemyMon(30, 100, 100);
      const { battle, internal } = rig(trainer, mon, { random: () => 254 });
      battle.enemy.turnsTaken = 0;
      expect(run(internal.aiTryItem()).used).toBe(true);
    }
    {
      trainer.items = [C.X_SPEED, 0];
      const mon = enemyMon(30, 100, 100);
      const { battle, internal } = rig(trainer, mon, { random: () => 0 });
      battle.enemy.turnsTaken = 0;
      expect(run(internal.aiTryItem()).used).toBe(false);
    }
    // Not the first turn out: ALWAYS_USE_F is required (CONTEXT_USE alone
    // is not enough), so this trainer never uses it again this way.
    {
      trainer.items = [C.X_SPEED, 0];
      const mon = enemyMon(30, 100, 100);
      const { battle, internal } = rig(trainer, mon, { random: () => 254 });
      battle.enemy.turnsTaken = 1;
      expect(run(internal.aiTryItem()).used).toBe(false);
    }
  });

  it("clears Bide, Fury Cutter, Protect, Rage and the last counter move only when an item is used", () => {
    const trainer = makeTrainer({ items: [C.POTION, 0] });
    const enemy = enemyMon(30, 10, 100);
    const { battle, internal } = rig(trainer, enemy);
    battle.enemy.set(3, C.SUBSTATUS_BIDE);
    battle.enemy.set(4, C.SUBSTATUS_RAGE);
    battle.enemy.furyCutterCount = 3;
    battle.enemy.protectCount = 2;
    battle.enemy.rageCounter = 4;
    battle.enemy.lastCounterMove = 33;
    expect(run(internal.aiTryItem()).used).toBe(true);
    expect(battle.enemyGoesFirst).toBe(1);
    expect(battle.enemy.has(3, C.SUBSTATUS_BIDE)).toBe(false);
    expect(battle.enemy.has(4, C.SUBSTATUS_RAGE)).toBe(false);
    expect(battle.enemy.furyCutterCount).toBe(0);
    expect(battle.enemy.protectCount).toBe(0);
    expect(battle.enemy.rageCounter).toBe(0);
    expect(battle.enemy.lastCounterMove).toBe(0);
  });

  it("leaves those substatuses untouched when nothing is used", () => {
    const trainer = makeTrainer({ items: [0, 0] });
    const enemy = enemyMon(30, 10, 100);
    const { battle, internal } = rig(trainer, enemy);
    battle.enemy.set(3, C.SUBSTATUS_BIDE);
    battle.enemy.furyCutterCount = 3;
    expect(run(internal.aiTryItem()).used).toBe(false);
    expect(battle.enemy.has(3, C.SUBSTATUS_BIDE)).toBe(true);
    expect(battle.enemy.furyCutterCount).toBe(3);
  });
});