import { expect } from "vitest";
import { mkdirSync, writeFileSync } from "node:fs";
import { encodeSave } from "../src/storage/saves";
import { CRYSTAL_ROM } from "../src/rom/validate";
import type { CrystalAssets } from "../src/game/rom/assets";
import { GameWorld, type NativeSave } from "../src/game/world/world";
import type { Direction } from "../src/game/world/types";
import { C } from "../src/game/battle/constants";
import { findPath } from "./world-driver";

const STEP: Record<Direction, [number, number]> = {
  up: [0, -1],
  down: [0, 1],
  left: [-1, 0],
  right: [1, 0],
};

/** Warp mats and edges that need their direction pressed (.CheckWarp). */
const WARP_EXITS: Partial<Record<number, Direction>> = {
  0x70: "down",
  0x76: "left",
  0x78: "up",
  0x7e: "right",
};

/** Plays the game through the world's own inputs, as tests/playthrough
 * does: scripts, battles and walking, with a seeded Random. A stage's save
 * can be dumped (PLAYTHROUGH_SAVES) and resumed with `resume`. */
export class Playthrough {
  world!: GameWorld;
  readonly log: string[] = [];
  /** A wild species to throw Poké Balls at instead of fighting. */
  wanted = 0;
  seed = 0x2a;
  private stage = 0;
  readonly now = () => new Date("2026-09-22T12:00:00");
  readonly random = () => {
    this.seed = (this.seed * 1103515245 + 12345) >>> 0;
    return (this.seed >>> 16) & 255;
  };
  constructor(readonly assets: CrystalAssets) {}

  /** A new world for the introduction. */
  start() {
    this.world = new GameWorld(this.assets, this.now, this.random);
  }
  /** Continue from a dumped stage. */
  resume(dump: { save: NativeSave; seed: number }) {
    this.seed = dump.seed;
    this.world = new GameWorld(this.assets, this.now, this.random);
    this.world.restore(dump.save);
  }

  /** The usable move with the most power, or the first with PP. */
  strongest = (mon: { moves: readonly number[]; pp: readonly number[] }) => {
    let best = -1;
    mon.moves.forEach((move, i) => {
      if (!move || !(mon.pp[i] & 63)) return;
      if (
        best < 0 ||
        this.assets.pokemon.move(move).power >
          this.assets.pokemon.move(mon.moves[best]).power
      )
        best = i;
    });
    return Math.max(0, best);
  };
  /** Run scripts and battles until the player is free again. Battles use
   * the strongest move with PP; a wild battle below half HP is run from, as
   * a cautious player would. New moves are learned when there is room,
   * and other questions take the queued answers or their defaults. */
  play = (answers: (number | string)[] = []) => {
    const world = this.world,
      log = this.log;
    for (let tick = 0; tick < 100_000; tick++) {
      expect(world.notice, world.diagnostic).toBe("");
      const battle = world.battle;
      if (battle) {
        if (battle.message && log.at(-1) !== battle.message.text)
          log.push(battle.message.text);
        const prompt = battle.prompt;
        if (prompt?.kind === "action") {
          const { engine } = battle,
            mon = engine.player.mon;
          const ball = world.state.bag.balls.findIndex(
            (slot) => slot.item === C.POKE_BALL,
          );
          if (
            engine.battleMode === C.WILD_BATTLE &&
            engine.enemy.mon.species === this.wanted &&
            !world.state.party.some((member) => member.species === this.wanted) &&
            ball >= 0
          )
            world.battleAction({ action: "item", item: C.POKE_BALL, slot: ball });
          else if (engine.battleMode === C.WILD_BATTLE && mon.hp * 2 < mon.maxHp)
            world.battleAction({ action: "run" });
          else world.battleAction({ action: "fight", move: this.strongest(mon) });
        } else if (prompt?.kind === "yesno") world.battleChoose(1);
        // SHIFT's party menu: keep the Pokémon out (or send the first
        // that can fight when one must go).
        else if (prompt?.kind === "party")
          world.battleChoose(
            prompt.cancel
              ? -1
              : world.state.party.findIndex(
                  (mon, i) =>
                    i !== battle.engine.curBattleMon && !mon.egg && mon.hp > 0,
                ),
          );
        else if (prompt?.kind === "forget") world.battleChoose(4);
        else if (prompt?.kind === "name") world.battleName("");
        else if (prompt?.kind === "stats" || battle.message?.prompt)
          world.interact();
        else world.tick();
        continue;
      }
      const dialogue = world.dialogue;
      if (dialogue) {
        const page = dialogue.pages[dialogue.index];
        const last = dialogue.index === dialogue.pages.length - 1;
        if (log.at(-1) !== page) log.push(page);
        if (last && dialogue.choice) {
          const answer = answers.shift();
          if (dialogue.choice.kind === "name")
            world.choose(typeof answer === "string" ? answer : "");
          else
            world.choose(
              typeof answer === "number"
                ? answer
                : dialogue.choice.kind === "yesno"
                  ? 1
                  : dialogue.choice.kind === "clock"
                    ? dialogue.choice.selected
                    : 0,
            );
        } else if (last && dialogue.holdTicks !== undefined) world.tick();
        else world.advanceDialogue();
        continue;
      }
      if (!world.busy) {
        world.tick(); // scene scripts and phone calls start on idle ticks
        if (!world.busy) return;
        continue;
      }
      world.tick();
    }
    throw new Error(`The world did not settle: ${world.diagnostic}`);
  };

  /** Walk to a tile on the current map, replanning after ledges, roaming
   * NPCs and scenes that move the player. A warp target leaves the map. */
  walk = (x: number, y: number) => {
    const world = this.world,
      map = world.mapId,
      warp = world.map.warps.some((warp) => warp.x === x && warp.y === y);
    for (let attempt = 0; attempt < 40; attempt++) {
      this.play();
      if (warp && world.mapId !== map) return;
      expect(world.mapId, `walking to ${x},${y}`).toBe(map);
      if (world.x === x && world.y === y) return;
      for (const direction of findPath(world, x, y)) {
        const [dx, dy] = STEP[direction];
        const from = [world.x, world.y];
        if (!world.move(direction)) {
          for (let tick = 0; tick < 64; tick++) world.tick();
          break;
        }
        this.play();
        if (
          world.mapId !== map ||
          world.x !== from[0] + dx ||
          world.y !== from[1] + dy
        )
          break;
      }
    }
    throw new Error(
      `Could not reach ${x},${y} on ${map} from ${world.x},${world.y}: ${world.notice}`,
    );
  };
  /** Step across a map connection from the nearest usable edge tile. */
  cross = (direction: Direction, target: string) => {
    const world = this.world,
      map = world.mapId;
    const [dx, dy] = STEP[direction];
    const edge = Array.from(
      { length: dx ? world.map.height : world.map.width },
      (_, i) =>
        dx
          ? [dx < 0 ? 0 : world.map.width - 1, i]
          : [i, dy < 0 ? 0 : world.map.height - 1],
    ).flatMap(([x, y]) => {
      try {
        return [{ x, y, length: findPath(world, x, y).length }];
      } catch {
        return [];
      }
    });
    edge.sort((a, b) => a.length - b.length);
    for (const { x, y } of edge) {
      this.walk(x, y);
      if (world.move(direction)) {
        this.play();
        if (world.mapId === target) return;
      }
      if (world.mapId !== map) break;
    }
    throw new Error(
      `Could not cross ${direction} from ${map} to ${target}: now ${world.mapId}`,
    );
  };
  /** Stand in front of a warp leading to `target` and take it. */
  enter = (target: string, direction: Direction) => {
    const world = this.world;
    const warp = world.map.warps.find((warp) => warp.targetMap === target)!;
    expect(warp, `a warp to ${target}`).toBeDefined();
    const [dx, dy] = STEP[direction];
    this.walk(warp.x - dx, warp.y - dy);
    expect(world.move(direction)).toBe(true);
    this.play();
    expect(world.mapId).toBe(target);
  };
  /** Leave through an exit mat, which needs the exit direction pressed. */
  exit = (target: string, direction: Direction = "down") => {
    const world = this.world;
    const warp = world.map.warps.find((warp) => warp.targetMap === target)!;
    this.walk(warp.x, warp.y);
    if (world.mapId !== target) {
      expect(world.move(direction)).toBe(true);
      this.play();
    }
    expect(world.mapId).toBe(target);
  };
  /** Serialize the save to JSON and load it into a fresh world. */
  reload = () => {
    const saved = JSON.parse(JSON.stringify(this.world.save()));
    // PLAYTHROUGH_SAVES=dir keeps every stage's save, for debugging a
    // later stage from where the run reached.
    if (process.env.PLAYTHROUGH_SAVES) {
      mkdirSync(process.env.PLAYTHROUGH_SAVES, { recursive: true });
      writeFileSync(
        `${process.env.PLAYTHROUGH_SAVES}/${String(++this.stage).padStart(3, "0")}.json`,
        JSON.stringify({ save: saved, seed: this.seed }),
      );
    }
    this.world = new GameWorld(this.assets, this.now, this.random);
    this.world.restore(saved);
    expect(this.world.save()).toEqual(saved);
  };
  lead = () => this.world.state.party[0];
  /** With MAKE_TEST_SAVES, a backup for the board's manual checks, as
   * tests/human-test-saves.test.ts writes them (kept out of git). */
  writeTestSave = (name: string) => {
    if (!process.env.MAKE_TEST_SAVES) return;
    mkdirSync("test-saves", { recursive: true });
    writeFileSync(
      `test-saves/${name}.crystal-save.json`,
      encodeSave({
        version: 1,
        romHash: CRYSTAL_ROM.sha1,
        coreId: "crystal-native-world-v1",
        savedAt: new Date().toISOString(),
        state: new TextEncoder().encode(JSON.stringify(this.world.save())),
      }),
    );
  };
  /** PokecenterNurseScript from in front of the counter, then back out. */
  heal = (center: string, city: string) => {
    this.enter(center, "up");
    this.walk(3, 3);
    this.world.move("up"); // the counter: this only turns the player
    this.world.interact();
    this.play();
    expect(
      this.world.state.party.every((mon) => mon.egg || mon.hp === mon.stats[0]),
    ).toBe(true);
    this.exit(city);
  };
  /** Pace between two neighbouring grass tiles (the nearest pair) until
   * the lead reaches `level`. `rest` heals and comes back here. */
  train = (level: number, rest: () => void) => {
    const world = this.world,
      map = world.mapId,
      grass = world.assets.grassCollisions();
    const isGrass = (x: number, y: number) =>
      x >= 0 &&
      y >= 0 &&
      x < world.map.width &&
      y < world.map.height &&
      grass.includes(world.assets.collision(world.map, x, y));
    for (let round = 0; round < 2000 && this.lead().level < level; round++) {
      if (this.lead().hp * 2 < this.lead().stats[0]) {
        rest();
        expect(this.world.mapId).toBe(map);
      }
      const pairs: { x: number; y: number; length: number }[] = [];
      for (let y = 0; y < world.map.height; y++)
        for (let x = 0; x < world.map.width; x++)
          if (isGrass(x, y) && isGrass(x + 1, y))
            try {
              pairs.push({ x, y, length: findPath(world, x, y).length });
            } catch {
              /* unreachable */
            }
      pairs.sort((a, b) => a.length - b.length);
      const { x, y } = pairs[0];
      this.walk(x, y);
      this.walk(x + 1, y);
    }
    expect(this.lead().level).toBeGreaterThanOrEqual(level);
  };

  /** Take the stairs (or another warp) to `target`, trying each. A warp
   * mat or cave edge needs its exit direction pressed (.CheckWarp). */
  stairs = (target: string) => {
    const world = this.world;
    for (const warp of world.map.warps.filter((warp) => warp.targetMap === target)) {
      try {
        findPath(world, warp.x, warp.y);
      } catch {
        continue;
      }
      this.walk(warp.x, warp.y);
      if (world.mapId === target) return;
      const exit = WARP_EXITS[world.assets.collision(world.map, warp.x, warp.y)];
      if (exit && world.move(exit)) {
        this.play();
        if (world.mapId === target) return;
      }
    }
    throw new Error(`No way from ${world.mapId} to ${target}`);
  };
  /** Find a way through warps among `maps` to `target`, as a player
   * trying staircases would: depth first, backing out of dead ends. */
  route = (
    target: string,
    maps: string[],
    depth = 6,
    goal?: { x: number; y: number },
  ): boolean => {
    const world = this.world;
    const reachable = () => {
      if (!goal) return true;
      try {
        findPath(world, goal.x, goal.y);
        return true;
      } catch {
        return false;
      }
    };
    if (world.mapId === target && reachable()) return true;
    if (!depth) return false;
    const here = world.save();
    for (const warp of world.map.warps) {
      if (!maps.includes(warp.targetMap) && warp.targetMap !== target) continue;
      try {
        findPath(world, warp.x, warp.y);
      } catch {
        continue;
      }
      const from = world.mapId;
      this.walk(warp.x, warp.y);
      if (world.mapId !== from && this.route(target, maps, depth - 1, goal))
        return true;
      world.restore(here);
    }
    return false;
  };
  /** Advance to the next menu choice, keeping its pages in the log. */
  toChoice = () => {
    const world = this.world,
      log = this.log;
    for (let tick = 0; tick < 2000; tick++) {
      const dialogue = world.dialogue;
      if (dialogue) {
        const page = dialogue.pages[dialogue.index];
        if (log.at(-1) !== page) log.push(page);
        if (dialogue.index === dialogue.pages.length - 1 && dialogue.choice)
          return dialogue.choice;
        if (dialogue.holdTicks !== undefined) world.tick();
        else world.advanceDialogue();
      } else world.tick();
    }
    throw new Error(`No choice appeared: ${world.diagnostic}`);
  };
  /** Choose a menu item by its label (or a pattern). */
  choose = (label: string | RegExp) => {
    const choice = this.toChoice();
    if (choice.kind !== "menu")
      throw new Error(`Expected a menu, got ${choice.kind}`);
    const index = choice.items.findIndex((item) =>
      typeof label === "string" ? item === label : label.test(item),
    );
    expect(index, `${label} in ${choice.items.join(", ")}`).toBeGreaterThanOrEqual(0);
    this.world.choose(index);
  };
  /** Choose an item in the pack. */
  choosePack = (item: number) => {
    const choice = this.toChoice();
    if (choice.kind !== "pack")
      throw new Error(`Expected the pack, got ${choice.kind}`);
    for (const [pocket, { entries }] of choice.pockets.entries()) {
      const index = entries.findIndex((entry) => entry.item === item);
      if (index >= 0) return this.world.choosePackEntry(pocket, index);
    }
    throw new Error(`Item ${item} is not in the pack.`);
  };
  /** Talk to an object wherever it stands. A trainer who spots the player
   * on the way battles and moves, so the approach is planned again. */
  talkTo = (id: number) => {
    const world = this.world;
    for (let attempt = 0; attempt < 4; attempt++)
      for (const [dx, dy, face] of [
        [-1, 0, "right"],
        [1, 0, "left"],
        [0, 1, "up"],
        [0, -1, "down"],
      ] as const) {
        const target = world.objects().find((object) => object.id === id)!;
        const x = target.x + dx,
          y = target.y + dy;
        try {
          if (!(world.x === x && world.y === y)) this.walk(x, y);
        } catch {
          continue;
        }
        const now = world.objects().find((object) => object.id === id)!;
        if (now.x !== target.x || now.y !== target.y) break;
        world.move(face);
        world.interact();
        return;
      }
    throw new Error(`No way to talk to object ${id}`);
  };
  /** PACK, the TM/HM pocket's `item`, USE, YES, then party slot `slot`;
   * a full move list forgets the first move. */
  teach = (item: number, slot: number) => {
    const world = this.world;
    expect(world.openStartMenu()).toBe(true);
    this.choose("PACK");
    this.choosePack(item);
    this.choose("USE");
    expect(this.toChoice().kind).toBe("yesno");
    world.choose(1);
    const party = this.toChoice();
    expect(party.kind === "menu" && party.details?.[slot]).toBe("ABLE");
    world.choose(slot);
    if (world.liveState.party[slot].moves.every(Boolean)) {
      expect(this.toChoice().kind).toBe("yesno");
      world.choose(1);
      this.toChoice();
      world.choose(0);
    }
    for (let i = 0; i < 10 && world.dialogue?.choice?.kind !== "pack"; i++)
      this.toChoice();
    // The menus work on a draft that is kept once they close.
    for (let i = 0; i < 10 && world.busy; i++) {
      if (world.dialogue?.choice) world.advanceDialogue();
      else world.tick();
    }
    this.play();
  };
  /** Cut the tree at (x, y) from a walkable side (TryCutOW, then YES). */
  cut = (x: number, y: number) => {
    const world = this.world;
    for (const [face, [dx, dy]] of Object.entries(STEP) as [Direction, [number, number]][]) {
      try {
        this.walk(x - dx, y - dy);
      } catch {
        continue;
      }
      world.move(face);
      world.interact();
      this.play([1]);
      return;
    }
    throw new Error(`No side to cut ${x},${y} from`);
  };
  /** The current location and party, then the last pages, for a failure. */
  trace = () =>
    `${this.world.mapId} ${this.world.x},${this.world.y}; party ${JSON.stringify(
      this.world.state.party.map(({ species, level, hp }) => ({
        species,
        level,
        hp,
      })),
    )}\n${this.log.slice(-30).join("\n---\n")}`;
}