import { describe, expect, it } from "vitest";
import { existsSync, readFileSync } from "node:fs";
import { CrystalAssets } from "../src/game/rom/assets";
import { RomReader } from "../src/game/rom/reader";
import { OVERWORLD } from "../src/game/rom/profile";
import { GameWorld, migrateSave } from "../src/game/world/world";
import {
  ScriptRun,
  emptyScriptState,
  type ScriptHost,
} from "../src/game/scripts/interpreter";
import { PokemonData } from "../src/game/rom/pokemon";
import { defaultTextContext } from "../src/game/scripts/text";
import { generatePartyMon } from "../src/game/party/pokemon";
import { C } from "../src/game/battle/constants";
import type { RoamMon } from "../src/game/battle/battle";
import {
  initRoamMons,
  checkEncounterRoamMon,
  updateRoamMons,
  jumpRoamMons,
} from "../src/game/world/roam-mons";
import { afterRestore } from "./world-driver";

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

// RAIKOU, ENTEI (constants/pokemon_constants.asm).
const RAIKOU = 243,
  ENTEI = 244,
  SUICUNE = 245;
// Open Johto routes that are also RoamMaps entries (confirmed against the
// ROM below): Route 29, Route 32 and Route 33, which directly connect.
const ROUTE_29 = "24:3",
  ROUTE_32 = "10:1",
  ROUTE_33 = "8:6";
// InitRoamMons' own starting maps: Route 42 and Route 37 (not open, but
// decodable like any of the ROM's 26 map groups).
const ROUTE_42 = "2:5",
  ROUTE_37 = "10:4";
/** special InitRoamMons' index in SpecialsPointers (data/events/special_pointers.asm). */
const INIT_ROAM_MONS_SPECIAL = 105;

function assets() {
  return new CrystalAssets(new Uint8Array(readFileSync(romPath)));
}

/** Every map RoamMaps lists, read straight from the ROM: a roaming beast's
 * new position must always be one of these sixteen. */
function roamMapIds(r: RomReader): Set<string> {
  const ids = new Set<string>();
  let p = OVERWORLD.RoamMaps;
  while (r.byte(p) !== 0xff) {
    ids.add(`${r.byte(p)}:${r.byte(p + 1)}`);
    p += 4 + 2 * r.byte(p + 2);
  }
  return ids;
}

const emptyRoamer = (): RoamMon => ({ species: 0, level: 0, mapId: null, hp: 0, dvs: 0 });

describe.skipIf(!existsSync(romPath))("roaming Pokémon (Raikou, Entei, Suicune)", () => {
  describe("the RoamMaps graph (direct ROM reads)", () => {
    it("lists Route 29, Route 32 and Route 33 with Route 32 between the other two", () => {
      const r = assets().reader;
      const ids = roamMapIds(r);
      expect(ids).toContain(ROUTE_29);
      expect(ids).toContain(ROUTE_32);
      expect(ids).toContain(ROUTE_33);
      expect(ids.size).toBe(16);
    });
  });

  describe("initRoamMons", () => {
    it("starts Raikou on Route 42 and Entei on Route 37 at level 40 with HP 0, leaving Suicune untouched", () => {
      const suicune: RoamMon = { species: SUICUNE, level: 12, mapId: "1:1", hp: 7, dvs: 0x55aa };
      const result = initRoamMons([emptyRoamer(), emptyRoamer(), suicune]);
      expect(result[0]).toEqual({ species: RAIKOU, level: 40, mapId: ROUTE_42, hp: 0, dvs: 0 });
      expect(result[1]).toEqual({ species: ENTEI, level: 40, mapId: ROUTE_37, hp: 0, dvs: 0 });
      expect(result[2]).toEqual(suicune);
    });

    it("runs through the real special dispatch (special 105), as the ported interpreter resolves it", () => {
      // special InitRoamMons; end, placed in an unused bank-0 spot, exactly
      // as tests/zz-specials.local.test.ts probes every special routine.
      const rom = new Uint8Array(new Uint8Array(readFileSync(romPath)));
      rom.set(
        [0x0f, INIT_ROAM_MONS_SPECIAL & 255, INIT_ROAM_MONS_SPECIAL >> 8, 0x91],
        0x3ff0,
      );
      const reader = new RomReader(rom);
      const host: ScriptHost = {
        mapId: ROUTE_29,
        lastTalked: 0,
        sceneOwner: () => undefined,
        timeOfDay: () => 1,
        clock: () => ({ weekday: 0, hours: 12, minutes: 0 }),
        clockDay: () => 0,
        text: () => defaultTextContext("A"),
        data: new PokemonData(reader),
        player: () => ({ id: 1, gender: 0 }),
        random: () => 0,
        landmark: () => 0,
        facing: () => 0,
        position: () => ({ x: 0, y: 0 }),
        objectPosition: () => undefined,
        playerCollision: () => 0,
        environment: () => 0,
        phoneService: () => 0,
        facingObject: () => undefined,
      };
      const state = emptyScriptState();
      state.roamMons[2] = { species: SUICUNE, level: 5, mapId: "1:1", hp: 9, dvs: 0x1234 };
      const run = new ScriptRun(reader, 0x3ff0, state, host);
      for (let i = 0; i < 10 && run.resume(0); i++);
      expect(run.state.roamMons[0]).toEqual({ species: RAIKOU, level: 40, mapId: ROUTE_42, hp: 0, dvs: 0 });
      expect(run.state.roamMons[1]).toEqual({ species: ENTEI, level: 40, mapId: ROUTE_37, hp: 0, dvs: 0 });
      expect(run.state.roamMons[2]).toEqual({ species: SUICUNE, level: 5, mapId: "1:1", hp: 9, dvs: 0x1234 });
    });
  });

  describe("checkEncounterRoamMon", () => {
    it("draws once: the top 100 values never encounter, a draw & 3 == 0 never encounters, and the rest pick Raikou/Entei/Suicune by index", () => {
      const roamMons: RoamMon[] = [
        { species: RAIKOU, level: 40, mapId: ROUTE_29, hp: 0, dvs: 0 },
        { species: ENTEI, level: 40, mapId: "9:9", hp: 0, dvs: 0 },
        { species: SUICUNE, level: 40, mapId: "9:9", hp: 0, dvs: 0 },
      ];
      expect(checkEncounterRoamMon(roamMons, ROUTE_29, () => 100)).toBeUndefined();
      expect(checkEncounterRoamMon(roamMons, ROUTE_29, () => 0)).toBeUndefined();
      expect(checkEncounterRoamMon(roamMons, ROUTE_29, () => 1)).toBe(roamMons[0]);
      expect(checkEncounterRoamMon(roamMons, ROUTE_29, () => 2)).toBeUndefined();
      expect(checkEncounterRoamMon(roamMons, ROUTE_29, () => 3)).toBeUndefined();
    });
  });

  describe("UpdateRoamMons and JumpRoamMons (direct ROM reads)", () => {
    it("picks a random connection of the beast's own RoamMaps entry, redrawing an out-of-range index", () => {
      const r = assets().reader;
      // Route 32 (10:1) lists three neighbors in this order: Route 36
      // (10:3), Route 31 (26:2), Route 33 (8:6). The first draw's index (3)
      // is past the connection count and must be redrawn.
      const draws = [3, 4];
      const moved = updateRoamMons(
        r,
        [{ species: RAIKOU, level: 40, mapId: ROUTE_32, hp: 0, dvs: 0 }],
        null,
        "9:9",
        () => draws.shift()!,
      );
      expect(moved[0].mapId).toBe("10:3");
    });

    it("redraws when the chosen connection repeats the last map it was on", () => {
      const r = assets().reader;
      const draws = [2, 1]; // index 2 (Route 33) repeats lastMapId, then index 1 (Route 31).
      const moved = updateRoamMons(
        r,
        [{ species: RAIKOU, level: 40, mapId: ROUTE_32, hp: 0, dvs: 0 }],
        ROUTE_33,
        "9:9",
        () => draws.shift()!,
      );
      expect(moved[0].mapId).toBe("26:2");
    });

    it("a 1-in-32 draw jumps instead, avoiding the player's own map rather than the beast's", () => {
      const r = assets().reader;
      // draw & 0x1f == 0 triggers JumpRoamMon; its own index draw (5) lands
      // on RoamMaps entry 5 (Route 34, 11:1), which is not the player's map.
      const draws = [0, 5];
      const moved = updateRoamMons(
        r,
        [{ species: RAIKOU, level: 40, mapId: ROUTE_32, hp: 0, dvs: 0 }],
        null,
        "9:9",
        () => draws.shift()!,
      );
      expect(moved[0].mapId).toBe("11:1");
    });

    it("leaves a beast on an unlisted map untouched and draws nothing", () => {
      const r = assets().reader;
      const moved = updateRoamMons(
        r,
        [{ species: RAIKOU, level: 40, mapId: "9:9", hp: 0, dvs: 0 }],
        null,
        "9:9",
        () => {
          throw new Error("should not draw");
        },
      );
      expect(moved[0].mapId).toBe("9:9");
    });

    it("skips a beast whose map is null (GROUP_N_A), drawing nothing", () => {
      const r = assets().reader;
      const moved = updateRoamMons(r, [emptyRoamer()], null, "9:9", () => {
        throw new Error("should not draw");
      });
      expect(moved[0].mapId).toBeNull();
    });

    it("JumpRoamMons picks uniformly among the 16 listed maps, redrawing only the player's own map", () => {
      const r = assets().reader;
      // Entry 0 is Route 29 itself, the player's map: redraw. Entry 1 is
      // Route 30 (26:1).
      const draws = [0, 1];
      const jumped = jumpRoamMons(
        r,
        [{ species: RAIKOU, level: 40, mapId: ROUTE_29, hp: 0, dvs: 0 }],
        ROUTE_29,
        () => draws.shift()!,
      );
      expect(jumped[0].mapId).toBe("26:1");
    });
  });

  describe("map transitions hook UpdateRoamMons/JumpRoamMons", () => {
    it("a map connection crossing moves an active beast and records the map", () => {
      const world = new GameWorld(assets());
      // Column x=7 runs clear from y=86 to the map's southern edge (y=90),
      // which connects straight into Route 33.
      world.warpTo(ROUTE_32, 7, 86);
      world.state.roamMons[0] = { species: RAIKOU, level: 40, mapId: ROUTE_32, hp: 0, dvs: 0 };
      let crossed = false;
      for (let tries = 0; tries < 6 && !crossed; tries++)
        crossed = world.move("down") && world.mapId === ROUTE_33;
      expect(crossed).toBe(true);
      expect(world.state.roamMonsMap).toBe(ROUTE_33);
      expect(roamMapIds(world.assets.reader)).toContain(world.state.roamMons[0].mapId);
    });

    it("a door warp moves an active beast too (MAPSETUP_DOOR falls through into MAPSETUP_TRAIN's UpdateRoamMons)", () => {
      const world = new GameWorld(assets());
      const warp = world.assets.map(ROUTE_32).warps.find((w) => w.targetMap === "10:13")!;
      world.warpTo(ROUTE_32, warp.x, warp.y - 1);
      world.state.roamMons[0] = { species: RAIKOU, level: 40, mapId: ROUTE_32, hp: 0, dvs: 0 };
      expect(world.move("down")).toBe(true);
      expect(world.mapId).toBe("10:13");
      expect(world.state.roamMonsMap).toBe("10:13");
      expect(roamMapIds(world.assets.reader)).toContain(world.state.roamMons[0].mapId);
    });

    it("continuing a save (JumpRoamMons) relocates an active beast off the loaded map", () => {
      const world = new GameWorld(assets());
      const saved = world.save();
      saved.map = ROUTE_32;
      saved.x = 10;
      saved.y = 80;
      saved.roamMons = [
        { species: RAIKOU, level: 40, mapId: ROUTE_32, hp: 0, dvs: 0 },
        emptyRoamer(),
        emptyRoamer(),
      ];
      world.restore(saved);
      expect(world.state.roamMonsMap).toBe(ROUTE_32);
      expect(world.state.roamMons[0].mapId).not.toBe(ROUTE_32);
      expect(roamMapIds(world.assets.reader)).toContain(world.state.roamMons[0].mapId);
    });

    it("a rollback restore (not a Continue) leaves the beasts where they were", () => {
      const world = new GameWorld(assets());
      const saved = world.save();
      saved.map = ROUTE_32;
      saved.x = 10;
      saved.y = 80;
      saved.roamMons = [
        { species: RAIKOU, level: 40, mapId: ROUTE_32, hp: 0, dvs: 0 },
        emptyRoamer(),
        emptyRoamer(),
      ];
      world.restore(saved, false);
      expect(world.save()).toEqual(saved);
    });
  });

  describe("a roaming encounter", () => {
    /** An open Johto route (Route 29) with a forced, deterministic
     * encounter rate: the roam check itself still runs for real. */
    function roamEncounterWorld() {
      const a = assets();
      a.grassCollisions = () => Array.from({ length: 256 }, (_, i) => i);
      a.grassWildMons = (id) =>
        id === ROUTE_29
          ? {
              rates: [256, 256, 256],
              slots: [0, 1, 2].map(() => Array.from({ length: 7 }, () => ({ species: 16, level: 3 }))),
            }
          : undefined;
      let mode: "fixed" | "lcg" = "fixed";
      let seed = 7;
      const world = new GameWorld(
        a,
        () => new Date("2026-09-22T12:00:00"),
        () => {
          if (mode === "fixed") return 1;
          seed = (seed * 1103515245 + 12345) >>> 0;
          return (seed >>> 16) & 255;
        },
      );
      const mon = generatePartyMon(a.pokemon, {
        species: 155, level: 30, item: 0, otId: world.playerId,
        ot: "CHRIS", dvs: 0x823b, caughtData: 0,
      });
      world.state.party = [mon];
      world.state.roamMons[0] = { species: RAIKOU, level: 40, mapId: ROUTE_29, hp: 0, dvs: 0 };
      world.warpTo(ROUTE_29, 30, 9);
      return { world, setMode: (next: "fixed" | "lcg") => (mode = next) };
    }
    /** Walk several steps in whichever direction is open, without depending
     * on the route's exact terrain: SetUpFiveStepWildEncounterCooldown
     * skips the encounter check on the first five steps after any map
     * entry, so a single step is never enough to reach it. */
    function stepSomewhere(world: GameWorld, steps = 6): boolean {
      for (let i = 0; i < steps; i++) {
        if (world.battle) return true;
        let moved = false;
        for (const direction of ["down", "right", "up", "left"] as const)
          if (world.move(direction)) {
            moved = true;
            break;
          }
        if (!moved) return false;
      }
      return true;
    }

    it("CheckEncounterRoamMon starts a BATTLETYPE_ROAMING battle naming the beast on this map", () => {
      const { world } = roamEncounterWorld();
      expect(stepSomewhere(world)).toBe(true);
      expect(world.notice, world.diagnostic).toBe("");
      expect(world.battle).toBeDefined();
      const engine = world.battle!.engine;
      expect(engine.battleType).toBe(C.BATTLETYPE_ROAMING);
      expect(engine.enemy.mon.species).toBe(RAIKOU);
    });

    it("catching it with a Master Ball clears the roaming slot and adds it to the party", () => {
      const { world, setMode } = roamEncounterWorld();
      world.state.bag.balls = [{ item: C.MASTER_BALL, quantity: 1 }];
      expect(stepSomewhere(world)).toBe(true);
      expect(world.battle).toBeDefined();
      setMode("lcg");
      for (let tick = 0; tick < 20_000 && world.busy; tick++) {
        const view = world.battle;
        if (!view) {
          if (world.dialogue) world.advanceDialogue();
          else world.tick();
          continue;
        }
        const prompt = view.prompt;
        if (prompt?.kind === "action")
          world.battleAction({ action: "item", item: C.MASTER_BALL, slot: 0 });
        else if (prompt?.kind === "yesno") world.battleChoose(0);
        else if (view.message?.prompt) world.interact();
        else world.tick();
      }
      expect(world.notice, world.diagnostic).toBe("");
      expect(world.state.party.some((p) => p.species === RAIKOU)).toBe(true);
      expect(world.state.roamMons[0]).toMatchObject({ species: 0, mapId: null, hp: 0 });
    });
  });

  describe("save format", () => {
    it("round-trips a beast's species, level, HP and DVs (the map itself may jump on continue)", () => {
      const world = new GameWorld(assets());
      world.state.roamMons = [
        { species: RAIKOU, level: 40, mapId: ROUTE_29, hp: 123, dvs: 0xabcd },
        emptyRoamer(),
        emptyRoamer(),
      ];
      const saved = world.save();
      world.restore(saved);
      const [raikou, entei, suicune] = world.state.roamMons;
      expect({ species: raikou.species, level: raikou.level, hp: raikou.hp, dvs: raikou.dvs }).toEqual(
        { species: RAIKOU, level: 40, hp: 123, dvs: 0xabcd },
      );
      expect(raikou.mapId).not.toBeNull();
      expect(entei.mapId).toBeNull();
      expect(suicune.mapId).toBeNull();
    });

    it("round-trips through save()/restore() with afterRestore's allowance", () => {
      const world = new GameWorld(assets());
      world.state.roamMons[1] = { species: ENTEI, level: 40, mapId: ROUTE_37, hp: 200, dvs: 0x4242 };
      const saved = world.save();
      world.restore(saved);
      const reloaded = world.save();
      expect(reloaded).toEqual(afterRestore(saved, reloaded));
    });

    it("rejects a save with an invalid roamMons entry", () => {
      const world = new GameWorld(assets());
      const saved = world.save();
      const bad = {
        ...saved,
        roamMons: [{ species: 999, level: 0, mapId: null, hp: 0, dvs: 0 }, emptyRoamer(), emptyRoamer()],
      };
      expect(() => world.restore(bad)).toThrow("Invalid native save");
    });

    it("rejects a save missing a roam slot", () => {
      const world = new GameWorld(assets());
      const saved = world.save();
      const bad = { ...saved, roamMons: [emptyRoamer(), emptyRoamer()] };
      expect(() => world.restore(bad)).toThrow("Invalid native save");
    });

    it("migrates an older save to three empty, GROUP_N_A roam slots", () => {
      const world = new GameWorld(assets());
      const saved = world.save() as Record<string, unknown>;
      delete saved.roamMons;
      delete saved.roamMonsMap;
      const migrated = migrateSave(saved, () => 1);
      expect(migrated?.roamMons).toEqual([emptyRoamer(), emptyRoamer(), emptyRoamer()]);
      expect(migrated?.roamMonsMap).toBeNull();
      expect(() => world.restore(migrated)).not.toThrow();
    });
  });
});