import { readFile } from "node:fs/promises";
import { join } from "node:path";
import { fileURLToPath } from "node:url";
import { buildingSchema, sceneSchema } from "@nengine/core-schema";
import type { SceneDef, SceneEntity } from "@nengine/core-schema";
import { parse, stringify } from "yaml";
import { describe, expect, it } from "vitest";
import {
  ANIMAL_COLOR,
  DEFAULT_SCENE_ID,
  NPC_COLOR,
  addAnimal,
  addBuilding,
  addNpc,
  canRedo,
  canUndo,
  clearHistory,
  createSceneModel,
  entityAt,
  entityColor,
  entityFootprint,
  entityIndexAt,
  markSaved,
  moveEntity,
  redo,
  removeEntity,
  sceneFitsAfterResize,
  sceneFitsIn,
  serialize,
  syncMapSize,
  undo,
} from "../src/renderer/scene-model.js";
import type { SceneFootprint, SceneModel } from "../src/renderer/scene-model.js";

const fixturesDir = fileURLToPath(new URL("./fixtures", import.meta.url));

const FOOTPRINTS: Record<string, SceneFootprint> = {
  house: { w: 2, h: 2 },
  shed: { w: 2, h: 2 },
  well: { w: 1, h: 1 },
};

function model(mapWidth = 10, mapHeight = 10, footprints: Record<string, SceneFootprint> = FOOTPRINTS): SceneModel {
  const m = createSceneModel(
    { id: "farm", entities: [] },
    { mapWidth, mapHeight, footprints },
  );
  if (m === null) throw new Error("expected a valid model");
  return m;
}

function entities(m: SceneModel): SceneEntity[] {
  return m.def.entities;
}

describe("createSceneModel", () => {
  it("builds a model from a valid def without mutating the input", () => {
    const def: SceneDef = {
      id: "farm",
      entities: [{ type: "building", buildingId: "well", x: 1, y: 1 }],
    };
    const snapshot = JSON.stringify(def);
    const m = createSceneModel(def, { mapWidth: 10, mapHeight: 10, footprints: FOOTPRINTS });
    expect(m).not.toBeNull();
    if (m === null) throw new Error("expected a valid model");
    expect(m.dirty).toBe(false);
    addNpc(m, "mayor", 3, 3);
    expect(JSON.stringify(def)).toBe(snapshot);
    expect(m.dirty).toBe(true);
  });

  it("rejects corrupt defs", () => {
    expect(createSceneModel({ id: 42 }, { mapWidth: 10, mapHeight: 10 })).toBeNull();
    expect(createSceneModel({ id: "farm", entities: [{ type: "npc", x: 1 }] }, { mapWidth: 10, mapHeight: 10 })).toBeNull();
    expect(
      createSceneModel({ id: "farm", entities: [{ type: "building", buildingId: "well", x: -1, y: 0 }] }, { mapWidth: 10, mapHeight: 10 }),
    ).toBeNull();
    expect(
      createSceneModel({ id: "farm", entities: [{ type: "silo", x: 1, y: 1 }] }, { mapWidth: 10, mapHeight: 10 }),
    ).toBeNull();
  });

  it("accepts an empty entities array", () => {
    const m = createSceneModel({ id: "farm", entities: [] }, { mapWidth: 10, mapHeight: 10 });
    expect(m?.def.entities).toEqual([]);
  });

  it("creates a new empty scene from undefined input with the default id", () => {
    const m = createSceneModel(undefined, { mapWidth: 10, mapHeight: 10 });
    expect(m).not.toBeNull();
    expect(m?.def).toEqual({ id: DEFAULT_SCENE_ID, entities: [] });
    expect(m?.dirty).toBe(false);
  });

  it("honours a custom default id for new scenes", () => {
    const m = createSceneModel(undefined, { mapWidth: 10, mapHeight: 10, defaultId: "farm" });
    expect(m?.def.id).toBe("farm");
  });

  it("deep-clones the footprints table", () => {
    const footprints: Record<string, SceneFootprint> = { house: { w: 2, h: 2 } };
    const m = model(10, 10, footprints);
    m.footprints.house = { w: 5, h: 5 };
    expect(footprints.house).toEqual({ w: 2, h: 2 });
  });
});

describe("addBuilding", () => {
  it("places a building and marks dirty", () => {
    const m = model();
    expect(m.dirty).toBe(false);
    const result = addBuilding(m, "well", 3, 4);
    expect(result).toEqual({ ok: true });
    expect(entities(m)).toEqual([{ type: "building", buildingId: "well", x: 3, y: 4 }]);
    expect(m.dirty).toBe(true);
  });

  it("clamps out-of-bounds coordinates footprint-aware", () => {
    const m = model(10, 10);
    addBuilding(m, "house", 9, 9);
    expect(entities(m)[0]).toEqual({ type: "building", buildingId: "house", x: 8, y: 8 });
    addBuilding(m, "well", -3, -3);
    expect(entities(m)[1]).toEqual({ type: "building", buildingId: "well", x: 0, y: 0 });
  });

  it("rejects non-integer coordinates", () => {
    const m = model();
    expect(addBuilding(m, "well", 1.5, 1)).toEqual({ ok: false, reason: expect.stringContaining("integer") });
    expect(addBuilding(m, "well", Number.NaN, 1)).toEqual({ ok: false, reason: expect.stringContaining("integer") });
    expect(entities(m)).toHaveLength(0);
    expect(m.dirty).toBe(false);
  });

  it("rejects an unknown building id", () => {
    const m = model();
    const result = addBuilding(m, "silo", 1, 1);
    expect(result).toEqual({ ok: false, reason: expect.stringContaining('unknown building "silo"') });
    expect(entities(m)).toHaveLength(0);
  });

  it("rejects an empty building id", () => {
    const m = model();
    expect(addBuilding(m, "", 1, 1)).toEqual({ ok: false, reason: expect.stringContaining("must not be empty") });
  });

  it("rejects overlap with another building's footprint", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    const result = addBuilding(m, "well", 1, 1);
    expect(result.ok).toBe(false);
    if (!result.ok) expect(result.reason).toContain("overlaps");
    expect(entities(m)).toHaveLength(1);
    expect(m.dirty).toBe(true);
  });

  it("rejects a duplicate building id at the same coordinates", () => {
    const m = model();
    addBuilding(m, "well", 2, 2);
    const result = addBuilding(m, "well", 2, 2);
    expect(result).toEqual({ ok: false, reason: expect.stringContaining('duplicate building "well" at (2,2)') });
    expect(entities(m)).toHaveLength(1);
  });

  it("rejects overlap with a placed npc or animal", () => {
    const m = model();
    addNpc(m, "mayor", 2, 2);
    expect(addBuilding(m, "house", 1, 1).ok).toBe(false);
    addAnimal(m, "chicken", 5, 5);
    expect(addBuilding(m, "house", 4, 4).ok).toBe(false);
    expect(entities(m).filter((e) => e.type === "building")).toHaveLength(0);
  });

  it("allows adjacent placement that only touches edges", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    const result = addBuilding(m, "well", 2, 0);
    expect(result).toEqual({ ok: true });
    expect(entities(m)).toHaveLength(2);
  });

  it("rejects a footprint larger than the map", () => {
    const m = model(1, 1);
    const result = addBuilding(m, "house", 0, 0);
    expect(result.ok).toBe(false);
    if (!result.ok) expect(result.reason).toContain("does not fit");
    expect(entities(m)).toHaveLength(0);
  });
});

describe("addNpc", () => {
  it("places an npc with optional dialogue and label", () => {
    const m = model();
    const result = addNpc(m, "mayor", 4, 4, { dialogue: "intro", label: "Mayor" });
    expect(result).toEqual({ ok: true });
    expect(entities(m)).toEqual([
      { type: "npc", npcId: "mayor", x: 4, y: 4, dialogue: "intro", label: "Mayor" },
    ]);
    expect(m.dirty).toBe(true);
  });

  it("omits empty dialogue and label", () => {
    const m = model();
    addNpc(m, "mayor", 4, 4, { dialogue: "", label: "" });
    expect(entities(m)).toEqual([{ type: "npc", npcId: "mayor", x: 4, y: 4 }]);
  });

  it("rejects a duplicate npc id", () => {
    const m = model();
    addNpc(m, "mayor", 1, 1);
    const result = addNpc(m, "mayor", 5, 5);
    expect(result).toEqual({ ok: false, reason: expect.stringContaining('duplicate npc id "mayor"') });
    expect(entities(m)).toHaveLength(1);
  });

  it("clamps out-of-bounds coordinates", () => {
    const m = model(10, 10);
    addNpc(m, "mayor", -5, 99);
    expect(entities(m)[0]).toEqual({ type: "npc", npcId: "mayor", x: 0, y: 9 });
  });

  it("rejects placement inside a building footprint", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    const result = addNpc(m, "mayor", 1, 1);
    expect(result.ok).toBe(false);
    if (!result.ok) expect(result.reason).toContain("overlaps");
    expect(entities(m)).toHaveLength(1);
  });
});

describe("addAnimal", () => {
  it("places an animal and marks dirty", () => {
    const m = model();
    const result = addAnimal(m, "chicken", 3, 3);
    expect(result).toEqual({ ok: true });
    expect(entities(m)).toEqual([{ type: "animal", animalId: "chicken", x: 3, y: 3 }]);
    expect(m.dirty).toBe(true);
  });

  it("clamps out-of-bounds coordinates", () => {
    const m = model(10, 10);
    addAnimal(m, "chicken", 10, -2);
    expect(entities(m)[0]).toEqual({ type: "animal", animalId: "chicken", x: 9, y: 0 });
  });

  it("allows multiple animals with the same animal id", () => {
    const m = model();
    addAnimal(m, "chicken", 1, 1);
    addAnimal(m, "chicken", 3, 3);
    expect(entities(m)).toHaveLength(2);
  });

  it("rejects overlap with a building", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    expect(addAnimal(m, "chicken", 0, 0).ok).toBe(false);
    expect(entities(m)).toHaveLength(1);
  });
});

describe("removeEntity", () => {
  it("removes the entity at the index and marks dirty", () => {
    const m = model();
    addBuilding(m, "well", 1, 1);
    addNpc(m, "mayor", 3, 3);
    const result = removeEntity(m, 0);
    expect(result).toEqual({ ok: true });
    expect(entities(m)).toHaveLength(1);
    expect(entities(m)[0]?.type).toBe("npc");
    expect(m.dirty).toBe(true);
  });

  it("rejects an out-of-range index", () => {
    const m = model();
    expect(removeEntity(m, 0)).toEqual({ ok: false, reason: expect.stringContaining("no entity at index") });
    addAnimal(m, "chicken", 1, 1);
    expect(removeEntity(m, 5)).toEqual({ ok: false, reason: expect.stringContaining("no entity at index") });
    expect(entities(m)).toHaveLength(1);
  });
});

describe("moveEntity", () => {
  it("moves an entity and marks dirty", () => {
    const m = model();
    addNpc(m, "mayor", 1, 1);
    const result = moveEntity(m, 0, 4, 5);
    expect(result).toEqual({ ok: true });
    expect(entities(m)[0]).toEqual({ type: "npc", npcId: "mayor", x: 4, y: 5 });
    expect(m.dirty).toBe(true);
  });

  it("re-clamps out-of-bounds targets footprint-aware", () => {
    const m = model(10, 10);
    addBuilding(m, "house", 1, 1);
    moveEntity(m, 0, -5, 99);
    expect(entities(m)[0]).toEqual({ type: "building", buildingId: "house", x: 0, y: 8 });
  });

  it("rejects a move into another entity's footprint without mutating", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    addNpc(m, "mayor", 6, 6);
    const before = JSON.stringify(m.def);
    const result = moveEntity(m, 0, 6, 6);
    expect(result.ok).toBe(false);
    if (!result.ok) expect(result.reason).toContain("overlaps");
    expect(JSON.stringify(m.def)).toBe(before);
    expect(m.dirty).toBe(true);
  });

  it("rejects a move into its own footprint (same entity excluded from overlap)", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    addNpc(m, "mayor", 6, 6);
    const result = moveEntity(m, 0, 1, 1);
    expect(result).toEqual({ ok: true });
    expect(entities(m)[0]).toEqual({ type: "building", buildingId: "house", x: 1, y: 1 });
  });

  it("rejects an invalid index and non-integer coordinates", () => {
    const m = model();
    expect(moveEntity(m, 0, 1, 1)).toEqual({ ok: false, reason: expect.stringContaining("no entity at index") });
    addAnimal(m, "chicken", 1, 1);
    expect(moveEntity(m, 0, 2.5, 1)).toEqual({ ok: false, reason: expect.stringContaining("integer") });
    expect(entities(m)[0]).toEqual({ type: "animal", animalId: "chicken", x: 1, y: 1 });
  });
});

describe("serialize", () => {
  it("roundtrips a valid scene as a fresh object", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    addNpc(m, "mayor", 3, 3, { dialogue: "intro" });
    const out = serialize(m);
    expect(out).not.toBeNull();
    expect(out).toEqual({
      id: "farm",
      entities: [
        { type: "building", buildingId: "house", x: 0, y: 0 },
        { type: "npc", npcId: "mayor", x: 3, y: 3, dialogue: "intro" },
      ],
    });
    expect(out).not.toBe(m.def);
    expect(out?.entities[0]).not.toBe(m.def.entities[0]);
    expect(sceneSchema.safeParse(out as SceneDef).success).toBe(true);
  });

  it("rejects an invalid working copy", () => {
    const m = model();
    addAnimal(m, "chicken", 1, 1);
    const invalid = entities(m)[0] as { animalId: string };
    delete invalid.animalId;
    expect(serialize(m)).toBeNull();
  });

  it("still serializes after a rejected op (invalid ops never corrupt)", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    addBuilding(m, "well", 1, 1);
    addNpc(m, "mayor", 1, 1);
    const out = serialize(m);
    expect(out).not.toBeNull();
    expect(out?.entities).toHaveLength(1);
  });

  it("serializes an empty scene", () => {
    const m = model();
    const out = serialize(m);
    expect(out).toEqual({ id: "farm", entities: [] });
  });
});

describe("entityAt / entityIndexAt", () => {
  it("finds entities by any footprint tile", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    addNpc(m, "mayor", 5, 5);
    expect(entityIndexAt(m, 0, 0)).toBe(0);
    expect(entityIndexAt(m, 1, 1)).toBe(0);
    expect(entityIndexAt(m, 0, 1)).toBe(0);
    expect(entityIndexAt(m, 5, 5)).toBe(1);
    expect(entityIndexAt(m, 3, 3)).toBe(-1);
    expect(entityAt(m, 1, 1)?.type).toBe("building");
    expect(entityAt(m, 3, 3)).toBeUndefined();
  });

  it("returns the topmost entity for overlapping loaded defs", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    const raw = m.def as SceneDef;
    raw.entities.push({ type: "npc", npcId: "mayor", x: 1, y: 1 });
    expect(entityIndexAt(m, 1, 1)).toBe(1);
    expect(entityAt(m, 1, 1)?.type).toBe("npc");
  });
});

describe("entityFootprint / entityColor", () => {
  it("uses the footprint table for buildings and 1x1 for others", () => {
    const m = model();
    addBuilding(m, "house", 0, 0);
    addNpc(m, "mayor", 5, 5);
    addAnimal(m, "chicken", 8, 8);
    expect(entityFootprint(m, entities(m)[0] as SceneEntity)).toEqual({ w: 2, h: 2 });
    expect(entityFootprint(m, entities(m)[1] as SceneEntity)).toEqual({ w: 1, h: 1 });
    expect(entityFootprint(m, entities(m)[2] as SceneEntity)).toEqual({ w: 1, h: 1 });
  });

  it("falls back to 1x1 for a building with no footprint entry", () => {
    const m = model(10, 10, {});
    const raw = m.def as SceneDef;
    raw.entities.push({ type: "building", buildingId: "silo", x: 0, y: 0 });
    expect(entityFootprint(m, entities(m)[0] as SceneEntity)).toEqual({ w: 1, h: 1 });
  });

  it("colors npc amber, animal red, buildings a stable hash hue", () => {
    expect(entityColor({ type: "npc", npcId: "mayor", x: 0, y: 0 })).toBe(NPC_COLOR);
    expect(entityColor({ type: "animal", animalId: "chicken", x: 0, y: 0 })).toBe(ANIMAL_COLOR);
    const shed = entityColor({ type: "building", buildingId: "shed", x: 0, y: 0 });
    const shedAgain = entityColor({ type: "building", buildingId: "shed", x: 0, y: 0 });
    expect(shed).toBe(shedAgain);
    expect(shed).toMatch(/^hsl\(\d+ 45% 45%\)$/);
  });
});

describe("dirty lifecycle", () => {
  it("tracks edits and clears on markSaved", () => {
    const m = model();
    expect(m.dirty).toBe(false);
    addBuilding(m, "well", 1, 1);
    expect(m.dirty).toBe(true);
    markSaved(m);
    expect(m.dirty).toBe(false);
    moveEntity(m, 0, 2, 2);
    expect(m.dirty).toBe(true);
    markSaved(m);
    removeEntity(m, 0);
    expect(m.dirty).toBe(true);
  });
});

describe("real scene fixture end-to-end", () => {
  it("edits a real scene through read → parse → model → place → serialize → stringify → parse", async () => {
    const sceneText = await readFile(join(fixturesDir, "scene-farm.yaml"), "utf8");
    const shedText = await readFile(join(fixturesDir, "buildings", "shed.yaml"), "utf8");
    const wellText = await readFile(join(fixturesDir, "buildings", "well.yaml"), "utf8");
    const footprints: Record<string, SceneFootprint> = {};
    for (const text of [shedText, wellText]) {
      const def = buildingSchema.safeParse(parse(text));
      expect(def.success).toBe(true);
      if (def.success) footprints[def.data.id] = def.data.footprint;
    }

    const m = createSceneModel(parse(sceneText), { mapWidth: 16, mapHeight: 16, footprints });
    expect(m).not.toBeNull();
    if (m === null) throw new Error("fixture must be a valid scene");
    expect(sceneSchema.safeParse(m.def).success).toBe(true);
    expect(m.def.id).toBe("farm-yard");
    expect(entities(m)).toHaveLength(3);

    const placed = addBuilding(m, "well", 8, 8);
    expect(placed).toEqual({ ok: true });
    const npc = addNpc(m, "farmer", 10, 10, { label: "Farmer" });
    expect(npc).toEqual({ ok: true });
    expect(addBuilding(m, "shed", 0, 0).ok).toBe(false);

    const out = serialize(m);
    expect(out).not.toBeNull();
    if (out === null) throw new Error("edited fixture must serialize");

    const yaml = stringify(out);
    const reparsed = parse(yaml);
    expect(reparsed).toEqual(out);
    expect(sceneSchema.safeParse(reparsed).success).toBe(true);

    const m2 = createSceneModel(reparsed, { mapWidth: 16, mapHeight: 16, footprints });
    expect(m2).not.toBeNull();
    expect(m2?.def.entities).toHaveLength(5);
    expect(m2?.def.entities[3]).toEqual({ type: "building", buildingId: "well", x: 8, y: 8 });
    expect(m2?.def.entities[4]).toEqual({ type: "npc", npcId: "farmer", x: 10, y: 10, label: "Farmer" });

    expect(await readFile(join(fixturesDir, "scene-farm.yaml"), "utf8")).toBe(sceneText);
  });
});

describe("undo/redo", () => {
  it("addBuilding/addNpc/addAnimal undo removes the entity and redo restores it", () => {
    const m = model();
    addBuilding(m, "house", 4, 4);
    addNpc(m, "mayor", 0, 0, { dialogue: "intro" });
    addAnimal(m, "chicken", 7, 7);
    expect(entities(m).length).toBe(3);
    expect(undo(m)).toBe(true);
    expect(entities(m).length).toBe(2);
    expect(undo(m)).toBe(true);
    expect(entities(m).length).toBe(1);
    expect(undo(m)).toBe(true);
    expect(entities(m).length).toBe(0);
    expect(m.dirty).toBe(false);
    expect(redo(m)).toBe(true);
    expect(entities(m)[0]).toEqual({ type: "building", buildingId: "house", x: 4, y: 4 });
    expect(redo(m)).toBe(true);
    expect(entities(m)[1]).toEqual({ type: "npc", npcId: "mayor", x: 0, y: 0, dialogue: "intro" });
    expect(m.dirty).toBe(true);
  });

  it("removeEntity undo re-inserts the snapshot at the original index", () => {
    const m = model();
    addBuilding(m, "house", 4, 4);
    addNpc(m, "mayor", 0, 0);
    expect(removeEntity(m, 0)).toEqual({ ok: true });
    expect(entities(m).map((e) => e.type)).toEqual(["npc"]);
    expect(undo(m)).toBe(true);
    expect(entities(m).map((e) => e.type)).toEqual(["building", "npc"]);
    expect(entities(m)[0]).toEqual({ type: "building", buildingId: "house", x: 4, y: 4 });
  });

  it("history entries snapshot entities: a later move never corrupts redo", () => {
    const m = model();
    addBuilding(m, "house", 4, 4); // add entry snapshots house at (4,4)
    expect(moveEntity(m, 0, 7, 7)).toEqual({ ok: true }); // live house → (7,7)
    expect(undo(m)).toBe(true); // undo the move
    expect(undo(m)).toBe(true); // undo the add
    expect(entities(m)).toHaveLength(0);
    expect(redo(m)).toBe(true); // redo the add — restores the SNAPSHOT coords, not (7,7)
    expect(entities(m)[0]).toEqual({ type: "building", buildingId: "house", x: 4, y: 4 });
  });

  it("moveEntity undo restores the previous coordinates", () => {
    const m = model();
    addNpc(m, "mayor", 2, 2);
    expect(moveEntity(m, 0, 8, 8)).toEqual({ ok: true });
    expect(entities(m)[0].x).toBe(8);
    expect(undo(m)).toBe(true);
    expect(entities(m)[0]).toEqual({ x: 2, y: 2, type: "npc", npcId: "mayor" });
  });

  it("rejected ops never enter the stack", () => {
    const m = model();
    addBuilding(m, "house", 4, 4);
    expect(addBuilding(m, "house", 4, 4)).toEqual({ ok: false, reason: expect.stringContaining("duplicate") });
    expect(addNpc(m, "mayor", 0, 0));
    expect(addNpc(m, "mayor", 1, 1)).toEqual({ ok: false, reason: expect.stringContaining("duplicate npc") });
    expect(moveEntity(m, 99, 0, 0)).toEqual({ ok: false, reason: expect.stringContaining("index") });
    expect(m.history.length).toBe(2); // only the two successful adds
  });

  it("markSaved is a checkpoint and undo-all returns clean", () => {
    const m = model();
    addNpc(m, "mayor", 0, 0);
    undo(m);
    markSaved(m);
    expect(m.history.length).toBe(0);
    expect(m.future.length).toBe(0);
    expect(m.dirty).toBe(false);
    addNpc(m, "mia", 1, 1);
    addNpc(m, "cow", 2, 2);
    while (undo(m)) {
      // drain
    }
    expect(m.dirty).toBe(false);
    expect(entities(m).length).toBe(0);
  });
});

describe("syncMapSize", () => {
  it("updates bounds and clamps entities into the new size", () => {
    const m = model(10, 10);
    addBuilding(m, "house", 8, 8); // 2×2 at 8,8 → fits in 10×10
    addNpc(m, "mayor", 9, 0);
    syncMapSize(m, 5, 5);
    expect(m.mapWidth).toBe(5);
    expect(m.mapHeight).toBe(5);
    expect(entities(m)[0]).toEqual({ type: "building", buildingId: "house", x: 3, y: 3 });
    expect(entities(m)[1]).toEqual({ type: "npc", npcId: "mayor", x: 4, y: 0 });
  });

  it("leaves a building whose footprint cannot fit in place (defensive — sceneFitsIn guards first)", () => {
    const m = model(10, 10);
    addBuilding(m, "house", 4, 4);
    syncMapSize(m, 1, 1);
    expect(entities(m)[0]).toEqual({ type: "building", buildingId: "house", x: 4, y: 4 });
  });
});

describe("sceneFitsIn", () => {
  it("rejects a size that cannot contain a placed building footprint", () => {
    const m = model(10, 10);
    addBuilding(m, "house", 4, 4); // 2×2
    expect(sceneFitsIn(m, 10, 10)).toEqual({ ok: true });
    expect(sceneFitsIn(m, 2, 2)).toEqual({ ok: true });
    const result = sceneFitsIn(m, 1, 1);
    expect(result).toEqual({ ok: false, reason: expect.stringContaining('building "house"') });
    expect(result).toEqual({ ok: false, reason: expect.stringContaining("1×1") });
  });

  it("always fits npc/animal (1×1)", () => {
    const m = model(10, 10);
    addNpc(m, "mayor", 9, 9);
    expect(addAnimal(m, "chicken", 8, 8)).toEqual({ ok: true });
    expect(sceneFitsIn(m, 1, 1)).toEqual({ ok: true });
  });
});

describe("clearHistory + sceneFitsAfterResize (bug-fix round)", () => {
  it("clearHistory keeps the dirty flag — the resize is an unsaved edit", () => {
    const m = model();
    addNpc(m, "mayor", 0, 0);
    clearHistory(m);
    expect(m.history.length).toBe(0);
    expect(m.dirty).toBe(true);
    expect(canUndo(m)).toBe(false);
  });

  it("sceneFitsAfterResize rejects a shrink whose clamping would overlap buildings", () => {
    const m = model(10, 10);
    addBuilding(m, "house", 0, 0); // 2×2
    addBuilding(m, "shed", 3, 0); // 2×2 — clamp target (1,0) would overlap the house
    const result = sceneFitsAfterResize(m, 3, 3);
    expect(result).toEqual({ ok: false, reason: expect.stringContaining("would overlap") });
    // per-building fit still passes at 3×3 (each 2×2 fits) — the overlap
    // simulation is what rejects it
    expect(sceneFitsIn(m, 3, 3)).toEqual({ ok: true });
  });

  it("sceneFitsAfterResize passes when clamped entities stay apart", () => {
    const m = model(10, 10);
    addBuilding(m, "house", 0, 0);
    addBuilding(m, "shed", 5, 0);
    addNpc(m, "mayor", 9, 9);
    expect(sceneFitsAfterResize(m, 4, 4)).toEqual({ ok: true });
  });

  it("sceneFitsAfterResize still rejects uncontainable buildings", () => {
    const m = model(10, 10);
    addBuilding(m, "house", 0, 0); // 2×2
    expect(sceneFitsAfterResize(m, 1, 1)).toEqual({ ok: false, reason: expect.stringContaining("does not fit") });
  });
});