import { describe, it, expect, beforeEach } from "vitest";
import {
  World,
  defineComponent,
  defineRelationship,
  type WorldSnapshot,
  query,
  type RelationshipUpdate,
} from "../src/index";

// ── Definitions ─────────────────────────────────────
const Position = defineComponent("position", { x: 0, y: 0 });
const Velocity = defineComponent("velocity", { vx: 0, vy: 0 });
const Health = defineComponent("health", { current: 100, max: 100 });
const Shield = defineComponent("shield", { armor: 5, broken: false });
const Name = defineComponent("name", { value: "" });
const Team = defineComponent("team", { id: 0, color: "#fff" });

const ChildOf = defineRelationship("childOf");
const Targeting = defineRelationship("targeting");
const OwnedBy = defineRelationship("ownedBy");

// ── Serialization helpers ────────────────────────────
function roundTrip(
  world: World,
  components = [Position, Velocity, Health, Shield, Name, Team],
  rels = [ChildOf, Targeting, OwnedBy],
): World {
  const json = JSON.stringify(world.toJSON());
  return World.fromJSON(JSON.parse(json), components, rels);
}

function sortedIds(snap: WorldSnapshot): string[] {
  return Object.keys(snap.entities).sort();
}

// ── Tests ────────────────────────────────────────────
describe("Serialization", () => {
  let world: World;

  beforeEach(() => {
    world = new World();
  });

  it("serializes components by name", () => {
    const e = world.spawn();
    world.add(e, Position, { x: 10, y: 20 });
    world.add(e, Velocity, { vx: 1, vy: 0 });

    const snap = world.toJSON();
    expect(snap.entities).toHaveProperty("e0");
    expect(snap.entities.e0.position).toEqual({ x: 10, y: 20 });
    expect(snap.entities.e0.velocity).toEqual({ vx: 1, vy: 0 });
  });

  it("round-trips components through JSON", () => {
    const e = world.spawn();
    world.add(e, Position, { x: 42, y: 99 });
    world.add(e, Velocity, { vx: 2, vy: -1 });

    const loaded = roundTrip(world);

    const loadedEnts = [...loaded.query(query(Position, Velocity))];
    expect(loadedEnts).toHaveLength(1);

    const loadedE = loadedEnts[0];
    expect(loaded.get(loadedE, Position)).toEqual({ x: 42, y: 99 });
    expect(loaded.get(loadedE, Velocity)).toEqual({ vx: 2, vy: -1 });
  });

  it("handles multiple entities", () => {
    world.spawn();
    world.spawn();

    const snap = world.toJSON();
    const entries = Object.entries(snap.entities);
    expect(entries).toHaveLength(2);
  });

  it("serializes relationships", () => {
    const parent = world.spawn();
    const child = world.spawn();
    world.relate(child, ChildOf, parent);

    const snap = world.toJSON();
    expect(snap.relationships.childOf).toHaveProperty("e1");
    expect(snap.relationships.childOf.e1).toBe("e0");
  });

  it("round-trips relationships", () => {
    const parent = world.spawn();
    const child = world.spawn();
    world.relate(child, ChildOf, parent);

    const loaded = roundTrip(world);

    const reSnap = loaded.toJSON();
    expect(Object.keys(reSnap.relationships.childOf)).toHaveLength(1);
  });

  it("throws on unknown component in snapshot", () => {
    const snap: WorldSnapshot = {
      entities: { e0: { unknownComp: { x: 1 } } },
      relationships: {},
    };
    expect(() => World.fromJSON(snap, [Position])).toThrow(
      'Unknown component "unknownComp"',
    );
  });

  it("throws on unknown relationship in snapshot", () => {
    const snap: WorldSnapshot = {
      entities: { e0: { position: { x: 0, y: 0 } } },
      relationships: { unknownRel: { e0: "e1" } },
    };
    expect(() => World.fromJSON(snap, [Position], [ChildOf])).toThrow(
      'Unknown relationship "unknownRel"',
    );
  });

  it("preserves entities with no components", () => {
    world.spawn();
    const snap = world.toJSON();
    expect(snap.entities).toHaveProperty("e0");
    expect(snap.entities.e0).toEqual({});
  });

  it("preserves bare entities on round-trip", () => {
    world.spawn();
    const loaded = roundTrip(world);
    expect(loaded.entityCount).toBe(1);

    const withPos = [...loaded.query(query(Position))];
    expect(withPos).toHaveLength(0);
    expect(loaded.entityCount).toBe(1);
  });

  it("entity IDs are re-sequential (hole collapsed)", () => {
    world.spawn(); // e0
    const b = world.spawn();
    world.spawn(); // e2
    world.destroy(b); // hole at e1

    const snap = world.toJSON();
    // Holes are collapsed during serialization
    expect(sortedIds(snap)).toEqual(["e0", "e1"]);
  });

  it("round-trips JSON stringify and parse", () => {
    const a = world.spawn();
    world.add(a, Position, { x: 10, y: 20 });
    world.add(a, Health, { current: 75, max: 100 });

    const loaded = roundTrip(world);
    const reSnap = loaded.toJSON();

    expect(reSnap.entities.e0.position).toEqual({ x: 10, y: 20 });
    expect(reSnap.entities.e0.health).toEqual({ current: 75, max: 100 });
  });

  it("empty world serializes to empty snapshot", () => {
    const snap = world.toJSON();
    expect(snap.entities).toEqual({});
    expect(snap.relationships).toEqual({});
  });
});

// ── Extended: rich mixed state ───────────────────────
describe("Serialization — complex state", () => {
  let world: World;

  function setupRichWorld() {
    const w = new World();

    // Player with many components
    const player = w.spawn();
    w.add(player, Position, { x: 100, y: 200 });
    w.add(player, Velocity, { vx: 0, vy: 0 });
    w.add(player, Health, { current: 85, max: 100 });
    w.add(player, Shield, { armor: 20, broken: false });
    w.add(player, Name, { value: "Hero" });
    w.add(player, Team, { id: 1, color: "#ff0000" });

    // Enemy
    const enemy = w.spawn();
    w.add(enemy, Position, { x: 500, y: 300 });
    w.add(enemy, Health, { current: 50, max: 50 });
    w.add(enemy, Team, { id: 2, color: "#0000ff" });

    // Bullet (few components)
    const bullet = w.spawn();
    w.add(bullet, Position, { x: 100, y: 200 });
    w.add(bullet, Velocity, { vx: 10, vy: 0 });

    // Bare entity
    w.spawn();

    // Relationships
    w.relate(bullet, OwnedBy, player);
    w.relate(enemy, Targeting, player);

    return { w, player, enemy, bullet };
  }

  it("round-trips a rich world", () => {
    const { w, player, enemy, bullet } = setupRichWorld();
    const loaded = roundTrip(w);

    expect(loaded.entityCount).toBe(4);

    // Find player by Name component
    const players = [...loaded.query(query(Name))];
    expect(players).toHaveLength(1);
    const p = players[0];
    expect(loaded.get(p, Position)).toEqual({ x: 100, y: 200 });
    expect(loaded.get(p, Velocity)).toEqual({ vx: 0, vy: 0 });
    expect(loaded.get(p, Health)).toEqual({ current: 85, max: 100 });
    expect(loaded.get(p, Shield)).toEqual({ armor: 20, broken: false });
    expect(loaded.get(p, Name)).toEqual({ value: "Hero" });
    expect(loaded.get(p, Team)).toEqual({ id: 1, color: "#ff0000" });

    // Find enemy
    const enemies = [...loaded.query(query(Health, Team))].filter(
      (e) => !loaded.has(e, Name),
    );
    expect(enemies).toHaveLength(1);
    const en = enemies[0];
    expect(loaded.get(en, Health)).toEqual({ current: 50, max: 50 });

    // Bullets
    const bullets = [...loaded.query(query(Position, Velocity))].filter(
      (e) =>
        !loaded.has(e, Health) &&
        !loaded.has(e, Name) &&
        !loaded.has(e, Shield),
    );
    expect(bullets).toHaveLength(1);
  });

  it("preserves relationships in rich world", () => {
    const { w } = setupRichWorld();
    const loaded = roundTrip(w);

    const snap = loaded.toJSON();

    // Verify relationship structure exists
    expect(snap.relationships).toHaveProperty("ownedBy");
    expect(snap.relationships).toHaveProperty("targeting");

    const ownedByEdges = snap.relationships.ownedBy;
    const targetingEdges = snap.relationships.targeting;

    // OwnedBy: exactly one edge
    expect(Object.keys(ownedByEdges)).toHaveLength(1);
    // Targeting: exactly one edge
    expect(Object.keys(targetingEdges)).toHaveLength(1);
  });

  it("relationships reference correct entities after round-trip", () => {
    const { w } = setupRichWorld();
    const snap = w.toJSON();

    // Let's trace: bullet has Position+Velocity, is OwnedBy
    // Find bullet's string id
    const bulletId = Object.keys(snap.entities).find((id) => {
      const comps = snap.entities[id];
      return comps.position && comps.velocity && !comps.health;
    })!;
    const playerId = snap.relationships.ownedBy[bulletId];

    // Player should have a name
    expect(snap.entities[playerId]).toHaveProperty("name");
    expect((snap.entities[playerId].name as any).value).toBe("Hero");
  });
});

// ── Extended: multiple relationship types ────────────
describe("Serialization — multiple relationships", () => {
  it("round-trips multiple relationship types on same entity", () => {
    const w = new World();
    const a = w.spawn();
    const b = w.spawn();
    const c = w.spawn();

    w.relate(a, ChildOf, b);
    w.relate(a, Targeting, c);

    const loaded = roundTrip(w);
    const snap = loaded.toJSON();

    expect(Object.keys(snap.relationships.childOf)).toHaveLength(1);
    expect(Object.keys(snap.relationships.targeting)).toHaveLength(1);
  });

  it("round-trips many-to-one relationships", () => {
    const w = new World();
    const parent = w.spawn();
    const c1 = w.spawn();
    const c2 = w.spawn();
    const c3 = w.spawn();

    w.relate(c1, ChildOf, parent);
    w.relate(c2, ChildOf, parent);
    w.relate(c3, ChildOf, parent);

    const loaded = roundTrip(w);
    const snap = loaded.toJSON();

    const edges = snap.relationships.childOf;
    const children = Object.keys(edges);
    expect(children).toHaveLength(3);

    // All three should point to the same parent
    const parentId = edges[children[0]];
    expect(edges[children[1]]).toBe(parentId);
    expect(edges[children[2]]).toBe(parentId);
  });

  it("round-trips replaced relationships correctly", () => {
    const w = new World();
    const a = w.spawn();
    const b = w.spawn();
    const c = w.spawn();

    w.relate(a, ChildOf, b);
    w.relate(a, ChildOf, c); // replace b → c

    const loaded = roundTrip(w);
    const snap = loaded.toJSON();

    const edges = snap.relationships.childOf;
    expect(Object.keys(edges)).toHaveLength(1);

    // Child pointer resolves forward
    const aId = Object.keys(snap.entities).find(
      (id) =>
        !snap.relationships.childOf[id] &&
        !Object.values(snap.relationships.childOf).includes(id),
    );
    // Actually, find a via exclusion: a has no components, b and c are targets.
    // Let's just check the edge count is right.
    expect(Object.keys(edges)).toHaveLength(1);
  });
});

// ── Extended: nested / array data ────────────────────
describe("Serialization — nested data", () => {
  const Inventory = defineComponent("inventory", {
    items: [] as string[],
    gold: 0,
  });

  const Transform = defineComponent("transform", {
    position: { x: 0, y: 0 },
    scale: { x: 1, y: 1 },
  });

  it("round-trips components with array values", () => {
    const w = new World();
    const e = w.spawn();
    w.add(e, Inventory, { items: ["sword", "shield", "potion"], gold: 42 });

    const loaded = roundTrip(w, [Inventory]);
    const loadedE = [...loaded.query(query(Inventory))][0];

    const inv = loaded.get(loadedE, Inventory);
    expect(inv.items).toEqual(["sword", "shield", "potion"]);
    expect(inv.gold).toBe(42);
  });

  it("round-trips components with nested object values", () => {
    const w = new World();
    const e = w.spawn();
    w.add(e, Transform, {
      position: { x: 10, y: 20 },
      scale: { x: 2, y: 2 },
    });

    const loaded = roundTrip(w, [Transform]);
    const loadedE = [...loaded.query(query(Transform))][0];

    const t = loaded.get(loadedE, Transform);
    expect(t.position).toEqual({ x: 10, y: 20 });
    expect(t.scale).toEqual({ x: 2, y: 2 });
  });

  it("empty arrays survive round-trip", () => {
    const w = new World();
    const e = w.spawn();
    w.add(e, Inventory, { items: [], gold: 0 });

    const loaded = roundTrip(w, [Inventory]);
    const loadedE = [...loaded.query(query(Inventory))][0];

    expect(loaded.get(loadedE, Inventory).items).toEqual([]);
  });
});

// ── Extended: observables still work after load ──────
describe("Serialization — observables after load", () => {
  it("loaded world emits events on mutation", () => {
    const w = new World();
    w.spawn();

    const loaded = roundTrip(w);
    const events: any[] = [];
    loaded.events$.subscribe((e: any) => events.push(e));

    const e = loaded.spawn();
    expect(events).toHaveLength(1);
    expect(events[0].type).toBe("spawned");
  });

  it("loaded world query observables work", () => {
    const w = new World();
    const e = w.spawn();
    w.add(e, Position, { x: 1, y: 2 });

    const loaded = roundTrip(w);
    const updates: any[] = [];
    loaded.observe(query(Position)).subscribe((u: any) => {
      if (u.added.length || u.removed.length || u.changed.length) {
        updates.push(u);
      }
    });

    // Add a new Position entity
    const e2 = loaded.spawn();
    loaded.add(e2, Position, { x: 3, y: 4 });

    expect(updates).toHaveLength(1);
    expect(updates[0].added).toHaveLength(1);
  });

  it("loaded world relationship observables work", () => {
    const w = new World();
    const a = w.spawn();
    const b = w.spawn();
    w.relate(a, ChildOf, b);

    const loaded = roundTrip(w);
    const relUpdates: RelationshipUpdate[] = [];
    loaded.observeRelated(ChildOf).subscribe((u) => relUpdates.push(u));

    const c = loaded.spawn();
    const d = loaded.spawn();
    loaded.relate(c, ChildOf, d);

    expect(relUpdates).toHaveLength(1);
    expect(relUpdates[0].added).toHaveLength(1);
  });
});

// ── Extended: stress ─────────────────────────────────
describe("Serialization — stress", () => {
  it("round-trips 500 entities with mixed components", () => {
    const w = new World();

    for (let i = 0; i < 500; i++) {
      const e = w.spawn();
      w.add(e, Position, { x: i, y: i * 2 });
      if (i % 2 === 0) {
        w.add(e, Velocity, { vx: 1, vy: 0 });
      }
      if (i % 3 === 0) {
        w.add(e, Health, { current: i, max: 1000 });
      }
      if (i % 5 === 0) {
        w.add(e, Name, { value: `entity_${i}` });
      }
    }

    // Add some relationships
    const all = [...w.query(query(Position))];
    for (let i = 0; i < 100; i++) {
      const src = all[i * 2];
      const tgt = all[i * 2 + 1];
      if (src && tgt) {
        w.relate(src, ChildOf, tgt);
      }
    }

    const loaded = roundTrip(w);
    expect(loaded.entityCount).toBe(500);

    const withPos = [...loaded.query(query(Position))];
    const withVel = [...loaded.query(query(Velocity))];
    const withHealth = [...loaded.query(query(Health))];

    expect(withPos).toHaveLength(500);
    expect(withVel).toHaveLength(250); // every 2nd
    expect(withHealth).toHaveLength(167); // every 3rd ≈ floor(499/3)+1

    // Verify a few random entities
    const e0 = withPos[0];
    expect(loaded.get(e0, Position).x).toBe(0);
  });

  it("repeated round-trips are idempotent", () => {
    const w = new World();
    const e = w.spawn();
    w.add(e, Position, { x: 10, y: 20 });
    w.add(e, Health, { current: 75, max: 100 });

    const loaded1 = roundTrip(w);
    const loaded2 = roundTrip(loaded1);

    expect(loaded2.entityCount).toBe(loaded1.entityCount);

    const e2 = [...loaded2.query(query(Position))][0];
    expect(loaded2.get(e2, Position)).toEqual({ x: 10, y: 20 });
    expect(loaded2.get(e2, Health)).toEqual({ current: 75, max: 100 });
  });
});