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

// ── Relationships ─────────────────────────────────────
const ChildOf = defineRelationship("childOf");
const Targeting = defineRelationship("targeting");
const Inside = defineRelationship("inside");

// ── Helpers ───────────────────────────────────────────
function collectEvents(world: World): WorldEvent[] {
  const log: WorldEvent[] = [];
  world.events$.subscribe((e: WorldEvent) => log.push(e));
  return log;
}

function collectRelUpdates(obs$: {
  subscribe: Function;
}): RelationshipUpdate[] {
  const log: RelationshipUpdate[] = [];
  obs$.subscribe((u: RelationshipUpdate) => log.push(u));
  return log;
}

// ── Basic relate / unrelate ───────────────────────────
describe("Relationships", () => {
  let world: World;

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

  it("relates two entities", () => {
    const parent = world.spawn();
    const child = world.spawn();

    world.relate(child, ChildOf, parent);
    expect(world.getRelated(child, ChildOf)).toBe(parent);
  });

  it("getRelated returns undefined when no relationship", () => {
    const e = world.spawn();
    expect(world.getRelated(e, ChildOf)).toBeUndefined();
  });

  it("getRelatedTo returns reverse lookup", () => {
    const parent = world.spawn();
    const a = world.spawn();
    const b = world.spawn();

    world.relate(a, ChildOf, parent);
    world.relate(b, ChildOf, parent);

    const children = [...world.getRelatedTo(parent, ChildOf)];
    expect(children).toHaveLength(2);
    expect(children).toContain(a);
    expect(children).toContain(b);
  });

  it("getRelatedTo returns empty when no edges", () => {
    const e = world.spawn();
    expect([...world.getRelatedTo(e, ChildOf)]).toEqual([]);
  });

  it("unrelate removes the relationship", () => {
    const parent = world.spawn();
    const child = world.spawn();

    world.relate(child, ChildOf, parent);
    world.unrelate(child, ChildOf);

    expect(world.getRelated(child, ChildOf)).toBeUndefined();
    expect([...world.getRelatedTo(parent, ChildOf)]).toEqual([]);
  });

  it("unrelate is idempotent", () => {
    const e = world.spawn();
    expect(() => world.unrelate(e, ChildOf)).not.toThrow();
  });

  it("relate replaces existing relationship", () => {
    const a = world.spawn();
    const b = world.spawn();
    const c = world.spawn();

    world.relate(a, ChildOf, b);
    expect(world.getRelated(a, ChildOf)).toBe(b);
    expect([...world.getRelatedTo(b, ChildOf)]).toContain(a);

    world.relate(a, ChildOf, c);
    expect(world.getRelated(a, ChildOf)).toBe(c);
    // a should no longer point to b
    expect([...world.getRelatedTo(b, ChildOf)]).toEqual([]);
    expect([...world.getRelatedTo(c, ChildOf)]).toContain(a);
  });
});

// ── Events ────────────────────────────────────────────
describe("Relationship events", () => {
  let world: World;

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

  it("emits relationshipAdded event", () => {
    const events = collectEvents(world);
    const a = world.spawn();
    const b = world.spawn();
    world.relate(a, ChildOf, b);

    const ev = events.find((e) => e.type === "relationshipAdded")!;
    expect(ev).toMatchObject({
      type: "relationshipAdded",
      source: a,
      target: b,
    });
  });

  it("emits relationshipRemoved on unrelate", () => {
    const a = world.spawn();
    const b = world.spawn();
    world.relate(a, ChildOf, b);

    const events = collectEvents(world);
    world.unrelate(a, ChildOf);

    const ev = events.find((e) => e.type === "relationshipRemoved")!;
    expect(ev).toMatchObject({
      type: "relationshipRemoved",
      source: a,
      target: b,
    });
  });

  it("emits relationshipRemoved when replacing an edge", () => {
    const a = world.spawn();
    const b = world.spawn();
    const c = world.spawn();
    world.relate(a, ChildOf, b);

    const events = collectEvents(world);
    world.relate(a, ChildOf, c);

    const removed = events.filter((e) => e.type === "relationshipRemoved");
    const added = events.filter((e) => e.type === "relationshipAdded");

    expect(removed).toHaveLength(1);
    expect(removed[0]).toMatchObject({ source: a, target: b });
    expect(added).toHaveLength(1);
    expect(added[0]).toMatchObject({ source: a, target: c });
  });
});

// ── Observable relationships ──────────────────────────
describe("Observable relationships", () => {
  let world: World;

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

  it("emits added on relate", () => {
    const log = collectRelUpdates(world.observeRelated(ChildOf));
    const a = world.spawn();
    const b = world.spawn();
    world.relate(a, ChildOf, b);

    expect(log).toHaveLength(1);
    expect(log[0].added).toEqual([{ source: a, target: b }]);
    expect(log[0].removed).toEqual([]);
  });

  it("emits removed on unrelate", () => {
    const a = world.spawn();
    const b = world.spawn();
    world.relate(a, ChildOf, b);

    const log = collectRelUpdates(world.observeRelated(ChildOf));
    world.unrelate(a, ChildOf);

    expect(log).toHaveLength(1);
    expect(log[0].removed).toEqual([{ source: a, target: b }]);
  });

  it("emits removed+added on replacement", () => {
    const a = world.spawn();
    const b = world.spawn();
    const c = world.spawn();
    world.relate(a, ChildOf, b);

    const log = collectRelUpdates(world.observeRelated(ChildOf));
    world.relate(a, ChildOf, c);

    // Should have two updates: one removed, one added
    expect(log).toHaveLength(2);
    expect(log[0].removed).toEqual([{ source: a, target: b }]);
    expect(log[1].added).toEqual([{ source: a, target: c }]);
  });

  it("seeds with existing relationships", () => {
    const a = world.spawn();
    const b = world.spawn();
    world.relate(a, ChildOf, b);

    const log = collectRelUpdates(world.observeRelated(ChildOf));

    // Unrelate should trigger removed — proving seed worked
    world.unrelate(a, ChildOf);
    expect(log).toHaveLength(1);
    expect(log[0].removed).toEqual([{ source: a, target: b }]);
  });

  it("observers are scoped to relationship type", () => {
    const childLog = collectRelUpdates(world.observeRelated(ChildOf));
    const targetLog = collectRelUpdates(world.observeRelated(Targeting));

    const a = world.spawn();
    const b = world.spawn();
    world.relate(a, ChildOf, b);

    expect(childLog).toHaveLength(1);
    expect(targetLog).toHaveLength(0);
  });
});

// ── Destroy cleanup ───────────────────────────────────
describe("Destroy cleanup", () => {
  let world: World;

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

  it("removes edges when source is destroyed", () => {
    const parent = world.spawn();
    const child = world.spawn();
    world.relate(child, ChildOf, parent);

    world.destroy(child);
    expect(world.getRelated(child, ChildOf)).toBeUndefined();
    expect([...world.getRelatedTo(parent, ChildOf)]).toEqual([]);
  });

  it("removes edges when target is destroyed", () => {
    const parent = world.spawn();
    const child = world.spawn();
    world.relate(child, ChildOf, parent);

    world.destroy(parent);
    expect([...world.getRelatedTo(parent, ChildOf)]).toEqual([]);
    expect(world.getRelated(child, ChildOf)).toBeUndefined();
  });

  it("emits relationshipRemoved events on destroy", () => {
    const a = world.spawn();
    const b = world.spawn();
    const c = world.spawn();

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

    const log = collectRelUpdates(world.observeRelated(ChildOf));
    const tLog = collectRelUpdates(world.observeRelated(Targeting));

    world.destroy(a);

    expect(log).toHaveLength(1);
    expect(log[0].removed).toEqual([{ source: a, target: c }]);

    expect(tLog).toHaveLength(1);
    expect(tLog[0].removed).toEqual([{ source: a, target: b }]);
  });

  it("detects cross-relationship observers when destroying target", () => {
    const parent = world.spawn();
    const child = world.spawn();
    world.relate(child, ChildOf, parent);

    const log = collectRelUpdates(world.observeRelated(ChildOf));
    world.destroy(parent);

    expect(log).toHaveLength(1);
    expect(log[0].removed).toEqual([{ source: child, target: parent }]);
  });

  it("handles destroy when entity is source for multiple relationships", () => {
    const a = world.spawn();
    const b = world.spawn();
    const c = world.spawn();

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

    const childLog = collectRelUpdates(world.observeRelated(ChildOf));
    const targetLog = collectRelUpdates(world.observeRelated(Targeting));

    world.destroy(a);

    expect(childLog).toHaveLength(1);
    expect(childLog[0].removed).toEqual([{ source: a, target: b }]);

    expect(targetLog).toHaveLength(1);
    expect(targetLog[0].removed).toEqual([{ source: a, target: c }]);
  });
});

// ── Multiple relationship types ──────────────────────
describe("Multiple relationships", () => {
  let world: World;

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

  it("an entity can have different relationship types simultaneously", () => {
    const e = world.spawn();
    const a = world.spawn();
    const b = world.spawn();

    world.relate(e, ChildOf, a);
    world.relate(e, Targeting, b);

    expect(world.getRelated(e, ChildOf)).toBe(a);
    expect(world.getRelated(e, Targeting)).toBe(b);
  });

  it("relationships of different types don't interfere", () => {
    const a = world.spawn();
    const b = world.spawn();
    const c = world.spawn();

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

    world.unrelate(a, ChildOf);

    expect(world.getRelated(a, ChildOf)).toBeUndefined();
    // Targeting should still be intact
    expect(world.getRelated(a, Targeting)).toBe(c);
  });
});

// ── Dead entities ─────────────────────────────────────
describe("Dead entity safety", () => {
  let world: World;

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

  it("relate throws on dead source", () => {
    const a = world.spawn();
    const b = world.spawn();
    world.destroy(a);
    expect(() => world.relate(a, ChildOf, b)).toThrow("not alive");
  });

  it("relate throws on dead target", () => {
    const a = world.spawn();
    const b = world.spawn();
    world.destroy(b);
    expect(() => world.relate(a, ChildOf, b)).toThrow("not alive");
  });

  it("getRelated returns undefined for dead entity", () => {
    const e = world.spawn();
    world.destroy(e);
    expect(world.getRelated(e, ChildOf)).toBeUndefined();
  });

  it("getRelatedTo returns empty for dead entity", () => {
    const e = world.spawn();
    world.destroy(e);
    expect([...world.getRelatedTo(e, ChildOf)]).toEqual([]);
  });
});

// ── Data-carrying relationships ───────────────────────
describe("Data-carrying relationships", () => {
  let world: World;

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

  it("defines a data-carrying relationship", () => {
    const Health = defineRelationship("health", { hp: 100, maxHp: 100 });
    expect(Health.name).toBe("health");
    expect(Health.defaults).toEqual({ hp: 100, maxHp: 100 });
  });

  it("relate stores defaults as data", () => {
    const Health = defineRelationship("health", { hp: 100 });
    const player = world.spawn();
    const game = world.spawn();

    world.relate(player, Health, game);
    const data = world.getRelData(player, Health);
    expect(data).toEqual({ hp: 100 });
  });

  it("relate accepts data override", () => {
    const Health = defineRelationship("health", { hp: 100 });
    const player = world.spawn();
    const game = world.spawn();

    world.relate(player, Health, game, { hp: 50 });
    const data = world.getRelData(player, Health);
    expect(data).toEqual({ hp: 50 });
  });

  it("setRelData updates relationship data", () => {
    const Health = defineRelationship("health", { hp: 100 });
    const player = world.spawn();
    const game = world.spawn();

    world.relate(player, Health, game);
    world.setRelData(player, Health, { hp: 75 });
    expect(world.getRelData(player, Health)).toEqual({ hp: 75 });
  });

  it("getRelData returns defaults when no data was set", () => {
    const Health = defineRelationship("health", { hp: 100 });
    const player = world.spawn();

    // Even without an edge, getRelData returns a copy of defaults
    expect(world.getRelData(player, Health)).toEqual({ hp: 100 });
  });

  it("setRelData works even without prior relate", () => {
    const Health = defineRelationship("health", { hp: 100 });
    const player = world.spawn();

    world.setRelData(player, Health, { hp: 50 });
    expect(world.getRelData(player, Health)).toEqual({ hp: 50 });
  });

  it("data survives unrelate and re-relate", () => {
    const Health = defineRelationship("health", { hp: 100 });
    const player = world.spawn();
    const game = world.spawn();

    world.relate(player, Health, game, { hp: 50 });
    world.unrelate(player, Health);

    // After unrelate, stored data is gone, returns defaults
    expect(world.getRelData(player, Health)).toEqual({ hp: 100 });

    world.relate(player, Health, game, { hp: 80 });
    // Note: this is a *new* relate with data, so stored data is { hp: 80 }
    expect(world.getRelData(player, Health)).toEqual({ hp: 80 });
  });

  it("data is cleaned up on destroy", () => {
    const Health = defineRelationship("health", { hp: 100 });
    const player = world.spawn();
    const game = world.spawn();

    world.relate(player, Health, game, { hp: 50 });
    world.destroy(player);

    // After destroy the entity is dead — assertAlive throws, not the data lookup
    expect(() => world.getRelData(player, Health)).toThrow("not alive");
  });

  it("setRelData with no prior edge stores data that getsRelated does not see", () => {
    const Health = defineRelationship("health", { hp: 100 });
    const player = world.spawn();

    world.setRelData(player, Health, { hp: 50 });
    // No edge exists yet
    expect(world.getRelated(player, Health)).toBeUndefined();
    // But data is stored (decoupled storage)
    expect(world.getRelData(player, Health)).toEqual({ hp: 50 });
  });

  it("data-carrying relationships serialize and deserialize", () => {
    const Health = defineRelationship("health", { hp: 100, maxHp: 100 });
    const player = world.spawn();
    const game = world.spawn();

    world.relate(player, Health, game, { hp: 50, maxHp: 100 });

    const snapshot = world.toJSON();

    // Verify the snapshot has data in the relationship structure
    const relSection = snapshot.relationships["health"];
    expect(relSection).toBeDefined();

    // Find the player source ID — it's the entity without components
    const playerId = Object.keys(snapshot.entities).find(
      (id) => Object.keys(snapshot.entities[id]).length === 0,
    )!;
    const edgeValue = relSection[playerId];
    expect(typeof edgeValue).toBe("object");
    expect((edgeValue as any).target).toBeDefined();
    expect((edgeValue as any).data).toEqual({ hp: 50, maxHp: 100 });

    // Check JSON round-trip preserves data
    const parsed = JSON.parse(JSON.stringify(snapshot));
    const world2 = World.fromJSON(parsed, [], [Health]);

    const snap2 = world2.toJSON();
    const playerId2 = Object.keys(snap2.entities).find(
      (id) => Object.keys(snap2.entities[id]).length === 0,
    )!;
    expect(snap2.relationships["health"]).toBeDefined();
    const edgeValue2 = snap2.relationships["health"][playerId2];
    expect((edgeValue2 as any).data).toEqual({ hp: 50, maxHp: 100 });
  });

  it("pure edge-defined relationships still work alongside data relationships", () => {
    const ChildOf2 = defineRelationship("childOf2");
    const Score = defineRelationship("score", { points: 0 });

    const parent = world.spawn();
    const child = world.spawn();
    const game = world.spawn();

    world.relate(child, ChildOf2, parent);
    world.relate(child, Score, game, { points: 42 });

    // Pure edge still works
    expect(world.getRelated(child, ChildOf2)).toBe(parent);

    // Data edge still works
    expect(world.getRelData(child, Score)).toEqual({ points: 42 });
  });
});