citation-evidence/src/engine/events/bus.test.ts

import { describe, expect, it, vi } from "vitest";
import type { DocumentId } from "@shared/ids";
import { createEventBus } from "./bus";

const docId = "doc_test" as DocumentId;
const minimalDoc = {
  id: docId,
  mediaType: "application/pdf",
  createdAt: "2026-05-25T00:00:00.000Z",
  updatedAt: "2026-05-25T00:00:00.000Z",
};

describe("EventBus", () => {
  it("delivers typed events to the registered listener", () => {
    const bus = createEventBus();
    const spy = vi.fn();
    bus.on("DocumentImported", spy);
    const result = bus.emit({ type: "DocumentImported", documentId: docId, document: minimalDoc });
    expect(spy).toHaveBeenCalledOnce();
    expect(spy.mock.calls[0]![0]).toMatchObject({ type: "DocumentImported", documentId: docId });
    expect(result.listenerCount).toBe(1);
    expect(result.errors).toEqual([]);
  });

  it("does not deliver an event to listeners of a different type", () => {
    const bus = createEventBus();
    const spy = vi.fn();
    bus.on("AnnotationCreated", spy);
    bus.emit({ type: "DocumentImported", documentId: docId, document: minimalDoc });
    expect(spy).not.toHaveBeenCalled();
  });

  it("delivers every event to onAny listeners", () => {
    const bus = createEventBus();
    const spy = vi.fn();
    bus.onAny(spy);
    bus.emit({ type: "DocumentImported", documentId: docId, document: minimalDoc });
    bus.emit({ type: "EvidenceItemActivated", evidenceItemId: "ev_x" as never });
    expect(spy).toHaveBeenCalledTimes(2);
  });

  it("returns an unsubscribe function from on()", () => {
    const bus = createEventBus();
    const spy = vi.fn();
    const off = bus.on("DocumentImported", spy);
    off();
    bus.emit({ type: "DocumentImported", documentId: docId, document: minimalDoc });
    expect(spy).not.toHaveBeenCalled();
  });

  it("captures listener errors and still calls subsequent listeners", () => {
    const bus = createEventBus();
    const boom = new Error("listener exploded");
    const a = vi.fn(() => { throw boom; });
    const b = vi.fn();
    bus.on("DocumentImported", a);
    bus.on("DocumentImported", b);
    const result = bus.emit({ type: "DocumentImported", documentId: docId, document: minimalDoc });
    expect(a).toHaveBeenCalledOnce();
    expect(b).toHaveBeenCalledOnce();
    expect(result.errors).toEqual([boom]);
    expect(result.listenerCount).toBe(2);
  });
});