// @vitest-environment node
/**
 * PresenceAnnouncer (TASK-0093, spec R5) — the ≤ 1/s, state-change-only
 * live-region text machine. Pure + injected clock (deterministic).
 */
import { describe, expect, it } from "vitest";
import { PresenceAnnouncer } from "../presence-announcer";
import type { Presence } from "../types";

function peer(
  userId: string,
  name: string,
  cursor: Presence["cursor"] = null,
  viewing?: boolean,
): Presence {
  return {
    userId,
    name,
    color: "blue",
    cursor,
    ...(viewing !== undefined ? { viewing } : {}),
    lastSeen: 1,
  };
}

function clock(start = 1_000_000) {
  let t = start;
  return { now: () => t, advance: (ms: number) => (t += ms) };
}

describe("PresenceAnnouncer", () => {
  it("announces a join (highest priority), then nothing on unchanged roster", () => {
    const c = clock();
    const a = new PresenceAnnouncer({ now: c.now });
    expect(a.update([peer("u1", "Ana")])?.text).toBe("Ana joined");
    expect(a.update([peer("u1", "Ana")])).toBeNull(); // no state change
  });

  it("announces editing start/stop only on the transition (not per frame)", () => {
    const c = clock();
    const a = new PresenceAnnouncer({ now: c.now });
    a.update([peer("u1", "Ana")]);
    c.advance(1100);
    a.update([peer("u1", "Ana", { blockId: "b1", offset: 2 })]);
    c.advance(1100);
    // Same cursor, repeated frames → NO announcement (typing is not a state
    // change).
    a.update([peer("u1", "Ana", { blockId: "b1", offset: 9 })]);
    expect(a.update([peer("u1", "Ana", { blockId: "b1", offset: 14 })])).toBeNull();
    c.advance(1100);
    a.update([peer("u1", "Ana", null)]);
  });

  it("editing-start text is '… is editing this page'; stop is '… stopped editing'", () => {
    const c = clock();
    const a = new PresenceAnnouncer({ now: c.now });
    a.update([peer("u1", "Ana")]);
    c.advance(1100);
    expect(a.update([peer("u1", "Ana", { blockId: "b", offset: 1 })])?.text).toBe(
      "Ana is editing this page",
    );
    c.advance(1100);
    expect(a.update([peer("u1", "Ana", null)])?.text).toBe("Ana stopped editing");
  });

  it("a backgrounded editor (viewing:false) is NOT 'editing'", () => {
    const c = clock();
    const a = new PresenceAnnouncer({ now: c.now });
    a.update([peer("u1", "Ana")]);
    c.advance(1100);
    a.update([peer("u1", "Ana", { blockId: "b", offset: 1 }, false)]);
    expect(a.update([peer("u1", "Ana", { blockId: "b", offset: 2 }, true)])?.text).toBe(
      "Ana is editing this page",
    );
  });

  it("rate-limits to ≤ 1/s and queues (flushed later)", () => {
    const c = clock();
    const a = new PresenceAnnouncer({ now: c.now });
    a.update([peer("u1", "Ana")]); // t=0 → "Ana joined"
    c.advance(100); // inside the 1 s window
    a.update([peer("u2", "Bob")]); // queued, not announced
    expect(a.flush()?.text).toBe("Bob joined");
    expect(a.flush()).toBeNull(); // nothing left
  });

  it("picks the highest-priority change in one update (join > edit-start)", () => {
    const c = clock();
    const a = new PresenceAnnouncer({ now: c.now });
    a.update([peer("u1", "Ana")]);
    c.advance(1100);
    // Both changes in a single update: Bob joins (rank 0) + Ana starts
    // editing (rank 1) → the JOIN wins.
    a.update([peer("u1", "Ana", { blockId: "b", offset: 1 }), peer("u2", "Bob")]);
    expect(
      a.update([peer("u1", "Ana", { blockId: "b", offset: 1 }), peer("u2", "Bob")]),
    ).toBeNull();
    // The edit-start was consumed in that update (no re-detection).
  });

  it("announces a leave when a peer drops out of the roster", () => {
    const c = clock();
    const a = new PresenceAnnouncer({ now: c.now });
    a.update([peer("u1", "Ana"), peer("u2", "Bob")]);
    c.advance(1100);
    expect(a.update([peer("u1", "Ana")])?.text).toBe("Bob left");
  });

  it("reset() clears the state map (a page switch re-joins from scratch)", () => {
    const c = clock();
    const a = new PresenceAnnouncer({ now: c.now });
    a.update([peer("u1", "Ana")]);
    a.reset();
    expect(a.update([peer("u1", "Ana")])?.text).toBe("Ana joined");
  });
});