import { describe, expect, it } from 'vitest';

import { Backoff } from '../../src/background/transport/backoff.js';

describe('Backoff', () => {
  it('grows geometrically and caps, with no jitter', () => {
    const b = new Backoff({ baseMs: 500, factor: 2, maxMs: 8000, jitter: 0 });
    expect([b.next(), b.next(), b.next(), b.next(), b.next(), b.next()]).toEqual([
      500, 1000, 2000, 4000, 8000, 8000,
    ]);
  });

  it('reset() returns to the base delay', () => {
    const b = new Backoff({ baseMs: 100, factor: 3, jitter: 0 });
    b.next();
    b.next();
    expect(b.attempts).toBe(2);
    b.reset();
    expect(b.attempts).toBe(0);
    expect(b.next()).toBe(100);
  });

  it('keeps jittered delays within +/- the jitter fraction', () => {
    const rand = [0, 0.5, 1];
    let i = 0;
    const b = new Backoff({ baseMs: 1000, factor: 1, maxMs: 1000, jitter: 0.2, random: () => rand[i++]! });
    expect(b.next()).toBe(800); // random 0   -> raw - spread
    expect(b.next()).toBe(1000); // random 0.5 -> raw
    expect(b.next()).toBe(1200); // random 1   -> raw + spread
  });
});