import { describe, expect, it } from "vitest";
import {
  DISPLAY_RETRY_BASE_MS,
  DISPLAY_RETRY_MAX_MS,
  displayRetryDelayMs,
} from "../../src/browser/backoff.js";

describe("display retry backoff", () => {
  it("doubles from one second and stops at one minute", () => {
    const longest = (attempt: number) => displayRetryDelayMs(attempt, () => 1);
    expect([0, 1, 2, 3, 4, 5, 6, 7, 50].map(longest)).toEqual([
      1_000, 2_000, 4_000, 8_000, 16_000, 32_000, 60_000, 60_000, 60_000,
    ]);
  });

  it("jitters between half and all of each step, and never waits zero", () => {
    for (const attempt of [0, 3, 6, 40]) {
      const step = Math.min(DISPLAY_RETRY_MAX_MS, DISPLAY_RETRY_BASE_MS * 2 ** attempt);
      expect(displayRetryDelayMs(attempt, () => 0)).toBe(step / 2);
      expect(displayRetryDelayMs(attempt, () => 1)).toBe(step);
      for (let index = 0; index < 50; index += 1) {
        const delay = displayRetryDelayMs(attempt);
        expect(delay).toBeGreaterThanOrEqual(step / 2);
        expect(delay).toBeLessThanOrEqual(step);
      }
    }
  });

  it("treats a nonsensical attempt or random value as the nearest sensible one", () => {
    expect(displayRetryDelayMs(-3, () => 1)).toBe(1_000);
    expect(displayRetryDelayMs(2, () => 7)).toBe(4_000);
    expect(displayRetryDelayMs(2, () => -1)).toBe(2_000);
  });
});