/**
 * DST-guard and date-math checks with fixed instants — the acceptance proof
 * that the double crons fire exactly once at 8 AM ET (digest) and midnight
 * Saturday ET (review issue) on BOTH UTC offsets.
 */
import { describe, expect, test } from "bun:test";

import { addDays, campaignDay, campaignWeek, etDate, etHour, isoWeek, rng, sample, weekdayOf } from "./srs.ts";

describe("DST-proof cron guard", () => {
  test("digest fires only at ET hour 8 — EDT (UTC-4)", () => {
    // Cron pair 12:00 / 13:00 UTC during EDT (2026-08-29 is EDT).
    expect(etHour(new Date("2026-08-29T12:00:00Z"))).toBe(8); // fires
    expect(etHour(new Date("2026-08-29T13:00:00Z"))).toBe(9); // no-op
  });
  test("digest fires only at ET hour 8 — EST (UTC-5)", () => {
    // DST ends 2026-11-01; 2026-11-05 is EST.
    expect(etHour(new Date("2026-11-05T12:00:00Z"))).toBe(7); // no-op
    expect(etHour(new Date("2026-11-05T13:00:00Z"))).toBe(8); // fires
  });
  test("saturday review fires only at ET midnight — both offsets", () => {
    // EDT Saturday: 4 UTC = 0 ET fires, 5 UTC = 1 ET no-op.
    expect(etHour(new Date("2026-08-29T04:00:00Z"))).toBe(0);
    expect(weekdayOf(etDate(new Date("2026-08-29T04:00:00Z")))).toBe(6);
    expect(etHour(new Date("2026-08-29T05:00:00Z"))).toBe(1);
    // EST Saturday (2026-11-07): 5 UTC = 0 ET fires, 4 UTC = 11 PM FRIDAY ET.
    expect(etHour(new Date("2026-11-07T05:00:00Z"))).toBe(0);
    expect(weekdayOf(etDate(new Date("2026-11-07T05:00:00Z")))).toBe(6);
    expect(etHour(new Date("2026-11-07T04:00:00Z"))).toBe(23);
    expect(etDate(new Date("2026-11-07T04:00:00Z"))).toBe("2026-11-06"); // still Friday ET
  });
});

describe("date math (noon-UTC anchored)", () => {
  test("addDays crosses the DST-end boundary without drift", () => {
    expect(addDays("2026-10-31", 2)).toBe("2026-11-02");
    expect(addDays("2026-08-24", 2)).toBe("2026-08-26");
  });
  test("campaign math", () => {
    expect(campaignDay("2026-08-17")).toBe(1);
    expect(campaignDay("2026-08-24")).toBe(8);
    expect(campaignWeek("2026-08-24")).toBe(2);
    expect(campaignWeek("2026-08-30")).toBe(2);
    expect(campaignWeek("2026-08-31")).toBe(3);
  });
  test("iso week is stable across a week", () => {
    expect(isoWeek("2026-08-24")).toBe(isoWeek("2026-08-29"));
    expect(isoWeek("2026-08-30")).toBe(isoWeek("2026-08-24")); // Sun ends the ISO week
    expect(isoWeek("2026-08-31")).toBe(isoWeek("2026-08-24") + 1);
  });
});

describe("deterministic sampling", () => {
  test("same seed, same picks", () => {
    const pool = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
    expect(sample(pool, 3, rng("drill-2026-08-31"))).toEqual(sample(pool, 3, rng("drill-2026-08-31")));
    expect(sample(pool, 3, rng("drill-2026-09-01"))).not.toEqual(sample(pool, 3, rng("drill-2026-08-31")));
  });
});