// Synthetic example for https://www.hirubix.com/blogs/booking-time-zones-daylight-saving
// Save as booking-time-zone-check.mjs; run with Node.js 20+: node booking-time-zone-check.mjs
import assert from "node:assert/strict";

const zone = "America/Denver";
const formatter = new Intl.DateTimeFormat("en-GB", {
  timeZone: zone,
  year: "numeric",
  month: "2-digit",
  day: "2-digit",
  hour: "2-digit",
  minute: "2-digit",
  hourCycle: "h23",
  timeZoneName: "longOffset",
});

function localLabel(instant) {
  const parts = Object.fromEntries(
    formatter.formatToParts(new Date(instant)).map(({ type, value }) => [type, value]),
  );
  return `${parts.year}-${parts.month}-${parts.day} ${parts.hour}:${parts.minute} ${parts.timeZoneName}`;
}

const rows = [
  ["First 01:30", "2026-11-01T07:30:00Z", "2026-11-01 01:30 GMT-06:00"],
  ["Second 01:30", "2026-11-01T08:30:00Z", "2026-11-01 01:30 GMT-07:00"],
  ["Before spring jump", "2026-03-08T08:59:00Z", "2026-03-08 01:59 GMT-07:00"],
  ["After spring jump", "2026-03-08T09:00:00Z", "2026-03-08 03:00 GMT-06:00"],
  ["Sunday at 09:00", "2026-10-25T15:00:00Z", "2026-10-25 09:00 GMT-06:00"],
  ["Add 168 elapsed hours", "2026-11-01T15:00:00Z", "2026-11-01 08:00 GMT-07:00"],
  ["Next Sunday at 09:00", "2026-11-01T16:00:00Z", "2026-11-01 09:00 GMT-07:00"],
];

for (const [label, utc, expected] of rows) {
  assert.equal(localLabel(utc), expected, label);
}
const elapsedHours = (start, end) => (Date.parse(end) - Date.parse(start)) / 3_600_000;
assert.equal(elapsedHours(rows[0][1], rows[1][1]), 1);
assert.equal(elapsedHours(rows[4][1], rows[5][1]), 168);
assert.equal(elapsedHours(rows[4][1], rows[6][1]), 169);

console.log(JSON.stringify({
  synthetic: true,
  runtime: { node: process.version, icu: process.versions.icu, tz: process.versions.tz },
  zone,
  checksPassed: 10,
  rows: rows.map(([label, utc]) => ({ label, utc, local: localLabel(utc) })),
}, null, 2));