import { expect, test } from 'vitest';

import {
  formatCount,
  formatDate,
  formatDateTime,
  formatMoney,
  formatMoneyShort,
  formatValue,
  parseDate,
} from './format';

test.each([
  { name: 'null', value: null },
  { name: 'undefined', value: undefined },
  { name: 'empty', value: '' },
  { name: 'Go’s zero time', value: '0001-01-01T00:00:00Z' },
  { name: 'not a date', value: 'soon' },
])('parseDate reads $name as no date', ({ value }) => {
  expect(parseDate(value)).toBeNull();
  expect(formatDate(value)).toBe('—');
});

test('dates are shown day, short month and year', () => {
  // Tests run in UK time (vite.config.ts), as dates are shown in local time.
  expect(parseDate('2026-03-03T12:00:00Z')?.toISOString()).toBe('2026-03-03T12:00:00.000Z');
  expect(formatDate('2026-03-03T12:00:00Z')).toBe('3 Mar 2026');
  // 23:30 UTC is already the next day in British Summer Time.
  expect(formatDate('2026-07-01T23:30:00Z')).toBe('2 Jul 2026');
});

test('money is shown in whole pounds, and nothing as a dash', () => {
  expect(formatMoney(125000.5)).toBe('£125,001');
  expect(formatMoney(0)).toBe('—');
  expect(formatMoney(-5)).toBe('—');
});

test.each([
  { value: 1, want: '£1' },
  { value: 500, want: '£500' },
  { value: 3563, want: '£3.6k' },
  { value: 12500, want: '£13k' },
  { value: 583333, want: '£583k' },
  { value: 1500000, want: '£1.5m' },
  { value: 9621987, want: '£9.6m' },
  { value: 36250000000, want: '£36bn' },
  { value: 0, want: '—' },
  { value: -5, want: '—' },
])('formatMoneyShort shows $value as $want', ({ value, want }) => {
  expect(formatMoneyShort(value)).toBe(want);
});

test('formatCount groups thousands', () => {
  expect(formatCount(4854)).toBe('4,854');
  expect(formatCount(7)).toBe('7');
});

test('formatValue shows the amount in its currency', () => {
  expect(formatValue(1200.5, 'EUR')).toBe('€1,201');
  expect(formatValue(250000, 'GBP')).toBe('£250,000');
  expect(formatValue(250000, '')).toBe('£250,000');
  expect(formatValue(1500, 'not a code')).toBe('1,500 not a code');
  expect(formatValue(0, 'EUR')).toBe('—');
});

test('formatDateTime shows the UK time', () => {
  expect(formatDateTime('2026-10-15T09:05:26Z')).toBe('15 Oct 2026, 10:05');
  expect(formatDateTime(null)).toBe('—');
});