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

import { diffOf } from './audit';

describe('diffOf', () => {
  it('reports nothing when nothing moved', () => {
    // A log full of empty changes is a log nobody reads.
    expect(diffOf({ a: 1 }, { a: 1 })).toBeNull();
    expect(diffOf(null, null)).toBeNull();
    expect(diffOf({}, {})).toBeNull();
  });

  it('reports a changed field', () => {
    expect(diffOf({ isClosed: false }, { isClosed: true })).toEqual({
      isClosed: { before: false, after: true },
    });
  });

  it('reports only the fields that moved', () => {
    expect(diffOf({ a: 1, b: 2 }, { a: 1, b: 3 })).toEqual({ b: { before: 2, after: 3 } });
  });

  it('reports an added and a removed field', () => {
    expect(diffOf({ a: 1 }, { a: 1, b: 2 })).toEqual({ b: { before: null, after: 2 } });
    expect(diffOf({ a: 1, b: 2 }, { a: 1 })).toEqual({ b: { before: 2, after: null } });
  });

  it('treats a missing field and an explicit null as the same absence', () => {
    expect(diffOf({ note: null }, {})).toBeNull();
    expect(diffOf({ note: undefined }, { note: null })).toBeNull();
  });

  it('compares slot arrays by value, not by identity', () => {
    const before = { slots: [{ open: '10:00', close: '18:30' }] };
    const after = { slots: [{ open: '10:00', close: '18:30' }] };
    expect(diffOf(before, after)).toBeNull();

    expect(diffOf(before, { slots: [{ open: '14:00', close: '18:30' }] })).toEqual({
      slots: {
        before: [{ open: '10:00', close: '18:30' }],
        after: [{ open: '14:00', close: '18:30' }],
      },
    });
  });

  it('compares dates by their instant, not their object', () => {
    const before = { startsAt: new Date('2026-09-20T00:00:00Z') };
    expect(diffOf(before, { startsAt: new Date('2026-09-20T00:00:00Z') })).toBeNull();

    const changed = diffOf(before, { startsAt: new Date('2026-09-21T00:00:00Z') });
    expect(changed?.startsAt).toEqual({
      before: '2026-09-20T00:00:00.000Z',
      after: '2026-09-21T00:00:00.000Z',
    });
  });

  it('records a creation and a deletion', () => {
    expect(diffOf(null, { textFr: 'Bonjour' })).toEqual({
      textFr: { before: null, after: 'Bonjour' },
    });
    expect(diffOf({ textFr: 'Bonjour' }, null)).toEqual({
      textFr: { before: 'Bonjour', after: null },
    });
  });

  it('distinguishes values that only look alike', () => {
    expect(diffOf({ priority: 1 }, { priority: '1' })).not.toBeNull();
    expect(diffOf({ isActive: false }, { isActive: null })).not.toBeNull();
  });
});