import assert from 'node:assert/strict';
import test from 'node:test';

import { saveWithOptimisticRollback } from './optimistic-persistence';

test('rolls back optimistic state when the save fails and state is unchanged', async () => {
  const previous = [{ id: 'old' }];
  const optimistic = [{ id: 'new' }];
  let current = optimistic;
  let rolledBack = false;

  await assert.rejects(
    () => saveWithOptimisticRollback({
      save: async () => {
        throw new Error('save failed');
      },
      expected: optimistic,
      getCurrent: () => current,
      rollback: () => {
        rolledBack = true;
        current = previous;
      },
    }),
    /save failed/,
  );

  assert.equal(rolledBack, true);
  assert.equal(current, previous);
});

test('does not roll back a newer optimistic state when an older save fails', async () => {
  const optimistic = [{ id: 'new' }];
  const newer = [{ id: 'newer' }];
  let current = newer;
  let rolledBack = false;

  await assert.rejects(
    () => saveWithOptimisticRollback({
      save: async () => {
        throw new Error('save failed');
      },
      expected: optimistic,
      getCurrent: () => current,
      rollback: () => {
        rolledBack = true;
      },
    }),
    /save failed/,
  );

  assert.equal(rolledBack, false);
  assert.equal(current, newer);
});