import { describe, it } from 'node:test';
import assert from 'node:assert/strict';
import { countChanges, wordDiff, WORD_DIFF_LIMIT } from './wordDiff';

const render = (tokens: ReturnType<typeof wordDiff>) =>
  tokens
    ?.map((t) =>
      t.op === 'same'
        ? t.text
        : `${t.op === 'add' ? '+' : '-'}[${t.text.trim()}]${t.text.endsWith(' ') ? ' ' : ''}`,
    )
    .join('');

describe('wordDiff', () => {
  it('returns undefined for identical text', () => {
    assert.equal(wordDiff('hello world', 'hello world'), undefined);
  });

  it('marks a replaced word', () => {
    assert.equal(render(wordDiff('see you at 5', 'see you at 6')), 'see you at -[5]+[6]');
  });

  it('marks insertions and deletions in place', () => {
    assert.equal(
      render(wordDiff('the quick fox', 'the quick brown fox jumps')),
      'the quick +[brown] fox +[jumps]',
    );
    assert.equal(render(wordDiff('a b c d', 'a d')), 'a -[b c] d');
  });

  it('ignores whitespace-only changes', () => {
    assert.equal(wordDiff('a  b', 'a b'), undefined);
    assert.equal(wordDiff('a b\n', 'a b'), undefined);
  });

  it('handles fully different text', () => {
    assert.deepEqual(wordDiff('one', 'two'), [
      { op: 'del', text: 'one' },
      { op: 'add', text: 'two' },
    ]);
  });

  it('gives up past the word limit', () => {
    const long = Array.from({ length: WORD_DIFF_LIMIT }, (_, i) => `w${i}`).join(' ');
    assert.equal(wordDiff(long, `${long} extra`), undefined);
  });

  it('counts changed words', () => {
    const d = wordDiff('a b c', 'a x y z c');
    assert.ok(d);
    assert.deepEqual(countChanges(d), { added: 3, removed: 1 });
  });
});