import 'package:flutter_test/flutter_test.dart';
import 'package:halkyon_learn_flutter/src/feature/dictionary/model/japanese_deinflection.dart';

/// The words [text] deinflects to that a dictionary entry of [pos] fits.
Set<String> wordsOf(String text, List<String> pos) => {
  for (final each in deinflect(text))
    if (each.fits(pos)) each.text,
};

void main() {
  test('the text as it stands comes first, and fits any word', () {
    final first = deinflect('天気').first;
    expect(first.text, '天気');
    expect(first.steps, isEmpty);
    expect(first.form, isNull);
    expect(first.fits(const ['n']), isTrue);
  });

  test('verbs come back to their dictionary form', () {
    expect(wordsOf('会いました', ['v5u']), contains('会う'));
    expect(wordsOf('読んだ', ['v5m']), contains('読む'));
    expect(wordsOf('読んでいない', ['v5m']), contains('読む'));
    expect(wordsOf('食べられなかった', ['v1']), contains('食べる'));
    expect(wordsOf('出ていった', ['v1']), contains('出る'));
    expect(wordsOf('残っている', ['v5r']), contains('残る'));
    expect(wordsOf('続けよう', ['v1']), contains('続ける'));
    expect(wordsOf('行かなければ', ['v5k-s']), contains('行く'));
    expect(wordsOf('なりたい', ['v5r']), contains('なる'));
    expect(wordsOf('使える', ['v5u']), contains('使う'));
    expect(wordsOf('食べちゃった', ['v1']), contains('食べる'));
    expect(wordsOf('読まれた', ['v5m']), contains('読む'));
    expect(wordsOf('来ない', ['vk']), contains('来る'));
    expect(wordsOf('きました', ['vk']), contains('くる'));
  });

  test('adjectives and nouns taking する come back too', () {
    expect(wordsOf('面白そう', ['adj-i']), contains('面白い'));
    expect(wordsOf('早く', ['adj-i']), contains('早い'));
    expect(wordsOf('高くなかった', ['adj-i']), contains('高い'));
    expect(wordsOf('高すぎた', ['adj-i']), contains('高い'));
    expect(wordsOf('勉強した', ['n', 'vs']), contains('勉強'));
  });

  test('a form only counts for a word of its class', () {
    // 読んだ as the past of an ichidan verb 読んる doesn't exist; as the
    // past of a godan verb in ぬ or ぶ it would, were there such a word.
    expect(wordsOf('読んだ', ['v1']), isNot(contains('読む')));
    expect(wordsOf('食べた', ['v5r']), isNot(contains('食べる')));
    expect(wordsOf('早く', ['v1']), isNot(contains('早い')));
  });

  test('stems and forms that only lead on are never offered as words', () {
    expect(
      deinflect('食べて').map((each) => each.form),
      isNot(contains(JapaneseForm.te)),
    );
    expect(
      deinflect('会いました').map((each) => each.form),
      isNot(contains(JapaneseForm.masuStem)),
    );
  });

  test('says how it got there, the last step first', () {
    final cake = deinflect('食べられなかった').firstWhere(
      (each) => each.text == '食べる' && each.form == JapaneseForm.ichidan,
    );
    expect(cake.steps, ['passive or potential', 'negative', 'past']);
  });
}