import 'package:flutter_test/flutter_test.dart';
import 'package:kouyu_english/core/app_state.dart';
import 'package:kouyu_english/core/courses/courses.dart';
import 'package:kouyu_english/core/models.dart';

/// Learning engine 2.2/2.2a/3.1: the same-day recall, the recognition step in
/// front of the first checkpoint, the daily review budget, and the re-ask of
/// an item missed earlier in the session.
void main() {
  ReviewItem due(String id) => ReviewItem(
    id: id,
    target: coreItemEnglish(id),
    prompt: coreReviewTemplate(id).prompt,
    hint: coreItemEnglish(id),
    dueAt: DateTime.now().subtract(const Duration(hours: 1)),
    skill: '回忆表达',
  );

  test('a same-day recap is scheduled for later today, not immediately', () {
    final state = AppState();
    state.scheduleSameDayRecap(['A0-W36']);
    final recap = state.reviewQueue.singleWhere(
      (item) => item.kind == ReviewKind.recap,
    );
    final now = DateTime.now();
    expect(recap.dueAt.isAfter(now), isTrue);
    // 「同一天」指的是隔几小时再提取一次，不是明天再说。深夜学习时它会落在
    // 次日凌晨，那仍然是同一轮学习，所以这里比的是间隔而不是日历日。
    expect(recap.dueAt.difference(now).inMinutes, closeTo(120, 2));
    // It is not offered until it comes due: the point is the delay.
    expect(state.dueRecaps, isEmpty);
  });

  test('finishing a same-day recap advances no checkpoint', () {
    final state = AppState();
    state.reviewQueue.add(
      due('A0-W36').copyWith(kind: ReviewKind.recap, dueAt: DateTime.now()),
    );
    state.completeReview(state.dueRecaps.single, assisted: false);
    expect(state.mastery['A0-W36']?.checkpoint ?? 0, 0);
    expect(state.reviewQueue.where((i) => i.kind == ReviewKind.recap), isEmpty);
  });

  test('missing a same-day recap is not a language failure', () {
    final state = AppState();
    state.reviewQueue.add(
      due('A0-W36').copyWith(kind: ReviewKind.recap, dueAt: DateTime.now()),
    );
    state.reportReviewFailure(state.dueRecaps.single);
    expect(state.mastery['A0-W36']?.needsReview ?? false, isFalse);
    expect(state.dueRecaps, isEmpty);
  });

  test('the first checkpoint opens with a recognition question', () {
    final state = AppState();
    final item = due('A0-W36');
    state.reviewQueue.add(item);
    expect(state.needsRecognitionGate(item), isTrue);
    expect(recognitionDistractors('A0-W36'), isNotEmpty);
  });

  test('passing recognition records 认识 but no checkpoint', () {
    final state = AppState();
    final item = due('A0-W36');
    state.reviewQueue.add(item);
    state.recordRecognitionGate(item, correct: true);
    final mastery = state.mastery['A0-W36']!;
    expect(mastery.checkpoint, 0);
    expect(mastery.status, MasteryStatus.recognize);
    // The checkpoint is still earned by producing the item afterwards.
    state.completeReview(state.dueReviews.single, assisted: false);
    expect(state.mastery['A0-W36']!.checkpoint, 1);
  });

  test('a recognition miss does not count against the item', () {
    final state = AppState();
    final item = due('A0-W36');
    state.reviewQueue.add(item);
    state.recordRecognitionGate(item, correct: false);
    final mastery = state.mastery['A0-W36']!;
    expect(mastery.needsReview, isFalse);
    expect(mastery.checkpoint, 0);
  });

  test('a recognition success survives rebuilding mastery from evidence', () {
    final state = AppState();
    final item = due('A0-W36');
    state.reviewQueue.add(item);
    state.recordRecognitionGate(item, correct: true);
    state.rebuildMasteryFromEvidence();
    expect(state.mastery['A0-W36']!.checkpoint, 0);
    expect(state.mastery['A0-W36']!.status, MasteryStatus.recognize);
  });

  test('due reviews beyond the daily budget wait, they are not dropped', () {
    final state = AppState();
    state.dailyMinutes = 20;
    for (final id in a0CoreItems.keys.take(10)) {
      state.reviewQueue.add(due(id));
    }
    expect(state.dueReviews.length, 10);
    expect(state.todayReviewPlan.length, 5);
    expect(state.postponedReviewCount, 5);
    // Nothing was rescheduled behind the learner's back.
    expect(state.dueReviews.length, 10);
  });

  test('a missed item comes back later in the same session', () {
    final state = AppState();
    state.dailyMinutes = 20;
    state.reviewQueue.add(due('A0-W36'));
    state.reviewQueue.add(due('A0-W37'));
    state.reportReviewFailure(state.dueReviews.first);
    final session = state.reviewSession;
    // The retry is asked after the other due tasks, not straight away.
    expect(session.first.id, 'A0-W37');
    expect(session.last.id, 'A0-W36');
    expect(session.last.kind, ReviewKind.recap);

    final checkpointBefore = state.mastery['A0-W36']!.checkpoint;
    state.completeReview(session.last, assisted: false);
    // The retry is practice: the real check still happens tomorrow.
    expect(state.mastery['A0-W36']!.checkpoint, checkpointBefore);
    expect(state.mastery['A0-W36']!.needsReview, isTrue);
  });
}