import 'models.dart';

/// Stable A0 core identities taught by each seed lesson. Wording can vary in
/// future exercises without creating a different mastery item.
const a0TargetItemIdsByLesson = <String, List<String>>{
  'a0-01': ['A0-W36', 'A0-W37', 'A0-W40', 'A0-P01', 'A0-P02', 'A0-P03'],
  'a0-02': ['A0-P04'],
  'a0-03': ['A0-W33', 'A0-W34', 'A0-W35', 'A0-P05', 'A0-P06'],
  'a0-04': [
    'A0-W01',
    'A0-W02',
    'A0-W03',
    'A0-W04',
    'A0-W05',
    'A0-W06',
    'A0-W07',
    'A0-W08',
    'A0-W09',
    'A0-W10',
    'A0-W11',
    'A0-W20',
    'A0-P07',
    'A0-P08',
  ],
  'a0-05': ['A0-W19', 'A0-W21', 'A0-W22', 'A0-W23', 'A0-P09', 'A0-P10'],
  'a0-06': ['A0-P11', 'A0-P12'],
  'a0-07': ['A0-W25', 'A0-W26', 'A0-W27', 'A0-W28', 'A0-P13'],
  'a0-08': [
    'A0-W12',
    'A0-W13',
    'A0-W14',
    'A0-W15',
    'A0-W16',
    'A0-W17',
    'A0-W18',
    'A0-P14',
    'A0-P15',
    'A0-P16',
    'A0-P17',
  ],
  'a0-09': [
    'A0-W29',
    'A0-W30',
    'A0-W31',
    'A0-W32',
    'A0-W38',
    'A0-W39',
    'A0-P18',
    'A0-P19',
  ],
  'a0-10': ['A0-W24', 'A0-P20'],
};

/// A topic may contain multiple independently resumable teaching segments.
/// Segment IDs are stable even if later wording or exercises change.
class LessonSegment {
  const LessonSegment({
    required this.id,
    required this.targetItemIds,
    required this.previewItemIds,
    this.dialogueRequiredTerms = const [],
    this.independentRequiredTerms = const [],
    this.estimatedMinutes = 12,
  });

  final String id;
  final List<String> targetItemIds;
  final List<String> previewItemIds;

  /// One accepted term group per controlled dialogue turn.  A learner only
  /// needs to use one term from the current group; the surrounding wording
  /// may vary naturally.
  final List<List<String>> dialogueRequiredTerms;

  /// Terms that show the independent attempt contains the taught content.
  final List<String> independentRequiredTerms;
  final int estimatedMinutes;
}

const a0LessonSegments = <String, List<LessonSegment>>{
  'a0-04': [
    LessonSegment(
      id: 'a0-04-a',
      targetItemIds: [
        'A0-W01',
        'A0-W02',
        'A0-W03',
        'A0-W04',
        'A0-W05',
        'A0-W06',
      ],
      previewItemIds: [
        'A0-W01',
        'A0-W02',
        'A0-W03',
        'A0-W04',
        'A0-W05',
        'A0-W06',
      ],
      dialogueRequiredTerms: [
        ['zero', 'one', 'two'],
        ['three', 'four', 'five'],
      ],
      independentRequiredTerms: ['zero', 'one', 'two', 'three', 'four', 'five'],
    ),
    LessonSegment(
      id: 'a0-04-b',
      targetItemIds: [
        'A0-W07',
        'A0-W08',
        'A0-W09',
        'A0-W10',
        'A0-W11',
        'A0-W20',
      ],
      previewItemIds: [
        'A0-W07',
        'A0-W08',
        'A0-W09',
        'A0-W10',
        'A0-W11',
        'A0-W20',
      ],
      dialogueRequiredTerms: [
        ['six', 'seven', 'eight'],
        ['it is a phone', "it's a phone"],
      ],
      independentRequiredTerms: ['six', 'seven', 'eight', 'nine', 'ten'],
    ),
    LessonSegment(
      id: 'a0-04-c',
      targetItemIds: ['A0-P07', 'A0-P08'],
      previewItemIds: ['A0-P07', 'A0-P08'],
      dialogueRequiredTerms: [
        [
          'my number is',
          'one',
          'two',
          'three',
          'four',
          'five',
          'six',
          'seven',
          'eight',
          'nine',
          'zero',
        ],
        [
          'one',
          'two',
          'three',
          'four',
          'five',
          'six',
          'seven',
          'eight',
          'nine',
          'zero',
        ],
      ],
      independentRequiredTerms: [
        'one',
        'two',
        'three',
        'four',
        'five',
        'six',
        'seven',
        'eight',
        'nine',
        'zero',
      ],
    ),
  ],
  'a0-08': [
    LessonSegment(
      id: 'a0-08-a',
      targetItemIds: ['A0-W12', 'A0-W13', 'A0-W14', 'A0-P14', 'A0-P15'],
      previewItemIds: ['A0-W12', 'A0-W13', 'A0-W14', 'A0-P14', 'A0-P15'],
      dialogueRequiredTerms: [
        ['what day'],
        ['monday', 'tuesday', 'wednesday'],
      ],
      independentRequiredTerms: ['monday', 'tuesday', 'wednesday'],
    ),
    LessonSegment(
      id: 'a0-08-b',
      targetItemIds: ['A0-W15', 'A0-W16', 'A0-W17', 'A0-W18'],
      previewItemIds: ['A0-W15', 'A0-W16', 'A0-W17', 'A0-W18'],
      dialogueRequiredTerms: [
        ['what day'],
        ['thursday', 'friday', 'saturday', 'sunday'],
      ],
      independentRequiredTerms: ['thursday', 'friday', 'saturday', 'sunday'],
    ),
    LessonSegment(
      id: 'a0-08-c',
      targetItemIds: ['A0-P16', 'A0-P17'],
      previewItemIds: ['A0-P16', 'A0-P17'],
      dialogueRequiredTerms: [
        ['what time'],
        ["o'clock", 'oclock'],
      ],
      independentRequiredTerms: ["o'clock", 'oclock'],
    ),
  ],
};

class SeedLesson {
  const SeedLesson({
    required this.id,
    required this.number,
    required this.title,
    required this.outcome,
    required this.vocabulary,
    this.schemaVersion = '1.0',
    this.revision = 1,
    this.stageVersion = 'A0-1.0',
    this.source = ContentSource.builtInOriginal,
    this.status = ContentStatus.approved,
    this.estimatedMinutes = 12,
  });
  final String id;
  final int number;
  final String title;
  final String outcome;
  final List<VocabularyItem> vocabulary;
  final String schemaVersion;
  final int revision;
  final String stageVersion;
  final ContentSource source;
  final ContentStatus status;
  final int estimatedMinutes;

  List<String> get targetItemIds =>
      a0TargetItemIdsByLesson[id] ?? const <String>[];
  List<String> get abilityIds => ['A0-C${number.toString().padLeft(2, '0')}'];
  List<String> get prerequisiteIds => number == 1
      ? const []
      : ['a0-${(number - 1).toString().padLeft(2, '0')}'];
  List<LessonSegment> get segments =>
      a0LessonSegments[id] ??
      [
        LessonSegment(
          id: '$id-a',
          targetItemIds: targetItemIds,
          previewItemIds: targetItemIds,
          estimatedMinutes: estimatedMinutes,
        ),
      ];
}

const a0SeedLessons = [
  SeedLesson(
    id: 'a0-01',
    number: 1,
    title: '你好，我是……',
    outcome: '介绍姓名并回应问候',
    vocabulary: [
      VocabularyItem(
        id: 'a0-01-hello',
        word: 'Hello',
        meaning: '你好',
        example: 'Hello. I’m Mia.',
        exampleMeaning: '你好。我是 Mia。',
        ipa: '/həˈləʊ/',
      ),
      VocabularyItem(
        id: 'a0-01-name',
        word: 'name',
        meaning: '名字',
        example: 'My name is Shen.',
        exampleMeaning: '我的名字是 Shen。',
        ipa: '/neɪm/',
      ),
      VocabularyItem(
        id: 'a0-01-nice',
        word: 'Nice to meet you',
        meaning: '很高兴认识你',
        example: 'Nice to meet you, too.',
        exampleMeaning: '我也很高兴认识你。',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-02',
    number: 2,
    title: '拼读我的名字',
    outcome: '听懂拼写，并说出名字字母',
    vocabulary: [
      VocabularyItem(
        id: 'a0-02-spell',
        word: 'spell',
        meaning: '拼写',
        example: 'How do you spell that?',
        exampleMeaning: '那个怎么拼？',
        ipa: '/spel/',
      ),
      VocabularyItem(
        id: 'a0-02-name',
        word: 'name',
        meaning: '名字',
        example: 'My name is Shen.',
        exampleMeaning: '我的名字是 Shen。',
        ipa: '/neɪm/',
      ),
      VocabularyItem(
        id: 'a0-02-question',
        word: 'How do you spell that?',
        meaning: '那个怎么拼？',
        example: 'How do you spell your name?',
        exampleMeaning: '你的名字怎么拼？',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-03',
    number: 3,
    title: '你好吗？',
    outcome: '问候并表达简单状态',
    vocabulary: [
      VocabularyItem(
        id: 'a0-03-good',
        word: 'good',
        meaning: '好的',
        example: 'I’m good, thanks.',
        exampleMeaning: '我很好，谢谢。',
        ipa: '/ɡʊd/',
      ),
      VocabularyItem(
        id: 'a0-03-tired',
        word: 'tired',
        meaning: '累的',
        example: 'I’m tired today.',
        exampleMeaning: '我今天有点累。',
        ipa: '/ˈtaɪəd/',
      ),
      VocabularyItem(
        id: 'a0-03-how',
        word: 'How are you?',
        meaning: '你好吗？',
        example: 'How are you today?',
        exampleMeaning: '你今天怎么样？',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-04',
    number: 4,
    title: '数字与电话号码',
    outcome: '说 0–10 与虚拟号码',
    vocabulary: [
      VocabularyItem(
        id: 'a0-04-three',
        word: 'three',
        meaning: '三',
        example: 'One, three, eight.',
        exampleMeaning: '一、三、八。',
        ipa: '/θriː/',
      ),
      VocabularyItem(
        id: 'a0-04-number',
        word: 'number',
        meaning: '号码',
        example: 'My number is 1-3-8.',
        exampleMeaning: '我的号码是 138。',
        ipa: '/ˈnʌmbə(r)/',
      ),
      VocabularyItem(
        id: 'a0-04-phone',
        word: 'phone',
        meaning: '电话',
        example: 'What’s your phone number?',
        exampleMeaning: '你的电话号码是多少？',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-05',
    number: 5,
    title: '这是什么？',
    outcome: '询问并说出常见物品',
    vocabulary: [
      VocabularyItem(
        id: 'a0-05-book',
        word: 'book',
        meaning: '书',
        example: 'It’s a book.',
        exampleMeaning: '这是一本书。',
        ipa: '/bʊk/',
      ),
      VocabularyItem(
        id: 'a0-05-pen',
        word: 'pen',
        meaning: '笔',
        example: 'It’s a pen.',
        exampleMeaning: '这是一支笔。',
        ipa: '/pen/',
      ),
      VocabularyItem(
        id: 'a0-05-this',
        word: 'What’s this?',
        meaning: '这是什么？',
        example: 'What’s this? It’s a key.',
        exampleMeaning: '这是什么？这是钥匙。',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-06',
    number: 6,
    title: '我来自哪里？',
    outcome: '说明来自哪里并反问',
    vocabulary: [
      VocabularyItem(
        id: 'a0-06-from',
        word: 'from',
        meaning: '来自',
        example: 'I’m from Hong Kong.',
        exampleMeaning: '我来自香港。',
        ipa: '/frəm/',
      ),
      VocabularyItem(
        id: 'a0-06-place',
        word: 'place',
        meaning: '地点',
        example: 'Where are you from?',
        exampleMeaning: '你来自哪里？',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-07',
    number: 7,
    title: '我的家人',
    outcome: '介绍一位家人',
    vocabulary: [
      VocabularyItem(
        id: 'a0-07-family',
        word: 'family',
        meaning: '家人',
        example: 'This is my family.',
        exampleMeaning: '这是我的家人。',
        ipa: '/ˈfæməli/',
      ),
      VocabularyItem(
        id: 'a0-07-mother',
        word: 'mother',
        meaning: '母亲',
        example: 'This is my mother.',
        exampleMeaning: '这是我的妈妈。',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-08',
    number: 8,
    title: '星期与时间',
    outcome: '说今天和整点',
    vocabulary: [
      VocabularyItem(
        id: 'a0-08-monday',
        word: 'Monday',
        meaning: '星期一',
        example: 'It is Monday.',
        exampleMeaning: '今天是星期一。',
      ),
      VocabularyItem(
        id: 'a0-08-oclock',
        word: 'o’clock',
        meaning: '整点',
        example: 'It’s three o’clock.',
        exampleMeaning: '现在三点整。',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-09',
    number: 9,
    title: '我喜欢……',
    outcome: '表达喜好并回答',
    vocabulary: [
      VocabularyItem(
        id: 'a0-09-like',
        word: 'like',
        meaning: '喜欢',
        example: 'I like tea.',
        exampleMeaning: '我喜欢茶。',
        ipa: '/laɪk/',
      ),
      VocabularyItem(
        id: 'a0-09-tea',
        word: 'tea',
        meaning: '茶',
        example: 'Do you like tea?',
        exampleMeaning: '你喜欢茶吗？',
      ),
    ],
  ),
  SeedLesson(
    id: 'a0-10',
    number: 10,
    title: 'A0 综合任务',
    outcome: '完成自我介绍、喜好和反问',
    vocabulary: [
      VocabularyItem(
        id: 'a0-10-again',
        word: 'Please say that again.',
        meaning: '请再说一遍。',
        example: 'Please say that again.',
        exampleMeaning: '请再说一遍。',
      ),
      VocabularyItem(
        id: 'a0-10-slowly',
        word: 'Please speak slowly.',
        meaning: '请说慢一点。',
        example: 'Please speak slowly.',
        exampleMeaning: '请说慢一点。',
      ),
    ],
  ),
];

SeedLesson lessonById(String id) =>
    a0SeedLessons.firstWhere((lesson) => lesson.id == id);

class LessonActivity {
  const LessonActivity({
    required this.listening,
    required this.listeningQuestion,
    required this.answers,
    required this.speaking,
    required this.reading,
    required this.readingQuestion,
    required this.readingAnswer,
    required this.writingPrompt,
    required this.writingExample,
    required this.independentPrompt,
    required this.independentHelp,
  });
  final String listening;
  final String listeningQuestion;
  final List<String> answers;
  final String speaking;
  final String reading;
  final String readingQuestion;
  final String readingAnswer;
  final String writingPrompt;
  final String writingExample;
  final String independentPrompt;
  final String independentHelp;
}

const a0Activities = <String, LessonActivity>{
  'a0-01': LessonActivity(
    listening: 'Hello. I’m Mia. Nice to meet you.',
    listeningQuestion: 'Mia 在做什么？',
    answers: ['自我介绍', '买东西', '问时间'],
    speaking: 'Hello. I’m Shen. Nice to meet you.',
    reading:
        'Mia: Hello. I’m Mia.\nShen: Hi. I’m Shen.\nMia: Nice to meet you.\nShen: Nice to meet you, too.',
    readingQuestion: '谁叫 Mia？',
    readingAnswer: '第一位说话的人',
    writingPrompt: '写一句问候和姓名介绍。',
    writingExample: 'Hello. I’m Shen.',
    independentPrompt: '不看句框，介绍你的名字并回应“Nice to meet you”。',
    independentHelp: 'Hi. I’m … / Nice to meet you, too.',
  ),
  'a0-02': LessonActivity(
    listening: 'How do you spell your name?',
    listeningQuestion: '这句话是什么意思？',
    answers: ['你的名字怎么拼？', '你的名字是什么？', '你来自哪里？'],
    speaking: 'S H E N',
    reading:
        'Mia: What’s your name?\nShen: Shen.\nMia: How do you spell that?\nShen: S-H-E-N.',
    readingQuestion: 'Shen 的名字怎么拼？',
    readingAnswer: 'S-H-E-N',
    writingPrompt: '把名字和拼写写完整。',
    writingExample: 'My name is Shen.\nS-H-E-N.',
    independentPrompt: '不看句框，用英文介绍名字并拼读它。',
    independentHelp: 'My name is … / A-B-C.',
  ),
  'a0-03': LessonActivity(
    listening: 'How are you today?',
    listeningQuestion: '对方在问什么？',
    answers: ['你的状态', '你的号码', '你的地点'],
    speaking: 'How are you? I’m good, thanks.',
    reading:
        'Mia: Hi, Shen. How are you?\nShen: I’m good, thanks. How are you?\nMia: I’m okay.',
    readingQuestion: 'Mia 状态如何？',
    readingAnswer: 'okay',
    writingPrompt: '写一句今天的状态。',
    writingExample: 'I’m okay today.',
    independentPrompt: '不看句框，问候并说出你的状态。',
    independentHelp: 'How are you? / I’m …',
  ),
  'a0-04': LessonActivity(
    listening: 'One, three, eight.',
    listeningQuestion: '你听到的是哪个号码？',
    answers: ['138', '183', '318'],
    speaking: 'My number is one-three-eight.',
    reading:
        'Mia: What’s your phone number?\nShen: One-three-eight.\nMia: Thank you.',
    readingQuestion: 'Shen 的号码是？',
    readingAnswer: '138',
    writingPrompt: '把虚拟号码 139 写成英文。',
    writingExample: 'one-three-nine',
    independentPrompt: '不看句框，说出一个三位虚拟号码。',
    independentHelp: 'My number is one-two-three.',
  ),
  'a0-05': LessonActivity(
    listening: 'What’s this? It’s a key.',
    listeningQuestion: '这是什么？',
    answers: ['钥匙', '书', '水'],
    speaking: 'What’s this? It’s a pen.',
    reading: 'Mia: What’s this?\nShen: It’s a book.',
    readingQuestion: '这是什么？',
    readingAnswer: 'a book',
    writingPrompt: '写一句“这是一支笔”。',
    writingExample: 'It’s a pen.',
    independentPrompt: '不看句框，说出一个身边物品。',
    independentHelp: 'It’s a …',
  ),
  'a0-06': LessonActivity(
    listening: 'Where are you from?',
    listeningQuestion: '对方在问什么？',
    answers: ['来自哪里', '叫什么', '喜欢什么'],
    speaking: 'I’m from Hong Kong.',
    reading: 'Mia: Where are you from?\nShen: I’m from Hong Kong.',
    readingQuestion: 'Shen 来自哪里？',
    readingAnswer: 'Hong Kong',
    writingPrompt: '写一句你来自哪里。',
    writingExample: 'I’m from Hong Kong.',
    independentPrompt: '不看句框，说来自哪里并反问对方。',
    independentHelp: 'I’m from … / Where are you from?',
  ),
  'a0-07': LessonActivity(
    listening: 'Who is this? This is my mother.',
    listeningQuestion: '这个人是谁？',
    answers: ['妈妈', '朋友', '老师'],
    speaking: 'This is my family.',
    reading: 'Mia: Who is this?\nShen: This is my mother.',
    readingQuestion: 'Shen 在介绍谁？',
    readingAnswer: 'my mother',
    writingPrompt: '介绍一位家人或朋友。',
    writingExample: 'This is my mother.',
    independentPrompt: '不看句框，介绍一位家人或朋友。',
    independentHelp: 'This is my …',
  ),
  'a0-08': LessonActivity(
    listening: 'It’s three o’clock on Monday.',
    listeningQuestion: '是什么时间？',
    answers: ['星期一三点', '星期三一点', '星期一一点'],
    speaking: 'It’s three o’clock.',
    reading: 'Mia: What day is it?\nShen: It’s Monday.',
    readingQuestion: '今天星期几？',
    readingAnswer: 'Monday',
    writingPrompt: '写一句今天和整点。',
    writingExample: 'It’s Monday. It’s three o’clock.',
    independentPrompt: '不看句框，说今天星期几或现在几点。',
    independentHelp: 'It’s … / It’s … o’clock.',
  ),
  'a0-09': LessonActivity(
    listening: 'Do you like tea? Yes, I do.',
    listeningQuestion: '对方喜欢茶吗？',
    answers: ['喜欢', '不喜欢', '不知道'],
    speaking: 'I like tea. Do you like tea?',
    reading: 'Mia: I like tea. Do you like tea?\nShen: Yes, I do.',
    readingQuestion: 'Shen 的回答是什么？',
    readingAnswer: 'Yes, I do.',
    writingPrompt: '写一句你的喜好。',
    writingExample: 'I like tea.',
    independentPrompt: '不看句框，说一个喜好并反问。',
    independentHelp: 'I like … / Do you like …?',
  ),
  'a0-10': LessonActivity(
    listening: 'Please say that again.',
    listeningQuestion: '对方希望什么？',
    answers: ['再说一遍', '说慢一点', '写下来'],
    speaking: 'Please speak slowly.',
    reading: 'Mia: Please say that again.\nShen: Please speak slowly.',
    readingQuestion: 'Shen 希望什么？',
    readingAnswer: 'speak slowly',
    writingPrompt: '写姓名、地点和喜好三句。',
    writingExample: 'I’m Shen.\nI’m from Hong Kong.\nI like tea.',
    independentPrompt: '不看帮助，完成姓名、地点、喜好和反问。',
    independentHelp: 'I’m … / I’m from … / I like …',
  ),
};

LessonActivity activityByLessonId(String id) => a0Activities[id]!;

/// Reviewed activities for split topics. They intentionally avoid values from
/// later segments so a segment can be completed independently.
const a0SegmentActivities = <String, LessonActivity>{
  'a0-04-a': LessonActivity(
    listening: 'One, two, three.',
    listeningQuestion: '听到哪一组数字？',
    answers: ['123', '132', '213'],
    speaking: 'Zero, one, two, three.',
    reading: 'Mia: One, two, three.\nShen: Four, five.',
    readingQuestion: 'Shen 说了哪两个数字？',
    readingAnswer: 'four, five',
    writingPrompt: '把 0、1、2、3 写成英文。',
    writingExample: 'zero, one, two, three',
    independentPrompt: '不看帮助，说出三个 0 到 5 的数字。',
    independentHelp: 'zero / one / two / three / four / five',
  ),
  'a0-04-b': LessonActivity(
    listening: 'Six, seven, eight.',
    listeningQuestion: '听到哪一组数字？',
    answers: ['678', '687', '768'],
    speaking: 'My phone is here.',
    reading: 'Mia: What is this?\nShen: It is a phone.',
    readingQuestion: '这是什么？',
    readingAnswer: 'a phone',
    writingPrompt: '把 6、7、8 写成英文。',
    writingExample: 'six, seven, eight',
    independentPrompt: '不看帮助，说出三个 6 到 10 的数字。',
    independentHelp: 'six / seven / eight / nine / ten',
  ),
  'a0-04-c': LessonActivity(
    listening: 'My number is one-three-eight.',
    listeningQuestion: '号码是多少？',
    answers: ['138', '183', '318'],
    speaking: 'My number is one-three-eight.',
    reading: 'Mia: What’s your phone number?\nShen: One-three-eight.',
    readingQuestion: 'Shen 的号码是？',
    readingAnswer: '138',
    writingPrompt: '把虚拟号码 139 写成英文。',
    writingExample: 'one-three-nine',
    independentPrompt: '不看句框，说出一个三位虚拟号码。',
    independentHelp: 'My number is one-two-three.',
  ),
  'a0-08-a': LessonActivity(
    listening: 'It is Monday.',
    listeningQuestion: '今天星期几？',
    answers: ['星期一', '星期二', '星期三'],
    speaking: 'It is Monday.',
    reading: 'Mia: What day is it?\nShen: It is Tuesday.',
    readingQuestion: '今天星期几？',
    readingAnswer: 'Tuesday',
    writingPrompt: '写一句今天是星期一、二或三。',
    writingExample: 'It is Monday.',
    independentPrompt: '不看帮助，说出星期一、二或三。',
    independentHelp: 'It is Monday / Tuesday / Wednesday.',
  ),
  'a0-08-b': LessonActivity(
    listening: 'It is Friday.',
    listeningQuestion: '今天星期几？',
    answers: ['星期五', '星期四', '星期日'],
    speaking: 'It is Friday.',
    reading: 'Mia: What day is it?\nShen: It is Sunday.',
    readingQuestion: '今天星期几？',
    readingAnswer: 'Sunday',
    writingPrompt: '写一句今天是星期四到日。',
    writingExample: 'It is Friday.',
    independentPrompt: '不看帮助，说出星期四到日。',
    independentHelp: 'It is Thursday / Friday / Saturday / Sunday.',
  ),
  'a0-08-c': LessonActivity(
    listening: 'It is three o’clock.',
    listeningQuestion: '是什么时间？',
    answers: ['三点', '一点', '星期三'],
    speaking: 'It is three o’clock.',
    reading: 'Mia: What time is it?\nShen: It is three o’clock.',
    readingQuestion: '几点？',
    readingAnswer: 'three o’clock',
    writingPrompt: '写一句整点时间。',
    writingExample: 'It is three o’clock.',
    independentPrompt: '不看帮助，说一个整点时间。',
    independentHelp: 'It is … o’clock.',
  ),
};

LessonActivity activityBySegmentId(String segmentId, String lessonId) =>
    a0SegmentActivities[segmentId] ?? activityByLessonId(lessonId);

/// Short, reviewed entries used before each split segment.  These are kept
/// separate from review prompts: a review hint is not a learner-facing
/// dictionary definition.
const a0SegmentVocabulary = <String, List<VocabularyItem>>{
  'a0-04-a': [
    VocabularyItem(
      id: 'A0-W01',
      word: 'zero',
      meaning: '零',
      example: 'Zero, one, two.',
      exampleMeaning: '零、一、二。',
      ipa: '/ˈzɪrəʊ/',
    ),
    VocabularyItem(
      id: 'A0-W02',
      word: 'one',
      meaning: '一',
      example: 'One, two, three.',
      exampleMeaning: '一、二、三。',
      ipa: '/wʌn/',
    ),
    VocabularyItem(
      id: 'A0-W03',
      word: 'two',
      meaning: '二',
      example: 'Two and three.',
      exampleMeaning: '二和三。',
      ipa: '/tuː/',
    ),
    VocabularyItem(
      id: 'A0-W04',
      word: 'three',
      meaning: '三',
      example: 'Three, four, five.',
      exampleMeaning: '三、四、五。',
      ipa: '/θriː/',
    ),
    VocabularyItem(
      id: 'A0-W05',
      word: 'four',
      meaning: '四',
      example: 'Four and five.',
      exampleMeaning: '四和五。',
      ipa: '/fɔː/',
    ),
    VocabularyItem(
      id: 'A0-W06',
      word: 'five',
      meaning: '五',
      example: 'Five, please.',
      exampleMeaning: '五，请。',
      ipa: '/faɪv/',
    ),
  ],
  'a0-04-b': [
    VocabularyItem(
      id: 'A0-W07',
      word: 'six',
      meaning: '六',
      example: 'Six, seven, eight.',
      exampleMeaning: '六、七、八。',
      ipa: '/sɪks/',
    ),
    VocabularyItem(
      id: 'A0-W08',
      word: 'seven',
      meaning: '七',
      example: 'Seven, eight, nine.',
      exampleMeaning: '七、八、九。',
      ipa: '/ˈsevən/',
    ),
    VocabularyItem(
      id: 'A0-W09',
      word: 'eight',
      meaning: '八',
      example: 'Eight, nine, ten.',
      exampleMeaning: '八、九、十。',
      ipa: '/eɪt/',
    ),
    VocabularyItem(
      id: 'A0-W10',
      word: 'nine',
      meaning: '九',
      example: 'Nine and ten.',
      exampleMeaning: '九和十。',
      ipa: '/naɪn/',
    ),
    VocabularyItem(
      id: 'A0-W11',
      word: 'ten',
      meaning: '十',
      example: 'Ten, please.',
      exampleMeaning: '十，请。',
      ipa: '/ten/',
    ),
    VocabularyItem(
      id: 'A0-W20',
      word: 'phone',
      meaning: '电话；手机',
      example: 'It is a phone.',
      exampleMeaning: '它是一部手机。',
      ipa: '/fəʊn/',
    ),
  ],
  'a0-04-c': [
    VocabularyItem(
      id: 'A0-P07',
      word: "What's your phone number?",
      meaning: '你的电话号码是多少？',
      example: "What's your phone number?",
      exampleMeaning: '你的电话号码是多少？',
    ),
    VocabularyItem(
      id: 'A0-P08',
      word: 'My number is one-three-eight.',
      meaning: '我的号码是 138。',
      example: 'My number is one-three-eight.',
      exampleMeaning: '我的号码是 138。',
    ),
  ],
  'a0-08-a': [
    VocabularyItem(
      id: 'A0-W12',
      word: 'Monday',
      meaning: '星期一',
      example: 'It is Monday.',
      exampleMeaning: '今天是星期一。',
      ipa: '/ˈmʌndeɪ/',
    ),
    VocabularyItem(
      id: 'A0-W13',
      word: 'Tuesday',
      meaning: '星期二',
      example: 'It is Tuesday.',
      exampleMeaning: '今天是星期二。',
      ipa: '/ˈtjuːzdeɪ/',
    ),
    VocabularyItem(
      id: 'A0-W14',
      word: 'Wednesday',
      meaning: '星期三',
      example: 'It is Wednesday.',
      exampleMeaning: '今天是星期三。',
      ipa: '/ˈwenzdeɪ/',
    ),
    VocabularyItem(
      id: 'A0-P14',
      word: 'What day is it today?',
      meaning: '今天星期几？',
      example: 'What day is it today?',
      exampleMeaning: '今天星期几？',
    ),
    VocabularyItem(
      id: 'A0-P15',
      word: "It's Monday.",
      meaning: '今天是星期一。',
      example: "It's Monday.",
      exampleMeaning: '今天是星期一。',
    ),
  ],
  'a0-08-b': [
    VocabularyItem(
      id: 'A0-W15',
      word: 'Thursday',
      meaning: '星期四',
      example: 'It is Thursday.',
      exampleMeaning: '今天是星期四。',
      ipa: '/ˈθɜːzdeɪ/',
    ),
    VocabularyItem(
      id: 'A0-W16',
      word: 'Friday',
      meaning: '星期五',
      example: 'It is Friday.',
      exampleMeaning: '今天是星期五。',
      ipa: '/ˈfraɪdeɪ/',
    ),
    VocabularyItem(
      id: 'A0-W17',
      word: 'Saturday',
      meaning: '星期六',
      example: 'It is Saturday.',
      exampleMeaning: '今天是星期六。',
      ipa: '/ˈsætədeɪ/',
    ),
    VocabularyItem(
      id: 'A0-W18',
      word: 'Sunday',
      meaning: '星期日',
      example: 'It is Sunday.',
      exampleMeaning: '今天是星期日。',
      ipa: '/ˈsʌndeɪ/',
    ),
  ],
  'a0-08-c': [
    VocabularyItem(
      id: 'A0-P16',
      word: 'What time is it?',
      meaning: '现在几点？',
      example: 'What time is it?',
      exampleMeaning: '现在几点？',
    ),
    VocabularyItem(
      id: 'A0-P17',
      word: "It's three o'clock.",
      meaning: '现在三点。',
      example: "It's three o'clock.",
      exampleMeaning: '现在三点。',
    ),
  ],
};

List<VocabularyItem> vocabularyBySegmentId(String segmentId, String lessonId) {
  if (!a0SegmentActivities.containsKey(segmentId)) {
    return lessonById(lessonId).vocabulary;
  }
  return a0SegmentVocabulary[segmentId] ?? const <VocabularyItem>[];
}

/// One practical rule per seed lesson. These are reminders for using a sentence
/// in context, not abstract grammar lectures.
const a0GrammarNotes = <String, String>{
  'a0-01': '介绍自己时，把名字放在 I’m 后面：I’m Mia. 不需要先学复杂时态。',
  'a0-02': 'My name is 后面接名字；拼读时每个字母之间稍微停顿。',
  'a0-03': '说状态用 I’m + 状态：I’m good / okay / tired。',
  'a0-04': '报号码时数字一个一个说：one-three-eight，不要当成一百三十八。',
  'a0-05': '问物品用 What’s this?；回答用 It’s a + 物品。',
  'a0-06': '说地点用 I’m from + 地点：I’m from Hong Kong。',
  'a0-07': '介绍人用 This is my + 人：This is my mother。',
  'a0-08': '星期和整点都可用 It’s：It’s Monday. / It’s three o’clock。',
  'a0-09': '说喜好用 I like + 东西；一般问句用 Do you like + 东西?',
  'a0-10': '礼貌请求以 Please 开头：Please say that again.',
};

String grammarNoteForLesson(String id) => a0GrammarNotes[id] ?? '';

const a0SegmentGrammarNotes = <String, String>{
  'a0-04-a': '数字单独说就可以：zero, one, two。每个词之间稍微停顿。',
  'a0-04-b': '认物品可以说 It is a phone. 口语里也常说 It’s a phone.',
  'a0-04-c': '报号码时一个数字一个数字说：one-three-eight，不把它读成一百三十八。',
  'a0-08-a': '问星期用 What day is it?；回答用 It is / It’s + 星期。',
  'a0-08-b': '星期四到星期日也沿用 It is / It’s + 星期这个句型。',
  'a0-08-c': '说整点用 It is / It’s + 数字 + o’clock，例如 It’s three o’clock。',
};

String grammarNoteForSegment(String segmentId, String lessonId) =>
    a0SegmentGrammarNotes[segmentId] ?? grammarNoteForLesson(lessonId);

bool matchesSegmentDialogue(String segmentId, int stage, String response) {
  final text = response.toLowerCase().replaceAll('’', "'");
  final segment = a0LessonSegments.values
      .expand((segments) => segments)
      .where((item) => item.id == segmentId)
      .firstOrNull;
  if (segment == null || stage >= segment.dialogueRequiredTerms.length) {
    return false;
  }
  bool hasAny(Iterable<String> terms) =>
      terms.any((term) => text.contains(term));
  // A phone-number report needs both the reporting frame and at least one
  // spoken digit. Other segment turns need one reviewed, task-specific term.
  if (segmentId == 'a0-04-c' && stage == 0) {
    return text.contains('my number is') &&
        hasAny(segment.dialogueRequiredTerms[stage].skip(1));
  }
  return hasAny(segment.dialogueRequiredTerms[stage]);
}

bool matchesSegmentIndependent(String segmentId, String response) {
  final text = response.toLowerCase().replaceAll('’', "'");
  final segment = a0LessonSegments.values
      .expand((segments) => segments)
      .where((item) => item.id == segmentId)
      .firstOrNull;
  if (segment == null) return true;
  if (segmentId == 'a0-04-a' || segmentId == 'a0-04-b') {
    final count = segment.independentRequiredTerms
        .where((term) => text.contains(term))
        .length;
    return count >= 3;
  }
  if (segmentId == 'a0-04-c') {
    return segment.independentRequiredTerms
            .where((term) => text.contains(term))
            .length >=
        3;
  }
  return segment.independentRequiredTerms.any((term) => text.contains(term));
}

class LessonDialogue {
  const LessonDialogue({
    required this.goal,
    required this.prompts,
    required this.hints,
  });
  final String goal;
  final List<String> prompts;
  final List<String> hints;
}

const a0Dialogues = <String, LessonDialogue>{
  'a0-01': LessonDialogue(
    goal: '问候、介绍姓名并回应见面问候',
    prompts: [
      'Hi! I’m Mia. What’s your name?',
      'Nice to meet you. Say: Nice to meet you, too.',
      'Great! Say hello one more time.',
      'Now ask me my name!',
    ],
    hints: [
      'I’m Alex.',
      'Nice to meet you, too.',
      'Hello!',
      'What’s your name?',
    ],
  ),
  'a0-02': LessonDialogue(
    goal: '介绍姓名并完整拼读名字',
    prompts: [
      'Hi! What’s your name?',
      'How do you spell that?',
      'Thank you. Spell it one more time.',
      'Now ask me my name!',
    ],
    hints: ['My name is Alex.', 'A-L-E-X.', 'A-L-E-X.', 'What’s your name?'],
  ),
  'a0-03': LessonDialogue(
    goal: '询问状态、回答并反问',
    prompts: [
      'Hi! How are you today?',
      'Good! Ask me: How are you?',
      'I’m okay. Say your state one more time.',
      'Now say goodbye!',
    ],
    hints: ['I’m good, thanks.', 'How are you?', 'I’m okay.', 'Bye!'],
  ),
  'a0-04': LessonDialogue(
    goal: '报告一个虚拟三位号码并确认',
    prompts: [
      'What’s your phone number? Use a fake three-digit number.',
      'I heard one-three-eight. Is that right?',
      'Please say the three numbers again.',
      'Now ask me for my number!',
    ],
    hints: [
      'My number is one-three-eight.',
      'Yes.',
      'One-three-eight.',
      'What’s your phone number?',
    ],
  ),
  'a0-05': LessonDialogue(
    goal: '询问并说出一个物品',
    prompts: [
      'What’s this? It is a pen.',
      'Now say: It’s a pen.',
      'Ask me: What’s this?',
      'Great! Say one more object.',
    ],
    hints: ['It’s a pen.', 'It’s a pen.', 'What’s this?', 'It’s a book.'],
  ),
  'a0-06': LessonDialogue(
    goal: '说来自哪里并反问',
    prompts: [
      'Where are you from?',
      'Nice! Ask me: Where are you from?',
      'Say where you are from one more time.',
      'Say goodbye!',
    ],
    hints: [
      'I’m from Hong Kong.',
      'Where are you from?',
      'I’m from Hong Kong.',
      'Bye!',
    ],
  ),
  'a0-07': LessonDialogue(
    goal: '介绍一位家人或朋友',
    prompts: [
      'Who is this?',
      'Good. Say: This is my mother.',
      'Ask me: Who is this?',
      'Introduce one person again.',
    ],
    hints: [
      'This is my mother.',
      'This is my mother.',
      'Who is this?',
      'This is my friend.',
    ],
  ),
  'a0-08': LessonDialogue(
    goal: '说明星期或整点',
    prompts: [
      'What day is it today?',
      'What time is it?',
      'Say one full time sentence.',
      'Now ask me the day!',
    ],
    hints: [
      'It’s Monday.',
      'It’s three o’clock.',
      'It’s three o’clock.',
      'What day is it?',
    ],
  ),
  'a0-09': LessonDialogue(
    goal: '表达喜好、回答和反问',
    prompts: [
      'What do you like?',
      'Do you like tea?',
      'Now ask me what I like.',
      'Say your like one more time.',
    ],
    hints: ['I like tea.', 'Yes, I do.', 'Do you like tea?', 'I like tea.'],
  ),
  'a0-10': LessonDialogue(
    goal: '请求重复或放慢语速，并完成基础沟通',
    prompts: [
      'Say: Please say that again.',
      'Say: Please speak slowly.',
      'Now ask me your name or where I am from.',
      'Say one thing you like.',
    ],
    hints: [
      'Please say that again.',
      'Please speak slowly.',
      'What’s your name?',
      'I like tea.',
    ],
  ),
};

const a0SegmentDialogues = <String, LessonDialogue>{
  'a0-04-a': LessonDialogue(
    goal: '听辨并说出 0 到 5',
    prompts: ['Say zero, one, two.', 'Now say three, four, five.'],
    hints: ['zero, one, two', 'three, four, five'],
  ),
  'a0-04-b': LessonDialogue(
    goal: '听辨 6 到 10 并认识 phone',
    prompts: ['Say six, seven, eight.', 'What is this? Say: It is a phone.'],
    hints: ['six, seven, eight', 'It is a phone.'],
  ),
  'a0-04-c': LessonDialogue(
    goal: '询问并报告三位号码',
    prompts: ['What is your phone number?', 'Say a three-digit number again.'],
    hints: ['My number is one-three-eight.', 'one-three-eight'],
  ),
  'a0-08-a': LessonDialogue(
    goal: '询问并说出星期一到三',
    prompts: ['What day is it?', 'Say Monday, Tuesday, or Wednesday.'],
    hints: ['What day is it?', 'It is Monday.'],
  ),
  'a0-08-b': LessonDialogue(
    goal: '说出星期四到日',
    prompts: ['What day is it?', 'Say Thursday, Friday, Saturday, or Sunday.'],
    hints: ['What day is it?', 'It is Friday.'],
  ),
  'a0-08-c': LessonDialogue(
    goal: '询问并说出整点',
    prompts: ['What time is it?', 'Say one full time sentence.'],
    hints: ['What time is it?', 'It is three o’clock.'],
  ),
};

LessonDialogue dialogueByLessonId(String id) => a0Dialogues[id]!;

LessonDialogue dialogueBySegmentId(String segmentId, String lessonId) =>
    a0SegmentDialogues[segmentId] ?? dialogueByLessonId(lessonId);