document.addEventListener('DOMContentLoaded', async () => {
  const script = document.querySelector('script[data-questions-src]');
  const testRoot = document.querySelector('[data-finalflux-test]');

  if (!script || !testRoot) {
    return;
  }

  const elements = {
    questionCounter: testRoot.querySelector('[data-question-counter]'),
    scoreCounter: testRoot.querySelector('[data-score-counter]'),
    categoryTitle: testRoot.querySelector('[data-category-title]'),
    categoryHint: testRoot.querySelector('[data-category-hint]'),
    questionText: testRoot.querySelector('[data-question-text]'),
    answerOptions: testRoot.querySelector('[data-answer-options]'),
    answerFeedback: testRoot.querySelector('[data-answer-feedback]'),
    checkAnswer: testRoot.querySelector('[data-check-answer]'),
    skipQuestion: testRoot.querySelector('[data-skip-question]'),
    nextQuestion: testRoot.querySelector('[data-next-question]'),
    testResult: document.querySelector('[data-test-result]'),
    resultSummary: document.querySelector('[data-result-summary]'),
    categorySummary: document.querySelector('[data-category-summary]'),
    restartTest: document.querySelector('[data-restart-test]')
  };

  let questions = [];
  let currentIndex = 0;
  let score = 0;
  let answered = false;
  const categoryStats = new Map();

  function setError(message) {
    elements.questionText.textContent = message;
    elements.answerOptions.innerHTML = '';
    elements.checkAnswer.disabled = true;
    elements.skipQuestion.disabled = true;
    elements.nextQuestion.disabled = true;
  }

  function ensureCategory(category) {
    if (!categoryStats.has(category)) {
      categoryStats.set(category, { correct: 0, total: 0, skipped: 0 });
    }

    return categoryStats.get(category);
  }

  function renderQuestion() {
    const question = questions[currentIndex];
    answered = false;

    elements.questionCounter.textContent = `Frage ${currentIndex + 1} von ${questions.length}`;
    elements.scoreCounter.textContent = `${score} richtig`;
    elements.categoryTitle.textContent = question.category;
    elements.categoryHint.textContent = question.hint || '';
    elements.questionText.textContent = question.text;
    elements.answerFeedback.textContent = '';
    elements.answerFeedback.className = 'fluxcheck-result';
    elements.nextQuestion.disabled = true;
    elements.checkAnswer.disabled = false;
    elements.skipQuestion.disabled = false;

    elements.answerOptions.innerHTML = '';
    question.answers.forEach((answer, index) => {
      const label = document.createElement('label');
      const input = document.createElement('input');
      const text = document.createElement('span');

      input.type = 'radio';
      input.name = 'answer';
      input.value = String(index);
      text.textContent = answer;

      label.append(input, text);
      elements.answerOptions.append(label);
    });
  }

  function markAnswered(isCorrect, skipped) {
    const question = questions[currentIndex];
    const stats = ensureCategory(question.category);
    stats.total += 1;

    if (skipped) {
      stats.skipped += 1;
    }

    if (isCorrect) {
      stats.correct += 1;
      score += 1;
    }
  }

  function finishIfDone() {
    if (currentIndex < questions.length - 1) {
      currentIndex += 1;
      renderQuestion();
      return;
    }

    testRoot.hidden = true;
    elements.testResult.hidden = false;
    elements.resultSummary.textContent = `Du hast ${score} von ${questions.length} Fragen richtig beantwortet.`;
    elements.categorySummary.innerHTML = '';
    Array.from(categoryStats.entries()).forEach(([category, stats]) => {
      const skipped = stats.skipped ? `, ${stats.skipped} übersprungen` : '';
      const item = document.createElement('li');
      const categoryLabel = document.createElement('strong');

      categoryLabel.textContent = `${category}:`;
      item.append(categoryLabel, ` ${stats.correct} von ${stats.total} richtig${skipped}`);
      elements.categorySummary.append(item);
    });
  }

  elements.checkAnswer.addEventListener('click', () => {
    if (answered) {
      return;
    }

    const question = questions[currentIndex];
    const selected = elements.answerOptions.querySelector('input[type="radio"]:checked');

    if (!selected) {
      elements.answerFeedback.textContent = 'Wähle zuerst eine Antwort aus oder überspringe die Frage.';
      elements.answerFeedback.className = 'fluxcheck-result wrong';
      return;
    }

    const isCorrect = Number(selected.value) === question.correct;
    markAnswered(isCorrect, false);
    answered = true;
    elements.answerFeedback.textContent = (isCorrect ? 'Richtig. ' : 'Noch nicht. ') + question.explanation;
    elements.answerFeedback.className = 'fluxcheck-result ' + (isCorrect ? 'correct' : 'wrong');
    elements.scoreCounter.textContent = `${score} richtig`;
    elements.nextQuestion.disabled = false;
    elements.checkAnswer.disabled = true;
    elements.skipQuestion.disabled = true;
  });

  elements.skipQuestion.addEventListener('click', () => {
    if (!answered) {
      markAnswered(false, true);
    }

    finishIfDone();
  });

  elements.nextQuestion.addEventListener('click', finishIfDone);

  elements.restartTest.addEventListener('click', () => {
    currentIndex = 0;
    score = 0;
    categoryStats.clear();
    testRoot.hidden = false;
    elements.testResult.hidden = true;
    renderQuestion();
  });

  try {
    const response = await fetch(script.dataset.questionsSrc);
    if (!response.ok) {
      throw new Error(`HTTP ${response.status}`);
    }

    const payload = await response.json();
    questions = Array.isArray(payload) ? payload : payload.questions;

    if (!Array.isArray(questions) || questions.length === 0) {
      setError('Dieser Fragenkatalog enthält noch keine Fragen.');
      return;
    }

    renderQuestion();
  } catch (error) {
    console.error(error);
    setError('Der Fragenkatalog konnte nicht geladen werden.');
  }
});