<?php
$user_id = require_auth();

// GET /api/quiz/generate?deck={slug}&count=10
if (get_method() === 'GET' && ($segments[1] ?? '') === 'generate') {
    $slug = get_param('deck', '');
    $count = max(1, min(50, (int) get_param('count', 10)));

    $query = "SELECT c.id, c.question, c.answer, c.level, d.slug AS deck_slug, d.name AS deck_name
              FROM cards c JOIN decks d ON d.id = c.deck_id";
    $params = [];
    if ($slug) {
        $query .= " WHERE d.slug = :slug";
        $params[':slug'] = $slug;
    }
    $query .= " ORDER BY RANDOM() LIMIT " . $count;

    $stmt = $pdo->prepare($query);
    $stmt->execute($params);
    $cards = $stmt->fetchAll();

    $all_answers = $pdo->query("SELECT DISTINCT answer FROM cards ORDER BY RANDOM() LIMIT 200")->fetchAll(PDO::FETCH_COLUMN);

    $questions = [];
    foreach ($cards as $card) {
        $wrong = [];
        $shuffled = $all_answers;
        shuffle($shuffled);
        foreach ($shuffled as $a) {
            if ($a !== $card['answer'] && count($wrong) < 3) {
                $wrong[] = mb_substr($a, 0, 120) . (mb_strlen($a) > 120 ? '...' : '');
            }
        }

        $correct_short = mb_substr($card['answer'], 0, 120) . (mb_strlen($card['answer']) > 120 ? '...' : '');
        $options = $wrong;
        $options[] = $correct_short;
        shuffle($options);

        $questions[] = [
            'card_id' => $card['id'],
            'question' => $card['question'],
            'options' => $options,
            'correct_index' => array_search($correct_short, $options),
            'full_answer' => $card['answer'],
            'deck_name' => $card['deck_name']
        ];
    }
    json_ok(['questions' => $questions, 'deck' => $slug ?: 'all']);
}

// POST /api/quiz/submit
if (get_method() === 'POST' && ($segments[1] ?? '') === 'submit') {
    $body = get_json_body();
    $total = (int) ($body['total'] ?? 0);
    $correct = (int) ($body['correct'] ?? 0);
    $score = $total > 0 ? round(($correct / $total) * 100) : 0;

    $stmt = $pdo->prepare("
        INSERT INTO quiz_results (user_id, deck_slug, quiz_type, score_percent, total_questions, correct_answers)
        VALUES (:uid, :deck, 'multiple_choice', :score, :total, :correct)
    ");
    $stmt->execute([':uid' => $user_id, ':deck' => $body['deck'] ?? 'all', ':score' => $score, ':total' => $total, ':correct' => $correct]);
    json_ok(['score' => $score]);
}

// GET /api/quiz/history
if (get_method() === 'GET' && ($segments[1] ?? '') === 'history') {
    $stmt = $pdo->prepare("
        SELECT deck_slug, quiz_type, score_percent, total_questions, correct_answers, created_at
        FROM quiz_results WHERE user_id = :uid ORDER BY created_at DESC LIMIT 20
    ");
    $stmt->execute([':uid' => $user_id]);
    json_ok(['results' => $stmt->fetchAll()]);
}

json_error('Unbekannter Quiz-Endpunkt', 404);