<?php
// GET  api/quiz.php?id=N   -> quiz questions + options (no answers) + user's results
// POST api/quiz.php        -> grade an attempt, save the result
//      JSON body: {quiz_id, answers: [[optIdx,...], ...]}  (one array per question)
//      Response includes the correct options so the UI can mark the attempt.
require_once __DIR__ . '/../includes/auth.php';
require_once __DIR__ . '/../includes/functions.php';

header('Content-Type: application/json');
$userId = requireLoginApi();

function quizProgressRow(int $userId, int $quizId): array
{
    $stmt = db()->prepare(
        'SELECT best_score, last_score, total_questions, attempts, completed
         FROM quiz_progress WHERE user_id = ? AND quiz_id = ?'
    );
    $stmt->execute([$userId, $quizId]);
    return $stmt->fetch()
        ?: ['best_score' => 0, 'last_score' => 0, 'total_questions' => 0,
            'attempts' => 0, 'completed' => 0];
}

if ($_SERVER['REQUEST_METHOD'] === 'GET') {
    $quiz = getQuiz((int)($_GET['id'] ?? 0));
    if (!$quiz) {
        http_response_code(404);
        echo json_encode(['error' => 'Quiz not found']);
        exit;
    }
    $file = quizFilePath($quiz);
    $questions = $file ? parseQuizFile($file) : [];
    if (!$questions) {
        http_response_code(404);
        echo json_encode(['error' => 'Quiz file is missing — rescan the library']);
        exit;
    }
    $folder = getFolder((int)$quiz['folder_id']);
    $p = quizProgressRow($userId, (int)$quiz['id']);
    echo json_encode([
        'quiz'        => ['id' => (int)$quiz['id'], 'name' => $quiz['name']],
        'folder'      => ['id' => (int)$folder['id'], 'name' => $folder['name']],
        'breadcrumbs' => array_map(
            fn($c) => ['id' => (int)$c['id'], 'name' => $c['name']],
            folderBreadcrumbs($folder)
        ),
        'questions'   => array_map(fn($q) => [
            'text'    => $q['text'],
            'multi'   => $q['multi'],
            'options' => $q['options'],
        ], $questions),
        'progress'    => [
            'attempts'   => (int)$p['attempts'],
            'best_score' => (int)$p['best_score'],
            'last_score' => (int)$p['last_score'],
            'total'      => count($questions),
            'completed'  => (bool)$p['completed'],
        ],
    ]);
    exit;
}

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    http_response_code(405);
    echo json_encode(['error' => 'Method not allowed']);
    exit;
}

$data = json_decode(file_get_contents('php://input'), true) ?: [];
verifyCsrfApi($data);
$quiz = getQuiz((int)($data['quiz_id'] ?? 0));
$answers = $data['answers'] ?? null;
if (!$quiz || !is_array($answers)) {
    http_response_code(400);
    echo json_encode(['error' => 'Bad request']);
    exit;
}

$file = quizFilePath($quiz);
$questions = $file ? parseQuizFile($file) : [];
if (!$questions) {
    http_response_code(404);
    echo json_encode(['error' => 'Quiz file is missing — rescan the library']);
    exit;
}

$score   = 0;
$results = [];
foreach ($questions as $i => $q) {
    $selected = array_values(array_unique(array_map('intval', (array)($answers[$i] ?? []))));
    sort($selected);
    $correct = $q['correct'];
    sort($correct);
    $isCorrect = $selected === $correct;
    if ($isCorrect) $score++;
    $results[] = [
        'correct'         => $isCorrect,
        'correct_options' => $correct,
        'selected'        => $selected,
    ];
}

$total     = count($questions);
$completed = ($score === $total) ? 1 : 0;

db()->prepare(
    'INSERT INTO quiz_progress
        (user_id, quiz_id, best_score, last_score, total_questions, attempts, completed)
     VALUES (?, ?, ?, ?, ?, 1, ?)
     ON DUPLICATE KEY UPDATE
        last_score      = VALUES(last_score),
        best_score      = GREATEST(best_score, VALUES(best_score)),
        total_questions = VALUES(total_questions),
        attempts        = attempts + 1,
        completed       = GREATEST(completed, VALUES(completed))'
)->execute([$userId, (int)$quiz['id'], $score, $score, $total, $completed]);

echo json_encode([
    'score'     => $score,
    'total'     => $total,
    'completed' => (bool)$completed,
    'results'   => $results,
]);