<?php

require_once __DIR__ . '/../includes/config.php';
require_once __DIR__ . '/../includes/functions.php';
require_once __DIR__ . '/../includes/jsondb.php';
require_once __DIR__ . '/../includes/srs.php';
require_once __DIR__ . '/../includes/auth.php';

requireLogin();

header('Content-Type: application/json; charset=utf-8');

$user = $_SESSION['user'];

$inputRaw = file_get_contents('php://input');
$input = json_decode($inputRaw, true);

if (!is_array($input)) {
    echo json_encode([
        'error' => 'invalid_json'
    ]);
    exit;
}

$lang = $input['lang'] ?? '';
$list = $input['list'] ?? '';
$wordId = (int)($input['wordId'] ?? 0);
$userAnswer = trim($input['answer'] ?? '');

$file = listPath($user, $lang, $list);
$data = JsonDB::read($file);

if (!isset($data['words']) || !is_array($data['words'])) {
    echo json_encode([
        'error' => 'list_not_found'
    ]);
    exit;
}

$correct = false;
$updated = false;

foreach ($data['words'] as &$word) {

    if ((int)$word['id'] === $wordId) {

        // init stats veilig
        if (!isset($word['correct'])) $word['correct'] = 0;
        if (!isset($word['wrong'])) $word['wrong'] = 0;

        // normalize compare
        $expected = strtolower(trim($word['answer']));
        $given = strtolower(trim($userAnswer));

        $correct = ($expected === $given);

        // update stats
        if ($correct) {
            $word['correct']++;
        } else {
            $word['wrong']++;
        }

        // SRS update (nextReview + interval)
        updateWordStats($word, $correct);

        $updated = true;
        break;
    }
}

// als woord niet gevonden is
if (!$updated) {
    echo json_encode([
        'error' => 'word_not_found',
        'wordId' => $wordId
    ]);
    exit;
}

// write back
$ok = JsonDB::write($file, $data);

if (!$ok) {
    echo json_encode([
        'error' => 'write_failed'
    ]);
    exit;
}

echo json_encode([
    'correct' => $correct,
    'stats' => [
        'wordId' => $wordId,
        'correct' => $correct ? 1 : 0
    ]
]);