<?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'];

$input = json_decode(file_get_contents('php://input'), 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;
$updatedWord = null;

foreach ($data['words'] as $i => $word) {

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

        // init stats
        if (!isset($data['words'][$i]['correct'])) {
            $data['words'][$i]['correct'] = 0;
        }

        if (!isset($data['words'][$i]['wrong'])) {
            $data['words'][$i]['wrong'] = 0;
        }

        // normalize
        $expected = strtolower(trim($data['words'][$i]['answer']));
        $given = strtolower(trim($userAnswer));

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

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

        // SRS update (nextReview etc.)
        updateWordStats($data['words'][$i], $correct);

        $updatedWord = $data['words'][$i];

        break;
    }
}

if ($updatedWord === null) {
    echo json_encode([
        'error' => 'word_not_found',
        'wordId' => $wordId
    ]);
    exit;
}

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

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

echo json_encode([
    'correct' => $correct,
    'debug' => [
        'wordId' => $wordId,
        'updatedCorrect' => $updatedWord['correct'] ?? null,
        'updatedWrong' => $updatedWord['wrong'] ?? null
    ],
    'stats' => [
        'wordId' => $wordId,
        'correct' => $correct ? 1 : 0
    ],
]);