<?php
define('CYBERCHAT_API', true);
require_once __DIR__ . '/../bootstrap.php';
require_once ROOT_DIR . '/lib/mailer.php';
sendCorsHeaders();

$action = $_POST['action'] ?? $_GET['action'] ?? '';
match ($action) {
    'captcha_challenge' => captchaChallenge(),
    'register' => registerUser(),
    'login' => loginUser(),
    'verify_2fa' => verifyTwoFactor(),
    'logout' => logoutUser(),
    'check' => checkSession(),
    default => jsonResponse(['error' => 'Unknown action'], 400),
};

function captchaChallenge(): never {
    $operation = trim((string)($_GET['operation'] ?? $_POST['operation'] ?? ''));
    jsonResponse(createAuthCaptchaChallenge($operation));
}

function registerUser(): never {
    validateAuthCaptcha('register');
    $db = getDB();
    $username = trim((string)($_POST['username'] ?? ''));
    $password = (string)($_POST['password'] ?? '');
    $maxUser = (int)getConfigVal('chat.max_username_length', 12);
    $minPass = (int)getConfigVal('security.min_password_length', 4);
    if ($username === '' || $password === '') jsonResponse(['error' => 'Username and password required'], 400);
    if (strlen($username) > $maxUser) jsonResponse(['error' => "Username max $maxUser characters"], 400);
    if (!preg_match('/^[a-zA-Z0-9_-]+$/', $username)) {
        jsonResponse(['error' => 'Username: letters, numbers, _ and - only'], 400);
    }
    if (strlen($password) < $minPass) jsonResponse(['error' => "Password min $minPass characters"], 400);
    $check = $db->prepare("SELECT 1 FROM users WHERE username=? COLLATE NOCASE");
    $check->execute([$username]);
    if ($check->fetchColumn()) jsonResponse(['error' => 'Username already taken'], 409);

    $palette = (array)getConfigVal('colors.user_palette', ['#00ff9f']);
    $color = $palette[array_rand($palette)];
    $hash = password_hash($password, PASSWORD_BCRYPT, ['cost' => (int)getConfigVal('security.bcrypt_cost', 10)]);
    $freeId = (int)$db->query("SELECT id FROM plans WHERE slug='free'")->fetchColumn();
    $db->prepare("INSERT INTO users (username,password_hash,color,plan_id,created_at) VALUES (?,?,?,?,?)")
        ->execute([$username, $hash, $color, $freeId, time()]);
    $userId = (int)$db->lastInsertId();
    createUserSession($db, $userId);
    $user = userById($userId);
    trackEvent('registration', '/api/auth.php', $userId);
    jsonResponse(['success' => true, 'user' => userPublicPayload($user)]);
}

function loginUser(): never {
    validateAuthCaptcha('login');
    $db = getDB();
    $username = trim((string)($_POST['username'] ?? ''));
    $password = (string)($_POST['password'] ?? '');
    if ($username === '' || $password === '') jsonResponse(['error' => 'Username and password required'], 400);
    $stmt = $db->prepare("SELECT * FROM users WHERE username=? COLLATE NOCASE");
    $stmt->execute([$username]);
    $user = $stmt->fetch();
    if (!$user || !password_verify($password, $user['password_hash'])) {
        trackEvent('login_failed', '/api/auth.php');
        jsonResponse(['error' => 'Invalid username or password'], 401);
    }

    assertUserSessionLoginAllowed($db, (int)$user['id']);

    if (!empty($user['two_factor_enabled']) && featureValue($user, 'email_2fa', false)) {
        if (empty($user['email_verified_at']) || empty($user['email'])) {
            jsonResponse(['error' => 'Two-factor authentication requires a verified email'], 403);
        }
        $challengeId = bin2hex(random_bytes(24));
        $code = (string)random_int(100000, 999999);
        $db->prepare("DELETE FROM login_challenges WHERE user_id=?")->execute([$user['id']]);
        $db->prepare("INSERT INTO login_challenges (id,user_id,code_hash,expires_at,created_at) VALUES (?,?,?,?,?)")
            ->execute([$challengeId, $user['id'], password_hash($code, PASSWORD_DEFAULT), time() + 600, time()]);
        try {
            sendTwoFactorCode($user, $challengeId, $code);
        } catch (Throwable $e) {
            $db->prepare("DELETE FROM login_challenges WHERE id=?")->execute([$challengeId]);
            jsonResponse(['error' => 'Could not send the login code: ' . $e->getMessage()], 503);
        }
        jsonResponse(['success' => true, 'requires_2fa' => true, 'challenge' => $challengeId]);
    }

    createUserSession($db, (int)$user['id']);
    trackEvent('login', '/api/auth.php', (int)$user['id']);
    jsonResponse(['success' => true, 'user' => userPublicPayload(userById((int)$user['id']))]);
}

function verifyTwoFactor(): never {
    $challenge = trim((string)($_POST['challenge'] ?? ''));
    $code = trim((string)($_POST['code'] ?? ''));
    if ($challenge === '' || !preg_match('/^\d{6}$/', $code)) jsonResponse(['error' => 'Enter the six-digit code'], 400);
    $db = getDB();
    $stmt = $db->prepare("SELECT * FROM login_challenges WHERE id=? AND expires_at>?");
    $stmt->execute([$challenge, time()]);
    $row = $stmt->fetch();
    if (!$row || (int)$row['attempts'] >= 5 || !password_verify($code, $row['code_hash'])) {
        if ($row) $db->prepare("UPDATE login_challenges SET attempts=attempts+1 WHERE id=?")->execute([$challenge]);
        jsonResponse(['error' => 'Invalid or expired login code'], 401);
    }
    assertUserSessionLoginAllowed($db, (int)$row['user_id']);
    $db->prepare("DELETE FROM login_challenges WHERE id=?")->execute([$challenge]);
    createUserSession($db, (int)$row['user_id']);
    trackEvent('login_2fa', '/api/auth.php', (int)$row['user_id']);
    jsonResponse(['success' => true, 'user' => userPublicPayload(userById((int)$row['user_id']))]);
}

function logoutUser(): never {
    $sid = $_COOKIE['cyberchat_sid'] ?? '';
    if ($sid !== '') getDB()->prepare("DELETE FROM sessions WHERE id=?")->execute([$sid]);
    setcookie('cyberchat_sid', '', [
        'expires' => time() - 3600, 'path' => '/', 'httponly' => true, 'samesite' => 'Strict',
        'secure' => !empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off',
    ]);
    jsonResponse(['success' => true]);
}

function checkSession(): never {
    $user = authUser(false);
    jsonResponse($user
        ? ['authenticated' => true, 'user' => userPublicPayload($user)]
        : ['authenticated' => false]);
}