select_library.php

<?php
declare(strict_types=1);

require_once __DIR__ . '/bootstrap.php';

header('Content-Type: application/json');

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

if (empty($_SESSION['user_data']['userid']) || empty($_SESSION['authorized'])) {
    http_response_code(401);
    echo json_encode(['error' => 'Authentication required']);
    exit;
}

$payload = json_decode(file_get_contents('php://input') ?: '[]', true);
$chatId = isset($payload['chat_id']) ? trim((string)$payload['chat_id']) : '';
$libraryId = isset($payload['library_id']) ? (int)$payload['library_id'] : 0;

if ($chatId === '' || $libraryId <= 0) {
    http_response_code(400);
    echo json_encode(['error' => 'chat_id and library_id are required']);
    exit;
}

$ok = select_library_for_chat($_SESSION['user_data']['userid'], $chatId, $libraryId);
if (!$ok) {
    http_response_code(404);
    echo json_encode(['error' => 'Unable to select library for this chat']);
    exit;
}

echo json_encode([
    'ok' => true,
    'chat_id' => $chatId,
    'library_id' => $libraryId,
    'enabled' => true,
]);