<?php
// This file should be included after db.php and session_start()

/**
 * Fetches all permission names for a given user and stores them in the session.
 * Should be called once upon user login.
 *
 * @param int $user_id The user's ID.
 * @param mysqli $conn The database connection object.
 */
function load_user_permissions($user_id, $conn) {
    $permissions = [];
    $sql = "SELECT p.name FROM permissions p 
            JOIN user_permissions up ON p.id = up.permission_id 
            WHERE up.user_id = ?";
    
    $stmt = $conn->prepare($sql);
    $stmt->bind_param("i", $user_id);
    $stmt->execute();
    $result = $stmt->get_result();
    
    while ($row = $result->fetch_assoc()) {
        $permissions[] = $row['name'];
    }
    
    $_SESSION['permissions'] = $permissions;
    $stmt->close();
}

/**
 * Checks if the currently logged-in user has a specific permission.
 *
 * @param string $permission_name The name of the permission to check (e.g., 'cars_edit').
 * @return bool True if the user has the permission, false otherwise.
 */
function has_permission($permission_name) {
    // The super admin (user ID 1) always has all permissions.
    if (isset($_SESSION['user_id']) && $_SESSION['user_id'] == 1) {
        return true;
    }
    
    // Check if the permission exists in the user's session permissions array.
    return isset($_SESSION['permissions']) && in_array($permission_name, $_SESSION['permissions']);
}

/**
 * A helper function to protect a page.
 * If the user doesn't have the required permission, it will stop script execution.
 *
 * @param string $permission_name The permission required to access the page.
 */
function require_permission($permission_name) {
    if (!has_permission($permission_name)) {
        // You can create a fancier "Access Denied" page if you want.
        die("Access Denied. You do not have the required permission ($permission_name).");
    }
}

?>