using System;
using System.ComponentModel;
using System.Linq;

namespace gehGassi.Permissions
{
    /// <summary>
    /// Hilfsklasse für die Überprüfung von Permissions
    /// </summary>
    public static class PermissionChecker
    {
        /// <summary>
        /// Püft ob der gepackte Permission-String eine gesuchte Permission beinhaltet
        /// </summary>
        /// <param name="packedPermissions">Gepackte Liste mit Permissions</param>
        /// <param name="permissionName">Gesuchte Permission</param>
        /// <returns>true wenn gefunden, false sonst</returns>
        public static bool ThisPermissionIsAllowed(this string packedPermissions, string permissionName)
        {
            var usersPermissions = packedPermissions.UnpackPermissionsFromString().ToArray();

            if (!Enum.TryParse(permissionName, true, out Permission permissionToCheck))
                throw new InvalidEnumArgumentException($"{permissionName} could not be converted to a {nameof(Permission)}.");

            return usersPermissions.Contains(permissionToCheck);
        }

        /// <summary>
        /// Fügt eine Permission einem gepackten Permissionstring hinzu
        /// </summary>
        /// <param name="packedPermissions">Gepackte Liste mit Permissions</param>
        /// <param name="permissionName">Gesuchte Permission</param>
        /// <returns>Neuer packed Permisison-String</returns>
        public static string AddPermission(this string packedPermissions, string permissionName)
        {
            var usersPermissions = packedPermissions.UnpackPermissionsFromString().ToList();

            if (!Enum.TryParse(permissionName, true, out Permission permissionToCheck))
                throw new InvalidEnumArgumentException($"{permissionName} could not be converted to a {nameof(Permission)}.");

            if (!usersPermissions.Contains(permissionToCheck))
                usersPermissions.Add(permissionToCheck);

            return usersPermissions.PackPermissionsIntoString();
        }
    }
}