using System;
using System.Collections.Generic;
using System.Linq;

namespace UserPermissionTest_CS_WinForms
{
    public static class SessionManager
    {
        private static readonly IUserRepository UserRepository = new JsonUserRepository();

        public static User? CurrentUser { get; private set; }
        
        public static List<User> Users { get; private set; } = new List<User>();
        
        public static List<string> AvailablePermissions { get; private set; } = new List<string>();

        public static event Action? SessionStateChanged;
        public static event Action? UsersUpdated;

        static SessionManager()
        {
            // Load state from repository
            Users = UserRepository.LoadUsers();
            AvailablePermissions = UserRepository.LoadPermissions();
        }

        public static bool Login(string username, string password)
        {
            var user = Users.FirstOrDefault(u => 
                u.Username.Equals(username, StringComparison.OrdinalIgnoreCase));

            if (user != null && PasswordHasher.VerifyPassword(password, user.Password))
            {
                CurrentUser = user;
                SessionStateChanged?.Invoke();
                return true;
            }
            return false;
        }

        public static void Logout()
        {
            if (CurrentUser != null)
            {
                CurrentUser = null;
                SessionStateChanged?.Invoke();
            }
        }

        public static void AddUser(User user)
        {
            Users.Add(user);
            UserRepository.SaveUsers(Users);
            UsersUpdated?.Invoke();
        }

        public static void UpdateUser(string oldUsername, User updatedUser)
        {
            var index = Users.FindIndex(u => u.Username.Equals(oldUsername, StringComparison.OrdinalIgnoreCase));
            if (index >= 0)
            {
                Users[index] = updatedUser;
                // If updated user is currently logged in, update current user too
                if (CurrentUser != null && CurrentUser.Username.Equals(oldUsername, StringComparison.OrdinalIgnoreCase))
                {
                    CurrentUser = updatedUser;
                    SessionStateChanged?.Invoke();
                }
                UserRepository.SaveUsers(Users);
                UsersUpdated?.Invoke();
            }
        }

        public static void DeleteUser(string username)
        {
            var user = Users.FirstOrDefault(u => u.Username.Equals(username, StringComparison.OrdinalIgnoreCase));
            if (user != null)
            {
                Users.Remove(user);
                // If deleted user is logged in, log out
                if (CurrentUser != null && CurrentUser.Username.Equals(username, StringComparison.OrdinalIgnoreCase))
                {
                    CurrentUser = null;
                    SessionStateChanged?.Invoke();
                }
                UserRepository.SaveUsers(Users);
                UsersUpdated?.Invoke();
            }
        }

        public static void AddPermission(string permission)
        {
            if (!AvailablePermissions.Contains(permission))
            {
                AvailablePermissions.Add(permission);
                UserRepository.SavePermissions(AvailablePermissions);
                UsersUpdated?.Invoke();
            }
        }
    }
}