using System;
using System.Threading.Tasks;
using Vanguard.Api;
using Vanguard.Api.Contracts;
using Vanguard.State;

namespace Vanguard.Auth
{
    /// <summary>
    /// Сессия игрока: login/register, восстановление по refresh-токену,
    /// обновление профиля и выход. Токены не покидают клиент.
    /// </summary>
    public sealed class AuthService
    {
        private readonly ApiClient _api;
        private readonly TokenStore _tokens;
        private readonly PlayerState _player;

        public AuthService(ApiClient api, TokenStore tokens, PlayerState player)
        {
            _api = api;
            _tokens = tokens;
            _player = player;
        }

        public bool IsAuthenticated => _tokens.HasRefreshToken;

        public async Task<AuthResponse> LoginAsync(string userName, string password)
        {
            var response = await _api.PostAsync<AuthResponse>(
                "/api/auth/login",
                new LoginRequest { UserName = userName, Password = password },
                authenticated: false);

            SaveSession(response);
            await TryRefreshMeAsync();
            return response;
        }

        public async Task<AuthResponse> RegisterAsync(string userName, string password)
        {
            var response = await _api.PostAsync<AuthResponse>(
                "/api/auth/register",
                new RegisterRequest { UserName = userName, Password = password },
                authenticated: false);

            SaveSession(response);
            await TryRefreshMeAsync();
            return response;
        }

        /// <summary>Восстановить сессию при старте. false — нужен логин.</summary>
        public async Task<bool> TryRestoreAsync()
        {
            if (!_tokens.HasRefreshToken || _tokens.RefreshExpiresAt <= DateTimeOffset.UtcNow)
                return false;

            try
            {
                await RefreshAsync();
                await TryRefreshMeAsync();
                return true;
            }
            catch (ApiException exception) when (exception.StatusCode == 401)
            {
                ClearSession();
                return false;
            }
            catch (Exception)
            {
                // Сервер временно недоступен: токены не трогаем, покажем логин.
                return false;
            }
        }

        public async Task<AuthResponse> RefreshAsync()
        {
            if (!_tokens.HasRefreshToken)
                throw new ApiException(401, "auth.no-refresh", "Нет refresh-токена.");

            var response = await _api.PostAsync<AuthResponse>(
                "/api/auth/refresh",
                new RefreshRequest { RefreshToken = _tokens.RefreshToken },
                authenticated: false);

            SaveSession(response);
            return response;
        }

        public async Task<MeResponse> RefreshMeAsync()
        {
            if (_tokens.IsAccessExpired && _tokens.HasRefreshToken)
                await RefreshAsync();

            try
            {
                var me = await _api.GetAsync<MeResponse>("/api/auth/me");
                _player.Apply(me);
                return me;
            }
            catch (ApiException exception) when (exception.StatusCode == 401 && _tokens.HasRefreshToken)
            {
                await RefreshAsync();
                var me = await _api.GetAsync<MeResponse>("/api/auth/me");
                _player.Apply(me);
                return me;
            }
        }

        public async Task LogoutAsync()
        {
            try
            {
                if (_tokens.HasRefreshToken)
                {
                    await _api.PostAsync(
                        "/api/auth/logout",
                        new RefreshRequest { RefreshToken = _tokens.RefreshToken },
                        authenticated: false);
                }
            }
            catch (Exception)
            {
                // Выход не должен зависеть от доступности сервера.
            }
            finally
            {
                ClearSession();
            }
        }

        private async Task TryRefreshMeAsync()
        {
            try
            {
                await RefreshMeAsync();
            }
            catch (Exception)
            {
                // Логин уже состоялся; профиль можно обновить на мета-экране.
            }
        }

        private void SaveSession(AuthResponse response)
        {
            _tokens.Save(
                response.AccessToken,
                response.RefreshToken,
                response.AccessExpiresAt,
                response.RefreshExpiresAt);

            _player.Apply(response);
        }

        private void ClearSession()
        {
            _tokens.Clear();
            _player.Clear();
        }
    }
}