using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


using Microsoft.AspNetCore.DataProtection.KeyManagement;
using Microsoft.AspNetCore.Identity;
using Nettention.Proud;
using Newtonsoft.Json;
using OtpNet;
using Pipelines.Sockets.Unofficial.Buffers;
using StackExchange.Redis;


using ServerCore;
using ServerBase;


using SESSION_ID = System.Int32;
using META_ID = System.UInt32;
using ENTITY_GUID = System.String;
using ACCOUNT_ID = System.String;
using OWNER_GUID = System.String;
using USER_GUID = System.String;
using CHARACTER_GUID = System.String;
using ITEM_GUID = System.String;



namespace ServerCommon;

public static class ServerConnectionSwitchHelper
{
    public static async Task<Result> registerUserOtpToTargetServer(UserBase entityUser, RedisConnector redisConnector
                                                                  , string destServer)
    {
        var result = new Result();
        var err_msg = string.Empty;

        (result, var reserved_to_switch_server) = await startServerSwitch(entityUser, redisConnector, destServer);
        if (result.isFail())
        {
            return result;
        }

        NullReferenceCheckHelper.throwIfNull(reserved_to_switch_server, () => $"reserved_to_switch_server is null !!!");

        var account_attribute = entityUser.getEntityAttribute<AccountAttribute>();
        NullReferenceCheckHelper.throwIfNull(account_attribute, () => $"account_attribute is null !!! - {entityUser.toBasicString()}");

        account_attribute.OtpForServerConnect = reserved_to_switch_server.OneTimeKey;

        return result;
    }

    public static async Task<(Result, LoginCache.ReservationToSwitchServer?)> startServerSwitch(UserBase entityUser, RedisConnector redisConnector, string destServer)
    {
        var result = new Result();
        var err_msg = string.Empty;

        try
        {
            var login_cache_request = new LoginCacheRequest(entityUser, redisConnector);
            result = await login_cache_request.onPrepareRequest();
            if (result.isFail())
            {
                return (result, null);
            }
            string key = login_cache_request.getKey();
            var database = login_cache_request.getDatabase();

            var value = await database.StringGetAsync(key, CommandFlags.PreferReplica);
            if (value.HasValue == false)
            {
                err_msg = $"Not found Key !!! : Key:{key} - {entityUser.toBasicString()}";
                result.setFail(ServerErrorCode.RedisLoginCacheGetFailed, err_msg);
                Log.getLogger().error(result.toBasicString());

                return (result, null);
            }

            var login_cache = JsonConvert.DeserializeObject<LoginCache>(value.ToString());
            if (null == login_cache)
            {
                err_msg = $"Failed to JsonConvert.DeserializeObject !!! : {login_cache_request.toBasicString()} - {entityUser.toBasicString()}";
                result.setFail(ServerErrorCode.JsonConvertDeserializeFailed, err_msg);
                Log.getLogger().error(result.toBasicString());

                return (result, null);
            }

            var otp = KeyGeneration.GenerateRandomKey(20);
            var otp_encoding_by_base32 = Base32Encoding.ToString(otp);

            login_cache.ReservedToSwitchServer = new LoginCache.ReservationToSwitchServer()
            {
                OneTimeKey = otp_encoding_by_base32,
                DestServer = destServer
            };

            var json_string = login_cache.toJsonString();

            if (await database.StringSetAsync(key, json_string, TimeSpan.FromMilliseconds(LoginCacheRequest.SERVER_SWITCH_CACHE_EXPIRY_TIME)) == false)
            {
                err_msg = $"Failed to StringSetAsync !!! : Key:{key}, JsonString:{json_string} - {entityUser.toBasicString()}";
                result.setFail(ServerErrorCode.RedisStringsWriteFailed, err_msg);
                Log.getLogger().error(result.toBasicString());

                return (result, null);
            }

            Log.getLogger().info($"Server Switching Start : currServer:{login_cache.CurrentServer}, destServer:{destServer} - {entityUser.toBasicString()}");

            return (result, login_cache.ReservedToSwitchServer);
        }
        catch (Exception e)
        {
            err_msg = $"Failed to startServerSwitch !!! : Exception:{e} - {entityUser.toBasicString()}";
            result.setFail(ServerErrorCode.TryCatchException, err_msg);
            Log.getLogger().error(result.toBasicString());

            return (result, null);
        }
    }

    public static async Task<Result> endServerSwitch(EntityBase entityUser, LoginCacheRequest loginCacheRequest
                                                    , string currConnectedServer
                                                    , DateTime switchedDateTime)
    {
        var result = new Result();
        var err_msg = string.Empty;

        try
        {
            var database = loginCacheRequest.getDatabase();
            var login_cache = loginCacheRequest.getLoginCache();

            NullReferenceCheckHelper.throwIfNull(login_cache, () => $"login_cache is null !!!");
            NullReferenceCheckHelper.throwIfNull(login_cache.ReservedToSwitchServer, () => $"login_cache.ReservedToSwitchServer is null !!!");

            string prev_connected_server = login_cache.CurrentServer;

            login_cache.LoginDateTime = switchedDateTime;

            login_cache.ServerSwitchCount += 1;
            login_cache.CurrentServer = login_cache.ReservedToSwitchServer.DestServer;
            login_cache.ReservedToSwitchServer = null;

            var key = loginCacheRequest.getKey();
            var json_string = login_cache.toJsonString();

            if (await database.StringSetAsync(key, json_string, TimeSpan.FromMilliseconds(LoginCacheRequest.LOGIN_CACHE_EXPIRY_TIME)) == false)
            {
                err_msg = $"Failed to StringSetAsync !!! : Key:{key}, JsonString:{json_string} - {entityUser.toBasicString()}";
                result.setFail(ServerErrorCode.RedisStringsWriteFailed, err_msg);
                Log.getLogger().error(result.toBasicString());

                return result;
            }

            Log.getLogger().info($"Server Switching End : prevServer:{prev_connected_server} => currServer:{currConnectedServer} - {entityUser.toBasicString()}");

            return result;
        }
        catch (Exception e)
        {
            err_msg = $"Failed to startServerSwitch !!! : Exception:{e} - {entityUser.toBasicString()}";
            result.setFail(ServerErrorCode.TryCatchException, err_msg);
            Log.getLogger().error(result.toBasicString());

            return result;
        }
    }
}