/*
* Copyright (c) 2023 Vaughn Nugent
* 
* Library: VNLib
* Package: VNLib.Plugins.Essentials.SocialOauth
* File: SocialOauthBase.cs 
*
* SocialOauthBase.cs is part of VNLib.Plugins.Essentials.SocialOauth which is part of the larger 
* VNLib collection of libraries and utilities.
*
* VNLib.Plugins.Essentials.SocialOauth is free software: you can redistribute it and/or modify 
* it under the terms of the GNU Affero General Public License as 
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* VNLib.Plugins.Essentials.SocialOauth is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program.  If not, see https://www.gnu.org/licenses/.
*/

using System;
using System.Net;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using System.Security.Cryptography;
using System.Text.Json.Serialization;
using System.Runtime.InteropServices;
using System.Diagnostics.CodeAnalysis;

using FluentValidation;

using RestSharp;

using VNLib.Net.Http;
using VNLib.Hashing;
using VNLib.Hashing.IdentityUtility;
using VNLib.Utils;
using VNLib.Utils.Memory;
using VNLib.Utils.Logging;
using VNLib.Utils.Extensions;
using VNLib.Net.Rest.Client.Construction;
using VNLib.Plugins.Essentials.Users;
using VNLib.Plugins.Essentials.Accounts;
using VNLib.Plugins.Essentials.Endpoints;
using VNLib.Plugins.Essentials.Extensions;
using VNLib.Plugins.Essentials.SocialOauth.Validators;
using VNLib.Plugins.Extensions.Loading;
using VNLib.Plugins.Extensions.Validation;
using VNLib.Plugins.Extensions.Loading.Users;

using ContentType = VNLib.Net.Http.ContentType;

namespace VNLib.Plugins.Essentials.SocialOauth
{

    /// <summary>
    /// Provides a base class for derriving commong OAuth2 implicit authentication
    /// </summary>
    public abstract class SocialOauthBase : UnprotectedWebEndpoint
    {
        const string AUTH_ERROR_MESSAGE = "You have no pending authentication requests.";

        const string AUTH_GRANT_SESSION_NAME = "auth";
        const string SESSION_SIG_KEY_NAME = "soa.sig";
        const string SESSION_TOKEN_KEY_NAME = "soa.tkn";
        const string CLAIM_COOKIE_NAME = "extern-claim";
        const int SIGNING_KEY_SIZE = 32;

        /// <summary>
        /// The client configuration struct passed during base class construction
        /// </summary>
        protected virtual OauthClientConfig Config { get; }
        
        ///<inheritdoc/>
        protected override ProtectionSettings EndpointProtectionSettings { get; } = new();

        /// <summary>
        /// The site adapter used to make requests to the OAuth2 provider
        /// </summary>
        protected OAuthSiteAdapter SiteAdapter { get; }

        /// <summary>
        /// The user manager used to create and manage user accounts
        /// </summary>
        protected IUserManager Users { get; }

        /// <summary>
        /// The password hashing provider used to hash user passwords
        /// </summary>
        protected IPasswordHashingProvider Passwords { get; }

        private readonly IValidator<LoginClaim> ClaimValidator;
        private readonly IValidator<string> NonceValidator;
        private readonly IValidator<AccountData> AccountDataValidator;

        protected SocialOauthBase(PluginBase plugin, IConfigScope config)
        {
            ClaimValidator = GetClaimValidator();
            NonceValidator = GetNonceValidator();
            AccountDataValidator = new AccountDataValidator();
         
            //Get the configuration element for the derrived type
            Config = plugin.CreateService<OauthClientConfig>(config);

            //Init endpoint 
            InitPathAndLog(Config.EndpointPath, plugin.Log);

            Users = plugin.GetOrCreateSingleton<UserManager>();
            Passwords = plugin.GetOrCreateSingleton<ManagedPasswordHashing>();

            //Define the site adapter
            SiteAdapter = new();

            //Define the the get-token request endpoint
            SiteAdapter.DefineSingleEndpoint()
                .WithEndpoint<GetTokenRequest>()
                .WithMethod(Method.Post)
                .WithUrl(Config.AccessTokenUrl)
                .WithHeader("Accept", HttpHelpers.GetContentTypeString(ContentType.Json))
                .WithParameter("client_id", c => Config.ClientID.Value)
                .WithParameter("client_secret", c => Config.ClientSecret.Value)
                .WithParameter("grant_type", "authorization_code")
                .WithParameter("code", r => r.Code)
                .WithParameter("redirect_uri", r => r.RedirectUrl);

        }

        private static IValidator<LoginClaim> GetClaimValidator()
        {
            InlineValidator<LoginClaim> val = new();
            val.RuleFor(static s => s.ClientId)
                .Length(10, 100)
                .WithMessage("Request is not valid")
                .AlphaNumericOnly()
                .WithMessage("Request is not valid");

            val.RuleFor(static s => s.PublicKey)
                .Length(50, 1024)
                .WithMessage("Request is not valid");

            val.RuleFor(static s => s.LocalLanguage)
                .Length(2, 10)
                .WithMessage("Request is not valid");

            return val;
        }

        private static IValidator<string> GetNonceValidator()
        {
            InlineValidator<string> val = new();
            val.RuleFor(static s => s)
                .Length(10, 200)
                //Nonces are base32, so only alpha num
                .AlphaNumeric();
            return val;
        }

        ///<inheritdoc/>
        protected override ERRNO PreProccess(HttpEntity entity)
        {
            if (!base.PreProccess(entity))
            {
                return false;
            }
            
            /*
             * Cross site checking is disabled because we need to allow cross site
             * for OAuth2 redirect flows
             */
            if (entity.Server.Method != HttpMethod.GET && entity.Server.IsCrossSite())
            {
                return false;
            }
            
            //Make sure the user is not logged in
            return !entity.IsClientAuthorized(AuthorzationCheckLevel.Any);
        }

        /// <summary>
        /// When derrived in a child class, exchanges an OAuth2 code grant type
        /// for an OAuth2 access token to make api requests
        /// </summary>
        /// <param name="ev"></param>
        /// <param name="code">The raw code from the remote OAuth2 granting server</param>
        /// <param name="cancellationToken">A token to cancel the operation</param>
        /// <returns>
        /// A task the resolves the <see cref="OAuthAccessState"/> that includes all relavent
        /// authorization data. Result may be null if authorzation is invalid or not granted
        /// </returns>
        protected virtual async Task<OAuthAccessState?> ExchangeCodeForTokenAsync(HttpEntity ev, string code, CancellationToken cancellationToken)
        {
            //Create new request object
            GetTokenRequest req = new(code, $"{ev.Server.RequestUri.Scheme}://{ev.Server.RequestUri.Authority}{Path}");
          
            //Execute request and attempt to recover the authorization response
            OAuthAccessState? response = await SiteAdapter.ExecuteAsync(req, cancellationToken).AsJson<OAuthAccessState>();
         
            return response;
        }

        /// <summary>
        /// Gets an object that represents the user's account data from the OAuth provider when 
        /// creating a new user for the current platform
        /// </summary>
        /// <param name="clientAccess">The access state from the code/token exchange</param>
        /// <param name="cancellationToken">A token to cancel the operation</param>
        /// <returns>The user's account data, null if not account exsits on the remote site, and process cannot continue</returns>
        protected abstract Task<AccountData?> GetAccountDataAsync(IOAuthAccessState clientAccess, CancellationToken cancellationToken);

        /// <summary>
        /// Gets an object that represents the required information for logging-in a user (namley unique user-id)
        /// </summary>
        /// <param name="clientAccess">The authorization information granted from the OAuth2 authorization server</param>
        /// <param name="cancellation">A token to cancel the operation</param>
        /// <returns></returns>
        protected abstract Task<UserLoginData?> GetLoginDataAsync(IOAuthAccessState clientAccess, CancellationToken cancellation);

       

        /*
         * Claims are considered indempodent because they require no previous state
         * and will return a new secret authentication "token" (url + nonce) that 
         * uniquely identifies the claim and authorization upgrade later
         */

        ///<inheritdoc/>
        protected override async ValueTask<VfReturnType> PutAsync(HttpEntity entity)
        {
            ValErrWebMessage webm = new();

            //Get the login message
            LoginClaim? claim = await entity.GetJsonFromFileAsync<LoginClaim>();

            if (webm.Assert(claim != null, "Emtpy message body"))
            {
                entity.CloseResponseJson(HttpStatusCode.BadRequest, webm);
                return VfReturnType.VirtualSkip;
            }

            //Validate the message
            if (!ClaimValidator.Validate(claim, webm))
            {
                entity.CloseResponseJson(HttpStatusCode.UnprocessableEntity, webm);
                return VfReturnType.VirtualSkip;
            }

            //Configure the login claim
            claim.IssuedAtTime = entity.RequestedTimeUtc.ToUnixTimeSeconds();

            //Set expiration time in seconds
            claim.ExpirationSeconds = entity.RequestedTimeUtc.Add(Config.InitClaimValidFor).ToUnixTimeMilliseconds();

            //Set nonce
            claim.ComputeNonce((int)Config.NonceByteSize);

            //Build the redirect uri
            webm.Result = new LoginUriBuilder(Config)
                .WithEncoding(entity.Server.Encoding)
                .WithUrl(entity.IsSecure ? "https" : "http", entity.Server.RequestUri.Authority, Path)
                .WithNonce(claim.Nonce!)
                .Encrypt(entity, claim);

            //Sign and set the claim cookie
            SignAndSetCookie(entity, claim);

            webm.Success = true;
            //Response
            entity.CloseResponse(webm);
            return VfReturnType.VirtualSkip;
        }

        /*
         * Get method is invoked when the remote OAuth2 control has been passed back
         * to this server. If successful should include a code that grants authorization
         * and include a state variable that the client decrypted from an initial claim
         * to prove its identity
         */

        ///<inheritdoc/>
        protected override async ValueTask<VfReturnType> GetAsync(HttpEntity entity)
        {
            //Make sure state and code parameters are available
            if (entity.QueryArgs.TryGetNonEmptyValue("state", out string? state) 
                && entity.QueryArgs.TryGetNonEmptyValue("code", out string? code))
            {
                //Disable refer headers when nonce is set
                entity.Server.Headers["Referrer-Policy"] = "no-referrer";
               
                //Check for security navigation headers. This should be a browser redirect,
                if (!entity.Server.IsNavigation() || !entity.Server.IsUserInvoked())
                {
                    ClearClaimData(entity);
                    //The connection was not a browser redirect
                    entity.Redirect(RedirectType.Temporary, $"{Path}?result=bad_sec");
                    return VfReturnType.VirtualSkip;
                }

                //Try to get the claim from the state parameter
                if (!VerifyAndGetClaim(entity, out LoginClaim? claim))
                {
                    ClearClaimData(entity);
                    entity.Redirect(RedirectType.Temporary, $"{Path}?result=expired");
                    return VfReturnType.VirtualSkip;
                }

                //Confirm the nonce matches the claim
                if (string.CompareOrdinal(claim.Nonce, state) != 0)
                {
                    ClearClaimData(entity);
                    entity.Redirect(RedirectType.Temporary, $"{Path}?result=invalid");
                    return VfReturnType.VirtualSkip;
                }

                //Exchange the OAuth code for a token (application specific)
                OAuthAccessState? token = await ExchangeCodeForTokenAsync(entity, code, entity.EventCancellation);

                //Token may be null
                if (token == null)
                {
                    ClearClaimData(entity);
                    entity.Redirect(RedirectType.Temporary, $"{Path}?result=invalid");
                    return VfReturnType.VirtualSkip;
                }

                //Create the new nonce
                claim.ComputeNonce((int)Config.NonceByteSize);

                //Store access state in the user's session
                entity.Session.SetObject(SESSION_TOKEN_KEY_NAME, token);

                //Sign and set cookie
                SignAndSetCookie(entity, claim);
                  
                //Prepare redirect
                entity.Redirect(RedirectType.Temporary, $"{Path}?result=authorized&nonce={claim.Nonce}");
                return VfReturnType.VirtualSkip;
            }
            
            //Check to see if there was an error code set
            if (entity.QueryArgs.TryGetNonEmptyValue("error", out string? errorCode))
            {
                ClearClaimData(entity);
                Log.Debug("{Type} error {err}:{des}", Config.AccountOrigin, errorCode, entity.QueryArgs["error_description"]);
                entity.Redirect(RedirectType.Temporary, $"{Path}?result=error");
                return VfReturnType.VirtualSkip;
            }
            
            return VfReturnType.ProcessAsFile;
        }

        /*
         * Post messages finalize a login from a nonce
         */

        ///<inheritdoc/>
        protected override async ValueTask<VfReturnType> PostAsync(HttpEntity entity)
        {
            ValErrWebMessage webm = new();
            
            //Get the finalization message
            using JsonDocument? request = await entity.GetJsonFromFileAsync();
            
            if (webm.Assert(request != null, "Request message is required"))
            {
                entity.CloseResponseJson(HttpStatusCode.BadRequest, webm);
                return VfReturnType.VirtualSkip;
            }
            
            //Recover the nonce
            string? base32Nonce = request.RootElement.GetPropString("nonce");

            if(webm.Assert(base32Nonce != null, message: "Nonce parameter is required"))
            {
                entity.CloseResponseJson(HttpStatusCode.UnprocessableEntity, webm);
                return VfReturnType.VirtualSkip;
            }
            
            //Validate nonce
            if (!NonceValidator.Validate(base32Nonce, webm))
            {
                entity.CloseResponseJson(HttpStatusCode.UnprocessableEntity, webm);
                return VfReturnType.VirtualSkip;
            }

            //Recover the access token
            bool cookieValid = VerifyAndGetClaim(entity, out LoginClaim? claim);

            if (webm.Assert(cookieValid, AUTH_ERROR_MESSAGE))
            {
                entity.CloseResponse(webm);
                return VfReturnType.VirtualSkip;
            }

            //We can clear the client's access claim
            ClearClaimData(entity);

            //Confirm nonce matches the client's nonce string
            bool nonceValid = string.CompareOrdinal(claim.Nonce, base32Nonce) == 0;

            if (webm.Assert(nonceValid, AUTH_ERROR_MESSAGE))
            {
                entity.CloseResponse(webm);
                return VfReturnType.VirtualSkip;
            }

            //Safe to recover the access token
            IOAuthAccessState token = entity.Session.GetObject<OAuthAccessState>(SESSION_TOKEN_KEY_NAME);
            
            //get the user's login information (ie userid)
            UserLoginData? userLogin = await GetLoginDataAsync(token, entity.EventCancellation);
            
            if(webm.Assert(userLogin?.UserId != null, AUTH_ERROR_MESSAGE))
            {
                entity.CloseResponse(webm);
                return VfReturnType.VirtualSkip;
            }
            
            //Fetch the user from the database
            IUser? user = await Users.GetUserFromIDAsync(userLogin.UserId, entity.EventCancellation);
            
            if(user == null)
            {
                //Get the clients personal info to being login process
                AccountData? userAccount = await GetAccountDataAsync(token, entity.EventCancellation);

                if (webm.Assert(userAccount != null, AUTH_ERROR_MESSAGE))
                {
                    entity.CloseResponse(webm);
                    return VfReturnType.VirtualSkip;
                }

                //Validate the account data
                if (webm.Assert(AccountDataValidator.Validate(userAccount).IsValid, AUTH_ERROR_MESSAGE))
                {
                    entity.CloseResponse(webm);
                    return VfReturnType.VirtualSkip;
                }

                //make sure registration is enabled
                if (webm.Assert(Config.AllowRegistration, AUTH_ERROR_MESSAGE))
                {
                    entity.CloseResponse(webm);
                    return VfReturnType.VirtualSkip;
                }
              
                //Generate a new random passowrd incase the user wants to use a local account to log in sometime in the future
                using PrivateString passhash = Passwords.GetRandomPassword(Config.RandomPasswordSize);
                try
                {
                    //Create the user with the specified email address, minimum privilage level, and an empty password
                    user = await Users.CreateUserAsync(userLogin.UserId!, userAccount.EmailAddress, AccountUtil.MINIMUM_LEVEL, passhash, entity.EventCancellation);
                    //Set active status
                    user.Status = UserStatus.Active;
                    //Store the new profile
                    user.SetProfile(userAccount);
                    //Set the account creation origin
                    user.SetAccountOrigin(Config.AccountOrigin);
                }
                catch(UserCreationFailedException)
                {
                    Log.Warn("Failed to create new user from new OAuth2 login, because a creation exception occured");
                    webm.Result = "Please try again later";
                    entity.CloseResponse(webm);
                    return VfReturnType.VirtualSkip;
                }
            }
            else
            {
                //Check for local only
                if (webm.Assert(!user.LocalOnly, AUTH_ERROR_MESSAGE))
                {
                    entity.CloseResponse(webm);
                    return VfReturnType.VirtualSkip;
                }

                //Make sure local accounts are allowed
                if (webm.Assert(!user.IsLocalAccount() || Config.AllowForLocalAccounts, AUTH_ERROR_MESSAGE))
                {
                    entity.CloseResponse(webm);
                    return VfReturnType.VirtualSkip;
                }

                //Reactivate inactive accounts
                if(user.Status == UserStatus.Inactive)
                {
                    user.Status = UserStatus.Active;
                }                
                
                //Make sure the account is active                
                if(webm.Assert(user.Status == UserStatus.Active, AUTH_ERROR_MESSAGE))
                {
                    entity.CloseResponse(webm);
                    return VfReturnType.VirtualSkip;
                }
            }

            //Finalze login
            try
            {
                //Generate authoization
                entity.GenerateAuthorization(claim, user, webm);

                //Store the user current oauth information in the current session for others to digest
                entity.Session.SetObject($"{Config.AccountOrigin}.{AUTH_GRANT_SESSION_NAME}", token);

                //Send the username back to the client
                webm.Result = new AccountData()
                {
                    EmailAddress = user.EmailAddress,
                };

                //Set the success flag
                webm.Success = true;
                //Write to log
                Log.Debug("Successful login for user {uid}... from {ip}", user.UserID[..8], entity.TrustedRemoteIp);
                //release the user 
                await user.ReleaseAsync();
            }
            catch (CryptographicException ce)
            {
                Log.Debug("Failed to generate authorization for {user}, error {err}", user.UserID, ce.Message);
                webm.Result = AUTH_ERROR_MESSAGE;
            }
            catch (OutOfMemoryException)
            {
                Log.Debug("Out of buffer space for token data encryption, for user {usr}, from ip {ip}", user.UserID, entity.TrustedRemoteIp);
                webm.Result = AUTH_ERROR_MESSAGE;
            }
            catch(UserUpdateException uue)
            {
                webm.Token = null;
                webm.Result = AUTH_ERROR_MESSAGE;
                webm.Success = false;
                
                //destroy any login data on failure
                entity.InvalidateLogin();
                
                Log.Error(uue);
            }
            finally
            {
                user.Dispose();
            }
            entity.CloseResponse(webm);
            return VfReturnType.VirtualSkip;
        }

        private static bool VerifyAndGetClaim(HttpEntity entity, [NotNullWhen(true)] out LoginClaim? claim)
        {
            claim = null;

            //Try to get the cookie
            if (!entity.Server.GetCookie(CLAIM_COOKIE_NAME, out string? cookieValue))
            {
                return false;
            }

            //Recover the signing key from the user's session
            string sigKey = entity.Session[SESSION_SIG_KEY_NAME];
            byte[]? key = VnEncoding.FromBase32String(sigKey);

            if (key == null)
            {
                return false;
            }

            try
            {
                //Try to parse the jwt
                using JsonWebToken jwt = JsonWebToken.Parse(cookieValue);

                //Verify the jwt
                if (!jwt.Verify(key, HashAlg.SHA256))
                {
                    return false;
                }

                //Recover the clam from the jwt
                claim = jwt.GetPayload<LoginClaim>();

                //Verify the expiration time
                return claim.ExpirationSeconds > entity.RequestedTimeUtc.ToUnixTimeSeconds();
            }
            catch (FormatException)
            {
                //JWT was corrupted and could not be parsed
                return false;
            }
            finally
            {
                MemoryUtil.InitializeBlock(key.AsSpan());
            }
        }

        private static void ClearClaimData(HttpEntity entity)
        {
            //Remove the upgrade cookie
            if (entity.Server.RequestCookies.ContainsKey(CLAIM_COOKIE_NAME))
            {
                //Expire cookie
                HttpCookie cookie = new(CLAIM_COOKIE_NAME, string.Empty)
                {
                    Secure = true,
                    HttpOnly = true,
                    ValidFor = TimeSpan.Zero,
                    SameSite = CookieSameSite.SameSite
                };

                entity.Server.SetCookie(in cookie);
            }

            //Clear the signing key from the session
            entity.Session[SESSION_SIG_KEY_NAME] = null!;
        }

        private void SignAndSetCookie(HttpEntity entity, LoginClaim claim)
        {
            //Setup Jwt
            using JsonWebToken jwt = new();

            //Write claim body, we dont need a header
            jwt.WritePayload(claim, Statics.SR_OPTIONS);

            //Generate signing key
            byte[] sigKey = RandomHash.GetRandomBytes(SIGNING_KEY_SIZE);

            //Sign the jwt
            jwt.Sign(sigKey, HashAlg.SHA256);

            //Build and set cookie
            HttpCookie cookie = new(CLAIM_COOKIE_NAME, jwt.Compile())
            {
                Secure = true,
                HttpOnly = true,
                ValidFor = Config.InitClaimValidFor,
                SameSite = CookieSameSite.SameSite,
                Path = this.Path
            };

            entity.Server.SetCookie(in cookie);

            //Encode and store the signing key in the clien't session
            entity.Session[SESSION_SIG_KEY_NAME] = VnEncoding.ToBase32String(sigKey);

            //Clear the signing key
            MemoryUtil.InitializeBlock(sigKey.AsSpan());
        }

        /*
         * Construct the client's redirect url based on their login claim, which contains
         * a public key which can be used to encrypt the url so that only the client 
         * private-key holder can decrypt the url and redirect themselves to the 
         * target OAuth website. 
         * 
         * The result is an encrypted nonce that should guard against replay attacks and MITM
         */

        sealed record class LoginUriBuilder(OauthClientConfig Config)
        {
            private string? redirectUrl;
            private string? nonce;
            private Encoding _encoding = Encoding.UTF8;
          
            public LoginUriBuilder WithUrl(ReadOnlySpan<char> scheme, ReadOnlySpan<char> authority, ReadOnlySpan<char> path)
            {
                //Alloc stack buffer for url
                Span<char> buffer = stackalloc char[1024];

                //buffer writer for easier syntax
                ForwardOnlyWriter<char> writer = new(buffer);
                //first build the redirect url to re-encode it
                writer.Append(scheme);
                writer.Append("://");
                //Create redirect url (current page, default action is to authorize the client)
                writer.Append(authority);
                writer.Append(path);
                //url encode the redirect path and save it for later
                redirectUrl = Uri.EscapeDataString(writer.ToString());

                return this;
            }

            public LoginUriBuilder WithEncoding(Encoding encoding) 
            {
                _encoding = encoding;
                return this;
            }

            public LoginUriBuilder WithNonce(string base32Nonce)
            {
                nonce = base32Nonce;
                return this;
            }            

            public string Encrypt(HttpEntity client, IClientSecInfo secInfo)
            {
                //Alloc buffer and split it into binary and char buffers
                using UnsafeMemoryHandle<byte> buffer = MemoryUtil.UnsafeAllocNearestPage(8000);

                Span<byte> binBuffer = buffer.Span[2048..];
                Span<char> charBuffer = MemoryMarshal.Cast<byte, char>(buffer.Span[..2048]);            


                /*
                 * Build the character uri so we can encode it to binary, 
                 * encrypt it and return it to the client
                 */

                ForwardOnlyWriter<char> writer = new(charBuffer);

                //Append the config redirect path
                writer.Append(Config.AccessCodeUrl.OriginalString);
                //begin query arguments
                writer.Append("&client_id=");
                writer.Append(Config.ClientID.Value);
                //add the redirect url
                writer.Append("&redirect_uri=");
                writer.Append(redirectUrl);
                //Append the state parameter
                writer.Append("&state=");
                writer.Append(nonce);

                //Collect the written character data
                ReadOnlySpan<char> url = writer.AsSpan();

                //Separate bin buffers for encryption and encoding
                Span<byte> encryptionBuffer = binBuffer[1024..];
                Span<byte> encodingBuffer = binBuffer[..1024];

                //Encode the url to binary
                int byteCount = _encoding.GetBytes(url, encodingBuffer);

                //Encrypt the binary data
                ERRNO count = client.TryEncryptClientData(secInfo, encodingBuffer[..byteCount], encryptionBuffer);

                //base64 encode the encrypted
                return Convert.ToBase64String(encryptionBuffer[0..(int)count]);
            }
        }
      

        sealed class LoginClaim : IClientSecInfo
        {
            [JsonPropertyName("exp")]
            public long ExpirationSeconds { get; set; }

            [JsonPropertyName("iat")]
            public long IssuedAtTime { get; set; }

            [JsonPropertyName("nonce")]
            public string? Nonce { get; set; }
           
            [JsonPropertyName("locallanguage")]
            public string? LocalLanguage { get; set; }
           
            [JsonPropertyName("pubkey")]
            public string? PublicKey { get; set; }

            [JsonPropertyName("clientid")]
            public string? ClientId { get; set; }
          

            public void ComputeNonce(int nonceSize)
            {
                //Alloc nonce buffer
                using UnsafeMemoryHandle<byte> buffer = MemoryUtil.UnsafeAlloc(nonceSize);
                try
                {
                    //fill the buffer with random data
                    RandomHash.GetRandomBytes(buffer.Span);

                    //Base32-Encode nonce and save it
                    Nonce = VnEncoding.ToBase32String(buffer.Span);
                }
                finally
                {
                    MemoryUtil.InitializeBlock(buffer.Span);
                }
            }
        }
    }
}