//
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Threading.Tasks;
using System.Xml;
using Microsoft.SqlServer.Management.Common;
using Microsoft.SqlServer.Management.Dmf;
using Microsoft.SqlServer.Management.Sdk.Sfc;
using Microsoft.SqlServer.Management.Smo;
using Microsoft.SqlTools.Hosting.Protocol;
using Microsoft.SqlTools.ServiceLayer.Connection;
using Microsoft.SqlTools.ServiceLayer.Hosting;
using Microsoft.SqlTools.ServiceLayer.Management;
using Microsoft.SqlTools.ServiceLayer.Security.Contracts;
using Microsoft.SqlTools.ServiceLayer.Utility;

namespace Microsoft.SqlTools.ServiceLayer.Security
{
    /// <summary>
    /// Main class for Security Service functionality
    /// </summary>
    public sealed class SecurityService : IDisposable
    {
        private bool disposed;

        private ConnectionService? connectionService;

        private static readonly Lazy<SecurityService> instance = new Lazy<SecurityService>(() => new SecurityService());

        private Dictionary<string, string> contextIdToConnectionUriMap = new Dictionary<string, string>();

        /// <summary>
        /// Construct a new SecurityService instance with default parameters
        /// </summary>
        public SecurityService()
        {
        }

        /// <summary>
        /// Gets the singleton instance object
        /// </summary>
        public static SecurityService Instance
        {
            get { return instance.Value; }
        }

        /// <summary>
        /// Internal for testing purposes only
        /// </summary>
        internal ConnectionService ConnectionServiceInstance
        {
            get
            {
                connectionService ??= ConnectionService.Instance;
                return connectionService;
            }

            set
            {
                connectionService = value;
            }
        }

        /// <summary>
        /// Service host object for sending/receiving requests/events.
        /// Internal for testing purposes.
        /// </summary>
        internal IProtocolEndpoint? ServiceHost
        {
            get;
            set;
        }

        /// <summary>
        /// Initializes the Security Service instance
        /// </summary>
        public void InitializeService(ServiceHost serviceHost)
        {
            this.ServiceHost = serviceHost;

            // Credential request handlers
            this.ServiceHost.SetRequestHandler(CreateCredentialRequest.Type, HandleCreateCredentialRequest, true);
            this.ServiceHost.SetRequestHandler(UpdateCredentialRequest.Type, HandleUpdateCredentialRequest, true);
            this.ServiceHost.SetRequestHandler(DeleteCredentialRequest.Type, HandleDeleteCredentialRequest, true);
            this.ServiceHost.SetRequestHandler(GetCredentialsRequest.Type, HandleGetCredentialsRequest, true);

            // Login request handlers
            this.ServiceHost.SetRequestHandler(CreateLoginRequest.Type, HandleCreateLoginRequest, true);
            this.ServiceHost.SetRequestHandler(UpdateLoginRequest.Type, HandleUpdateLoginRequest, true);
            this.ServiceHost.SetRequestHandler(DeleteLoginRequest.Type, HandleDeleteLoginRequest, true);
            this.ServiceHost.SetRequestHandler(InitializeLoginViewRequest.Type, HandleInitializeLoginViewRequest, true);
            this.ServiceHost.SetRequestHandler(DisposeLoginViewRequest.Type, HandleDisposeLoginViewRequest, true);

            // User request handlers
            this.ServiceHost.SetRequestHandler(InitializeUserViewRequest.Type, HandleInitializeUserViewRequest, true);
            this.ServiceHost.SetRequestHandler(CreateUserRequest.Type, HandleCreateUserRequest, true);
            this.ServiceHost.SetRequestHandler(DeleteUserRequest.Type, HandleDeleteUserRequest, true);
        }


        #region "Login Handlers"        

        /// <summary>
        /// Handle request to create a login
        /// </summary>
        internal async Task HandleCreateLoginRequest(CreateLoginParams parameters, RequestContext<object> requestContext)
        {
            ConnectionInfo connInfo;
            string ownerUri;
            contextIdToConnectionUriMap.TryGetValue(parameters.ContextId, out ownerUri);
            ConnectionServiceInstance.TryFindConnection(ownerUri, out connInfo);

            if (connInfo == null) 
            {
                    // raise error here
            }

            CDataContainer dataContainer = CDataContainer.CreateDataContainer(connInfo, databaseExists: true);
            LoginPrototype prototype = new LoginPrototype(dataContainer.Server, parameters.Login);

            if (prototype.LoginType == SqlServer.Management.Smo.LoginType.SqlLogin)
            {
                // check that there is a password
                // this check is made if policy enforcement is off
                // with policy turned on we do not display this message, instead we let server
                // return the error associated with null password (coming from policy) - see bug 124377
                if (prototype.SqlPassword.Length == 0 && prototype.EnforcePolicy == false)
                {
                    // raise error here
                }

                // check that password and confirm password controls' text matches
                if (0 != string.Compare(prototype.SqlPassword, prototype.SqlPasswordConfirm, StringComparison.Ordinal))
                {
                    // raise error here
                }
            }

            prototype.ApplyGeneralChanges(dataContainer.Server);

            // TODO move this to LoginData
            // TODO support role assignment for Azure
            LoginPrototype newPrototype = new LoginPrototype(dataContainer.Server, dataContainer.Server.Logins[parameters.Login.Name]);
            var _ =newPrototype.ServerRoles.ServerRoleNames;

            foreach (string role in parameters.Login.ServerRoles)
            {
                newPrototype.ServerRoles.SetMember(role, true);
            }

            newPrototype.ApplyServerRoleChanges(dataContainer.Server);
            await requestContext.SendResult(new object());
        }

        /// <summary>
        /// Handle request to delete a credential
        /// </summary>
        internal async Task HandleDeleteLoginRequest(DeleteLoginParams parameters, RequestContext<object> requestContext)
        {
            ConnectionInfo connInfo;
            ConnectionServiceInstance.TryFindConnection(parameters.ConnectionUri, out connInfo);
            // if (connInfo == null) 
            // {
            //     // raise an error
            // }

            CDataContainer dataContainer = CDataContainer.CreateDataContainer(connInfo, databaseExists: true);
            Login login = dataContainer.Server?.Logins[parameters.Name];
     
            dataContainer.SqlDialogSubject = login;
            DoDropObject(dataContainer);

            await requestContext.SendResult(new ResultStatus()
            {
                Success = true,
                ErrorMessage = string.Empty
            });
        }

        internal async Task HandleUpdateLoginRequest(UpdateLoginParams parameters, RequestContext<object> requestContext)
        {
            ConnectionInfo connInfo;
            string ownerUri;
            contextIdToConnectionUriMap.TryGetValue(parameters.ContextId, out ownerUri);
            ConnectionServiceInstance.TryFindConnection(ownerUri, out connInfo);
            if (connInfo == null) 
            {
                    // raise error here
            }

            CDataContainer dataContainer = CDataContainer.CreateDataContainer(connInfo, databaseExists: true);
            LoginPrototype prototype = new LoginPrototype(dataContainer.Server, dataContainer.Server.Logins[parameters.Login.Name]);

            var login = parameters.Login;
            prototype.SqlPassword = login.Password;
            if (0 != String.Compare(login.DefaultLanguage, SR.DefaultLanguagePlaceholder, StringComparison.Ordinal))
            {
                prototype.DefaultLanguage = login.DefaultLanguage.Split(" - ")[1];
            }
            prototype.DefaultDatabase = login.DefaultDatabase;
            prototype.EnforcePolicy = login.EnforcePasswordPolicy;
            prototype.EnforceExpiration = login.EnforcePasswordPolicy ? login.EnforcePasswordExpiration : false;
            prototype.IsLockedOut = login.IsLockedOut;
            prototype.IsDisabled = !login.IsEnabled;
            prototype.MustChange = login.EnforcePasswordPolicy ? login.MustChangePassword : false;
            prototype.WindowsGrantAccess = login.ConnectPermission;

            if (prototype.LoginType == SqlServer.Management.Smo.LoginType.SqlLogin)
            {
                // check that there is a password
                // this check is made if policy enforcement is off
                // with policy turned on we do not display this message, instead we let server
                // return the error associated with null password (coming from policy) - see bug 124377
                if (prototype.SqlPassword.Length == 0 && prototype.EnforcePolicy == false)
                {
                    // raise error here
                }

                // check that password and confirm password controls' text matches
                if (0 != String.Compare(prototype.SqlPassword, prototype.SqlPasswordConfirm, StringComparison.Ordinal))
                {
                    // raise error here
                }
            }

            var _ = prototype.ServerRoles.ServerRoleNames;

            foreach (string role in prototype.ServerRoles.ServerRoleNames)
            {
                prototype.ServerRoles.SetMember(role, false);
            }

            foreach (string role in login.ServerRoles)
            {
                prototype.ServerRoles.SetMember(role, true);
            }

            prototype.ApplyGeneralChanges(dataContainer.Server);
            prototype.ApplyServerRoleChanges(dataContainer.Server);
            prototype.ApplyDatabaseRoleChanges(dataContainer.Server);
            await requestContext.SendResult(new object());
        }

        internal async Task HandleInitializeLoginViewRequest(InitializeLoginViewRequestParams parameters, RequestContext<LoginViewInfo> requestContext)
        {
            contextIdToConnectionUriMap.Add(parameters.ContextId, parameters.ConnectionUri);
            ConnectionInfo connInfo;
            ConnectionServiceInstance.TryFindConnection(parameters.ConnectionUri, out connInfo);
            if (connInfo == null) 
            {
                // raise an error
            }
            CDataContainer dataContainer = CDataContainer.CreateDataContainer(connInfo, databaseExists: true);
            LoginViewInfo loginViewInfo = new LoginViewInfo();

            // TODO cache databases and languages
            string[] databases = new string[dataContainer.Server.Databases.Count];
            for (int i = 0; i < dataContainer.Server.Databases.Count; i++)
            {
                databases[i] = dataContainer.Server.Databases[i].Name;
            }

            var languageOptions = GetDefaultLanguageOptions(dataContainer);
            var languageOptionsList = languageOptions.Select(FormatLanguageDisplay).ToList();
            if (parameters.IsNewObject)
            {
                languageOptionsList.Insert(0, SR.DefaultLanguagePlaceholder);
            }
            string[] languages = languageOptionsList.ToArray();
            LoginPrototype prototype = parameters.IsNewObject 
            ? new LoginPrototype(dataContainer.Server) 
            : new LoginPrototype(dataContainer.Server, dataContainer.Server.Logins[parameters.Name]);

            List<string> loginServerRoles = new List<string>();
            foreach(string role in prototype.ServerRoles.ServerRoleNames)
            {
                if (prototype.ServerRoles.IsMember(role))
                {
                    loginServerRoles.Add(role);
                }
            }

            LoginInfo loginInfo = new LoginInfo()
            {
                Name = prototype.LoginName,
                Password = prototype.SqlPassword,
                OldPassword = prototype.OldPassword,
                AuthenticationType = LoginTypeToAuthenticationType(prototype.LoginType),
                EnforcePasswordExpiration = prototype.EnforceExpiration,
                EnforcePasswordPolicy = prototype.EnforcePolicy,
                MustChangePassword = prototype.MustChange,
                DefaultDatabase = prototype.DefaultDatabase,
                DefaultLanguage = FormatLanguageDisplay(languageOptions.FirstOrDefault(o => o?.Language.Name == prototype.DefaultLanguage || o?.Language.Alias == prototype.DefaultLanguage, null)),
                ServerRoles = loginServerRoles.ToArray(),
                ConnectPermission = prototype.WindowsGrantAccess,
                IsEnabled = !prototype.IsDisabled,
                IsLockedOut = prototype.IsLockedOut,
                UserMapping = new ServerLoginDatabaseUserMapping[0]
            };

            await requestContext.SendResult(new LoginViewInfo()
            {
                ObjectInfo = loginInfo,
                SupportWindowsAuthentication = prototype.WindowsAuthSupported,
                SupportAADAuthentication = prototype.AADAuthSupported,
                SupportSQLAuthentication = true, // SQL Auth support for login, not necessarily mean SQL Auth support for CONNECT etc.
                CanEditLockedOutState = true,
                Databases = databases,
                Languages = languages,
                ServerRoles = prototype.ServerRoles.ServerRoleNames,
                SupportAdvancedPasswordOptions = dataContainer.Server.DatabaseEngineType == DatabaseEngineType.Standalone || dataContainer.Server.DatabaseEngineEdition == DatabaseEngineEdition.SqlDataWarehouse,
                SupportAdvancedOptions = dataContainer.Server.DatabaseEngineType == DatabaseEngineType.Standalone || dataContainer.Server.DatabaseEngineEdition == DatabaseEngineEdition.SqlManagedInstance
            });
        }

        private LoginAuthenticationType LoginTypeToAuthenticationType(LoginType loginType)
        {
            switch (loginType)
            {
                case LoginType.WindowsUser:
                case LoginType.WindowsGroup:
                    return LoginAuthenticationType.Windows;
                case LoginType.SqlLogin:
                    return LoginAuthenticationType.Sql;
                case LoginType.ExternalUser:
                case LoginType.ExternalGroup:
                    return LoginAuthenticationType.AAD;
                default:
                    return LoginAuthenticationType.Others;
            }
        }

        internal async Task HandleDisposeLoginViewRequest(DisposeLoginViewRequestParams parameters, RequestContext<object> requestContext)
        {
            await requestContext.SendResult(new object());
        }

        private string FormatLanguageDisplay(LanguageDisplay? l)
        {
            if (l == null) return null;
             return string.Format("{0} - {1}", l.Language.Alias, l.Language.Name);
        }
        #endregion

        #region "User Handlers"

        internal Task<Tuple<bool, string>> ConfigureUser(
            string? ownerUri,
            UserInfo? user,
            ConfigAction configAction,
            RunType runType)
        {
            return Task<Tuple<bool, string>>.Run(() =>
            {
                try
                {
                    ConnectionInfo connInfo;
                    ConnectionServiceInstance.TryFindConnection(ownerUri, out connInfo);
                    if (connInfo == null)
                    {
                        throw new ArgumentException("Invalid connection URI '{0}'", ownerUri);
                    }

                    var serverConnection = ConnectionService.OpenServerConnection(connInfo, "DataContainer");
                    var connectionInfoWithConnection = new SqlConnectionInfoWithConnection();
                    connectionInfoWithConnection.ServerConnection = serverConnection;

                    string urn = string.Format(System.Globalization.CultureInfo.InvariantCulture,
                        "Server/Database[@Name='{0}']",
                        Urn.EscapeString(serverConnection.DatabaseName));

                    ActionContext context = new ActionContext(serverConnection, "new_user", urn);
                    DataContainerXmlGenerator containerXml = new DataContainerXmlGenerator(context);
                    containerXml.AddProperty("itemtype", "User");

                    XmlDocument xmlDoc = containerXml.GenerateXmlDocument();
                    bool objectExists = configAction != ConfigAction.Create;
                    CDataContainer dataContainer = CDataContainer.CreateDataContainer(connectionInfoWithConnection, xmlDoc);

                    using (var actions = new UserActions(dataContainer, user, configAction))
                    {
                        var executionHandler = new ExecutonHandler(actions);
                        executionHandler.RunNow(runType, this);
                    }

                    return new Tuple<bool, string>(true, string.Empty);
                }
                catch (Exception ex)
                {
                    return new Tuple<bool, string>(false, ex.ToString());
                }
            });
        }

        private Dictionary<string, SchemaOwnership> LoadSchemas(string databaseName, string dbroleName, ServerConnection serverConnection)
        {
            bool isPropertiesMode = false;
            Dictionary<string, SchemaOwnership> schemaOwnership = new Dictionary<string, SchemaOwnership>();

            Enumerator en = new Enumerator();
            Request req = new Request();
            req.Fields = new String[] { "Name", "Owner" };
            req.Urn = "Server/Database[@Name='" + Urn.EscapeString(databaseName) + "']/Schema";

            DataTable dt = en.Process(serverConnection, req);
            System.Diagnostics.Debug.Assert((dt != null) && (0 < dt.Rows.Count), "enumerator did not return schemas");
            System.Diagnostics.Debug.Assert(!isPropertiesMode || (dbroleName.Length != 0), "role name is not known");

            foreach (DataRow dr in dt.Rows)
            {
                string schemaName = Convert.ToString(dr["Name"], System.Globalization.CultureInfo.InvariantCulture);
                string schemaOwner = Convert.ToString(dr["Owner"], System.Globalization.CultureInfo.InvariantCulture);
                bool roleOwnsSchema = isPropertiesMode && (0 == String.Compare(dbroleName, schemaOwner, StringComparison.Ordinal));
                if (schemaName != null)
                {
                    schemaOwnership[schemaName] = new SchemaOwnership(roleOwnsSchema);
                }
            }
            return schemaOwnership;
        }

        private string[] LoadDatabaseRoles(ServerConnection serverConnection, string databaseName)
        {
            var server = new Server(serverConnection);
            string dbUrn = "Server/Database[@Name='" + Urn.EscapeString(databaseName) + "']";
            Database? parent = server.GetSmoObject(new Urn(dbUrn)) as Database;
            var roles = new List<string>();
            if (parent != null)
            {
                foreach (DatabaseRole dbRole in parent.Roles)
                {
                    var comparer = parent.GetStringComparer();
                    if (comparer.Compare(dbRole.Name, "public") != 0)
                    {
                        roles.Add(dbRole.Name);
                    }
                }
            }
            return roles.ToArray();
        }

        private string[] LoadSqlLogins(ServerConnection serverConnection)
        {
            return LoadItems(serverConnection, "Server/Login");
        }

        private string[] LoadItems(ServerConnection serverConnection, string urn)
        {
            List<string> items = new List<string>();
            Request req = new Request();
            req.Urn = urn;
            req.ResultType = ResultType.IDataReader;
            req.Fields = new string[] { "Name" };

            Enumerator en = new Enumerator();
            using (IDataReader reader = en.Process(serverConnection, req).Data as IDataReader)
            {
                if (reader != null)
                {
                    string name;
                    while (reader.Read())
                    {
                        // Get the permission name
                        name = reader.GetString(0);
                        items.Add(name);
                    }
                }
            }
            return items.ToArray();
        }

        /// <summary>
        /// Handle request to initialize user view
        /// </summary>
        internal async Task HandleInitializeUserViewRequest(InitializeUserViewParams parameters, RequestContext<UserViewInfo> requestContext)
        {
            ConnectionInfo connInfo;
            ConnectionServiceInstance.TryFindConnection(parameters.ConnectionUri, out connInfo);
            if (connInfo == null)
            {
                throw new ArgumentException("Invalid connection URI '{0}'", parameters.ConnectionUri);
            }

            if (parameters.ContextId != null && parameters.ConnectionUri != null)
            {
                this.contextIdToConnectionUriMap.Add(parameters.ContextId, parameters.ConnectionUri);
            }

            var serverConnection = ConnectionService.OpenServerConnection(connInfo, "DataContainer");

            string databaseName = parameters.Database ?? "master";
            var schemaMap = LoadSchemas(databaseName, string.Empty, serverConnection);

            UserViewInfo userViewInfo = new UserViewInfo()
            {
                ObjectInfo = new UserInfo()
                {
                    Type = DatabaseUserType.WithLogin,
                    Name = string.Empty,
                    LoginName = string.Empty,
                    Password = string.Empty,
                    DefaultSchema = string.Empty,
                    OwnedSchemas = new string[] { },
                    DatabaseRoles = new string[] { },
                },
                SupportContainedUser = true,
                SupportWindowsAuthentication = true,
                SupportAADAuthentication = true,
                SupportSQLAuthentication = true,
                Languages = new string[] { },
                Schemas = schemaMap.Keys.ToArray(),
                Logins = LoadSqlLogins(serverConnection),
                DatabaseRoles = LoadDatabaseRoles(serverConnection, databaseName)
            };

            await requestContext.SendResult(userViewInfo);
        }

        /// <summary>
        /// Handle request to create a user
        /// </summary>
        internal async Task HandleCreateUserRequest(CreateUserParams parameters, RequestContext<CreateUserResult> requestContext)
        {
            if (parameters.ContextId == null || !this.contextIdToConnectionUriMap.ContainsKey(parameters.ContextId))
            {
                throw new ArgumentException("Invalid context ID");
            }

            string connectionUri = this.contextIdToConnectionUriMap[parameters.ContextId];
            var result = await ConfigureUser(connectionUri,
                parameters.User,
                ConfigAction.Create,
                RunType.RunNow);

            await requestContext.SendResult(new CreateUserResult()
            {
                User = parameters.User,
                Success = result.Item1,
                ErrorMessage = result.Item2
            });
        }

        /// <summary>
        /// Handle request to delete a user
        /// </summary>
        internal async Task HandleDeleteUserRequest(DeleteUserParams parameters, RequestContext<ResultStatus> requestContext)
        {
            ConnectionInfo connInfo;
            ConnectionServiceInstance.TryFindConnection(parameters.ConnectionUri, out connInfo);
            // if (connInfo == null) 
            // {
            //     // raise an error
            // }

            CDataContainer dataContainer = CDataContainer.CreateDataContainer(connInfo, databaseExists: true);
            string dbUrn = "Server/Database[@Name='" + Urn.EscapeString(parameters.Database) + "']";
            Database? parent = dataContainer.Server.GetSmoObject(new Urn(dbUrn)) as Database;
            User user = parent.Users[parameters.Name];
            dataContainer.SqlDialogSubject = user;
            DoDropObject(dataContainer);

            await requestContext.SendResult(new ResultStatus()
            {
                Success = true,
                ErrorMessage = string.Empty
            });
        }

        private IList<LanguageDisplay> GetDefaultLanguageOptions(CDataContainer dataContainer)
        {
            // this.defaultLanguageComboBox.Items.Clear();            
            // this.defaultLanguageComboBox.Items.Add(defaultLanguagePlaceholder);            

            // sort the languages alphabetically by alias
            SortedList sortedLanguages = new SortedList(Comparer.Default);

            LanguageUtils.SetLanguageDefaultInitFieldsForDefaultLanguages(dataContainer.Server);
            if (dataContainer.Server != null && dataContainer.Server.Languages != null)
            {
                foreach (Language language in dataContainer.Server.Languages)
                {
                    LanguageDisplay listValue = new LanguageDisplay(language);
                    sortedLanguages.Add(language.Alias, listValue);
                }
            }

            IList<LanguageDisplay> res = new List<LanguageDisplay>();
            foreach (LanguageDisplay ld in sortedLanguages.Values)
            {
                res.Add(ld);
            }

            return res;
        }

        // code needs to be ported into the useraction class
        // public void UserMemberships_OnRunNow(object sender, CDataContainer dataContainer)
        // {
        //     UserPrototype currentPrototype = UserPrototypeFactory.GetInstance(dataContainer).CurrentPrototype;

        //     //In case the UserGeneral/OwnedSchemas pages are loaded,
        //     //those will takes care of applying membership changes also.
        //     //Hence, we only need to apply changes in this method when those are not loaded.
        //     if (!currentPrototype.IsRoleMembershipChangesApplied)
        //     {
        //         //base.OnRunNow(sender);

        //         User user = currentPrototype.ApplyChanges();

        //         //this.ExecutionMode = ExecutionMode.Success;
        //         dataContainer.ObjectName = currentPrototype.Name;
        //         dataContainer.SqlDialogSubject = user;
        //     }

        //     //setting back to original after changes are applied
        //     currentPrototype.IsRoleMembershipChangesApplied = false;
        // }

        // /// <summary>
        // /// implementation of OnPanelRunNow
        // /// </summary>
        // /// <param name="node"></param>
        // public void UserOwnedSchemas_OnRunNow(object sender, CDataContainer dataContainer)
        // {
        //     UserPrototype currentPrototype = UserPrototypeFactory.GetInstance(dataContainer).CurrentPrototype;

        //     //In case the UserGeneral/Membership pages are loaded,
        //     //those will takes care of applying schema ownership changes also.
        //     //Hence, we only need to apply changes in this method when those are not loaded.
        //     if (!currentPrototype.IsSchemaOwnershipChangesApplied)
        //     {
        //         //base.OnRunNow(sender);

        //         User user = currentPrototype.ApplyChanges();

        //         //this.ExecutionMode = ExecutionMode.Success;
        //         dataContainer.ObjectName = currentPrototype.Name;
        //         dataContainer.SqlDialogSubject = user;                
        //     }

        //     //setting back to original after changes are applied
        //     currentPrototype.IsSchemaOwnershipChangesApplied = false;
        // }

        // how to populate defaults from prototype, will delete once refactored
        // private void InitializeValuesInUiControls()
        // {

        //     IUserPrototypeWithDefaultLanguage defaultLanguagePrototype = this.currentUserPrototype
        //                                                                             as IUserPrototypeWithDefaultLanguage;
        //     if (defaultLanguagePrototype != null
        //         && defaultLanguagePrototype.IsDefaultLanguageSupported)
        //     {
        //         string defaultLanguageAlias = defaultLanguagePrototype.DefaultLanguageAlias;

        //         //If engine returns default language as empty or null, that means the default language of  
        //         //database will be used.
        //         //Default language is not applicable for users inside an uncontained authentication.
        //         if (string.IsNullOrEmpty(defaultLanguageAlias)
        //             && (this.DataContainer.Server.GetSmoObject(this.parentDbUrn) as Database).ContainmentType != ContainmentType.None)
        //         {
        //             defaultLanguageAlias = this.defaultLanguagePlaceholder;
        //         }
        //         this.defaultLanguageComboBox.Text = defaultLanguageAlias;
        //     }

        //     IUserPrototypeWithDefaultSchema defaultSchemaPrototype = this.currentUserPrototype
        //                                                                         as IUserPrototypeWithDefaultSchema;
        //     if (defaultSchemaPrototype != null
        //         && defaultSchemaPrototype.IsDefaultSchemaSupported)
        //     {
        //         this.defaultSchemaTextBox.Text = defaultSchemaPrototype.DefaultSchema;
        //     }
        //     IUserPrototypeWithPassword userWithPwdPrototype = this.currentUserPrototype
        //                                                                 as IUserPrototypeWithPassword;
        //     if (userWithPwdPrototype != null
        //         && !this.DataContainer.IsNewObject)
        //     {
        //         this.passwordTextBox.Text = FAKE_PASSWORD;
        //         this.confirmPwdTextBox.Text = FAKE_PASSWORD;                
        //     }
        // }




        #endregion

        #region "Credential Handlers"

        /// <summary>
        /// Handle request to create a credential
        /// </summary>
        internal async Task HandleCreateCredentialRequest(CreateCredentialParams parameters, RequestContext<CredentialResult> requestContext)
        {
            var result = await ConfigureCredential(parameters.OwnerUri,
                parameters.Credential,
                ConfigAction.Create,
                RunType.RunNow);

            await requestContext.SendResult(new CredentialResult()
            {
                Credential = parameters.Credential,
                Success = result.Item1,
                ErrorMessage = result.Item2
            });
        }

        /// <summary>
        /// Handle request to update a credential
        /// </summary>
        internal async Task HandleUpdateCredentialRequest(UpdateCredentialParams parameters, RequestContext<CredentialResult> requestContext)
        {
            var result = await ConfigureCredential(parameters.OwnerUri,
                parameters.Credential,
                ConfigAction.Update,
                RunType.RunNow);

            await requestContext.SendResult(new CredentialResult()
            {
                Credential = parameters.Credential,
                Success = result.Item1,
                ErrorMessage = result.Item2
            });
        }

        /// <summary>
        /// Handle request to delete a credential
        /// </summary>
        internal async Task HandleDeleteCredentialRequest(DeleteCredentialParams parameters, RequestContext<ResultStatus> requestContext)
        {
            var result = await ConfigureCredential(parameters.OwnerUri,
                parameters.Credential,
                ConfigAction.Drop,
                RunType.RunNow);

            await requestContext.SendResult(new ResultStatus()
            {
                Success = result.Item1,
                ErrorMessage = result.Item2
            });
        }


        /// <summary>
        /// Handle request to get all credentials
        /// </summary>
        internal async Task HandleGetCredentialsRequest(GetCredentialsParams parameters, RequestContext<GetCredentialsResult> requestContext)
        {
            var result = new GetCredentialsResult();
            try
            {
                ConnectionInfo connInfo;
                ConnectionServiceInstance.TryFindConnection(parameters.OwnerUri, out connInfo);
                CDataContainer dataContainer = CDataContainer.CreateDataContainer(connInfo, databaseExists: true);

                var credentials = dataContainer.Server?.Credentials;
                int credentialsCount = credentials != null ? credentials.Count : 0;
                CredentialInfo[] credentialsInfos = new CredentialInfo[credentialsCount];
                if (credentials != null)
                {
                    for (int i = 0; i < credentialsCount; ++i)
                    {
                        credentialsInfos[i] = new CredentialInfo();
                        credentialsInfos[i].Name = credentials[i].Name;
                        credentialsInfos[i].Identity = credentials[i].Identity;
                        credentialsInfos[i].Id = credentials[i].ID;
                        credentialsInfos[i].DateLastModified = credentials[i].DateLastModified;
                        credentialsInfos[i].CreateDate = credentials[i].CreateDate;
                        credentialsInfos[i].ProviderName = credentials[i].ProviderName;
                    }
                }
                result.Credentials = credentialsInfos;
                result.Success = true;
            }
            catch (Exception ex)
            {
                result.Success = false;
                result.ErrorMessage = ex.ToString();
            }

            await requestContext.SendResult(result);
        }

        /// <summary>
        /// Disposes the service
        /// </summary>
        public void Dispose()
        {
            if (!disposed)
            {
                disposed = true;
            }
        }

        #endregion

        #region "Helpers"

        internal Task<Tuple<bool, string>> ConfigureCredential(
            string ownerUri,
            CredentialInfo credential,
            ConfigAction configAction,
            RunType runType)
        {
            return Task<Tuple<bool, string>>.Run(() =>
            {
                try
                {
                    ConnectionInfo connInfo;
                    ConnectionServiceInstance.TryFindConnection(ownerUri, out connInfo);
                    CDataContainer dataContainer = CDataContainer.CreateDataContainer(connInfo, databaseExists: true);

                    using (CredentialActions actions = new CredentialActions(dataContainer, credential, configAction))
                    {
                        var executionHandler = new ExecutonHandler(actions);
                        executionHandler.RunNow(runType, this);
                    }

                    return new Tuple<bool, string>(true, string.Empty);
                }
                catch (Exception ex)
                {
                    return new Tuple<bool, string>(false, ex.ToString());
                }
            });
        }

        /// <summary>
        /// this is the main method that is called by DropAllObjects for every object
        /// in the grid
        /// </summary>
        /// <param name="objectRowNumber"></param>
        private void DoDropObject(CDataContainer dataContainer)
        {
            // if a server isn't connected then there is nothing to do      
            if (dataContainer.Server == null)
            {
                return;
            }

            var executionMode = dataContainer.Server.ConnectionContext.SqlExecutionModes;
            var subjectExecutionMode = executionMode;

            //For Azure the ExecutionManager is different depending on which ExecutionManager
            //used - one at the Server level and one at the Database level. So to ensure we
            //don't use the wrong execution mode we need to set the mode for both (for on-prem
            //this will essentially be a no-op)
            SqlSmoObject sqlDialogSubject = null;
            try
            {
                sqlDialogSubject = dataContainer.SqlDialogSubject;
            }
            catch (System.Exception)
            {
                //We may not have a valid dialog subject here (such as if the object hasn't been created yet)
                //so in that case we'll just ignore it as that's a normal scenario. 
            }
            if (sqlDialogSubject != null)
            {
                subjectExecutionMode =
                    sqlDialogSubject.ExecutionManager.ConnectionContext.SqlExecutionModes;
            }

            Urn objUrn = sqlDialogSubject?.Urn;
            System.Diagnostics.Debug.Assert(objUrn != null);

            SfcObjectQuery objectQuery = new SfcObjectQuery(dataContainer.Server);

            IDroppable droppableObj = null;
            string[] fields = null;

            foreach (object obj in objectQuery.ExecuteIterator(new SfcQueryExpression(objUrn.ToString()), fields, null))
            {
                System.Diagnostics.Debug.Assert(droppableObj == null, "there is only one object");
                droppableObj = obj as IDroppable;
            }

            // For Azure databases, the SfcObjectQuery executions above may have overwritten our desired execution mode, so restore it
            dataContainer.Server.ConnectionContext.SqlExecutionModes = executionMode;
            if (sqlDialogSubject != null)
            {
                sqlDialogSubject.ExecutionManager.ConnectionContext.SqlExecutionModes = subjectExecutionMode;
            }

            if (droppableObj == null)
            {
                string objectName = objUrn.GetAttribute("Name");
                objectName ??= string.Empty;
                throw new Microsoft.SqlServer.Management.Smo.MissingObjectException("DropObjectsSR.ObjectDoesNotExist(objUrn.Type, objectName)");
            }

            //special case database drop - see if we need to delete backup and restore history
            SpecialPreDropActionsForObject(dataContainer, droppableObj,
                deleteBackupRestoreOrDisableAuditSpecOrDisableAudit: false,
                dropOpenConnections: false);

            droppableObj.Drop();

            //special case Resource Governor reconfigure - for pool, external pool, group  Drop(), we need to issue
            SpecialPostDropActionsForObject(dataContainer, droppableObj);

        }

        private void SpecialPreDropActionsForObject(CDataContainer dataContainer, IDroppable droppableObj,
            bool deleteBackupRestoreOrDisableAuditSpecOrDisableAudit, bool dropOpenConnections)
        {
            // if a server isn't connected then there is nothing to do      
            if (dataContainer.Server == null)
            {
                return;
            }

            Database db = droppableObj as Database;

            if (deleteBackupRestoreOrDisableAuditSpecOrDisableAudit)
            {
                if (db != null)
                {
                    dataContainer.Server.DeleteBackupHistory(db.Name);
                }
                else
                {
                    // else droppable object should be a server or database audit specification
                    ServerAuditSpecification sas = droppableObj as ServerAuditSpecification;
                    if (sas != null)
                    {
                        sas.Disable();
                    }
                    else
                    {
                        DatabaseAuditSpecification das = droppableObj as DatabaseAuditSpecification;
                        if (das != null)
                        {
                            das.Disable();
                        }
                        else
                        {
                            Audit aud = droppableObj as Audit;
                            if (aud != null)
                            {
                                aud.Disable();
                            }
                        }
                    }
                }
            }

            // special case database drop - drop existing connections to the database other than this one
            if (dropOpenConnections)
            {
                if (db?.ActiveConnections > 0)
                {
                    // force the database to be single user
                    db.DatabaseOptions.UserAccess = DatabaseUserAccess.Single;
                    db.Alter(TerminationClause.RollbackTransactionsImmediately);
                }
            }
        }

        private void SpecialPostDropActionsForObject(CDataContainer dataContainer, IDroppable droppableObj)
        {
            // if a server isn't connected then there is nothing to do      
            if (dataContainer.Server == null)
            {
                return;
            }

            if (droppableObj is Policy)
            {
                Policy policyToDrop = (Policy)droppableObj;
                if (!string.IsNullOrEmpty(policyToDrop.ObjectSet))
                {
                    ObjectSet objectSet = policyToDrop.Parent.ObjectSets[policyToDrop.ObjectSet];
                    objectSet.Drop();
                }
            }

            ResourcePool rp = droppableObj as ResourcePool;
            ExternalResourcePool erp = droppableObj as ExternalResourcePool;
            WorkloadGroup wg = droppableObj as WorkloadGroup;

            if (null != rp || null != erp || null != wg)
            {
                // Alter() Resource Governor to reconfigure
                dataContainer.Server.ResourceGovernor.Alter();
            }
        }

        #endregion // "Helpers"

        // some potentially useful code for working with server & db roles to be refactored later
        #region "Roles" 
        private class SchemaOwnership
        {
            public bool initiallyOwned;
            public bool currentlyOwned;

            public SchemaOwnership(bool initiallyOwned)
            {
                this.initiallyOwned = initiallyOwned;
                this.currentlyOwned = initiallyOwned;
            }
        }

        private class RoleMembership
        {
            public bool initiallyAMember;
            public bool currentlyAMember;

            public RoleMembership(bool initiallyAMember)
            {
                this.initiallyAMember = initiallyAMember;
                this.currentlyAMember = initiallyAMember;
            }

            public RoleMembership(bool initiallyAMember, bool currentlyAMember)
            {
                this.initiallyAMember = initiallyAMember;
                this.currentlyAMember = currentlyAMember;
            }
        }

        // private void DbRole_LoadMembership(string databaseName, string dbroleName, ServerConnection serverConnection)
        // {
        //     var roleMembers = new HybridDictionary();
        //     bool isPropertiesMode = false;
        //     if (isPropertiesMode)
        //     {
        //         Enumerator  enumerator  = new Enumerator();
        //         Urn         urn         = String.Format(System.Globalization.CultureInfo.InvariantCulture,
        //                                                 "Server/Database[@Name='{0}']/Role[@Name='{1}']/Member",
        //                                                 Urn.EscapeString(databaseName),
        //                                                 Urn.EscapeString(dbroleName));
        //         string[]    fields      = new string[] { "Name" };
        //         OrderBy[]   orderBy     = new OrderBy[] { new OrderBy("Name", OrderBy.Direction.Asc)};
        //         Request     request     = new Request(urn, fields, orderBy);
        //         DataTable   dt          = enumerator.Process(serverConnection, request);

        //         foreach (DataRow dr in dt.Rows)
        //         {
        //             string memberName = dr["Name"].ToString();
        //             if (memberName != null)
        //             {
        //                 roleMembers[memberName] = new RoleMembership(true);
        //             }
        //         }
        //     }
        // }

        // /// <summary>
        // /// sends to server user changes related to membership
        // /// </summary>
        // private void DbRole_SendToServerMembershipChanges(Database db, DatabaseRole dbrole)
        // {
        //     var roleMembers = new HybridDictionary();
        //     IDictionaryEnumerator enumerator = roleMembers.GetEnumerator();
        //     enumerator.Reset();

        //     while (enumerator.MoveNext())
        //     {
        //         DictionaryEntry entry       = enumerator.Entry;
        //         string          memberName  = entry.Key.ToString();
        //         RoleMembership  membership  = (RoleMembership) entry.Value;
        //         if (membership != null)
        //         {
        //             if (!membership.initiallyAMember && membership.currentlyAMember)
        //             {
        //                 dbrole.AddMember(memberName);
        //             }
        //             else if (membership.initiallyAMember && !membership.currentlyAMember)
        //             {
        //                 dbrole.DropMember(memberName);
        //             }
        //         }
        //     }
        // }

        // private void InitProp(ServerConnection serverConnection, string serverName, string databaseName, 
        //     string dbroleName, string dbroleUrn, bool isPropertiesMode)
        // {            
        //     System.Diagnostics.Debug.Assert(serverName!=null);
        //     System.Diagnostics.Debug.Assert((databaseName!=null) && (databaseName.Trim().Length!=0));

        //     // LoadSchemas();
        //     // LoadMembership();

        //     if (isPropertiesMode == true)
        //     {
        //         // initialize from enumerator in properties mode
        //         System.Diagnostics.Debug.Assert(dbroleName!=null);
        //         System.Diagnostics.Debug.Assert(dbroleName.Trim().Length !=0);
        //         System.Diagnostics.Debug.Assert(dbroleUrn!=null);
        //         System.Diagnostics.Debug.Assert(dbroleUrn.Trim().Length != 0);

        //         Enumerator en = new Enumerator();
        //         Request req = new Request();
        //         req.Fields = new String [] { "Owner" };

        //         if ((dbroleUrn!=null) && (dbroleUrn.Trim().Length != 0))
        //         {
        //             req.Urn = dbroleUrn;
        //         }
        //         else
        //         {
        //             req.Urn = "Server/Database[@Name='" + Urn.EscapeString(databaseName) + "']/Role[@Name='" + Urn.EscapeString(dbroleName) + "]";
        //         }

        //         DataTable dt = en.Process(serverConnection, req);
        //         System.Diagnostics.Debug.Assert(dt!=null);
        //         System.Diagnostics.Debug.Assert(dt.Rows.Count==1);

        //         if (dt.Rows.Count==0)
        //         {
        //             throw new Exception("DatabaseRoleSR.ErrorDbRoleNotFound");
        //         }

        //         // DataRow dr = dt.Rows[0];
        //         // this.initialOwner = Convert.ToString(dr[DatabaseRoleGeneral.ownerField],System.Globalization.CultureInfo.InvariantCulture);
        //         // this.textBoxOwner.Text = this.initialOwner;
        //     }
        // }

        // private void DbRole_SendDataToServer(CDataContainer dataContainer, string databaseName, 
        //     string dbroleName, string ownerName, string initialOwner, string roleName, bool isPropertiesMode)
        // {
        //     System.Diagnostics.Debug.Assert(databaseName != null && databaseName.Trim().Length != 0, "database name is empty");
        //     System.Diagnostics.Debug.Assert(dataContainer.Server != null, "server is null");

        //     Database database = dataContainer.Server.Databases[databaseName];
        //     System.Diagnostics.Debug.Assert(database!= null, "database is null");

        //     DatabaseRole role;

        //     if (isPropertiesMode == true) // in properties mode -> alter role
        //     {
        //         System.Diagnostics.Debug.Assert(dbroleName != null && dbroleName.Trim().Length != 0, "role name is empty");

        //         role = database.Roles[dbroleName];
        //         System.Diagnostics.Debug.Assert(role != null, "role is null");

        //         if (0 != String.Compare(ownerName, initialOwner, StringComparison.Ordinal))
        //         {
        //             role.Owner = ownerName;
        //             role.Alter();
        //         }
        //     }
        //     else // not in properties mode -> create role
        //     {
        //         role = new DatabaseRole(database, roleName);
        //         if (ownerName.Length != 0)
        //         {
        //             role.Owner = ownerName;
        //         }

        //         role.Create();
        //     }

        //     // SendToServerSchemaOwnershipChanges(database, role);
        //     // SendToServerMembershipChanges(database, role);
        // }


        // /// <summary>
        // /// sends to server changes related to schema ownership
        // /// </summary>
        // private void DbRole_SendToServerSchemaOwnershipChanges(CDataContainer dataContainer, Database db, DatabaseRole dbrole)
        // {
        //     if (dataContainer.Server == null)
        //     {
        //         return;
        //     }

        //     HybridDictionary schemaOwnership = new HybridDictionary();
        //     if (9 <= dataContainer.Server.Information.Version.Major)
        //     {
        //         IDictionaryEnumerator enumerator = schemaOwnership.GetEnumerator();
        //         enumerator.Reset();
        //         while (enumerator.MoveNext())
        //         {
        //             DictionaryEntry de          = enumerator.Entry;
        //             string          schemaName  = de.Key.ToString();
        //             SchemaOwnership ownership   = (SchemaOwnership)de.Value;

        //             // If we are creating a new role, then no schema will have been initially owned by this role.
        //             // If we are modifying an existing role, we can only take ownership of roles.  (Ownership can't
        //             // be renounced, it can only be positively assigned to a principal.)
        //             if (ownership != null && (ownership.currentlyOwned && !ownership.initiallyOwned))
        //             {
        //                 Schema schema = db.Schemas[schemaName];
        //                 schema.Owner = dbrole.Name;
        //                 schema.Alter();
        //             }
        //         }
        //     }
        // }

        #endregion

    }
}