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 * 
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 * with or without modification, are permitted provided 
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 *     following disclaimer in the documentation and/or other 
 *     materials provided with the distribution. 
 * 
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 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
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 */

using System;
using System.Threading;
using System.Xml;
using XenAdmin.Core;
using XenAdmin.Network;
using XenAPI;


namespace XenAdmin.Actions
{
    public abstract class AsyncAction : CancellingAction
    {
        private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        private string _result;

        protected AsyncAction(IXenConnection connection, string title, string description, bool suppressHistory)
            : base(title, description, suppressHistory)
        {
            this.Connection = connection;
            Pool = Helpers.GetPoolOfOne(connection);
        }

        protected AsyncAction(IXenConnection connection, string title, string description)
            : this(connection, title, description, false)
        {
        }

        protected AsyncAction(IXenConnection connection, string title)
            : this(connection, title, "", false)
        {
        }

        protected AsyncAction(IXenConnection connection, string title, bool suppress_history)
            : this(connection, title, "", suppress_history)
        {
        }

        public string Result
        {
            get
            {
                if (Exception != null)
                {
                    throw Exception;
                }
                else
                {
                    return _result;
                }
            }
            set { _result = value; }
        }

        /// <summary>
        /// If you want the action to run a pre-check that the current user can perform all the necessary api calls, list them under this field.
        /// If empty, then no checks will be run.
        /// </summary>
        protected RbacMethodList ApiMethodsToRoleCheck = new RbacMethodList();
        public virtual RbacMethodList GetApiMethodsToRoleCheck => ApiMethodsToRoleCheck;

        /// <summary>
        /// If the sudoUsername and sudoPassword fields are both not null, then the action will use these credentials when making new sessions.
        /// </summary>
        public string sudoUsername;
        /// <summary>
        /// If the sudoUsername and sudoPassword fields are both not null, then the action will use these credentials when making new sessions.
        /// </summary>
        public string sudoPassword;

        /// <summary>
        /// Checks to see if we are using elevated credentials for this action. Returns a session using them if they exist, otherwise
        /// using the basic credentials of the IXenConnection. Important - will throw exceptions similar to connection.NewSession
        /// </summary>
        /// <returns></returns>
        protected override Session NewSession()
        {
            if (Connection == null)
                return null;

            if (String.IsNullOrEmpty(sudoPassword) || String.IsNullOrEmpty(sudoUsername))
                return Connection.DuplicateSession();

            return Connection.ElevatedSession(sudoUsername, sudoPassword);
        }

        /// <summary>
        /// Used for cross connection actions (e.g adding a host to a pool, we need to get a session from the connection we are joining)
        /// Checks to see if we are using elevated credentials for this action. Returns a session using them if they exist, otherwise
        /// using the basic credentials of the _supplied_ IXenConnection. Important - will throw exceptions similar to connection.NewSession
        /// </summary>
        /// <param name="xc"></param>
        /// <returns></returns>
        protected Session NewSession(IXenConnection xc)
        {
            if (Connection == null)
                return null;

            if (String.IsNullOrEmpty(sudoPassword) || String.IsNullOrEmpty(sudoUsername))
                return xc.DuplicateSession();

            return xc.ElevatedSession(sudoUsername, sudoPassword);
        }

        /// <summary>
        /// Prepare the action's task for exit by removing the XenCenterUUID.
        /// A call here just before exit will mean that the task will get picked 
        /// up as a meddling action on restart of xencenter, and thus reappear in the EventsTab.
        /// </summary>
        public void PrepareForEventReloadAfterRestart()
        {
            try
            {
                if (Session != null && !string.IsNullOrEmpty(RelatedTask?.opaque_ref))
                    Task.remove_from_other_config(Session, RelatedTask.opaque_ref, "XenCenterUUID");
            }
            catch (Failure f)
            {
                // Read only user without task.other_config rights - just ignore this request
                if (f.ErrorDescription.Count > 0 && f.ErrorDescription[0] == Failure.RBAC_PERMISSION_DENIED)
                    return;

                log.Debug($"Removing XenCenterUUID failed: {f.Message}");
            }
            catch (Exception e)
            {
                log.Debug("Removing XenCenterUUID failed", e);
            }
        }

        public void RunAsync()
        {
            RunAsync(null);
        }

        public void RunAsync(SudoElevationResult sudoElevationResult)
        {
            AuditLogStarted();
            ThreadPool.QueueUserWorkItem(RunWorkerThread, sudoElevationResult);
        }

        /// <summary>
        /// Use this function to run this action non-async, but do the appropriate tidy up code.
        /// If a session is passed in, which it always should be if called from another Action,
        /// use that session for the action: it is then the responsibility of the calling function
        /// to make sure the session has the appropriate privileges and tidy it up afterwards.
        /// </summary>
        public void RunSync(Session session)
        {
            RunWorkerThread(session);
            if (Exception != null)
                throw Exception;
        }

        protected abstract void Run();

        private void RunWorkerThread(object o)
        {
            StartedRunning = true;
            if (Cancelled)  // already cancelled before it's started
                return;

            try
            {
                if (o is Session session)
                    Session = session;
                else if (o is SudoElevationResult ser)
                {
                    sudoUsername = ser.ElevatedUsername;
                    sudoPassword = ser.ElevatedPassword;
                    Session = ser.ElevatedSession ?? NewSession();
                }
                else
                    SetSessionByRole(); //construct a new session and sudo it if necessary

                Run();
                AuditLogSuccess();
                MarkCompleted();
            }
            catch (CancelledException e)
            {
                Cancelled = true;
                AuditLogCancelled();
                MarkCompleted(e);
            }
            catch (Exception e)
            {
                if (e is Failure f && Connection != null && f.ErrorDescription[0] == Failure.RBAC_PERMISSION_DENIED)
                    Failure.ParseRBACFailure(f, Connection, Session ?? Connection.Session);

                log.Error(e);
                AuditLogFailure();
                MarkCompleted(e);
            }
            finally
            {
                Clean();

                if (Exception != null)
                    CleanOnError();

                if (o == null && Session != null && Session.IsElevatedSession)
                {
                    // The session is a new, sudo-ed session: we need to log these ones out
                    try
                    {
                        Session.logout();
                    }
                    catch (Failure f)
                    {
                        log.Debug("Session.logout() failed. ", f);
                    }
                }

                Session = null;
                LogoutCancelSession();
            }
        }

        protected void DestroyTask()
        {
            //Null or empty RelatedTask.opaque_ref can happen during an RBAC dry-run
            if (Session == null || string.IsNullOrEmpty(Session.opaque_ref) ||
                RelatedTask == null || string.IsNullOrEmpty(RelatedTask.opaque_ref))
                return;

            try
            {
                PerformSilentTaskOp(() => Task.destroy(Session, RelatedTask));
            }
            finally
            {
                RelatedTask = null;
            }
        }

        public void PollToCompletion(double start = 0, double finish = 100, bool suppressFailures = false)
        {
            //Null or empty RelatedTask.opaque_ref can happen during an RBAC dry-run
            if (RelatedTask == null || string.IsNullOrEmpty(RelatedTask.opaque_ref))
                return;

            try
            {
                DateTime startTime = DateTime.Now;
                int lastDebug = 0;
                log.InfoFormat("Started polling task {0}", RelatedTask.opaque_ref);
                log.DebugFormat("Polling for action {0}", Description); //log once we start

                while (true)
                {
                    if (XenAdminConfigManager.Provider.ForcedExiting && !SafeToExit)
                        throw new CancelledException();

                    //then log every 30sec
                    int currDebug = (int)(DateTime.Now - startTime).TotalSeconds / 30;
                    if (currDebug > lastDebug)
                    {
                        lastDebug = currDebug;
                        log.DebugFormat("Polling for action {0}", Description);
                    }

                    try
                    {
                        if (Poll(start, finish))
                            break;
                    }
                    catch
                    {
                        if (suppressFailures)
                            break;
                        throw;
                    }

                    Thread.Sleep(900);
                }
            }
            finally
            {
                DestroyTask();
            }
        }

        /// <summary>
        /// Polls task and returns whether it is completed
        /// </summary>
        private bool Poll(double start, double finish)
        {
            Session session = Session;
            Task task;
            Result = "";

            try
            {
                task = (Task)DoWithSessionRetry(ref session, (Task.TaskGetRecordOp)Task.get_record,
                    RelatedTask.opaque_ref);
            }
            catch (Failure exn)
            {
                if (exn.ErrorDescription.Count > 1 && 
                    exn.ErrorDescription[0] == Failure.HANDLE_INVALID &&
                    exn.ErrorDescription[1] == "task")
                {
                    log.WarnFormat("Invalid task handle {0} - task is finished.", RelatedTask.opaque_ref);
                    PercentComplete = (int)finish;
                    return true;
                }
                else
                    throw;
            }
            finally
            {
                Session = session;
            }

            PercentComplete = (int)(start + task.progress * (finish - start));

            switch (task.status)
            {
                case task_status_type.failure:
                    if (task.error_info.Length > 1 &&
                        task.error_info[0] == Failure.HANDLE_INVALID &&
                        task.error_info[1] == "task")
                    {
                        log.WarnFormat("Invalid task handle {0} - task is finished.", RelatedTask.opaque_ref);
                        PercentComplete = (int)finish;
                        return true;
                    }
                    else
                    {
                        log.WarnFormat("Task {0} failed: {1}", RelatedTask.opaque_ref,
                            task.error_info.Length > 0 ? task.error_info[0] : "Unknown failure");
                        throw new Failure(task.error_info);
                    }

                case task_status_type.success:
                    log.InfoFormat("Task {0} finished successfully", RelatedTask.opaque_ref);
                    if (task.result != "") // Work around CA-6597
                    {
                        try
                        {
                            var doc = new XmlDocument();
                            doc.LoadXml(task.result);
                            var nodes = doc.GetElementsByTagName("value");

                            if (nodes.Count > 0)
                            {
                                Result = nodes[0].InnerText;
                            }
                        }
                        catch //CA-352946
                        {
                            log.WarnFormat("Task {0} result is not valid xml", RelatedTask.opaque_ref);
                            Result = task.result;
                        }
                    }
                    return true;

                case task_status_type.cancelled:
                    log.InfoFormat("Task {0} was cancelled", RelatedTask.opaque_ref);
                    throw new CancelledException();

                default:
                    return false;
            }
        }

        /// <summary>
        /// Finds the roles allowed to perform the API calls this action has listed as subject to RBAC checks.
        /// If the current user's role is not on the list, show the Role Elevation Dialog so they can enter
        /// credentials of a user with a permitted role.
        /// </summary>
        private void SetSessionByRole()
        {
            if (Connection == null
                || Connection.Session == null
                || Session != null) // We have been pre-seeded with a Session to use
                return;

            RbacMethodList rbacMethodList;

            if (Connection.Session.IsLocalSuperuser || XenAdminConfigManager.Provider.DontSudo)
                rbacMethodList = new RbacMethodList();
            else
                rbacMethodList = GetApiMethodsToRoleCheck;

            if (rbacMethodList.Count == 0)
            {
                Session = NewSession();
                return;
            }

            bool ableToCompleteAction = Role.CanPerform(rbacMethodList, Connection, out var allowedRoles);

            log.DebugFormat("Roles able to complete action: {0}", Role.FriendlyCSVRoleList(allowedRoles));
            log.DebugFormat("Subject {0} has roles: {1}", Connection.Session.UserLogName(), Role.FriendlyCSVRoleList(Connection.Session.Roles));

            if (ableToCompleteAction)
            {
                log.Debug("Subject authorized to complete action");
                Session = Connection.Session;
                return;
            }

            log.Debug("Subject not authorized to complete action, showing sudo dialog");
            var result = XenAdminConfigManager.Provider.ElevatedSessionDelegate(allowedRoles, Connection, Title);
            if (result == null)
            {
                log.Debug("User cancelled sudo dialog, cancelling action");
                throw new CancelledException();
            }

            sudoUsername = result.ElevatedUsername;
            sudoPassword = result.ElevatedPassword;
            Session = result.ElevatedSession;
        }

        public class SudoElevationResult
        {
            public readonly string ElevatedUsername;
            public readonly string ElevatedPassword;
            public readonly Session ElevatedSession;

            public SudoElevationResult(string user, string password, Session session)
            {
                ElevatedUsername = user;
                ElevatedPassword = password;
                ElevatedSession = session;
            }
        }

        protected void AddCommonAPIMethodsToRoleCheck()
        {
            ApiMethodsToRoleCheck.AddRange(Role.CommonTaskApiList);
            ApiMethodsToRoleCheck.AddRange(Role.CommonSessionApiList);
        }
    }
}