//-----------------------------------------------------------------------------
// Copyright (c) Microsoft Corporation.  All rights reserved.
//-----------------------------------------------------------------------------

namespace System.Activities.Statements
{
    using System;
    using System.Activities;
    using System.Runtime;
    using System.ComponentModel;
    using System.Activities.Persistence;
    using System.Collections.Generic;
    using System.Xml.Linq;
    using System.Activities.Hosting;
    using System.Threading;

    [Fx.Tag.XamlVisible(false)]
    public class DurableTimerExtension : TimerExtension, IWorkflowInstanceExtension, IDisposable, ICancelable
    {
        WorkflowInstanceProxy instance;
        TimerTable registeredTimers;
        Action<object> onTimerFiredCallback;
        TimerPersistenceParticipant timerPersistenceParticipant;
        static AsyncCallback onResumeBookmarkComplete = Fx.ThunkCallback(new AsyncCallback(OnResumeBookmarkComplete));

        static readonly XName timerTableName = XNamespace.Get("urn:schemas-microsoft-com:System.Activities/4.0/properties").GetName("RegisteredTimers");
        static readonly XName timerExpirationTimeName = XNamespace.Get("urn:schemas-microsoft-com:System.Activities/4.0/properties").GetName("TimerExpirationTime");
        bool isDisposed; 

        [Fx.Tag.SynchronizationObject()]
        object thisLock;

        public DurableTimerExtension()
            : base()
        {
            this.onTimerFiredCallback = new Action<object>(this.OnTimerFired);
            this.thisLock = new object();
            this.timerPersistenceParticipant = new TimerPersistenceParticipant(this);
            this.isDisposed = false; 
        }

        object ThisLock
        {
            get
            {
                return this.thisLock;
            }
        }

        internal Action<object> OnTimerFiredCallback
        {
            get
            {
                return this.onTimerFiredCallback;
            }
        }

        internal TimerTable RegisteredTimers
        {
            get
            {
                if (this.registeredTimers == null)
                {
                    this.registeredTimers = new TimerTable(this);
                }
                return this.registeredTimers;
            }
        }

        public virtual IEnumerable<object> GetAdditionalExtensions()
        {
            yield return this.timerPersistenceParticipant;
        }

        public virtual void SetInstance(WorkflowInstanceProxy instance)
        {
            if (this.instance != null && instance != null)
            {
                throw FxTrace.Exception.AsError(new InvalidOperationException(SR.TimerExtensionAlreadyAttached));
            }

            this.instance = instance;
        }

        protected override void OnRegisterTimer(TimeSpan timeout, Bookmark bookmark)
        {
            // This lock is to synchronize with the Timer callback
            if (timeout < TimeSpan.MaxValue)
            {
                lock (this.ThisLock)
                {
                    Fx.Assert(!this.isDisposed, "DurableTimerExtension is already disposed, it cannot be used to register a new timer.");
                    this.RegisteredTimers.AddTimer(timeout, bookmark);
                }
            }
        }

        protected override void OnCancelTimer(Bookmark bookmark)
        {
            // This lock is to synchronize with the Timer callback
            lock (this.ThisLock)
            {
                this.RegisteredTimers.RemoveTimer(bookmark);
            }
        }

        internal void OnSave(out IDictionary<XName, object> readWriteValues, out IDictionary<XName, object> writeOnlyValues)
        {
            readWriteValues = null;
            writeOnlyValues = null;
            
            // Using a lock here to prevent the timer firing back without us being ready
            lock (this.ThisLock)
            {
                this.RegisteredTimers.MarkAsImmutable();
                if (this.registeredTimers != null && this.registeredTimers.Count > 0)
                {
                    readWriteValues = new Dictionary<XName, object>(1);
                    writeOnlyValues = new Dictionary<XName, object>(1);
                    readWriteValues.Add(timerTableName, this.registeredTimers);
                    writeOnlyValues.Add(timerExpirationTimeName, this.registeredTimers.GetNextDueTime());
                }
            }
        }

        internal void PersistenceDone()
        {
            lock (this.ThisLock)
            {
                this.RegisteredTimers.MarkAsMutable();
            }
        }

        internal void OnLoad(IDictionary<XName, object> readWriteValues)
        {
            lock (this.ThisLock)
            {
                object timerTable;
                if (readWriteValues != null && readWriteValues.TryGetValue(timerTableName, out timerTable))
                {
                    this.registeredTimers = timerTable as TimerTable;
                    Fx.Assert(this.RegisteredTimers != null, "Timer Table cannot be null");
                    this.RegisteredTimers.OnLoad(this);
                }
            }
        }

        void OnTimerFired(object state)
        {
            Bookmark timerBookmark = state as Bookmark;

            WorkflowInstanceProxy targetInstance = this.instance;
            // it's possible that we've been unloaded while the timer was in the process of firing, in
            // which case targetInstance will be null
            if (targetInstance != null)
            {
                BookmarkResumptionResult resumptionResult;
                IAsyncResult result = null;
                bool completed = false;

                result = targetInstance.BeginResumeBookmark(timerBookmark, null, TimeSpan.MaxValue,
                    onResumeBookmarkComplete, new BookmarkResumptionState(timerBookmark, this, targetInstance));
                completed = result.CompletedSynchronously; 

                if (completed && result != null)
                {
                    try
                    {
                        resumptionResult = targetInstance.EndResumeBookmark(result);
                        ProcessBookmarkResumptionResult(timerBookmark, resumptionResult);
                    }
                    catch (TimeoutException)
                    {
                        ProcessBookmarkResumptionResult(timerBookmark, BookmarkResumptionResult.NotReady);
                    }
                }
            }
        }

        static void OnResumeBookmarkComplete(IAsyncResult result)
        {
            if (result.CompletedSynchronously)
            {
                return;
            }

            BookmarkResumptionState state = (BookmarkResumptionState)result.AsyncState;

            BookmarkResumptionResult resumptionResult = state.Instance.EndResumeBookmark(result);
            state.TimerExtension.ProcessBookmarkResumptionResult(state.TimerBookmark, resumptionResult);
        }


        void ProcessBookmarkResumptionResult(Bookmark timerBookmark, BookmarkResumptionResult result)
        {
            switch (result)
            {
                case BookmarkResumptionResult.NotFound:
                case BookmarkResumptionResult.Success:
                    // The bookmark is removed maybe due to WF cancel, abort or the bookmark succeeds
                    // no need to keep the timer around
                    lock (this.ThisLock)
                    {
                        if (!this.isDisposed)
                        {
                            this.RegisteredTimers.RemoveTimer(timerBookmark);
                        }
                    }
                    break;
                case BookmarkResumptionResult.NotReady:
                    // The workflow maybe in one of these states: Completed, Aborted, Abandoned, unloading, Suspended
                    // In the first 3 cases, we will let TimerExtension.CancelTimer take care of the cleanup.
                    // In the 4th case, we want the timer to retry when it is loaded back, in all 4 cases we don't need to delete the timer 
                    // In the 5th case, we want the timer to retry until it succeeds. 
                    // Retry:
                    lock (this.ThisLock)
                    {
                        this.RegisteredTimers.RetryTimer(timerBookmark);
                    }
                    break;
            }
        }

        public void Dispose()
        {
            if (this.registeredTimers != null)
            {
                lock (this.ThisLock)
                {
                    this.isDisposed = true; 
                    if (this.registeredTimers != null)
                    {
                        this.registeredTimers.Dispose();
                    }
                }
            }
            GC.SuppressFinalize(this);
        }
        
        void ICancelable.Cancel()
        {
            Dispose();
        }

        class BookmarkResumptionState
        {
            public BookmarkResumptionState(Bookmark timerBookmark, DurableTimerExtension timerExtension, WorkflowInstanceProxy instance)
            {
                this.TimerBookmark = timerBookmark;
                this.TimerExtension = timerExtension;
                this.Instance = instance;
            }

            public Bookmark TimerBookmark
            {
                get;
                private set;
            }

            public DurableTimerExtension TimerExtension
            {
                get;
                private set;
            }

            public WorkflowInstanceProxy Instance
            {
                get;
                private set;
            }
        }

        class TimerPersistenceParticipant : PersistenceIOParticipant
        {
            DurableTimerExtension defaultTimerExtension;

            public TimerPersistenceParticipant(DurableTimerExtension timerExtension)
                : base(false, false)
            {
                this.defaultTimerExtension = timerExtension;
            }

            protected override void CollectValues(out IDictionary<XName, object> readWriteValues, out IDictionary<XName, object> writeOnlyValues)
            {
                this.defaultTimerExtension.OnSave(out readWriteValues, out writeOnlyValues);
            }

            protected override void PublishValues(IDictionary<XName, object> readWriteValues)
            {
                this.defaultTimerExtension.OnLoad(readWriteValues);
            }

            protected override IAsyncResult BeginOnSave(IDictionary<XName, object> readWriteValues, IDictionary<XName, object> writeOnlyValues, TimeSpan timeout, AsyncCallback callback, object state)
            {
                this.defaultTimerExtension.PersistenceDone();
                return base.BeginOnSave(readWriteValues, writeOnlyValues, timeout, callback, state);
            }

            protected override void Abort()
            {
                this.defaultTimerExtension.PersistenceDone();
            }
        }
    }
}