#if SECURITY_DEP
//
// AsyncProtocolRequest.cs
//
// Author:
//       Martin Baulig <martin.baulig@xamarin.com>
//
// Copyright (c) 2015 Xamarin, Inc.
//
using System;
using System.IO;
using System.Net;
using System.Net.Security;
using SD = System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;

namespace Mono.Net.Security
{
	delegate AsyncOperationStatus AsyncOperation (AsyncProtocolRequest asyncRequest, AsyncOperationStatus status);

	class BufferOffsetSize
	{
		public byte[] Buffer;
		public int Offset;
		public int Size;
		public int TotalBytes;
		public bool Complete;

		public int EndOffset {
			get { return Offset + Size; }
		}

		public int Remaining {
			get { return Buffer.Length - Offset - Size; }
		}

		public BufferOffsetSize (byte[] buffer, int offset, int size)
		{
			Buffer = buffer;
			Offset = offset;
			Size = size;
			Complete = false;
		}

		public override string ToString ()
		{
			return string.Format ("[BufferOffsetSize: {0} {1}]", Offset, Size);
		}
	}

	class BufferOffsetSize2 : BufferOffsetSize
	{
		public readonly int InitialSize;

		public BufferOffsetSize2 (int size)
			: base (new byte [size], 0, 0)
		{
			InitialSize = size;
		}

		public void Reset ()
		{
			Offset = Size = 0;
			TotalBytes = 0;
			Buffer = new byte [InitialSize];
			Complete = false;
		}

		public void MakeRoom (int size)
		{
			if (Remaining >= size)
				return;

			int missing = size - Remaining;
			if (Offset == 0 && Size == 0) {
				Buffer = new byte [size];
				return;
			}

			var buffer = new byte [Buffer.Length + missing];
			Buffer.CopyTo (buffer, 0);
			Buffer = buffer;
		}

		public void AppendData (byte[] buffer, int offset, int size)
		{
			MakeRoom (size);
			System.Buffer.BlockCopy (buffer, offset, Buffer, EndOffset, size);
			Size += size;
		}
	}

	enum AsyncOperationStatus {
		NotStarted,
		Initialize,
		Continue,
		Running,
		Complete,
		WantRead,
		WantWrite,
		ReadDone,
		FinishWrite
	}

	class AsyncProtocolRequest
	{
		public readonly MobileAuthenticatedStream Parent;
		public readonly BufferOffsetSize UserBuffer;

		int RequestedSize;
		public int CurrentSize;
		public int UserResult;

		AsyncOperation Operation;
		int Status;

		public readonly int ID = ++next_id;
		static int next_id;

		public readonly LazyAsyncResult UserAsyncResult;

		public AsyncProtocolRequest (MobileAuthenticatedStream parent, LazyAsyncResult lazyResult, BufferOffsetSize userBuffer = null)
		{
			Parent = parent;
			UserAsyncResult = lazyResult;
			UserBuffer = userBuffer;
		}

		public bool CompleteWithError (Exception ex)
		{
			Status = (int)AsyncOperationStatus.Complete;
			if (UserAsyncResult == null)
				return true;
			if (!UserAsyncResult.InternalPeekCompleted)
				UserAsyncResult.InvokeCallback (ex);
			return false;
		}

		[SD.Conditional ("MARTIN_DEBUG")]
		protected void Debug (string message, params object[] args)
		{
			Parent.Debug ("AsyncProtocolRequest({0}:{1}): {2}", Parent.ID, ID, string.Format (message, args));
		}

		internal void RequestRead (int size)
		{
			var oldStatus = (AsyncOperationStatus)Interlocked.CompareExchange (ref Status, (int)AsyncOperationStatus.WantRead, (int)AsyncOperationStatus.Running);
			Debug ("RequestRead: {0} {1}", oldStatus, size);
			if (oldStatus == AsyncOperationStatus.Running)
				RequestedSize = size;
			else if (oldStatus == AsyncOperationStatus.WantRead)
				RequestedSize += size;
			else if (oldStatus != AsyncOperationStatus.WantWrite)
				throw new InvalidOperationException ();
		}

		internal void ResetRead ()
		{
			var oldStatus = (AsyncOperationStatus)Interlocked.CompareExchange (ref Status, (int)AsyncOperationStatus.Complete, (int)AsyncOperationStatus.WantRead);
			Debug ("ResetRead: {0} {1}", oldStatus, Status);
		}

		internal void ResetWrite ()
		{
			var oldStatus = (AsyncOperationStatus)Interlocked.CompareExchange (ref Status, (int)AsyncOperationStatus.Complete, (int)AsyncOperationStatus.WantWrite);
			Debug ("ResetWrite: {0} {1}", oldStatus, Status);
		}

		internal void RequestWrite ()
		{
			var oldStatus = (AsyncOperationStatus)Interlocked.CompareExchange (ref Status, (int)AsyncOperationStatus.WantWrite, (int)AsyncOperationStatus.Running);
			Debug ("RequestWrite: {0} {1}", oldStatus, Status);
			if (oldStatus == AsyncOperationStatus.Running)
				return;
			else if (oldStatus != AsyncOperationStatus.WantRead && oldStatus != AsyncOperationStatus.WantWrite)
				throw new InvalidOperationException ();
		}

		internal void StartOperation (AsyncOperation operation)
		{
			Debug ("Start Operation: {0} {1}", Status, operation);
			if (Interlocked.CompareExchange (ref Status, (int)AsyncOperationStatus.Initialize, (int)AsyncOperationStatus.NotStarted) != (int)AsyncOperationStatus.NotStarted)
				throw new InvalidOperationException ();

			Operation = operation;

			if (UserAsyncResult == null) {
				StartOperation ();
				return;
			}

			ThreadPool.QueueUserWorkItem (_ => StartOperation ());
		}

		void StartOperation ()
		{
			try {
				ProcessOperation ();
				if (UserAsyncResult != null && !UserAsyncResult.InternalPeekCompleted)
					UserAsyncResult.InvokeCallback (UserResult);
			} catch (Exception ex) {
				if (UserAsyncResult == null)
					throw;
				if (!UserAsyncResult.InternalPeekCompleted)
					UserAsyncResult.InvokeCallback (ex);
			}
		}

		void ProcessOperation ()
		{
			AsyncOperationStatus status;
			do {
				status = (AsyncOperationStatus)Interlocked.Exchange (ref Status, (int)AsyncOperationStatus.Running);

				Debug ("ProcessOperation: {0}", status);

				status = ProcessOperation (status);

				Debug ("ProcessOperation done: {0}", status);

				AsyncOperationStatus oldStatus;
				if (status == AsyncOperationStatus.Complete) {
					oldStatus = (AsyncOperationStatus)Interlocked.CompareExchange (ref Status, (int)AsyncOperationStatus.FinishWrite, (int)AsyncOperationStatus.WantWrite);
					if (oldStatus == AsyncOperationStatus.WantWrite) {
						// We are done, but still need to flush the write queue.
						status = AsyncOperationStatus.FinishWrite;
						continue;
					}
				}

				oldStatus = (AsyncOperationStatus)Interlocked.CompareExchange (ref Status, (int)status, (int)AsyncOperationStatus.Running);
				Debug ("ProcessOperation done: {0} -> {1}", oldStatus, status);

				if (oldStatus != AsyncOperationStatus.Running) {
					if (status == oldStatus || status == AsyncOperationStatus.Continue || status == AsyncOperationStatus.Complete)
						status = oldStatus;
					else
						throw new InvalidOperationException ();
				}
			} while (status != AsyncOperationStatus.Complete);
		}

		AsyncOperationStatus ProcessOperation (AsyncOperationStatus status)
		{
			if (status == AsyncOperationStatus.WantRead) {
				if (RequestedSize < 0)
					throw new InvalidOperationException ();
				else if (RequestedSize == 0)
					return AsyncOperationStatus.Continue;

				Debug ("ProcessOperation - read inner: {0}", RequestedSize);
				var ret = Parent.InnerRead (RequestedSize);
				Debug ("ProcessOperation - read inner done: {0} - {1}", RequestedSize, ret);

				if (ret < 0)
					return AsyncOperationStatus.ReadDone;

				RequestedSize -= ret;

				if (ret == 0 || RequestedSize == 0)
					return AsyncOperationStatus.Continue;
				else
					return AsyncOperationStatus.WantRead;
			} else if (status == AsyncOperationStatus.WantWrite) {
				Debug ("ProcessOperation - want write");
				Parent.InnerWrite ();
				Debug ("ProcessOperation - want write done");
				return AsyncOperationStatus.Continue;
			} else if (status == AsyncOperationStatus.Initialize || status == AsyncOperationStatus.Continue) {
				Debug ("ProcessOperation - continue");
				status = Operation (this, status);
				Debug ("ProcessOperation - continue done: {0}", status);
				return status;
			} else if (status == AsyncOperationStatus.ReadDone) {
				Debug ("ProcessOperation - read done");
				status = Operation (this, status);
				Debug ("ProcessOperation - read done: {0}", status);
				return status;
			} else if (status == AsyncOperationStatus.FinishWrite) {
				Debug ("ProcessOperation - finish write");
				Parent.InnerWrite ();
				Debug ("ProcessOperation - finish write done");
				return AsyncOperationStatus.Complete;
			}

			throw new InvalidOperationException ();
		}
	}
}
#endif