//
// Buffers.cs:
//
// Author:
//   Leonardo Taglialegne <leonardo.taglialegne@gmail.com>
//
// Copyright (c) 2013 Leonardo Taglialegne.
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;
using Mono.WebServer.FastCgi.Compatibility;

namespace Mono.WebServer.FastCgi
{
	public class Buffers
	{
		public CompatArraySegment<byte>? Header { get; private set; }
		public CompatArraySegment<byte>? Body { get; private set; }
		public CompatArraySegment<byte>? Padding { get; private set; }

		readonly BufferManager bigBufferManager;
		readonly BufferManager smallBufferManager;

		public Buffers ()
		{
		}

		public Buffers (BufferManager bigBufferManager, BufferManager smallBufferManager)
		{
			if (bigBufferManager == null)
				throw new ArgumentNullException ("bigBufferManager");
			if (smallBufferManager == null)
				throw new ArgumentNullException ("smallBufferManager");

			this.bigBufferManager = bigBufferManager;
			this.smallBufferManager = smallBufferManager;
			Header = smallBufferManager.ClaimBuffer ();
			Body = bigBufferManager.ClaimBuffer ();
			Padding = smallBufferManager.ClaimBuffer ();
		}

		public Buffers (byte[] buffer, int headerSize, int bodySize)
		{
			Header = MaybeSegment (buffer, 0, headerSize);
			Body = MaybeSegment (buffer, headerSize, bodySize);
			Padding = MaybeSegment (buffer, headerSize + bodySize);
		}

		public CompatArraySegment<byte> EnforceHeaderLength (int length)
		{
			if (Header == null || Header.Value.Count < length) {
				if (Header != null)
					smallBufferManager.ReturnBuffer (Header.Value);
				Header = new CompatArraySegment<byte> (new byte[length]);
			}
			return Header.Value;
		}

		public CompatArraySegment<byte> EnforceBodyLength (int length)
		{
			if (Body == null || Body.Value.Count < length) {
				if (Body != null)
					bigBufferManager.ReturnBuffer (Body.Value);
				Body = new CompatArraySegment<byte> (new byte[length]);
			}

			return Body.Value;
		}

		public CompatArraySegment<byte> EnforcePaddingLength (int length)
		{
			if (Padding == null || Padding.Value.Count < length) {
				if (Padding != null)
					smallBufferManager.ReturnBuffer (Padding.Value);
				Padding = new CompatArraySegment<byte> (new byte[length]);
			}
			return Padding.Value;
		}

		static CompatArraySegment<byte>? MaybeSegment (byte[] buffer, int offset)
		{
			return buffer == null ? null : MaybeSegment (buffer, offset, buffer.Length - offset);
		}

		static CompatArraySegment<byte>? MaybeSegment (byte[] buffer, int offset, int count)
		{
			if (buffer == null || offset < 0 || count < 0 || offset + count > buffer.Length)
				return null;

			return new CompatArraySegment<byte> (buffer, offset, count);
		}

		public void Return ()
		{
			if (smallBufferManager != null) {
				if (Header != null) {
					smallBufferManager.ReturnBuffer (Header.Value);
					Header = null;
				}
				if (Padding != null) {
					smallBufferManager.ReturnBuffer (Padding.Value);
					Padding = null;
				}
			}

			if (bigBufferManager == null || Body == null)
				return;
			bigBufferManager.ReturnBuffer (Body.Value);
			Body = null;
		}
	}
}