#region Copyright notice and license

// Copyright 2015, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#endregion

using System;
using System.Runtime.InteropServices;
using System.Threading;

namespace Grpc.Core.Internal
{
	/// <summary>
	/// gpr_timespec from grpc/support/time.h
	/// </summary>
	[StructLayout(LayoutKind.Sequential)]
	internal struct Timespec
	{
        const int nanosPerSecond = 1000 * 1000 * 1000;
        const int nanosPerTick = 100;

        [DllImport("grpc_csharp_ext.dll")]
        static extern Timespec gprsharp_now();

        [DllImport("grpc_csharp_ext.dll")]
        static extern Timespec gprsharp_inf_future();

        [DllImport("grpc_csharp_ext.dll")]
        static extern int gprsharp_sizeof_timespec();

        // TODO: revisit this.
		// NOTE: on linux 64bit  sizeof(gpr_timespec) = 16, on windows 32bit sizeof(gpr_timespec) = 8
        // so IntPtr seems to have the right size to work on both.
		public System.IntPtr tv_sec;
		public System.IntPtr tv_nsec;

		/// <summary>
		/// Timespec a long time in the future.
		/// </summary>
		public static Timespec InfFuture
		{
			get
			{
                return gprsharp_inf_future();
			}
		}

        public static Timespec Now
        {
            get
            {
                return gprsharp_now();
            }
        }

        internal static int NativeSize
        {
            get
            {
                return gprsharp_sizeof_timespec();
            }
        }

        /// <summary>
        /// Creates a GPR deadline from current instant and given timeout.
        /// </summary>
        /// <returns>The from timeout.</returns>
        public static Timespec DeadlineFromTimeout(TimeSpan timeout) {
            if (timeout == Timeout.InfiniteTimeSpan)
            {
                return Timespec.InfFuture;
            }
            return Timespec.Now.Add(timeout);
        }

        public Timespec Add(TimeSpan timeSpan) {
            long nanos = tv_nsec.ToInt64() + (timeSpan.Ticks % TimeSpan.TicksPerSecond) * nanosPerTick;
            long overflow_sec = (nanos > nanosPerSecond) ? 1 : 0;

            Timespec result;
            result.tv_nsec = new IntPtr(nanos % nanosPerSecond);
            result.tv_sec = new IntPtr(tv_sec.ToInt64() + (timeSpan.Ticks / TimeSpan.TicksPerSecond) + overflow_sec);
            return result;
        }
	}
}