//
// InterLock.cs
//
// Author:
//       Carsten Sonne Larsen <cs@innolan.dk>
//
// Copyright (c) 2016 Carsten Sonne Larsen
//
// 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 System.Net.Sockets;
using System.Text;
using System.Threading;
using System.IO;
using Ntp.Analyzer.Log;

namespace Ntp.System
{
    #if __MonoCS__
    using Mono.Unix;

    public static class InterLock
    {
        public static bool Release (string name, LogBase log)
        {
            using (Socket socket = new Socket (AddressFamily.Unix, SocketType.Stream, ProtocolType.IP)) {
                try {
                    socket.Connect (new UnixEndPoint (name));
                    byte[] bytes = Encoding.UTF8.GetBytes ("RELEASE");
                    socket.Send (bytes);
                    socket.Close ();
                } catch (Exception e) {
                    log.WriteLine ("Could not release lock.", Severity.Error);
                    log.WriteLine (e, Severity.Trace);
                    return false;
                }
            }

            return true;
        }

        public static bool Wait (string name, LogBase log)
        {
            byte[] buf = new byte[64];
            UnixEndPoint endPoint = null;

            using (Socket socket = new Socket (AddressFamily.Unix, SocketType.Stream, ProtocolType.IP)) {
                try {
                    // Unix socket "hack" 
                    endPoint = new UnixEndPoint (name);
                    if (File.Exists (endPoint.Filename)) {
                        File.Delete (endPoint.Filename);
                    }
                    socket.Bind (endPoint);
                    socket.Listen (5);
                    Socket sock = socket.Accept ();
                    sock.Receive (buf);
                    sock.Close ();
                } catch (Exception e) {
                    log.WriteLine ("Could not create socket.", Severity.Error);
                    log.WriteLine (e, Severity.Trace);
                    return false;
                } finally {
                    if (socket != null && socket.IsBound) {
                        socket.Close ();
                    }
                    if (endPoint != null && File.Exists (endPoint.Filename)) {
                        File.Delete (endPoint.Filename);
                    }
                }
            }

            return true;
        }
    }

    #else
    
    public static class InterLock
    {
        public static string Release (string name)
        {
            try {
                EventWaitHandle handle = EventWaitHandle.OpenExisting (name);                                             
                handle.Set ();
            } catch (Exception e) {
                return e.Message;
            }

            return null;
        }

        public static string Wait (string name)
        {
            try {
                EventWaitHandle handle = new EventWaitHandle (
                             false, EventResetMode.ManualReset,
                             name);
                handle.WaitOne ();
            } catch (Exception e) {
                return e.Message;
            }

            return null;
        }
    }

    #endif
}
