#region License Information (GPL v3)

/*
    ShareX - A program that allows you to take screenshots and share any file type
    Copyright (c) 2007-2024 ShareX Team

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

    Optionally you can also view the license at <http://www.gnu.org/licenses/>.
*/

#endregion License Information (GPL v3)

using System;
using System.IO;
using System.IO.Pipes;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ShareX.HelpersLib
{
    public class SingleInstanceManager : IDisposable
    {
        public event Action<string[]> ArgumentsReceived;

        public string MutexName { get; private set; }
        public string PipeName { get; private set; }
        public bool IsSingleInstance { get; private set; }
        public bool IsFirstInstance { get; private set; }

        private const int MaxArgumentsLength = 100;
        private const int ConnectTimeout = 5000;

        private readonly Mutex mutex;
        private CancellationTokenSource cts;

        public SingleInstanceManager(string mutexName, string pipeName, string[] args) : this(mutexName, pipeName, true, args)
        {
        }

        public SingleInstanceManager(string mutexName, string pipeName, bool isSingleInstance, string[] args)
        {
            MutexName = mutexName;
            PipeName = pipeName;
            IsSingleInstance = isSingleInstance;

            mutex = new Mutex(false, MutexName);

            try
            {
                IsFirstInstance = mutex.WaitOne(100, false);

                if (IsSingleInstance)
                {
                    if (IsFirstInstance)
                    {
                        cts = new CancellationTokenSource();

                        Task.Run(ListenForConnectionsAsync, cts.Token);
                    }
                    else
                    {
                        RedirectArgumentsToFirstInstance(args);
                    }
                }
            }
            catch (AbandonedMutexException)
            {
                DebugHelper.WriteLine("Single instance mutex found abandoned from another process.");

                IsFirstInstance = true;
            }
        }

        protected virtual void OnArgumentsReceived(string[] arguments)
        {
            if (ArgumentsReceived != null)
            {
                Task.Run(() => ArgumentsReceived?.Invoke(arguments));
            }
        }

        private async Task ListenForConnectionsAsync()
        {
            while (!cts.IsCancellationRequested)
            {
                bool namedPipeServerCreated = false;

                try
                {
                    using (NamedPipeServerStream namedPipeServer = new NamedPipeServerStream(PipeName, PipeDirection.InOut, 1, PipeTransmissionMode.Byte, PipeOptions.Asynchronous))
                    {
                        namedPipeServerCreated = true;

                        await namedPipeServer.WaitForConnectionAsync(cts.Token).ConfigureAwait(false);

                        using (BinaryReader reader = new BinaryReader(namedPipeServer, Encoding.UTF8))
                        {
                            int length = reader.ReadInt32();

                            if (length < 0 || length > MaxArgumentsLength)
                            {
                                throw new Exception("Invalid length: " + length);
                            }

                            string[] args = new string[length];

                            for (int i = 0; i < length; i++)
                            {
                                args[i] = reader.ReadString();
                            }

                            OnArgumentsReceived(args);
                        }
                    }
                }
                catch (OperationCanceledException)
                {
                }
                catch (Exception e)
                {
                    DebugHelper.WriteException(e);

                    if (!namedPipeServerCreated)
                    {
                        break;
                    }
                }
            }
        }

        private void RedirectArgumentsToFirstInstance(string[] args)
        {
            try
            {
                using (NamedPipeClientStream namedPipeClient = new NamedPipeClientStream(".", PipeName, PipeDirection.Out))
                {
                    namedPipeClient.Connect(ConnectTimeout);

                    using (BinaryWriter writer = new BinaryWriter(namedPipeClient, Encoding.UTF8))
                    {
                        writer.Write(args.Length);

                        foreach (string argument in args)
                        {
                            writer.Write(argument);
                        }
                    }
                }
            }
            catch (Exception e)
            {
                DebugHelper.WriteException(e);
            }
        }

        public void Dispose()
        {
            if (cts != null)
            {
                cts.Cancel();
                cts.Dispose();
            }

            if (mutex != null)
            {
                if (IsFirstInstance)
                {
                    mutex.ReleaseMutex();
                }

                mutex.Dispose();
            }
        }
    }
}