// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
using Microsoft.Win32.SafeHandles;
 
namespace System.Threading
{
    public sealed partial class Mutex
    {
        private void CreateMutexCore(bool initiallyOwned) => SafeWaitHandle = WaitSubsystem.NewMutex(initiallyOwned);
 
        private void CreateMutexCore(
            bool initiallyOwned,
            string? name,
            NamedWaitHandleOptionsInternal options,
            out bool createdNew)
        {
            if (!string.IsNullOrEmpty(name))
            {
                name = BuildNameForOptions(name, options);
 
                SafeWaitHandle? safeWaitHandle = WaitSubsystem.CreateNamedMutex(initiallyOwned, name, isUserScope: options.WasSpecified && options.CurrentUserOnly, out createdNew);
                if (safeWaitHandle == null)
                {
                    throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
                }
                SafeWaitHandle = safeWaitHandle;
                return;
            }
 
            SafeWaitHandle = WaitSubsystem.NewMutex(initiallyOwned);
            createdNew = true;
        }
 
        private static OpenExistingResult OpenExistingWorker(
            string name,
            NamedWaitHandleOptionsInternal options,
            out Mutex? result)
        {
            ArgumentException.ThrowIfNullOrEmpty(name);
 
            name = BuildNameForOptions(name, options);
 
            OpenExistingResult status = WaitSubsystem.OpenNamedMutex(name, isUserScope: options.WasSpecified && options.CurrentUserOnly, out SafeWaitHandle? safeWaitHandle);
            result = status == OpenExistingResult.Success ? new Mutex(safeWaitHandle!) : null;
            return status;
        }
 
        private static string BuildNameForOptions(string name, NamedWaitHandleOptionsInternal options)
        {
            if (options.WasSpecified)
            {
                name = options.GetNameWithSessionPrefix(name);
            }
 
            if (name.StartsWith(NamedWaitHandleOptionsInternal.CurrentSessionPrefix) &&
                name.Length > NamedWaitHandleOptionsInternal.CurrentSessionPrefix.Length)
            {
                name = name.Substring(NamedWaitHandleOptionsInternal.CurrentSessionPrefix.Length);
            }
 
            return name;
        }
 
        public void ReleaseMutex()
        {
            // The field value is modifiable via the public <see cref="WaitHandle.SafeWaitHandle"/> property, save it locally
            // to ensure that one instance is used in all places in this method
            SafeWaitHandle waitHandle = SafeWaitHandle;
            if (waitHandle.IsInvalid)
            {
                ThrowInvalidHandleException();
            }
 
            waitHandle.DangerousAddRef();
            try
            {
                WaitSubsystem.ReleaseMutex(waitHandle.DangerousGetHandle());
            }
            finally
            {
                waitHandle.DangerousRelease();
            }
        }
    }
}