using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace TGServerService
{
	/// <summary>
	/// Helpers to <see cref="Suspend(Process)"/>ing and <see cref="Resume(Process)"/> a <see cref="Process"/>. Lightly massaged code from https://stackoverflow.com/a/13109774. Documentation linked from MSDN on 20/10/2017
	/// </summary>
	static class ProcessExtension
	{
		/// <summary>
		/// https://msdn.microsoft.com/en-us/library/windows/desktop/ms686769(v=vs.85).aspx
		/// </summary>
		enum ThreadAccess : int
		{
			SUSPEND_RESUME = (0x0002),
		}
		/// <summary>
		/// https://msdn.microsoft.com/en-us/library/windows/desktop/ms684335(v=vs.85).aspx
		/// </summary>
		[DllImport("kernel32.dll")]
		static extern IntPtr OpenThread(ThreadAccess dwDesiredAccess, bool bInheritHandle, uint dwThreadId);
		/// <summary>
		/// https://msdn.microsoft.com/en-us/library/windows/desktop/ms724211(v=vs.85).aspx
		/// </summary>
		[DllImport("kernel32.dll")]
		static extern bool CloseHandle(IntPtr hObject);
		/// <summary>
		/// https://msdn.microsoft.com/en-us/library/windows/desktop/ms686345(v=vs.85).aspx
		/// </summary>
		[DllImport("kernel32.dll")]
		static extern uint SuspendThread(IntPtr hThread);
		/// <summary>
		/// https://msdn.microsoft.com/en-us/library/windows/desktop/ms685086(v=vs.85).aspx
		/// </summary>
		[DllImport("kernel32.dll")]
		static extern int ResumeThread(IntPtr hThread);

		/// <summary>
		/// Suspends all threads for a running <see cref="Process"/>
		/// </summary>
		/// <param name="process">The <see cref="Process"/> to suspend</param>
		public static void Suspend(this Process process)
		{
			foreach (ProcessThread thread in process.Threads)
			{
				var pOpenThread = OpenThread(ThreadAccess.SUSPEND_RESUME, false, (uint)thread.Id);
				if (pOpenThread == IntPtr.Zero)
					continue;
				SuspendThread(pOpenThread);
				CloseHandle(pOpenThread);
			}
		}

		/// <summary>
		/// Resumes all threads for a running <see cref="Process"/>
		/// </summary>
		/// <param name="process">The <see cref="Process"/> to suspend</param>
		public static void Resume(this Process process)
		{
			foreach (ProcessThread thread in process.Threads)
			{
				var pOpenThread = OpenThread(ThreadAccess.SUSPEND_RESUME, false, (uint)thread.Id);
				if (pOpenThread == IntPtr.Zero)
					continue;
				ResumeThread(pOpenThread);
				CloseHandle(pOpenThread);
			}
		}
	}
}