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

namespace NaGet.InteropServices
{
	/// <summary>
	/// Win32 API の<code>CreateProcess</code>を直に叩くためのクラス。
	/// </summary>
	/// <remarks>
	/// .NETのProcess.Startは、<code>CreateProcess(NULL, cmdLine, ...)</code>
	/// のように第一引数が<code>NULL</code>に相当する呼び出しが、
	/// *厳密な意味*でできない。厳密な意味で、
	/// これと同じ呼び出しを実現する必要があるときに使われる。
	/// </remarks>
	public class CreateProcessCaller : IDisposable
	{
		#region Win32API
		
		/*
		[StructLayout(LayoutKind.Sequential)]
		internal struct SECURITY_ATTRIBUTES
		{
		    public int nLength;
		    public IntPtr lpSecurityDescriptor;
		    public int bInheritHandle;
		}
		*/
		
		[StructLayout(LayoutKind.Sequential)]
		internal struct PROCESS_INFORMATION
		{
			public IntPtr hProcess;
			public IntPtr hThread;
			public int dwProcessId;
			public int dwThreadId;
		}
		
		[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
		struct STARTUPINFO
		{
			public Int32 cb;
			string lpReserved;
			string lpDesktop;
			string lpTitle;
			Int32 dwX;
			Int32 dwY;
			Int32 dwXSize;
			Int32 dwYSize;
			Int32 dwXCountChars;
			Int32 dwYCountChars;
			Int32 dwFillAttribute;
			Int32 dwFlags;
			Int16 wShowWindow;
			Int16 cbReserved2;
			IntPtr lpReserved2;
			IntPtr hStdInput;
			IntPtr hStdOutput;
			IntPtr hStdError;
		}
		
		[DllImport("kernel32.dll", CharSet= CharSet.Auto, SetLastError=true)]
		static extern bool CreateProcess(string lpApplicationName,
			string lpCommandLine,
			/* ref SECURITY_ATTRIBUTES lpProcessAttributes, */
			IntPtr lpProcessAttributes,
			/* ref SECURITY_ATTRIBUTES lpThreadAttributes, */
			IntPtr lpThreadAttributes,
			bool bInheritHandles,
			uint dwCreationFlags, IntPtr lpEnvironment, string lpCurrentDirectory,
			[In] ref STARTUPINFO lpStartupInfo,
			out PROCESS_INFORMATION lpProcessInformation);
		
		[DllImport("kernel32", SetLastError=true, ExactSpelling=true)]
		static extern UInt32 WaitForSingleObject(IntPtr handle, UInt32 milliseconds);
		
		[DllImport("kernel32.dll", SetLastError=true)]
		[return: MarshalAs(UnmanagedType.Bool)]
		static extern bool CloseHandle(IntPtr hObject);
		
		[DllImport("kernel32.dll", SetLastError = true)]
		[return: MarshalAs(UnmanagedType.Bool)]
		static extern bool GetExitCodeProcess(IntPtr hProcess, out int lpExitCode);
		
		#endregion
		
		STARTUPINFO si;
		PROCESS_INFORMATION pi;
		
		/// <summary>
		/// プロセスを生成する
		/// </summary>
		/// <param name="procInfo">プロセス起動情報。
		/// なお、<code>procInfo.UseShellExecute</code>は必ずfalseでなければならない</param>
		public CreateProcessCaller(ProcessStartInfo procInfo)
		{
			if (procInfo.UseShellExecute) {
				throw new ArgumentException("UseShellExecute must be false");
			}
			si.cb = Marshal.SizeOf(si);
			
			string lpFileName = (string.IsNullOrEmpty(procInfo.FileName))? null : procInfo.FileName;
			
			uint dwCreationFlags = 0x0020; // NORMAL_PRIORITY_CLASS
			if (procInfo.CreateNoWindow) dwCreationFlags |= 0x08000000; // CREATE_NO_WINDOW
			string lpCurrentDirectory = (System.IO.Directory.Exists(procInfo.WorkingDirectory))? procInfo.WorkingDirectory : null;
			
			bool retValue = CreateProcess(lpFileName, procInfo.Arguments,
			                              IntPtr.Zero, IntPtr.Zero,
			                              false, dwCreationFlags,
			                              IntPtr.Zero, lpCurrentDirectory, ref si, out pi);
			if (! retValue) {
				throw new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
			}
			CloseHandle(pi.hThread);
		}
		
		/// <summary>
		/// 関連付けられたプロセスが終了するまで、最大指定したミリ秒間待機。 
		/// </summary>
		/// <param name="timeout">最大待機時間(ミリ秒単位)</param>
		/// <returns>終了コード</returns>
		public uint WaitForExit(uint timeout)
		{
			return WaitForSingleObject(pi.hProcess, timeout);
		}
		
		/// <summary>
		/// 関連付けられたプロセスが終了するまで無期限に待機。
		/// </summary>
		/// <returns>終了コード</returns>
		public uint WaitForExit()
		{
			// return WaitForExit(INFINITE)
			return WaitForExit(0xFFFFFFFF);
		}
		
		/// <summary>
		/// 終了コード
		/// </summary>
		public int ExitCode {
			get {
				int lpExitCode;
				if (! GetExitCodeProcess(pi.hProcess, out lpExitCode) ) {
					throw new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
				}
				return lpExitCode;
			}
		}
		
		/// <summary>
		/// プロセスのハンドルを開放する
		/// </summary>
		public void Dispose()
		{
			CloseHandle(pi.hProcess);
		}
		
	}
}