// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

using System;
using System.Diagnostics;
using System.Management.Automation;
using System.Runtime.InteropServices;

namespace Microsoft.PowerShell
{
 /// <summary>
 /// Helper functions for process info.
 /// </summary>
 public static class ProcessCodeMethods
 {
 const int InvalidProcessId = -1;

 internal static Process GetParent(this Process process)
 {
 try
 {
 var pid = GetParentPid(process);
 if (pid == InvalidProcessId)
 {
 return null;
 }

 var candidate = Process.GetProcessById(pid);

 // if the candidate was started later than process, the pid has been recycled
 return candidate.StartTime > process.StartTime ? null : candidate;
 }
 catch (Exception)
 {
 return null;
 }
 }

 /// <summary>
 /// CodeMethod for getting the parent process of a process.
 /// </summary>
 /// <param name="obj"></param>
 /// <returns>The parent process, or null if the parent is no longer running.</returns>
 public static object GetParentProcess(PSObject obj)
 {
 var process = PSObject.Base(obj) as Process;
 return process?.GetParent();
 }

 /// <summary>
 /// Returns the parent id of a process or -1 if it fails.
 /// </summary>
 /// <param name="process"></param>
 /// <returns>The pid of the parent process.</returns>
#if UNIX
 internal static int GetParentPid(Process process)
 {
 return Platform.NonWindowsGetProcessParentPid(process.Id);
 }
#else
 internal static int GetParentPid(Process process)
 {
 Diagnostics.Assert(process != null, "Ensure process is not null before calling");
 PROCESS_BASIC_INFORMATION pbi;
 int size;
 var res = NtQueryInformationProcess(process.Handle, 0, out pbi, Marshal.SizeOf<PROCESS_BASIC_INFORMATION>(), out size);

 return res != 0 ? InvalidProcessId : pbi.InheritedFromUniqueProcessId.ToInt32();
 }

 [StructLayout(LayoutKind.Sequential)]
 struct PROCESS_BASIC_INFORMATION
 {
 public IntPtr ExitStatus;
 public IntPtr PebBaseAddress;
 public IntPtr AffinityMask;
 public IntPtr BasePriority;
 public IntPtr UniqueProcessId;
 public IntPtr InheritedFromUniqueProcessId;
 }

 [DllImport("ntdll.dll", SetLastError = true)]
 static extern int NtQueryInformationProcess(
 IntPtr processHandle,
 int processInformationClass,
 out PROCESS_BASIC_INFORMATION processInformation,
 int processInformationLength,
 out int returnLength);
#endif

 }
}