/*

  Version: MPL 1.1/GPL 2.0/LGPL 2.1

  The contents of this file are subject to the Mozilla Public License Version

  1.1 (the "License"); you may not use this file except in compliance with

  the License. You may obtain a copy of the License at

  http://www.mozilla.org/MPL/

  Software distributed under the License is distributed on an "AS IS" basis,

  WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License

  for the specific language governing rights and limitations under the License.

  The Original Code is the Open Hardware Monitor code.

  The Initial Developer of the Original Code is 

  Michael Möller <m.moeller@gmx.ch>.

  Portions created by the Initial Developer are Copyright (C) 2009-2010

  the Initial Developer. All Rights Reserved.

  Contributor(s):

  Alternatively, the contents of this file may be used under the terms of

  either the GNU General Public License Version 2 or later (the "GPL"), or

  the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),

  in which case the provisions of the GPL or the LGPL are applicable instead

  of those above. If you wish to allow use of your version of this file only

  under the terms of either the GPL or the LGPL, and not to allow others to

  use your version of this file under the terms of the MPL, indicate your

  decision by deleting the provisions above and replace them with the notice

  and other provisions required by the GPL or the LGPL. If you do not delete

  the provisions above, a recipient may use your version of this file under

  the terms of any one of the MPL, the GPL or the LGPL.

*/

using System;

using System.Runtime.InteropServices;

namespace OpenHardwareMonitor.Hardware.CPU {

  internal class CPULoad {

    [StructLayout(LayoutKind.Sequential)]

    protected struct SystemProcessorPerformanceInformation {

      public long IdleTime;

      public long KernelTime;

      public long UserTime;

      public long Reserved0;

      public long Reserved1;

      public ulong Reserved2;

    }

    protected enum SystemInformationClass {

      SystemBasicInformation = 0,

      SystemCpuInformation = 1,

      SystemPerformanceInformation = 2,

      SystemTimeOfDayInformation = 3,

      SystemProcessInformation = 5,

      SystemProcessorPerformanceInformation = 8

    }

    private readonly CPUID[][] cpuid;

    private long systemTime;

    private long[] idleTimes;

    private float totalLoad;

    private readonly float[] coreLoads;

    private readonly bool available;

    private static long[] GetIdleTimes() {      

      SystemProcessorPerformanceInformation[] informations = new

        SystemProcessorPerformanceInformation[64];

      int size = Marshal.SizeOf(typeof(SystemProcessorPerformanceInformation));

      IntPtr returnLength;

      if (NativeMethods.NtQuerySystemInformation(

        SystemInformationClass.SystemProcessorPerformanceInformation,

        informations, informations.Length * size, out returnLength) != 0)

        return null;

      long[] result = new long[(int)returnLength / size];

      for (int i = 0; i < result.Length; i++)

        result[i] = informations[i].IdleTime;

      return result;

    }

    public CPULoad(CPUID[][] cpuid) {

      this.cpuid = cpuid;

      this.coreLoads = new float[cpuid.Length];         

      this.systemTime = DateTime.Now.Ticks;

      this.totalLoad = 0;

      try {

        this.idleTimes = GetIdleTimes();

      } catch (Exception) {

        this.idleTimes = null;

      }

      if (idleTimes != null)

        available = true;

    }

    public bool IsAvailable {

      get { return available; }

    }

    public float GetTotalLoad() {

      return totalLoad;

    }

    public float GetCoreLoad(int core) {

      return coreLoads[core];

    }

    public void Update() {

      if (this.idleTimes == null)

        return;

      long newSystemTime = DateTime.Now.Ticks;

      long[] newIdleTimes = GetIdleTimes();

      if (newSystemTime - this.systemTime < 10000)

        return;

      if (newIdleTimes == null)

        return;

      float total = 0;

      int count = 0;

      for (int i = 0; i < cpuid.Length; i++) {

        float value = 0;

        for (int j = 0; j < cpuid[i].Length; j++) {

          long index = cpuid[i][j].Thread;

          if (index < newIdleTimes.Length) {

            long delta = newIdleTimes[index] - this.idleTimes[index];

            value += delta;

            total += delta;

            count++;

          }

        }

        value = 1.0f - value / (cpuid[i].Length * 

          (newSystemTime - this.systemTime));

        value = value < 0 ? 0 : value;

        coreLoads[i] = value * 100;

      }

      if (count > 0) {

        total = 1.0f - total / (count * (newSystemTime - this.systemTime));

        total = total < 0 ? 0 : total;

      } else {

        total = 0;

      }

      this.totalLoad = total * 100;

      this.systemTime = newSystemTime;

      this.idleTimes = newIdleTimes;

    }

    protected static class NativeMethods {

      [DllImport("ntdll.dll")]

      public static extern int NtQuerySystemInformation(

        SystemInformationClass informationClass,

        [Out] SystemProcessorPerformanceInformation[] informations,

        int structSize, out IntPtr returnLength);

    }

  }

}