/*
    * Copyright 2020-2022 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.software.common;
   
   import static oshi.util.Memoizer.defaultExpiration;
   import static oshi.util.Memoizer.memoize;
   
  import java.util.function.Supplier;
  
  import oshi.annotation.concurrent.ThreadSafe;
  import oshi.software.os.OSProcess;
  
  /**
   * A process is an instance of a computer program that is being executed. It contains the program code and its current
   * activity. Depending on the operating system (OS), a process may be made up of multiple threads of execution that
   * execute instructions concurrently.
   */
  @ThreadSafe
  public abstract class AbstractOSProcess implements OSProcess {
  
      private final Supplier<Double> cumulativeCpuLoad = memoize(this::queryCumulativeCpuLoad, defaultExpiration());
  
      private int processID;
  
      protected AbstractOSProcess(int pid) {
          this.processID = pid;
      }
  
      @Override
      public int getProcessID() {
          return this.processID;
      }
  
      @Override
      public double getProcessCpuLoadCumulative() {
          return cumulativeCpuLoad.get();
      }
  
      private double queryCumulativeCpuLoad() {
          return getUpTime() > 0d ? (getKernelTime() + getUserTime()) / (double) getUpTime() : 0d;
      }
  
      @Override
      public double getProcessCpuLoadBetweenTicks(OSProcess priorSnapshot) {
          if (priorSnapshot != null && this.processID == priorSnapshot.getProcessID()
                  && getUpTime() > priorSnapshot.getUpTime()) {
              return (getUserTime() - priorSnapshot.getUserTime() + getKernelTime() - priorSnapshot.getKernelTime())
                      / (double) (getUpTime() - priorSnapshot.getUpTime());
          }
          return getProcessCpuLoadCumulative();
      }
  
      @Override
      public String toString() {
          StringBuilder builder = new StringBuilder("OSProcess@");
          builder.append(Integer.toHexString(hashCode()));
          builder.append("[processID=").append(this.processID);
          builder.append(", name=").append(getName()).append(']');
          return builder.toString();
      }
  }