/*
    * Copyright 2019-2022 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.hardware.platform.mac;
   
   import static oshi.util.Memoizer.defaultExpiration;
   import static oshi.util.Memoizer.memoize;
   
  import java.util.function.Supplier;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.sun.jna.Native;
  import com.sun.jna.platform.mac.SystemB;
  
  import oshi.annotation.concurrent.ThreadSafe;
  import oshi.hardware.common.AbstractVirtualMemory;
  import oshi.jna.ByRef.CloseableIntByReference;
  import oshi.jna.Struct.CloseableVMStatistics;
  import oshi.jna.Struct.CloseableXswUsage;
  import oshi.util.ParseUtil;
  import oshi.util.platform.mac.SysctlUtil;
  import oshi.util.tuples.Pair;
  
  /**
   * Memory obtained by host_statistics (vm_stat) and sysctl.
   */
  @ThreadSafe
  final class MacVirtualMemory extends AbstractVirtualMemory {
  
      private static final Logger LOG = LoggerFactory.getLogger(MacVirtualMemory.class);
  
      private final MacGlobalMemory global;
  
      private final Supplier<Pair<Long, Long>> usedTotal = memoize(MacVirtualMemory::querySwapUsage, defaultExpiration());
  
      private final Supplier<Pair<Long, Long>> inOut = memoize(MacVirtualMemory::queryVmStat, defaultExpiration());
  
      /**
       * Constructor for MacVirtualMemory.
       *
       * @param macGlobalMemory The parent global memory class instantiating this
       */
      MacVirtualMemory(MacGlobalMemory macGlobalMemory) {
          this.global = macGlobalMemory;
      }
  
      @Override
      public long getSwapUsed() {
          return usedTotal.get().getA();
      }
  
      @Override
      public long getSwapTotal() {
          return usedTotal.get().getB();
      }
  
      @Override
      public long getVirtualMax() {
          return this.global.getTotal() + getSwapTotal();
      }
  
      @Override
      public long getVirtualInUse() {
          return this.global.getTotal() - this.global.getAvailable() + getSwapUsed();
      }
  
      @Override
      public long getSwapPagesIn() {
          return inOut.get().getA();
      }
  
      @Override
      public long getSwapPagesOut() {
          return inOut.get().getB();
      }
  
      private static Pair<Long, Long> querySwapUsage() {
          long swapUsed = 0L;
          long swapTotal = 0L;
          try (CloseableXswUsage xswUsage = new CloseableXswUsage()) {
              if (SysctlUtil.sysctl("vm.swapusage", xswUsage)) {
                  swapUsed = xswUsage.xsu_used;
                  swapTotal = xswUsage.xsu_total;
              }
          }
          return new Pair<>(swapUsed, swapTotal);
      }
  
      private static Pair<Long, Long> queryVmStat() {
          long swapPagesIn = 0L;
          long swapPagesOut = 0L;
          try (CloseableVMStatistics vmStats = new CloseableVMStatistics();
                  CloseableIntByReference size = new CloseableIntByReference(vmStats.size() / SystemB.INT_SIZE)) {
              if (0 == SystemB.INSTANCE.host_statistics(SystemB.INSTANCE.mach_host_self(), SystemB.HOST_VM_INFO, vmStats,
                      size)) {
                  swapPagesIn = ParseUtil.unsignedIntToLong(vmStats.pageins);
                 swapPagesOut = ParseUtil.unsignedIntToLong(vmStats.pageouts);
             } else {
                 LOG.error("Failed to get host VM info. Error code: {}", Native.getLastError());
             }
         }
         return new Pair<>(swapPagesIn, swapPagesOut);
     }
 }