/**
    * Copyright 2014-2014 The Kuali Foundation
    *
    * Licensed under the Educational Community License, Version 2.0 (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.opensource.org/licenses/ecl2.php
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.kuali.common.jute.runtime;
  
  import static org.kuali.common.jute.base.Precondition.checkMin;
  
  import javax.inject.Provider;
  
  import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
  
  @JsonDeserialize(builder = Memory.Builder.class)
  public final class Memory {
  
      private final long used;
      private final long free;
      private final long allocated;
      private final long max;
  
      private Memory(Builder builder) {
          this.used = builder.used;
          this.free = builder.free;
          this.allocated = builder.allocated;
          this.max = builder.max;
      }
  
      public static Memory build() {
          // Total amount of memory the JVM is allowed to use
          long max = Runtime.getRuntime().maxMemory();
  
          // Total amount of memory currently allocated
          long allocated = Runtime.getRuntime().totalMemory();
  
          // The JDK method "freeMemory()" reports what is free in the currently allocated heap
          // The amount of memory currently being used by the JVM is the difference between what has been allocated and what is still free
          long used = allocated - Runtime.getRuntime().freeMemory();
  
          // The true amount of free memory is the difference between max and what is currently being used
          long free = max - used;
  
          return builder().withAllocated(allocated).withFree(free).withMax(max).withUsed(used).build();
      }
  
      public static Builder builder() {
          return new Builder();
      }
  
      public static class Builder implements org.apache.commons.lang3.builder.Builder<Memory>, Provider<Memory> {
  
          // Total amount of memory the JVM is allowed to use
          private long max;
  
          // Total amount of memory currently allocated
          private long allocated;
  
          // The amount of memory currently being used by the JVM
          private long used;
  
          // The total amount of memory still available to the JVM
          private long free;
  
          public Builder withUsed(long used) {
              this.used = used;
              return this;
          }
  
          public Builder withFree(long free) {
              this.free = free;
              return this;
          }
  
          public Builder withAllocated(long allocated) {
              this.allocated = allocated;
              return this;
          }
  
          public Builder withMax(long max) {
              this.max = max;
              return this;
          }
  
          @Override
          public Memory get() {
              return build();
          }
  
          @Override
         public Memory build() {
             return validate(new Memory(this));
         }
 
         private static Memory validate(Memory instance) {
             checkMin(instance.used, 0, "used");
             checkMin(instance.free, 0, "free");
             checkMin(instance.allocated, 0, "allocated");
             checkMin(instance.max, 0, "max");
             return instance;
         }
 
     }
 
     public long getUsed() {
         return used;
     }
 
     public long getFree() {
         return free;
     }
 
     public long getAllocated() {
         return allocated;
     }
 
     public long getMax() {
         return max;
     }
 
 }