/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache 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.apache.org/licenses/LICENSE-2.0
 *
 * 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.apache.hadoop.yarn.api.records;

import org.apache.commons.lang.NotImplementedException;
import org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.hadoop.classification.InterfaceStability.Evolving;
import org.apache.hadoop.classification.InterfaceStability.Stable;
import org.apache.hadoop.yarn.api.ApplicationMasterProtocol;


/**
 * <p><code>Resource</code> models a set of computer resources in the 
 * cluster.</p>
 * 
 * <p>Currently it models both <em>memory</em> and <em>CPU</em>.</p>
 * 
 * <p>The unit for memory is megabytes. CPU is modeled with virtual cores
 * (vcores), a unit for expressing parallelism. A node's capacity should
 * be configured with virtual cores equal to its number of physical cores. A
 * container should be requested with the number of cores it can saturate, i.e.
 * the average number of threads it expects to have runnable at a time.</p>
 * 
 * <p>Virtual cores take integer values and thus currently CPU-scheduling is
 * very coarse.  A complementary axis for CPU requests that represents processing
 * power will likely be added in the future to enable finer-grained resource
 * configuration.</p>
 * 
 * <p>Typically, applications request <code>Resource</code> of suitable
 * capability to run their component tasks.</p>
 * 
 * @see ResourceRequest
 * @see ApplicationMasterProtocol#allocate(org.apache.hadoop.yarn.api.protocolrecords.AllocateRequest)
 */
@Public
@Stable
public abstract class Resource implements Comparable<Resource> {

  private static class SimpleResource extends Resource {
    private long memory;
    private long vcores;
    SimpleResource(long memory, long vcores) {
      this.memory = memory;
      this.vcores = vcores;
    }
    @Override
    public int getMemory() {
      return castToIntSafely(memory);
    }
    @Override
    public void setMemory(int memory) {
      this.memory = memory;
    }
    @Override
    public long getMemorySize() {
      return memory;
    }
    @Override
    public void setMemorySize(long memory) {
      this.memory = memory;
    }
    @Override
    public int getVirtualCores() {
      return castToIntSafely(vcores);
    }
    @Override
    public void setVirtualCores(int vcores) {
      this.vcores = vcores;
    }
  }

  @Public
  @Stable
  public static Resource newInstance(int memory, int vCores) {
    return new SimpleResource(memory, vCores);
  }

  @Public
  @Stable
  public static Resource newInstance(long memory, int vCores) {
    return new SimpleResource(memory, vCores);
  }

  /**
   * This method is DEPRECATED:
   * Use {@link Resource#getMemorySize()} instead
   *
   * Get <em>memory</em> of the resource.
   * @return <em>memory</em> of the resource
   */
  @Public
  @Deprecated
  public abstract int getMemory();

  /**
   * Get <em>memory</em> of the resource.
   * @return <em>memory</em> of the resource
   */
  @Public
  @Stable
  public long getMemorySize() {
    throw new NotImplementedException(
        "This method is implemented by ResourcePBImpl");
  }

  /**
   * Set <em>memory</em> of the resource.
   * @param memory <em>memory</em> of the resource
   */
  @Public
  @Deprecated
  public abstract void setMemory(int memory);

  /**
   * Set <em>memory</em> of the resource.
   * @param memory <em>memory</em> of the resource
   */
  @Public
  @Stable
  public void setMemorySize(long memory) {
    throw new NotImplementedException(
        "This method is implemented by ResourcePBImpl");
  }


  /**
   * Get <em>number of virtual cpu cores</em> of the resource.
   * 
   * Virtual cores are a unit for expressing CPU parallelism. A node's capacity
   * should be configured with virtual cores equal to its number of physical cores.
   * A container should be requested with the number of cores it can saturate, i.e.
   * the average number of threads it expects to have runnable at a time.
   *   
   * @return <em>num of virtual cpu cores</em> of the resource
   */
  @Public
  @Evolving
  public abstract int getVirtualCores();
  
  /**
   * Set <em>number of virtual cpu cores</em> of the resource.
   * 
   * Virtual cores are a unit for expressing CPU parallelism. A node's capacity
   * should be configured with virtual cores equal to its number of physical cores.
   * A container should be requested with the number of cores it can saturate, i.e.
   * the average number of threads it expects to have runnable at a time.
   *    
   * @param vCores <em>number of virtual cpu cores</em> of the resource
   */
  @Public
  @Evolving
  public abstract void setVirtualCores(int vCores);

  @Override
  public int hashCode() {
    final int prime = 263167;

    int result = (int) (939769357
        + getMemorySize()); // prime * result = 939769357 initially
    result = prime * result + getVirtualCores();
    return result;
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (!(obj instanceof Resource))
      return false;
    Resource other = (Resource) obj;
    if (getMemorySize() != other.getMemorySize() ||
        getVirtualCores() != other.getVirtualCores()) {
      return false;
    }
    return true;
  }

  @Override
  public int compareTo(Resource other) {
    long diff = this.getMemorySize() - other.getMemorySize();
    if (diff == 0) {
      diff = this.getVirtualCores() - other.getVirtualCores();
    }
    return diff == 0 ? 0 : (diff > 0 ? 1 : -1);
  }

  @Override
  public String toString() {
    return "<memory:" + getMemorySize() + ", vCores:" + getVirtualCores() + ">";
  }

  /**
   * Convert long to int for a resource value safely. This method assumes
   * resource value is positive.
   *
   * @param value long resource value
   * @return int resource value
   */
  protected static int castToIntSafely(long value) {
    if (value > Integer.MAX_VALUE) {
      return Integer.MAX_VALUE;
    }
    return Long.valueOf(value).intValue();
  }
}