/**
 * 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.hadoop.classification.InterfaceAudience.Private;
import org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.hadoop.classification.InterfaceStability.Stable;
import org.apache.hadoop.classification.InterfaceStability.Unstable;
import org.apache.hadoop.util.FastNumberFormat;
import org.apache.hadoop.yarn.util.Records;

/**
 * <p><code>ApplicationId</code> represents the <em>globally unique</em> 
 * identifier for an application.</p>
 * 
 * <p>The globally unique nature of the identifier is achieved by using the 
 * <em>cluster timestamp</em> i.e. start-time of the 
 * <code>ResourceManager</code> along with a monotonically increasing counter
 * for the application.</p>
 */
@Public
@Stable
public abstract class ApplicationId implements Comparable<ApplicationId> {

  @Private
  @Unstable
  public static final String appIdStrPrefix = "application";

  private static final String APPLICATION_ID_PREFIX = appIdStrPrefix + '_';

  @Public
  @Unstable
  public static ApplicationId newInstance(long clusterTimestamp, int id) {
    ApplicationId appId = Records.newRecord(ApplicationId.class);
    appId.setClusterTimestamp(clusterTimestamp);
    appId.setId(id);
    appId.build();
    return appId;
  }

  /**
   * Get the short integer identifier of the <code>ApplicationId</code>
   * which is unique for all applications started by a particular instance
   * of the <code>ResourceManager</code>.
   * @return short integer identifier of the <code>ApplicationId</code>
   */
  @Public
  @Stable
  public abstract int getId();
  
  @Private
  @Unstable
  protected abstract void setId(int id);
  
  /**
   * Get the <em>start time</em> of the <code>ResourceManager</code> which is 
   * used to generate globally unique <code>ApplicationId</code>.
   * @return <em>start time</em> of the <code>ResourceManager</code>
   */
  @Public
  @Stable
  public abstract long getClusterTimestamp();
  
  @Private
  @Unstable
  protected abstract void setClusterTimestamp(long clusterTimestamp);

  protected abstract void build();
  
  private static final int APP_ID_MIN_DIGITS = 4;

  @Override
  public int compareTo(ApplicationId other) {
    if (this.getClusterTimestamp() - other.getClusterTimestamp() == 0) {
      return this.getId() - other.getId();
    } else {
      return this.getClusterTimestamp() > other.getClusterTimestamp() ? 1 : 
        this.getClusterTimestamp() < other.getClusterTimestamp() ? -1 : 0;
    }
  }

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder(64);
    sb.append(APPLICATION_ID_PREFIX);
    sb.append(getClusterTimestamp());
    sb.append('_');
    FastNumberFormat.format(sb, getId(), APP_ID_MIN_DIGITS);
    return sb.toString();
  }
  
  @Public
  @Stable
  public static ApplicationId fromString(String appIdStr) {
    if (!appIdStr.startsWith(APPLICATION_ID_PREFIX)) {
      throw new IllegalArgumentException("Invalid ApplicationId prefix: "
          + appIdStr + ". The valid ApplicationId should start with prefix "
          + appIdStrPrefix);
    }
    try {
      int pos1 = APPLICATION_ID_PREFIX.length() - 1;
      int pos2 = appIdStr.indexOf('_', pos1 + 1);
      if (pos2 < 0) {
        throw new IllegalArgumentException("Invalid ApplicationId: "
            + appIdStr);
      }
      long rmId = Long.parseLong(appIdStr.substring(pos1 + 1, pos2));
      int appId = Integer.parseInt(appIdStr.substring(pos2 + 1));
      ApplicationId applicationId = ApplicationId.newInstance(rmId, appId);
      return applicationId;
    } catch (NumberFormatException n) {
      throw new IllegalArgumentException("Invalid ApplicationId: "
          + appIdStr, n);
    }
  }
  @Override
  public int hashCode() {
    // Generated by eclipse.
    final int prime = 371237;
    int result = 6521;
    long clusterTimestamp = getClusterTimestamp();
    result = prime * result
        + (int) (clusterTimestamp ^ (clusterTimestamp >>> 32));
    result = prime * result + getId();
    return result;
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null)
      return false;
    if (getClass() != obj.getClass())
      return false;
    ApplicationId other = (ApplicationId) obj;
    if (this.getClusterTimestamp() != other.getClusterTimestamp())
      return false;
    if (this.getId() != other.getId())
      return false;
    return true;
  }
}