/**
 * 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.mapred;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;

import java.io.FileReader;
import java.io.BufferedReader;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.Closeable;

/**
 * Implements persistent storage for queue budget and spending
 * information in a file.
 */
public class FileAllocationStore extends AllocationStore {
  private static final Log LOG = LogFactory.getLog(FileAllocationStore.class);
  private String fileName = "";
  private boolean loaded = false;

  /** {@inheritDoc} */
  public void init(Configuration conf) {
    fileName = conf.get(PrioritySchedulerOptions.DYNAMIC_SCHEDULER_BUDGET_FILE,
        "/etc/hadoop.budget");
  }

  /** {@inheritDoc} */
  public void save() {
    PrintWriter out = null; 
    try {
      out = new PrintWriter(new BufferedWriter(new FileWriter(fileName)));
      for (BudgetQueue queue: getQueues()) {
        out.printf("%s %.20f %.20f\n", queue.name, queue.budget, 
            queue.spending);
      }
    } catch (Exception e) {
      LOG.error("Error writing to file: " + fileName, e);
    } finally {
      close(out);
    }
  }

  private void close(Closeable closeable) {
    if (closeable != null) {
      try {
        closeable.close();
      } catch (Exception ce) {
        LOG.error("Error closing file: " + fileName, ce);
      }
    }
  }

  /** {@inheritDoc} */
  public void load() {
    if (loaded) {
      return;
    }
    BufferedReader in = null;
    try {
      in = new BufferedReader(new FileReader(fileName));
      String line = in.readLine();
      while (line != null) {
        String[] nameValue = line.split(" ");
        if (nameValue.length != 3) {
          continue;
        }
        queueCache.put(nameValue[0], new BudgetQueue(nameValue[0],
            Float.parseFloat(nameValue[1]), Float.parseFloat(nameValue[2])));
        line = in.readLine();
      } 
      loaded = true;
    } catch (Exception e) {
      LOG.error("Error reading file: " + fileName, e);
    } finally {
       close(in);
    }
  }
}