/*
 * 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.iotdb.db.storageengine.rescon.memory;

import org.apache.iotdb.db.conf.IoTDBConfig;
import org.apache.iotdb.db.conf.IoTDBDescriptor;
import org.apache.iotdb.db.exception.WriteProcessException;
import org.apache.iotdb.db.storageengine.dataregion.memtable.IMemTable;
import org.apache.iotdb.db.storageengine.dataregion.memtable.PrimitiveMemTable;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MemTableManager {

  private static final IoTDBConfig CONFIG = IoTDBDescriptor.getInstance().getConfig();

  private static final Logger logger = LoggerFactory.getLogger(MemTableManager.class);

  private static final int WAIT_TIME = 100;
  public static final int MEMTABLE_NUM_FOR_EACH_PARTITION = 4;
  private int currentMemtableNumber = 0;

  private MemTableManager() {}

  public static MemTableManager getInstance() {
    return InstanceHolder.INSTANCE;
  }

  public synchronized IMemTable getAvailableMemTable(String storageGroup, String dataRegionId)
      throws WriteProcessException {
    if (CONFIG.isEnableMemControl()) {
      currentMemtableNumber++;
      return new PrimitiveMemTable(storageGroup, dataRegionId, CONFIG.isEnableMemControl());
    }

    if (!reachMaxMemtableNumber()) {
      currentMemtableNumber++;
      return new PrimitiveMemTable(storageGroup, dataRegionId);
    }

    // wait until the total number of memtable is less than the system capacity
    int waitCount = 1;
    while (true) {
      if (!reachMaxMemtableNumber()) {
        currentMemtableNumber++;
        return new PrimitiveMemTable(storageGroup, dataRegionId);
      }
      try {
        wait(WAIT_TIME);
      } catch (InterruptedException e) {
        logger.error("{} fails to wait for memtables {}, continue to wait", storageGroup, e);
        Thread.currentThread().interrupt();
        throw new WriteProcessException(e);
      }
      if (waitCount++ % 10 == 0) {
        logger.info("{} has waited for a memtable for {}ms", storageGroup, waitCount * WAIT_TIME);
      }
    }
  }

  public int getCurrentMemtableNumber() {
    return currentMemtableNumber;
  }

  public synchronized void decreaseMemtableNumber() {
    currentMemtableNumber--;
    notifyAll();
  }

  /** Called when memory control is disabled */
  private boolean reachMaxMemtableNumber() {
    return currentMemtableNumber >= CONFIG.getMaxMemtableNumber();
  }

  /** Called when memory control is disabled */
  public synchronized void addOrDeleteStorageGroup(int diff) {
    int maxMemTableNum = CONFIG.getMaxMemtableNumber();
    maxMemTableNum +=
        MEMTABLE_NUM_FOR_EACH_PARTITION * CONFIG.getConcurrentWritingTimePartition() * diff;
    CONFIG.setMaxMemtableNumber(maxMemTableNum);
    notifyAll();
  }

  public synchronized void close() {
    currentMemtableNumber = 0;
  }

  private static class InstanceHolder {

    private static final MemTableManager INSTANCE = new MemTableManager();

    private InstanceHolder() {}
  }
}
