/*
 * Copyright 2013-2014 eBay Software Foundation
 *
 * Licensed 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.
 */
/** This class will come with HBase 2.0 in package org.apache.hadoop.hbase.util **/
package com.kylinolap.common.util;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.*;
import org.apache.hadoop.hbase.client.HBaseAdmin;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.util.Bytes;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.*;

public class HBaseRegionSizeCalculator {

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

    /**
     * Maps each region to its size in bytes.
     */
    private final Map<byte[], Long> sizeMap = new TreeMap<byte[], Long>(Bytes.BYTES_COMPARATOR);

    static final String ENABLE_REGIONSIZECALCULATOR = "hbase.regionsizecalculator.enable";

    /**
     * Computes size of each region for table and given column families.
     */
    public HBaseRegionSizeCalculator(HTable table) throws IOException {
        this(table, new HBaseAdmin(table.getConfiguration()));
    }

    /**
     * Constructor for unit testing
     */
    HBaseRegionSizeCalculator(HTable table, HBaseAdmin hBaseAdmin) throws IOException {

        try {
            if (!enabled(table.getConfiguration())) {
                logger.info("Region size calculation disabled.");
                return;
            }

            logger.info("Calculating region sizes for table \"" + new String(table.getTableName()) + "\".");

            // Get regions for table.
            Set<HRegionInfo> tableRegionInfos = table.getRegionLocations().keySet();
            Set<byte[]> tableRegions = new TreeSet<byte[]>(Bytes.BYTES_COMPARATOR);

            for (HRegionInfo regionInfo : tableRegionInfos) {
                tableRegions.add(regionInfo.getRegionName());
            }

            ClusterStatus clusterStatus = hBaseAdmin.getClusterStatus();
            Collection<ServerName> servers = clusterStatus.getServers();
            final long megaByte = 1024L * 1024L;

            // Iterate all cluster regions, filter regions from our table and compute their size.
            for (ServerName serverName : servers) {
                ServerLoad serverLoad = clusterStatus.getLoad(serverName);

                for (RegionLoad regionLoad : serverLoad.getRegionsLoad().values()) {
                    byte[] regionId = regionLoad.getName();

                    if (tableRegions.contains(regionId)) {

                        long regionSizeBytes = regionLoad.getStorefileSizeMB() * megaByte;
                        sizeMap.put(regionId, regionSizeBytes);

                        //logger.info("Region " + regionLoad.getNameAsString() + " has size " + regionSizeBytes);
                    }
                }
            }
        } finally {
            hBaseAdmin.close();
        }

    }

    boolean enabled(Configuration configuration) {
        return configuration.getBoolean(ENABLE_REGIONSIZECALCULATOR, true);
    }

    /**
     * Returns size of given region in bytes. Returns 0 if region was not found.
     */
    public long getRegionSize(byte[] regionId) {
        Long size = sizeMap.get(regionId);
        if (size == null) {
            logger.info("Unknown region:" + Arrays.toString(regionId));
            return 0;
        } else {
            return size;
        }
    }

    public Map<byte[], Long> getRegionSizeMap() {
        return Collections.unmodifiableMap(sizeMap);
    }
}