/*
 * 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.eagle.log.entity.old;

import java.io.IOException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

import org.apache.eagle.common.config.EagleConfigFactory;
import org.apache.eagle.log.entity.InternalLog;
import org.apache.eagle.log.entity.LogReader;
import org.apache.hadoop.hbase.client.HTableFactory;
import org.apache.hadoop.hbase.client.HTableInterface;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.ResultScanner;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
import org.apache.hadoop.hbase.filter.FilterList;
import org.apache.hadoop.hbase.filter.RegexStringComparator;
import org.apache.hadoop.hbase.filter.RowFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.eagle.common.ByteUtil;
import org.apache.eagle.common.EagleBase64Wrapper;

public class HBaseLogReader implements LogReader {
    private static Logger LOG = LoggerFactory.getLogger(HBaseLogReader.class);

    protected byte[][] qualifiers;
    private HTableInterface tbl;
    private byte[] startKey;
    private byte[] stopKey;
    protected Map<String, List<String>> searchTags;

    private ResultScanner rs;
    private boolean isOpen = false;

    private Schema schema;

    public HBaseLogReader(Schema schema, Date startTime, Date endTime, Map<String, List<String>> searchTags,
                          String lastScanKey, byte[][] outputQualifier) {
        this.schema = schema;
        this.qualifiers = outputQualifier;
        this.startKey = buildRowKey(schema.getPrefix(), startTime);
        if (lastScanKey == null) {
            this.stopKey = buildRowKey(schema.getPrefix(), endTime);
        } else {
            // build stop key
            this.stopKey = EagleBase64Wrapper.decode(lastScanKey);
            // concat byte 0 to exclude this stopKey
            this.stopKey = ByteUtil.concat(this.stopKey, new byte[] { 0 });
        }
        this.searchTags = searchTags;
    }

    /**
     * TODO If the required field is null for a row, then this row will not be fetched. That could be a
     * problem for counting Need another version of read to strictly get the number of rows which will return
     * all the columns for a column family
     */
    @Override
    public void open() throws IOException {
        if (isOpen) {
            return; // silently return
        }
        try {
            tbl = EagleConfigFactory.load().getHTable(schema.getTable());
        } catch (RuntimeException ex) {
            throw new IOException(ex);
        }

        String rowkeyRegex = buildRegex2(searchTags);
        RegexStringComparator regexStringComparator = new RegexStringComparator(rowkeyRegex);
        regexStringComparator.setCharset(Charset.forName("ISO-8859-1"));
        RowFilter filter = new RowFilter(CompareOp.EQUAL, regexStringComparator);
        FilterList filterList = new FilterList();
        filterList.addFilter(filter);
        Scan s1 = new Scan();
        // reverse timestamp, startRow is stopKey, and stopRow is startKey
        s1.setStartRow(stopKey);
        s1.setStopRow(startKey);
        s1.setFilter(filterList);
        // TODO the # of cached rows should be minimum of (pagesize and 100)
        s1.setCaching(100);
        // TODO not optimized for all applications
        s1.setCacheBlocks(true);
        // scan specified columnfamily and qualifiers
        for (byte[] qualifier : qualifiers) {
            s1.addColumn(schema.getColumnFamily().getBytes(), qualifier);
        }
        rs = tbl.getScanner(s1);
        isOpen = true;
    }

    @Override
    public void close() throws IOException {
        if (tbl != null) {
            new HTableFactory().releaseHTableInterface(tbl);
        }
        if (rs != null) {
            rs.close();
        }
    }

    public void flush() throws IOException {
        tbl.flushCommits();
    }

    private byte[] buildRowKey(String appName, Date t) {
        byte[] key = new byte[4 + 8];
        byte[] b = ByteUtil.intToBytes(appName.hashCode());
        System.arraycopy(b, 0, key, 0, 4);
        // reverse timestamp
        long ts = Long.MAX_VALUE - t.getTime();
        System.arraycopy(ByteUtil.longToBytes(ts), 0, key, 4, 8);
        return key;
    }

    /**
     * one search tag may have multiple values which have OR relationship, and relationship between different
     * search tags is AND the query is like "(TAG1=value11 OR TAG1=value12) AND TAG2=value2".
     *
     * @param tags
     * @return
     */
    protected String buildRegex2(Map<String, List<String>> tags) {
        // TODO need consider that \E could be part of tag, refer to
        // https://github.com/OpenTSDB/opentsdb/blob/master/src/core/TsdbQuery.java
        SortedMap<Integer, List<Integer>> tagHash = new TreeMap<Integer, List<Integer>>();

        for (Map.Entry<String, List<String>> entry : tags.entrySet()) {
            String tagName = entry.getKey();
            List<String> stringValues = entry.getValue();
            List<Integer> hashValues = new ArrayList<Integer>(1);
            for (String value : stringValues) {
                hashValues.add(value.hashCode());
            }
            tagHash.put(tagName.hashCode(), hashValues);
        }
        // <tag1:3><value1:3> ... <tagn:3><valuen:3>
        StringBuilder sb = new StringBuilder();
        sb.append("(?s)");
        sb.append("^(?:.{12})");
        sb.append("(?:.{").append(8).append("})*"); // for any number of tags
        for (Map.Entry<Integer, List<Integer>> entry : tagHash.entrySet()) {
            try {
                sb.append("\\Q");
                sb.append(new String(ByteUtil.intToBytes(entry.getKey()), "ISO-8859-1")).append("\\E");
                List<Integer> hashValues = entry.getValue();
                sb.append("(?:");
                boolean first = true;
                for (Integer value : hashValues) {
                    if (!first) {
                        sb.append('|');
                    }
                    sb.append("\\Q");
                    sb.append(new String(ByteUtil.intToBytes(value), "ISO-8859-1"));
                    sb.append("\\E");
                    first = false;
                }
                sb.append(")");
                sb.append("(?:.{").append(8).append("})*"); // for any number of tags
            } catch (Exception ex) {
                LOG.error("Constructing regex error", ex);
            }
        }
        sb.append("$");
        if (LOG.isDebugEnabled()) {
            LOG.debug("Pattern is " + sb.toString());
        }
        return sb.toString();
    }

    @Override
    public InternalLog read() throws IOException {
        if (rs == null) {
            throw new IllegalArgumentException("ResultScanner must be initialized before reading");
        }

        InternalLog t = null;

        Result r = rs.next();
        if (r != null) {
            byte[] row = r.getRow();
            // skip the first 4 bytes : prefix
            long timestamp = ByteUtil.bytesToLong(row, 4);
            // reverse timestamp
            timestamp = Long.MAX_VALUE - timestamp;
            int count = 0;
            if (qualifiers != null) {
                count = qualifiers.length;
            }
            byte[][] values = new byte[count][];
            Map<String, byte[]> allQualifierValues = new HashMap<String, byte[]>();
            for (int i = 0; i < count; i++) {
                // TODO if returned value is null, it means no this column for this row, so why set null to
                // the object?
                values[i] = r.getValue(schema.getColumnFamily().getBytes(), qualifiers[i]);
                allQualifierValues.put(new String(qualifiers[i]), values[i]);
            }
            t = buildObject(row, timestamp, allQualifierValues);
        }

        return t;
    }

    public InternalLog buildObject(byte[] row, long timestamp, Map<String, byte[]> allQualifierValues) {
        InternalLog alertDetail = new InternalLog();
        String myRow = EagleBase64Wrapper.encodeByteArray2URLSafeString(row);
        alertDetail.setEncodedRowkey(myRow);
        alertDetail.setPrefix(schema.getPrefix());
        alertDetail.setSearchTags(searchTags);
        alertDetail.setTimestamp(timestamp);

        Map<String, byte[]> logQualifierValues = new HashMap<String, byte[]>();
        Map<String, String> logTags = new HashMap<String, String>();
        for (Map.Entry<String, byte[]> entry : allQualifierValues.entrySet()) {
            if (schema.isTag(entry.getKey())) {
                if (entry.getValue() != null) {
                    logTags.put(entry.getKey(), new String(entry.getValue()));
                }
            } else {
                logQualifierValues.put(entry.getKey(), entry.getValue());
            }
        }
        alertDetail.setQualifierValues(logQualifierValues);
        alertDetail.setTags(logTags);
        return alertDetail;
    }
}