package com.cerner.kepler.filters;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;

import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.filter.FilterBase;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.Pair;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class RowRangeFilter extends FilterBase {

    /**
     * Logger
     */
    private static final Logger LOG = LoggerFactory.getLogger(RowRangeFilter.class);

    /**
     * Boolean to indicate if we have loaded our scan into the first range
     */
    private boolean loaded = false;

    /**
     * Boolean to indicate if we should abort the scan (true=abort)
     */
    private boolean filterAllRemaining = false;

    /**
     * An object which determines what our filter does
     */
    private ReturnCode returnCode;

    /**
     * The current byte[] pair that represents our row key range we are in
     */
    private Pair<byte[], byte[]> currentRange;

    /**
     * A sorted iterator contained our row key ranges
     */
    private Iterator<Pair<byte[], byte[]>> rowKeyIterator;

    private int iteratorCount;
    
    /**
     * Constructor used by HBase. DO NOT USE!
     */
    public RowRangeFilter() {
        super();
        LOG.debug("Creating new filter server side");
    }

    /**
     * Constructs the filter from a set of row key ranges represented by {@link Pair}s of byte[]'s.
     * 
     * @param ranges
     *            the set of row key ranges we want to filter on
     * @throws IllegalArgumentException
     *             if ranges is null or empty, or if any range's starting value is < then its end, or if any range overlaps with
     *             another range
     */
    public RowRangeFilter(Set<Pair<byte[], byte[]>> ranges) {

        if (ranges == null)
            throw new IllegalArgumentException("ranges cannot be null");
        if (ranges.isEmpty())
            throw new IllegalArgumentException("ranges must contain at least 1 pair");

        // By moving our data to a TreeSet we sort our data into the correct order before handing it off to hbase-server
        TreeSet<Pair<byte[], byte[]>> treeSet = new TreeSet<Pair<byte[], byte[]>>(
                new FirstValuePairByteComparator());

        // TODO: Do we combine or throw exception or even ignore?

        Iterator<Pair<byte[], byte[]>> iterator = ranges.iterator();
        while (iterator.hasNext()) {
            Pair<byte[], byte[]> range = iterator.next();

            // Verify that each range is valid (i.e. start <= end)
            if (Bytes.compareTo(range.getFirst(), range.getSecond()) > 0)
                throw new IllegalArgumentException(
                        "The following range is invalid since its starting value is less then its end : "
                                + bytePairToString(range));

            // Verify that this new range does not overlap any existing ranges
            for (Pair<byte[], byte[]> addedRange : treeSet) {
                // Verify that range's start point is not contained in addedRange
                if (Bytes.compareTo(range.getFirst(), addedRange.getFirst()) >= 0
                        && Bytes.compareTo(range.getFirst(), addedRange.getSecond()) < 0)
                    throw new IllegalArgumentException("The range : " + bytePairToString(range)
                            + " overlaps an existing range : " + treeSet.remove(range));

                // Verify that range's end point is not contained in addedRange
                if (Bytes.compareTo(range.getSecond(), addedRange.getFirst()) > 0
                        && Bytes.compareTo(range.getSecond(), addedRange.getSecond()) <= 0)
                    throw new IllegalArgumentException("The range : " + bytePairToString(range)
                            + " overlaps an existing range : " + bytePairToString(addedRange));
            }

            treeSet.add(range);
        }
        rowKeyIterator = treeSet.iterator();
        iteratorCount = treeSet.size();
    }

    @Override
    public ReturnCode filterKeyValue(KeyValue ignored) {
        return returnCode;
    }

    @Override
    public boolean filterAllRemaining() {
        return filterAllRemaining;
    }

    @Override
    public KeyValue getNextKeyHint(KeyValue kv) {
        return KeyValue.createFirstOnRow(currentRange.getFirst());
    }

    @Override
    public boolean filterRowKey(byte[] buffer, int offset, int length) {

        byte[] rowKey = Arrays.copyOfRange(buffer, offset, offset + length);

        // If this is the first time filtering seek to the appropriate range
        if (!loaded) {
            LOG.debug("Loading currentRange");
            while (rowKeyIterator.hasNext()) {
                currentRange = rowKeyIterator.next();
                if (Bytes.compareTo(rowKey, currentRange.getSecond()) < 0) {
                    break;
                }
            }

            loaded = true;

            if (Bytes.compareTo(rowKey, currentRange.getFirst()) < 0) {
                if (LOG.isDebugEnabled())
                    LOG.debug(
                            "Current rowKey: {} is not in first range : {}, seeking to start of range",
                            Bytes.toStringBinary(rowKey), bytePairToString(currentRange));
                returnCode = ReturnCode.SEEK_NEXT_USING_HINT;
                return true;
            }
        }

        // Verify that the rowKey is still within our range
        if (Bytes.compareTo(rowKey, currentRange.getSecond()) < 0) {
            if (LOG.isDebugEnabled())
                LOG.debug("Current rowKey : {} is contained within range : {}",
                        Bytes.toStringBinary(rowKey), bytePairToString(currentRange));
            returnCode = ReturnCode.INCLUDE;
            return false;
        }

        if (rowKeyIterator.hasNext()) {
            if (LOG.isDebugEnabled())
                LOG.debug(
                        "Current rowKey : {} is not contained by range : {}, seeking to next range",
                        Bytes.toStringBinary(rowKey), bytePairToString(currentRange));
            // Seek to the next range
            currentRange = rowKeyIterator.next();
            returnCode = ReturnCode.SEEK_NEXT_USING_HINT;
            return true;
        }

        if (LOG.isDebugEnabled())
            LOG.debug("Current rowKey : {} is not contained within any ranges, aborting scan",
                    Bytes.toStringBinary(rowKey));

        // We don't have another range to seek to so abort the scan
        filterAllRemaining = true;
        // Not sure if I have to set this here
        returnCode = ReturnCode.NEXT_ROW;
        return true;
    }

    public void write(DataOutput out) throws IOException {
        LOG.debug("Writing out filter data");
        out.writeInt(iteratorCount);
        LOG.debug("iteratorCount : {}", iteratorCount);
        while (rowKeyIterator.hasNext()) {
            LOG.debug("Writing range");
            Pair<byte[], byte[]> range = rowKeyIterator.next();
            Bytes.writeByteArray(out, range.getFirst());
            Bytes.writeByteArray(out, range.getSecond());
        }
    }

    public void readFields(DataInput in) throws IOException {
        TreeSet<Pair<byte[], byte[]>> ranges = new TreeSet<Pair<byte[], byte[]>>(
                new FirstValuePairByteComparator());

        LOG.debug("Reading fields");
        
        // Load ranges into treeset so we can create a sorted iterator
        int totalRanges = in.readInt();
        
        LOG.debug("Read ranges {}", totalRanges);
        
        for(int i=0; i<totalRanges; i++){
            LOG.debug("Reading range #{}", i+1);
            byte[] first = Bytes.readByteArray(in);
            LOG.debug("Read first range with length {}", first.length);
            byte[] second = Bytes.readByteArray(in);
            LOG.debug("Read second range with length {}", second.length);

            Pair<byte[], byte[]> range = Pair.newPair(first, second);
            
            LOG.debug("Read in range {}", bytePairToString(range));
            
            ranges.add(range);
        }
    
        rowKeyIterator = ranges.iterator();
        
        if (LOG.isDebugEnabled())
            LOG.debug("Finished reading fields. Loaded : {} ranges", ranges.size());
    }

    private static class FirstValuePairByteComparator implements Comparator<Pair<byte[], byte[]>>, Serializable {
        /**
         * Generated serial version
         */
        private static final long serialVersionUID = 8426766119633439881L;

        public int compare(Pair<byte[], byte[]> pair1, Pair<byte[], byte[]> pair2) {
            return Bytes.compareTo(pair1.getFirst(), pair2.getFirst());
        }
    }

    /**
     * Simple function used in logging/exceptions to write out a range as a string
     * 
     * @param pair
     *            the row key range
     * @return the string representing the row key range
     */
    private static String bytePairToString(Pair<byte[], byte[]> pair) {
        StringBuilder builder = new StringBuilder();
        builder.append("[");
        builder.append(Bytes.toStringBinary(pair.getFirst()));
        builder.append(", ");
        builder.append(Bytes.toStringBinary(pair.getSecond()));
        builder.append("]");
        return builder.toString();
    }
}