/*
 * 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.cassandra.db.compaction;

import java.util.*;


import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Joiner;
import com.google.common.collect.*;
import com.google.common.primitives.Doubles;

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

import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.config.Config;
import org.apache.cassandra.db.ColumnFamilyStore;
import org.apache.cassandra.db.lifecycle.LifecycleTransaction;
import org.apache.cassandra.db.rows.UnfilteredRowIterator;
import org.apache.cassandra.dht.Range;
import org.apache.cassandra.dht.Token;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.io.sstable.ISSTableScanner;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.node.JsonNodeFactory;
import org.codehaus.jackson.node.ObjectNode;

public class LeveledCompactionStrategy extends AbstractCompactionStrategy
{
    private static final Logger logger = LoggerFactory.getLogger(LeveledCompactionStrategy.class);
    private static final String SSTABLE_SIZE_OPTION = "sstable_size_in_mb";
    private static final boolean tolerateSstableSize = Boolean.getBoolean(Config.PROPERTY_PREFIX + "tolerate_sstable_size");
    private static final String LEVEL_FANOUT_SIZE_OPTION = "fanout_size";
    public static final int DEFAULT_LEVEL_FANOUT_SIZE = 10;

    @VisibleForTesting
    final LeveledManifest manifest;
    private final int maxSSTableSizeInMB;
    private final int levelFanoutSize;

    public LeveledCompactionStrategy(ColumnFamilyStore cfs, Map<String, String> options)
    {
        super(cfs, options);
        int configuredMaxSSTableSize = 160;
        int configuredLevelFanoutSize = DEFAULT_LEVEL_FANOUT_SIZE;
        SizeTieredCompactionStrategyOptions localOptions = new SizeTieredCompactionStrategyOptions(options);
        if (options != null)
        {
            if (options.containsKey(SSTABLE_SIZE_OPTION))
            {
                configuredMaxSSTableSize = Integer.parseInt(options.get(SSTABLE_SIZE_OPTION));
                if (!tolerateSstableSize)
                {
                    if (configuredMaxSSTableSize >= 1000)
                        logger.warn("Max sstable size of {}MB is configured for {}.{}; having a unit of compaction this large is probably a bad idea",
                                configuredMaxSSTableSize, cfs.name, cfs.getColumnFamilyName());
                    if (configuredMaxSSTableSize < 50)
                        logger.warn("Max sstable size of {}MB is configured for {}.{}.  Testing done for CASSANDRA-5727 indicates that performance improves up to 160MB",
                                configuredMaxSSTableSize, cfs.name, cfs.getColumnFamilyName());
                }
            }

            if (options.containsKey(LEVEL_FANOUT_SIZE_OPTION))
            {
                configuredLevelFanoutSize = Integer.parseInt(options.get(LEVEL_FANOUT_SIZE_OPTION));
            }
        }
        maxSSTableSizeInMB = configuredMaxSSTableSize;
        levelFanoutSize = configuredLevelFanoutSize;

        manifest = new LeveledManifest(cfs, this.maxSSTableSizeInMB, this.levelFanoutSize, localOptions);
        logger.trace("Created {}", manifest);
    }

    public int getLevelSize(int i)
    {
        return manifest.getLevelSize(i);
    }

    public int[] getAllLevelSize()
    {
        return manifest.getAllLevelSize();
    }

    @Override
    public void startup()
    {
        manifest.calculateLastCompactedKeys();
        super.startup();
    }

    
the only difference between background and maximal in LCS is that maximal is still allowed
(by explicit user request) even when compaction is disabled.
/**
     * the only difference between background and maximal in LCS is that maximal is still allowed
     * (by explicit user request) even when compaction is disabled.
     */
    @SuppressWarnings("resource") // transaction is closed by AbstractCompactionTask::execute
    public AbstractCompactionTask getNextBackgroundTask(int gcBefore)
    {
        Collection<SSTableReader> previousCandidate = null;
        while (true)
        {
            OperationType op;
            LeveledManifest.CompactionCandidate candidate = manifest.getCompactionCandidates();
            if (candidate == null)
            {
                // if there is no sstable to compact in standard way, try compacting based on droppable tombstone ratio
                SSTableReader sstable = findDroppableSSTable(gcBefore);
                if (sstable == null)
                {
                    logger.trace("No compaction necessary for {}", this);
                    return null;
                }
                candidate = new LeveledManifest.CompactionCandidate(Collections.singleton(sstable),
                                                                    sstable.getSSTableLevel(),
                                                                    getMaxSSTableBytes());
                op = OperationType.TOMBSTONE_COMPACTION;
            }
            else
            {
                op = OperationType.COMPACTION;
            }

            // Already tried acquiring references without success. It means there is a race with
            // the tracker but candidate SSTables were not yet replaced in the compaction strategy manager
            if (candidate.sstables.equals(previousCandidate))
            {
                logger.warn("Could not acquire references for compacting SSTables {} which is not a problem per se," +
                            "unless it happens frequently, in which case it must be reported. Will retry later.",
                            candidate.sstables);
                return null;
            }

            LifecycleTransaction txn = cfs.getTracker().tryModify(candidate.sstables, OperationType.COMPACTION);
            if (txn != null)
            {
                LeveledCompactionTask newTask = new LeveledCompactionTask(cfs, txn, candidate.level, gcBefore, candidate.maxSSTableBytes, false);
                newTask.setCompactionType(op);
                return newTask;
            }
            previousCandidate = candidate.sstables;
        }
    }

    @SuppressWarnings("resource") // transaction is closed by AbstractCompactionTask::execute
    public synchronized Collection<AbstractCompactionTask> getMaximalTask(int gcBefore, boolean splitOutput)
    {
        Iterable<SSTableReader> sstables = manifest.getAllSSTables();

        Iterable<SSTableReader> filteredSSTables = filterSuspectSSTables(sstables);
        if (Iterables.isEmpty(sstables))
            return null;
        LifecycleTransaction txn = cfs.getTracker().tryModify(filteredSSTables, OperationType.COMPACTION);
        if (txn == null)
            return null;
        return Arrays.<AbstractCompactionTask>asList(new LeveledCompactionTask(cfs, txn, 0, gcBefore, getMaxSSTableBytes(), true));

    }

    @Override
    @SuppressWarnings("resource") // transaction is closed by AbstractCompactionTask::execute
    public AbstractCompactionTask getUserDefinedTask(Collection<SSTableReader> sstables, int gcBefore)
    {

        if (sstables.isEmpty())
            return null;

        LifecycleTransaction transaction = cfs.getTracker().tryModify(sstables, OperationType.COMPACTION);
        if (transaction == null)
        {
            logger.trace("Unable to mark {} for compaction; probably a background compaction got to it first.  You can disable background compactions temporarily if this is a problem", sstables);
            return null;
        }
        int level = sstables.size() > 1 ? 0 : sstables.iterator().next().getSSTableLevel();
        return new LeveledCompactionTask(cfs, transaction, level, gcBefore, level == 0 ? Long.MAX_VALUE : getMaxSSTableBytes(), false);
    }

    @Override
    public AbstractCompactionTask getCompactionTask(LifecycleTransaction txn, int gcBefore, long maxSSTableBytes)
    {
        assert txn.originals().size() > 0;
        int level = -1;
        // if all sstables are in the same level, we can set that level:
        for (SSTableReader sstable : txn.originals())
        {
            if (level == -1)
                level = sstable.getSSTableLevel();
            if (level != sstable.getSSTableLevel())
                level = 0;
        }
        return new LeveledCompactionTask(cfs, txn, level, gcBefore, maxSSTableBytes, false);
    }

    
Leveled compaction strategy has guarantees on the data contained within each level so we
have to make sure we only create groups of SSTables with members from the same level.
This way we won't end up creating invalid sstables during anti-compaction.
Params:
ssTablesToGroup – 
Returns:
Groups of sstables from the same level/**
     * Leveled compaction strategy has guarantees on the data contained within each level so we
     * have to make sure we only create groups of SSTables with members from the same level.
     * This way we won't end up creating invalid sstables during anti-compaction.
     * @param ssTablesToGroup
     * @return Groups of sstables from the same level
     */
    @Override
    public Collection<Collection<SSTableReader>> groupSSTablesForAntiCompaction(Collection<SSTableReader> ssTablesToGroup)
    {
        int groupSize = 2;
        Map<Integer, Collection<SSTableReader>> sstablesByLevel = new HashMap<>();
        for (SSTableReader sstable : ssTablesToGroup)
        {
            Integer level = sstable.getSSTableLevel();
            Collection<SSTableReader> sstablesForLevel = sstablesByLevel.get(level);
            if (sstablesForLevel == null)
            {
                sstablesForLevel = new ArrayList<SSTableReader>();
                sstablesByLevel.put(level, sstablesForLevel);
            }
            sstablesForLevel.add(sstable);
        }

        Collection<Collection<SSTableReader>> groupedSSTables = new ArrayList<>();

        for (Collection<SSTableReader> levelOfSSTables : sstablesByLevel.values())
        {
            Collection<SSTableReader> currGroup = new ArrayList<>();
            for (SSTableReader sstable : levelOfSSTables)
            {
                currGroup.add(sstable);
                if (currGroup.size() == groupSize)
                {
                    groupedSSTables.add(currGroup);
                    currGroup = new ArrayList<>();
                }
            }

            if (currGroup.size() != 0)
                groupedSSTables.add(currGroup);
        }
        return groupedSSTables;

    }

    public int getEstimatedRemainingTasks()
    {
        int n = manifest.getEstimatedTasks();
        cfs.getCompactionStrategyManager().compactionLogger.pending(this, n);
        return n;
    }

    public long getMaxSSTableBytes()
    {
        return maxSSTableSizeInMB * 1024L * 1024L;
    }

    public int getLevelFanoutSize()
    {
        return levelFanoutSize;
    }

    public ScannerList getScanners(Collection<SSTableReader> sstables, Collection<Range<Token>> ranges)
    {
        Set<SSTableReader>[] sstablesPerLevel = manifest.getSStablesPerLevelSnapshot();

        Multimap<Integer, SSTableReader> byLevel = ArrayListMultimap.create();
        for (SSTableReader sstable : sstables)
        {
            int level = sstable.getSSTableLevel();
            // if an sstable is not on the manifest, it was recently added or removed
            // so we add it to level -1 and create exclusive scanners for it - see below (#9935)
            if (level >= sstablesPerLevel.length || !sstablesPerLevel[level].contains(sstable))
            {
                logger.warn("Live sstable {} from level {} is not on corresponding level in the leveled manifest." +
                            " This is not a problem per se, but may indicate an orphaned sstable due to a failed" +
                            " compaction not cleaned up properly.",
                             sstable.getFilename(), level);
                level = -1;
            }
            byLevel.get(level).add(sstable);
        }

        List<ISSTableScanner> scanners = new ArrayList<ISSTableScanner>(sstables.size());
        try
        {
            for (Integer level : byLevel.keySet())
            {
                // level can be -1 when sstables are added to Tracker but not to LeveledManifest
                // since we don't know which level those sstable belong yet, we simply do the same as L0 sstables.
                if (level <= 0)
                {
                    // L0 makes no guarantees about overlapping-ness.  Just create a direct scanner for each
                    for (SSTableReader sstable : byLevel.get(level))
                        scanners.add(sstable.getScanner(ranges, null));
                }
                else
                {
                    // Create a LeveledScanner that only opens one sstable at a time, in sorted order
                    Collection<SSTableReader> intersecting = LeveledScanner.intersecting(byLevel.get(level), ranges);
                    if (!intersecting.isEmpty())
                    {
                        @SuppressWarnings("resource") // The ScannerList will be in charge of closing (and we close properly on errors)
                        ISSTableScanner scanner = new LeveledScanner(intersecting, ranges);
                        scanners.add(scanner);
                    }
                }
            }
        }
        catch (Throwable t)
        {
            try
            {
                new ScannerList(scanners).close();
            }
            catch (Throwable t2)
            {
                t.addSuppressed(t2);
            }
            throw t;
        }

        return new ScannerList(scanners);
    }

    @Override
    public void replaceSSTables(Collection<SSTableReader> removed, Collection<SSTableReader> added)
    {
        manifest.replace(removed, added);
    }

    @Override
    public void addSSTable(SSTableReader added)
    {
        manifest.add(added);
    }

    @Override
    public void removeSSTable(SSTableReader sstable)
    {
        manifest.remove(sstable);
    }

    // Lazily creates SSTableBoundedScanner for sstable that are assumed to be from the
    // same level (e.g. non overlapping) - see #4142
    private static class LeveledScanner extends AbstractIterator<UnfilteredRowIterator> implements ISSTableScanner
    {
        private final Collection<Range<Token>> ranges;
        private final List<SSTableReader> sstables;
        private final Iterator<SSTableReader> sstableIterator;
        private final long totalLength;
        private final long compressedLength;

        private ISSTableScanner currentScanner;
        private long positionOffset;
        private long totalBytesScanned = 0;

        public LeveledScanner(Collection<SSTableReader> sstables, Collection<Range<Token>> ranges)
        {
            this.ranges = ranges;

            // add only sstables that intersect our range, and estimate how much data that involves
            this.sstables = new ArrayList<>(sstables.size());
            long length = 0;
            long cLength = 0;
            for (SSTableReader sstable : sstables)
            {
                this.sstables.add(sstable);
                long estimatedKeys = sstable.estimatedKeys();
                double estKeysInRangeRatio = 1.0;

                if (estimatedKeys > 0 && ranges != null)
                    estKeysInRangeRatio = ((double) sstable.estimatedKeysForRanges(ranges)) / estimatedKeys;

                length += sstable.uncompressedLength() * estKeysInRangeRatio;
                cLength += sstable.onDiskLength() * estKeysInRangeRatio;
            }

            totalLength = length;
            compressedLength = cLength;
            Collections.sort(this.sstables, SSTableReader.sstableComparator);
            sstableIterator = this.sstables.iterator();
            assert sstableIterator.hasNext(); // caller should check intersecting first
            SSTableReader currentSSTable = sstableIterator.next();
            currentScanner = currentSSTable.getScanner(ranges, null);

        }

        public static Collection<SSTableReader> intersecting(Collection<SSTableReader> sstables, Collection<Range<Token>> ranges)
        {
            if (ranges == null)
                return Lists.newArrayList(sstables);

            Set<SSTableReader> filtered = new HashSet<>();
            for (Range<Token> range : ranges)
            {
                for (SSTableReader sstable : sstables)
                {
                    Range<Token> sstableRange = new Range<>(sstable.first.getToken(), sstable.last.getToken());
                    if (range == null || sstableRange.intersects(range))
                        filtered.add(sstable);
                }
            }
            return filtered;
        }


        public boolean isForThrift()
        {
            return false;
        }

        public CFMetaData metadata()
        {
            return sstables.get(0).metadata; // The ctor checks we have at least one sstable
        }

        protected UnfilteredRowIterator computeNext()
        {
            if (currentScanner == null)
                return endOfData();

            while (true)
            {
                if (currentScanner.hasNext())
                    return currentScanner.next();

                positionOffset += currentScanner.getLengthInBytes();
                totalBytesScanned += currentScanner.getBytesScanned();

                currentScanner.close();
                if (!sstableIterator.hasNext())
                {
                    // reset to null so getCurrentPosition does not return wrong value
                    currentScanner = null;
                    return endOfData();
                }
                SSTableReader currentSSTable = sstableIterator.next();
                currentScanner = currentSSTable.getScanner(ranges, null);
            }
        }

        public void close()
        {
            if (currentScanner != null)
                currentScanner.close();
        }

        public long getLengthInBytes()
        {
            return totalLength;
        }

        public long getCurrentPosition()
        {
            return positionOffset + (currentScanner == null ? 0L : currentScanner.getCurrentPosition());
        }

        public long getCompressedLengthInBytes()
        {
            return compressedLength;
        }

        public long getBytesScanned()
        {
            return currentScanner == null ? totalBytesScanned : totalBytesScanned + currentScanner.getBytesScanned();
        }

        public String getBackingFiles()
        {
            return Joiner.on(", ").join(sstables);
        }
    }

    @Override
    public String toString()
    {
        return String.format("LCS@%d(%s)", hashCode(), cfs.name);
    }

    private SSTableReader findDroppableSSTable(final int gcBefore)
    {
        level:
        for (int i = manifest.getLevelCount(); i >= 0; i--)
        {
            // sort sstables by droppable ratio in descending order
            SortedSet<SSTableReader> sstables = manifest.getLevelSorted(i, new Comparator<SSTableReader>()
            {
                public int compare(SSTableReader o1, SSTableReader o2)
                {
                    double r1 = o1.getEstimatedDroppableTombstoneRatio(gcBefore);
                    double r2 = o2.getEstimatedDroppableTombstoneRatio(gcBefore);
                    return -1 * Doubles.compare(r1, r2);
                }
            });
            if (sstables.isEmpty())
                continue;

            Set<SSTableReader> compacting = cfs.getTracker().getCompacting();
            for (SSTableReader sstable : sstables)
            {
                if (sstable.getEstimatedDroppableTombstoneRatio(gcBefore) <= tombstoneThreshold)
                    continue level;
                else if (!compacting.contains(sstable) && !sstable.isMarkedSuspect() && worthDroppingTombstones(sstable, gcBefore))
                    return sstable;
            }
        }
        return null;
    }

    public CompactionLogger.Strategy strategyLogger()
    {
        return new CompactionLogger.Strategy()
        {
            public JsonNode sstable(SSTableReader sstable)
            {
                ObjectNode node = JsonNodeFactory.instance.objectNode();
                node.put("level", sstable.getSSTableLevel());
                node.put("min_token", sstable.first.getToken().toString());
                node.put("max_token", sstable.last.getToken().toString());
                return node;
            }

            public JsonNode options()
            {
                return null;
            }
        };
    }

    public static Map<String, String> validateOptions(Map<String, String> options) throws ConfigurationException
    {
        Map<String, String> uncheckedOptions = AbstractCompactionStrategy.validateOptions(options);

        String size = options.containsKey(SSTABLE_SIZE_OPTION) ? options.get(SSTABLE_SIZE_OPTION) : "1";
        try
        {
            int ssSize = Integer.parseInt(size);
            if (ssSize < 1)
            {
                throw new ConfigurationException(String.format("%s must be larger than 0, but was %s", SSTABLE_SIZE_OPTION, ssSize));
            }
        }
        catch (NumberFormatException ex)
        {
            throw new ConfigurationException(String.format("%s is not a parsable int (base10) for %s", size, SSTABLE_SIZE_OPTION), ex);
        }

        uncheckedOptions.remove(SSTABLE_SIZE_OPTION);

        // Validate the fanout_size option
        String levelFanoutSize = options.containsKey(LEVEL_FANOUT_SIZE_OPTION) ? options.get(LEVEL_FANOUT_SIZE_OPTION) : String.valueOf(DEFAULT_LEVEL_FANOUT_SIZE);
        try
        {
            int fanoutSize = Integer.parseInt(levelFanoutSize);
            if (fanoutSize < 1)
            {
                throw new ConfigurationException(String.format("%s must be larger than 0, but was %s", LEVEL_FANOUT_SIZE_OPTION, fanoutSize));
            }
        }
        catch (NumberFormatException ex)
        {
            throw new ConfigurationException(String.format("%s is not a parsable int (base10) for %s", size, LEVEL_FANOUT_SIZE_OPTION), ex);
        }

        uncheckedOptions.remove(LEVEL_FANOUT_SIZE_OPTION);

        uncheckedOptions = SizeTieredCompactionStrategyOptions.validateOptions(options, uncheckedOptions);

        return uncheckedOptions;
    }
}