/*
 * 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.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.TimeUnit;

import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;

import org.apache.cassandra.db.Directories;
import org.apache.cassandra.db.compaction.writers.CompactionAwareWriter;
import org.apache.cassandra.db.compaction.writers.DefaultCompactionWriter;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.ColumnFamilyStore;
import org.apache.cassandra.db.SystemKeyspace;
import org.apache.cassandra.db.compaction.CompactionManager.CompactionExecutorStatsCollector;
import org.apache.cassandra.db.lifecycle.LifecycleTransaction;
import org.apache.cassandra.service.ActiveRepairService;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.concurrent.Refs;

public class CompactionTask extends AbstractCompactionTask
{
    protected static final Logger logger = LoggerFactory.getLogger(CompactionTask.class);
    protected final int gcBefore;
    protected final boolean offline;
    protected final boolean keepOriginals;
    protected static long totalBytesCompacted = 0;
    private CompactionExecutorStatsCollector collector;

    public CompactionTask(ColumnFamilyStore cfs, LifecycleTransaction txn, int gcBefore)
    {
        this(cfs, txn, gcBefore, false, false);
    }

    public CompactionTask(ColumnFamilyStore cfs, LifecycleTransaction txn, int gcBefore, boolean offline, boolean keepOriginals)
    {
        super(cfs, txn);
        this.gcBefore = gcBefore;
        this.offline = offline;
        this.keepOriginals = keepOriginals;
    }

    public static synchronized long addToTotalBytesCompacted(long bytesCompacted)
    {
        return totalBytesCompacted += bytesCompacted;
    }

    protected int executeInternal(CompactionExecutorStatsCollector collector)
    {
        this.collector = collector;
        run();
        return transaction.originals().size();
    }

    public boolean reduceScopeForLimitedSpace()
    {
        if (partialCompactionsAcceptable() && transaction.originals().size() > 1)
        {
            // Try again w/o the largest one.
            logger.warn("insufficient space to compact all requested files {}", StringUtils.join(transaction.originals(), ", "));
            // Note that we have removed files that are still marked as compacting.
            // This suboptimal but ok since the caller will unmark all the sstables at the end.
            SSTableReader removedSSTable = cfs.getMaxSizeFile(transaction.originals());
            transaction.cancel(removedSSTable);
            return true;
        }
        return false;
    }

    /**
     * For internal use and testing only.  The rest of the system should go through the submit* methods,
     * which are properly serialized.
     * Caller is in charge of marking/unmarking the sstables as compacting.
     */
    protected void runMayThrow() throws Exception
    {
        // The collection of sstables passed may be empty (but not null); even if
        // it is not empty, it may compact down to nothing if all rows are deleted.
        assert transaction != null;

        if (transaction.originals().isEmpty())
            return;

        // Note that the current compaction strategy, is not necessarily the one this task was created under.
        // This should be harmless; see comments to CFS.maybeReloadCompactionStrategy.
        CompactionStrategyManager strategy = cfs.getCompactionStrategyManager();

        if (DatabaseDescriptor.isSnapshotBeforeCompaction())
            cfs.snapshotWithoutFlush(System.currentTimeMillis() + "-compact-" + cfs.name);

        // note that we need to do a rough estimate early if we can fit the compaction on disk - this is pessimistic, but
        // since we might remove sstables from the compaction in checkAvailableDiskSpace it needs to be done here
        long expectedWriteSize = cfs.getExpectedCompactedFileSize(transaction.originals(), compactionType);
        long earlySSTableEstimate = Math.max(1, expectedWriteSize / strategy.getMaxSSTableBytes());
        checkAvailableDiskSpace(earlySSTableEstimate, expectedWriteSize);

        // sanity check: all sstables must belong to the same cfs
        assert !Iterables.any(transaction.originals(), new Predicate<SSTableReader>()
        {
            @Override
            public boolean apply(SSTableReader sstable)
            {
                return !sstable.descriptor.cfname.equals(cfs.name);
            }
        });

        UUID taskId = transaction.opId();

        // new sstables from flush can be added during a compaction, but only the compaction can remove them,
        // so in our single-threaded compaction world this is a valid way of determining if we're compacting
        // all the sstables (that existed when we started)
        StringBuilder ssTableLoggerMsg = new StringBuilder("[");
        for (SSTableReader sstr : transaction.originals())
        {
            ssTableLoggerMsg.append(String.format("%s:level=%d, ", sstr.getFilename(), sstr.getSSTableLevel()));
        }
        ssTableLoggerMsg.append("]");

        logger.debug("Compacting ({}) {}", taskId, ssTableLoggerMsg);

        long start = System.nanoTime();
        long totalKeysWritten = 0;
        long estimatedKeys = 0;
        try (CompactionController controller = getCompactionController(transaction.originals()))
        {
            Set<SSTableReader> actuallyCompact = Sets.difference(transaction.originals(), controller.getFullyExpiredSSTables());

            Collection<SSTableReader> newSStables;

            long[] mergedRowCounts;

            // SSTableScanners need to be closed before markCompactedSSTablesReplaced call as scanners contain references
            // to both ifile and dfile and SSTR will throw deletion errors on Windows if it tries to delete before scanner is closed.
            // See CASSANDRA-8019 and CASSANDRA-8399
            int nowInSec = FBUtilities.nowInSeconds();
            try (Refs<SSTableReader> refs = Refs.ref(actuallyCompact);
                 AbstractCompactionStrategy.ScannerList scanners = strategy.getScanners(actuallyCompact);
                 CompactionIterator ci = new CompactionIterator(compactionType, scanners.scanners, controller, nowInSec, taskId))
            {
                if (collector != null)
                    collector.beginCompaction(ci);
                long lastCheckObsoletion = start;

                if (!controller.cfs.getCompactionStrategyManager().isActive)
                    throw new CompactionInterruptedException(ci.getCompactionInfo());

                try (CompactionAwareWriter writer = getCompactionAwareWriter(cfs, getDirectories(), transaction, actuallyCompact))
                {
                    estimatedKeys = writer.estimatedKeys();
                    while (ci.hasNext())
                    {
                        if (ci.isStopRequested())
                            throw new CompactionInterruptedException(ci.getCompactionInfo());

                        if (writer.append(ci.next()))
                            totalKeysWritten++;

                        if (System.nanoTime() - lastCheckObsoletion > TimeUnit.MINUTES.toNanos(1L))
                        {
                            controller.maybeRefreshOverlaps();
                            lastCheckObsoletion = System.nanoTime();
                        }
                    }

                    // point of no return
                    newSStables = writer.finish();
                }
                finally
                {
                    if (collector != null)
                        collector.finishCompaction(ci);

                    mergedRowCounts = ci.getMergedRowCounts();
                }
            }

            // log a bunch of statistics about the result and save to system table compaction_history
            long dTime = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start);
            long startsize = SSTableReader.getTotalBytes(transaction.originals());
            long endsize = SSTableReader.getTotalBytes(newSStables);
            double ratio = (double) endsize / (double) startsize;

            StringBuilder newSSTableNames = new StringBuilder();
            for (SSTableReader reader : newSStables)
                newSSTableNames.append(reader.descriptor.baseFilename()).append(",");

            double mbps = dTime > 0 ? (double) endsize / (1024 * 1024) / ((double) dTime / 1000) : 0;
            long totalSourceRows = 0;
            String mergeSummary = updateCompactionHistory(cfs.keyspace.getName(), cfs.getColumnFamilyName(), mergedRowCounts, startsize, endsize);
            logger.debug(String.format("Compacted (%s) %d sstables to [%s] to level=%d.  %,d bytes to %,d (~%d%% of original) in %,dms = %fMB/s.  %,d total partitions merged to %,d.  Partition merge counts were {%s}",
                                      taskId, transaction.originals().size(), newSSTableNames.toString(), getLevel(), startsize, endsize, (int) (ratio * 100), dTime, mbps, totalSourceRows, totalKeysWritten, mergeSummary));
            logger.trace(String.format("CF Total Bytes Compacted: %,d", CompactionTask.addToTotalBytesCompacted(endsize)));
            logger.trace("Actual #keys: {}, Estimated #keys:{}, Err%: {}", totalKeysWritten, estimatedKeys, ((double)(totalKeysWritten - estimatedKeys)/totalKeysWritten));

            if (offline)
                Refs.release(Refs.selfRefs(newSStables));
        }
    }

    @Override
    public CompactionAwareWriter getCompactionAwareWriter(ColumnFamilyStore cfs,
                                                          Directories directories,
                                                          LifecycleTransaction transaction,
                                                          Set<SSTableReader> nonExpiredSSTables)
    {
        return new DefaultCompactionWriter(cfs, directories, transaction, nonExpiredSSTables, offline, keepOriginals);
    }

    public static String updateCompactionHistory(String keyspaceName, String columnFamilyName, long[] mergedRowCounts, long startSize, long endSize)
    {
        StringBuilder mergeSummary = new StringBuilder(mergedRowCounts.length * 10);
        Map<Integer, Long> mergedRows = new HashMap<>();
        for (int i = 0; i < mergedRowCounts.length; i++)
        {
            long count = mergedRowCounts[i];
            if (count == 0)
                continue;

            int rows = i + 1;
            mergeSummary.append(String.format("%d:%d, ", rows, count));
            mergedRows.put(rows, count);
        }
        SystemKeyspace.updateCompactionHistory(keyspaceName, columnFamilyName, System.currentTimeMillis(), startSize, endSize, mergedRows);
        return mergeSummary.toString();
    }

    protected Directories getDirectories()
    {
        return cfs.getDirectories();
    }

    public static long getMinRepairedAt(Set<SSTableReader> actuallyCompact)
    {
        long minRepairedAt= Long.MAX_VALUE;
        for (SSTableReader sstable : actuallyCompact)
            minRepairedAt = Math.min(minRepairedAt, sstable.getSSTableMetadata().repairedAt);
        if (minRepairedAt == Long.MAX_VALUE)
            return ActiveRepairService.UNREPAIRED_SSTABLE;
        return minRepairedAt;
    }

    protected void checkAvailableDiskSpace(long estimatedSSTables, long expectedWriteSize)
    {
        if(!cfs.isCompactionDiskSpaceCheckEnabled() && compactionType == OperationType.COMPACTION)
        {
            logger.info("Compaction space check is disabled");
            return;
        }

        while (!getDirectories().hasAvailableDiskSpace(estimatedSSTables, expectedWriteSize))
        {
            if (!reduceScopeForLimitedSpace())
                throw new RuntimeException(String.format("Not enough space for compaction, estimated sstables = %d, expected write size = %d", estimatedSSTables, expectedWriteSize));
        }
    }

    protected int getLevel()
    {
        return 0;
    }

    protected CompactionController getCompactionController(Set<SSTableReader> toCompact)
    {
        return new CompactionController(cfs, toCompact, gcBefore);
    }

    protected boolean partialCompactionsAcceptable()
    {
        return !isUserDefined;
    }

    public static long getMaxDataAge(Collection<SSTableReader> sstables)
    {
        long max = 0;
        for (SSTableReader sstable : sstables)
        {
            if (sstable.maxDataAge > max)
                max = sstable.maxDataAge;
        }
        return max;
    }
}