/*
 * 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;

import java.io.File;
import java.io.FileFilter;
import java.io.IOError;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.*;
import java.util.concurrent.ThreadLocalRandom;
import java.util.function.BiFunction;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Iterables;

import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.config.*;
import org.apache.cassandra.db.lifecycle.LifecycleTransaction;
import org.apache.cassandra.io.FSDiskFullWriteError;
import org.apache.cassandra.io.FSError;
import org.apache.cassandra.io.FSWriteError;
import org.apache.cassandra.io.util.FileUtils;
import org.apache.cassandra.io.sstable.*;
import org.apache.cassandra.utils.DirectorySizeCalculator;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.Pair;

Encapsulate handling of paths to the data files.
 
  /<path_to_data_dir>/ks/<cf dir>/ks-cf1-jb-1-Data.db
                        /<cf dir>/la-2-Data.db
                        /<cf dir>/.<index name>/ks-cf1.idx-jb-1-Data.db
                        /<cf dir>/.<index name>/la-1-Data.db
                        ...
 
 Until v2.0, <cf dir> is just column family name. Since v2.1, <cf dir> has column family ID(cfId) added to its end. SSTables from secondary indexes were put in the same directory as their parent. Since v2.2, they have their own directory under the parent directory whose name is index name. Upon startup, those secondary index files are moved to new directory when upgrading. For backward compatibility, Directories can use directory without cfId if exists. In addition, more that one 'root' data directory can be specified so that <path_to_data_dir> potentially represents multiple locations. Note that in the case of multiple locations, the manifest for the leveled compaction is only in one of the location. Snapshots (resp. backups) are always created along the sstables there are snapshotted (resp. backuped) but inside a subdirectory named 'snapshots' (resp. backups) (and snapshots are further inside a subdirectory of the name of the snapshot). For secondary indexes, snapshots (backups) are not created in their own directory, but are in their parent's snapshot (backup) directory. This class abstracts all those details from the rest of the code. /**
 * Encapsulate handling of paths to the data files.
 *
 * <pre> {@code
 *   /<path_to_data_dir>/ks/<cf dir>/ks-cf1-jb-1-Data.db
 *                         /<cf dir>/la-2-Data.db
 *                         /<cf dir>/.<index name>/ks-cf1.idx-jb-1-Data.db
 *                         /<cf dir>/.<index name>/la-1-Data.db
 *                         ...
 * } </pre>
 *
 * Until v2.0, {@code <cf dir>} is just column family name.
 * Since v2.1, {@code <cf dir>} has column family ID(cfId) added to its end.
 *
 * SSTables from secondary indexes were put in the same directory as their parent.
 * Since v2.2, they have their own directory under the parent directory whose name is index name.
 * Upon startup, those secondary index files are moved to new directory when upgrading.
 *
 * For backward compatibility, Directories can use directory without cfId if exists.
 *
 * In addition, more that one 'root' data directory can be specified so that
 * {@code <path_to_data_dir>} potentially represents multiple locations.
 * Note that in the case of multiple locations, the manifest for the leveled
 * compaction is only in one of the location.
 *
 * Snapshots (resp. backups) are always created along the sstables there are
 * snapshotted (resp. backuped) but inside a subdirectory named 'snapshots'
 * (resp. backups) (and snapshots are further inside a subdirectory of the name
 * of the snapshot). For secondary indexes, snapshots (backups) are not created in
 * their own directory, but are in their parent's snapshot (backup) directory.
 *
 * This class abstracts all those details from the rest of the code.
 */
public class Directories
{
    private static final Logger logger = LoggerFactory.getLogger(Directories.class);

    public static final String BACKUPS_SUBDIR = "backups";
    public static final String SNAPSHOT_SUBDIR = "snapshots";
    public static final String TMP_SUBDIR = "tmp";
    public static final String SECONDARY_INDEX_NAME_SEPARATOR = ".";

    public static final DataDirectory[] dataDirectories;

    static
    {
        String[] locations = DatabaseDescriptor.getAllDataFileLocations();
        dataDirectories = new DataDirectory[locations.length];
        for (int i = 0; i < locations.length; ++i)
            dataDirectories[i] = new DataDirectory(new File(locations[i]));
    }

    
Checks whether Cassandra has RWX permissions to the specified directory.  Logs an error with
the details if it does not.
Params:
dir – File object of the directory.
dataDir – String representation of the directory's location
Returns:
status representing Cassandra's RWX permissions to the supplied folder location./**
     * Checks whether Cassandra has RWX permissions to the specified directory.  Logs an error with
     * the details if it does not.
     *
     * @param dir File object of the directory.
     * @param dataDir String representation of the directory's location
     * @return status representing Cassandra's RWX permissions to the supplied folder location.
     */
    public static boolean verifyFullPermissions(File dir, String dataDir)
    {
        if (!dir.isDirectory())
        {
            logger.error("Not a directory {}", dataDir);
            return false;
        }
        else if (!FileAction.hasPrivilege(dir, FileAction.X))
        {
            logger.error("Doesn't have execute permissions for {} directory", dataDir);
            return false;
        }
        else if (!FileAction.hasPrivilege(dir, FileAction.R))
        {
            logger.error("Doesn't have read permissions for {} directory", dataDir);
            return false;
        }
        else if (dir.exists() && !FileAction.hasPrivilege(dir, FileAction.W))
        {
            logger.error("Doesn't have write permissions for {} directory", dataDir);
            return false;
        }

        return true;
    }

    public enum FileAction
    {
        X, W, XW, R, XR, RW, XRW;

        FileAction()
        {
        }

        public static boolean hasPrivilege(File file, FileAction action)
        {
            boolean privilege = false;

            switch (action)
            {
                case X:
                    privilege = file.canExecute();
                    break;
                case W:
                    privilege = file.canWrite();
                    break;
                case XW:
                    privilege = file.canExecute() && file.canWrite();
                    break;
                case R:
                    privilege = file.canRead();
                    break;
                case XR:
                    privilege = file.canExecute() && file.canRead();
                    break;
                case RW:
                    privilege = file.canRead() && file.canWrite();
                    break;
                case XRW:
                    privilege = file.canExecute() && file.canRead() && file.canWrite();
                    break;
            }
            return privilege;
        }
    }

    private final CFMetaData metadata;
    private final DataDirectory[] paths;
    private final File[] dataPaths;

    public Directories(final CFMetaData metadata)
    {
        this(metadata, dataDirectories);
    }

    public Directories(final CFMetaData metadata, Collection<DataDirectory> paths)
    {
        this(metadata, paths.toArray(new DataDirectory[paths.size()]));
    }

    
Create Directories of given ColumnFamily.
SSTable directories are created under data_directories defined in cassandra.yaml if not exist at this time.
Params:
metadata – metadata of ColumnFamily/**
     * Create Directories of given ColumnFamily.
     * SSTable directories are created under data_directories defined in cassandra.yaml if not exist at this time.
     *
     * @param metadata metadata of ColumnFamily
     */
    public Directories(final CFMetaData metadata, DataDirectory[] paths)
    {
        this.metadata = metadata;
        this.paths = paths;

        String cfId = ByteBufferUtil.bytesToHex(ByteBufferUtil.bytes(metadata.cfId));
        int idx = metadata.cfName.indexOf(SECONDARY_INDEX_NAME_SEPARATOR);
        String cfName = idx >= 0 ? metadata.cfName.substring(0, idx) : metadata.cfName;
        String indexNameWithDot = idx >= 0 ? metadata.cfName.substring(idx) : null;

        this.dataPaths = new File[paths.length];
        // If upgraded from version less than 2.1, use existing directories
        String oldSSTableRelativePath = join(metadata.ksName, cfName);
        for (int i = 0; i < paths.length; ++i)
        {
            // check if old SSTable directory exists
            dataPaths[i] = new File(paths[i].location, oldSSTableRelativePath);
        }
        boolean olderDirectoryExists = Iterables.any(Arrays.asList(dataPaths), new Predicate<File>()
        {
            public boolean apply(File file)
            {
                return file.exists();
            }
        });
        if (!olderDirectoryExists)
        {
            // use 2.1+ style
            String newSSTableRelativePath = join(metadata.ksName, cfName + '-' + cfId);
            for (int i = 0; i < paths.length; ++i)
                dataPaths[i] = new File(paths[i].location, newSSTableRelativePath);
        }
        // if index, then move to its own directory
        if (indexNameWithDot != null)
        {
            for (int i = 0; i < paths.length; ++i)
                dataPaths[i] = new File(dataPaths[i], indexNameWithDot);
        }

        for (File dir : dataPaths)
        {
            try
            {
                FileUtils.createDirectory(dir);
            }
            catch (FSError e)
            {
                // don't just let the default exception handler do this, we need the create loop to continue
                logger.error("Failed to create {} directory", dir);
                FileUtils.handleFSError(e);
            }
        }

        // if index, move existing older versioned SSTable files to new directory
        if (indexNameWithDot != null)
        {
            for (File dataPath : dataPaths)
            {
                File[] indexFiles = dataPath.getParentFile().listFiles(new FileFilter()
                {
                    @Override
                    public boolean accept(File file)
                    {
                        if (file.isDirectory())
                            return false;

                        Pair<Descriptor, Component> pair = SSTable.tryComponentFromFilename(file.getParentFile(),
                                                                                            file.getName());
                        return pair != null && pair.left.ksname.equals(metadata.ksName) && pair.left.cfname.equals(metadata.cfName);

                    }
                });
                for (File indexFile : indexFiles)
                {
                    File destFile = new File(dataPath, indexFile.getName());
                    logger.trace("Moving index file {} to {}", indexFile, destFile);
                    FileUtils.renameWithConfirm(indexFile, destFile);
                }
            }
        }
    }

    
Returns SSTable location which is inside given data directory.
Params:
dataDirectory – 
Returns:
SSTable location/**
     * Returns SSTable location which is inside given data directory.
     *
     * @param dataDirectory
     * @return SSTable location
     */
    public File getLocationForDisk(DataDirectory dataDirectory)
    {
        if (dataDirectory != null)
            for (File dir : dataPaths)
                if (dir.getAbsolutePath().startsWith(dataDirectory.location.getAbsolutePath()))
                    return dir;
        return null;
    }

    public DataDirectory getDataDirectoryForFile(File directory)
    {
        if (directory != null)
        {
            for (DataDirectory dataDirectory : paths)
            {
                if (directory.getAbsolutePath().startsWith(dataDirectory.location.getAbsolutePath()))
                    return dataDirectory;
            }
        }
        return null;
    }

    public Descriptor find(String filename)
    {
        for (File dir : dataPaths)
        {
            if (new File(dir, filename).exists())
                return Descriptor.fromFilename(dir, filename).left;
        }
        return null;
    }

    
Basically the same as calling getWriteableLocationAsFile(long) with an unknown size (-1L), which may return any non-blacklisted directory - even a data directory that has no usable space. Do not use this method in production code. 
Throws:
FSWriteError – if all directories are blacklisted./**
     * Basically the same as calling {@link #getWriteableLocationAsFile(long)} with an unknown size ({@code -1L}),
     * which may return any non-blacklisted directory - even a data directory that has no usable space.
     * Do not use this method in production code.
     *
     * @throws FSWriteError if all directories are blacklisted.
     */
    public File getDirectoryForNewSSTables()
    {
        return getWriteableLocationAsFile(-1L);
    }

    
Returns a non-blacklisted data directory that _currently_ has writeSize bytes as usable space. 
Throws:
FSWriteError – if all directories are blacklisted./**
     * Returns a non-blacklisted data directory that _currently_ has {@code writeSize} bytes as usable space.
     *
     * @throws FSWriteError if all directories are blacklisted.
     */
    public File getWriteableLocationAsFile(long writeSize)
    {
        File location = getLocationForDisk(getWriteableLocation(writeSize));
        if (location == null)
            throw new FSWriteError(new IOException("No configured data directory contains enough space to write " + writeSize + " bytes"), "");
        return location;
    }

    
Returns a temporary subdirectory on non-blacklisted data directory that _currently_ has writeSize bytes as usable space. This method does not create the temporary directory. 
Throws:
IOError – if all directories are blacklisted./**
     * Returns a temporary subdirectory on non-blacklisted data directory
     * that _currently_ has {@code writeSize} bytes as usable space.
     * This method does not create the temporary directory.
     *
     * @throws IOError if all directories are blacklisted.
     */
    public File getTemporaryWriteableDirectoryAsFile(long writeSize)
    {
        File location = getLocationForDisk(getWriteableLocation(writeSize));
        if (location == null)
            return null;
        return new File(location, TMP_SUBDIR);
    }

    public void removeTemporaryDirectories()
    {
        for (File dataDir : dataPaths)
        {
            File tmpDir = new File(dataDir, TMP_SUBDIR);
            if (tmpDir.exists())
            {
                logger.debug("Removing temporary directory {}", tmpDir);
                FileUtils.deleteRecursive(tmpDir);
            }
        }
    }

    
Returns a non-blacklisted data directory that _currently_ has writeSize bytes as usable space, null if there is not enough space left in all directories. 
Throws:
FSWriteError – if all directories are blacklisted./**
     * Returns a non-blacklisted data directory that _currently_ has {@code writeSize} bytes as usable space, null if
     * there is not enough space left in all directories.
     *
     * @throws FSWriteError if all directories are blacklisted.
     */
    public DataDirectory getWriteableLocation(long writeSize)
    {
        List<DataDirectoryCandidate> candidates = new ArrayList<>();

        long totalAvailable = 0L;

        // pick directories with enough space and so that resulting sstable dirs aren't blacklisted for writes.
        boolean tooBig = false;
        for (DataDirectory dataDir : paths)
        {
            if (BlacklistedDirectories.isUnwritable(getLocationForDisk(dataDir)))
            {
                logger.trace("removing blacklisted candidate {}", dataDir.location);
                continue;
            }
            DataDirectoryCandidate candidate = new DataDirectoryCandidate(dataDir);
            // exclude directory if its total writeSize does not fit to data directory
            if (candidate.availableSpace < writeSize)
            {
                logger.trace("removing candidate {}, usable={}, requested={}", candidate.dataDirectory.location, candidate.availableSpace, writeSize);
                tooBig = true;
                continue;
            }
            candidates.add(candidate);
            totalAvailable += candidate.availableSpace;
        }

        if (candidates.isEmpty())
            if (tooBig)
                throw new FSDiskFullWriteError(new IOException("Insufficient disk space to write " + writeSize + " bytes"), "");
            else
                throw new FSWriteError(new IOException("All configured data directories have been blacklisted as unwritable for erroring out"), "");

        // shortcut for single data directory systems
        if (candidates.size() == 1)
            return candidates.get(0).dataDirectory;

        sortWriteableCandidates(candidates, totalAvailable);

        return pickWriteableDirectory(candidates);
    }

    // separated for unit testing
    static DataDirectory pickWriteableDirectory(List<DataDirectoryCandidate> candidates)
    {
        // weighted random
        double rnd = ThreadLocalRandom.current().nextDouble();
        for (DataDirectoryCandidate candidate : candidates)
        {
            rnd -= candidate.perc;
            if (rnd <= 0)
                return candidate.dataDirectory;
        }

        // last resort
        return candidates.get(0).dataDirectory;
    }

    // separated for unit testing
    static void sortWriteableCandidates(List<DataDirectoryCandidate> candidates, long totalAvailable)
    {
        // calculate free-space-percentage
        for (DataDirectoryCandidate candidate : candidates)
            candidate.calcFreePerc(totalAvailable);

        // sort directories by perc
        Collections.sort(candidates);
    }

    public boolean hasAvailableDiskSpace(long estimatedSSTables, long expectedTotalWriteSize)
    {
        long writeSize = expectedTotalWriteSize / estimatedSSTables;
        long totalAvailable = 0L;

        for (DataDirectory dataDir : paths)
        {
            if (BlacklistedDirectories.isUnwritable(getLocationForDisk(dataDir)))
                continue;
            DataDirectoryCandidate candidate = new DataDirectoryCandidate(dataDir);
            // exclude directory if its total writeSize does not fit to data directory
            if (candidate.availableSpace < writeSize)
                continue;
            totalAvailable += candidate.availableSpace;
        }
        return totalAvailable > expectedTotalWriteSize;
    }

    public DataDirectory[] getWriteableLocations()
    {
        List<DataDirectory> nonBlacklistedDirs = new ArrayList<>();
        for (DataDirectory dir : paths)
        {
            if (!BlacklistedDirectories.isUnwritable(dir.location))
                nonBlacklistedDirs.add(dir);
        }

        Collections.sort(nonBlacklistedDirs, new Comparator<DataDirectory>()
        {
            @Override
            public int compare(DataDirectory o1, DataDirectory o2)
            {
                return o1.location.compareTo(o2.location);
            }
        });
        return nonBlacklistedDirs.toArray(new DataDirectory[nonBlacklistedDirs.size()]);
    }

    public static File getSnapshotDirectory(Descriptor desc, String snapshotName)
    {
        return getSnapshotDirectory(desc.directory, snapshotName);
    }

    
Returns directory to write snapshot. If directory does not exist, then one is created. If given location indicates secondary index, this will return <cf dir>/snapshots/<snapshot name>/.<index name>. Otherwise, this will return <cf dir>/snapshots/<snapshot name>. 
Params:
location – base directory
snapshotName – snapshot name
Returns:
directory to write snapshot/**
     * Returns directory to write snapshot. If directory does not exist, then one is created.
     *
     * If given {@code location} indicates secondary index, this will return
     * {@code <cf dir>/snapshots/<snapshot name>/.<index name>}.
     * Otherwise, this will return {@code <cf dir>/snapshots/<snapshot name>}.
     *
     * @param location base directory
     * @param snapshotName snapshot name
     * @return directory to write snapshot
     */
    public static File getSnapshotDirectory(File location, String snapshotName)
    {
        if (location.getName().startsWith(SECONDARY_INDEX_NAME_SEPARATOR))
        {
            return getOrCreate(location.getParentFile(), SNAPSHOT_SUBDIR, snapshotName, location.getName());
        }
        else
        {
            return getOrCreate(location, SNAPSHOT_SUBDIR, snapshotName);
        }
    }

    public File getSnapshotManifestFile(String snapshotName)
    {
        File snapshotDir = getSnapshotDirectory(getDirectoryForNewSSTables(), snapshotName);
        return new File(snapshotDir, "manifest.json");
    }

    public File getSnapshotSchemaFile(String snapshotName)
    {
        File snapshotDir = getSnapshotDirectory(getDirectoryForNewSSTables(), snapshotName);
        return new File(snapshotDir, "schema.cql");
    }

    public File getNewEphemeralSnapshotMarkerFile(String snapshotName)
    {
        File snapshotDir = new File(getWriteableLocationAsFile(1L), join(SNAPSHOT_SUBDIR, snapshotName));
        return getEphemeralSnapshotMarkerFile(snapshotDir);
    }

    private static File getEphemeralSnapshotMarkerFile(File snapshotDirectory)
    {
        return new File(snapshotDirectory, "ephemeral.snapshot");
    }

    public static File getBackupsDirectory(Descriptor desc)
    {
        return getBackupsDirectory(desc.directory);
    }

    public static File getBackupsDirectory(File location)
    {
        if (location.getName().startsWith(SECONDARY_INDEX_NAME_SEPARATOR))
        {
            return getOrCreate(location.getParentFile(), BACKUPS_SUBDIR, location.getName());
        }
        else
        {
            return getOrCreate(location, BACKUPS_SUBDIR);
        }
    }

    public static class DataDirectory
    {
        public final File location;

        public DataDirectory(File location)
        {
            this.location = location;
        }

        public long getAvailableSpace()
        {
            long availableSpace = FileUtils.getUsableSpace(location) - DatabaseDescriptor.getMinFreeSpacePerDriveInBytes();
            return availableSpace > 0 ? availableSpace : 0;
        }

        @Override
        public boolean equals(Object o)
        {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;

            DataDirectory that = (DataDirectory) o;

            return location.equals(that.location);
        }

        @Override
        public int hashCode()
        {
            return location.hashCode();
        }

        public String toString()
        {
            return "DataDirectory{" +
                   "location=" + location +
                   '}';
        }
    }

    static final class DataDirectoryCandidate implements Comparable<DataDirectoryCandidate>
    {
        final DataDirectory dataDirectory;
        final long availableSpace;
        double perc;

        public DataDirectoryCandidate(DataDirectory dataDirectory)
        {
            this.dataDirectory = dataDirectory;
            this.availableSpace = dataDirectory.getAvailableSpace();
        }

        void calcFreePerc(long totalAvailableSpace)
        {
            double w = availableSpace;
            w /= totalAvailableSpace;
            perc = w;
        }

        public int compareTo(DataDirectoryCandidate o)
        {
            if (this == o)
                return 0;

            int r = Double.compare(perc, o.perc);
            if (r != 0)
                return -r;
            // last resort
            return System.identityHashCode(this) - System.identityHashCode(o);
        }
    }

    
The type of files that can be listed by SSTableLister, we never return txn logs,
use LifecycleTransaction.getFiles() if you need txn logs. /** The type of files that can be listed by SSTableLister, we never return txn logs,
     * use LifecycleTransaction.getFiles() if you need txn logs. */
    public enum FileType
    {
        
A permanent sstable file that is safe to use. /** A permanent sstable file that is safe to use. */
        FINAL,

        
A temporary sstable file that will soon be deleted. /** A temporary sstable file that will soon be deleted. */
        TEMPORARY,

        
A transaction log file (contains information on final and temporary files). /** A transaction log file (contains information on final and temporary files). */
        TXN_LOG;
    }

    
How to handle a failure to read a txn log file. Note that we will try a few
times before giving up.
/**
     * How to handle a failure to read a txn log file. Note that we will try a few
     * times before giving up.
     **/
    public enum OnTxnErr
    {
        
Throw the exception /** Throw the exception */
        THROW,

        
Ignore the problematic parts of the txn log file /** Ignore the problematic parts of the txn log file */
        IGNORE
    }

    public SSTableLister sstableLister(OnTxnErr onTxnErr)
    {
        return new SSTableLister(onTxnErr);
    }

    public class SSTableLister
    {
        private final OnTxnErr onTxnErr;
        private boolean skipTemporary;
        private boolean includeBackups;
        private boolean onlyBackups;
        private int nbFiles;
        private final Map<Descriptor, Set<Component>> components = new HashMap<>();
        private boolean filtered;
        private String snapshotName;

        private SSTableLister(OnTxnErr onTxnErr)
        {
            this.onTxnErr = onTxnErr;
        }

        public SSTableLister skipTemporary(boolean b)
        {
            if (filtered)
                throw new IllegalStateException("list() has already been called");
            skipTemporary = b;
            return this;
        }

        public SSTableLister includeBackups(boolean b)
        {
            if (filtered)
                throw new IllegalStateException("list() has already been called");
            includeBackups = b;
            return this;
        }

        public SSTableLister onlyBackups(boolean b)
        {
            if (filtered)
                throw new IllegalStateException("list() has already been called");
            onlyBackups = b;
            includeBackups = b;
            return this;
        }

        public SSTableLister snapshots(String sn)
        {
            if (filtered)
                throw new IllegalStateException("list() has already been called");
            snapshotName = sn;
            return this;
        }

        public Map<Descriptor, Set<Component>> list()
        {
            filter();
            return ImmutableMap.copyOf(components);
        }

        public List<File> listFiles()
        {
            filter();
            List<File> l = new ArrayList<>(nbFiles);
            for (Map.Entry<Descriptor, Set<Component>> entry : components.entrySet())
            {
                for (Component c : entry.getValue())
                {
                    l.add(new File(entry.getKey().filenameFor(c)));
                }
            }
            return l;
        }

        private void filter()
        {
            if (filtered)
                return;

            for (File location : dataPaths)
            {
                if (BlacklistedDirectories.isUnreadable(location))
                    continue;

                if (snapshotName != null)
                {
                    LifecycleTransaction.getFiles(getSnapshotDirectory(location, snapshotName).toPath(), getFilter(), onTxnErr);
                    continue;
                }

                if (!onlyBackups)
                    LifecycleTransaction.getFiles(location.toPath(), getFilter(), onTxnErr);

                if (includeBackups)
                    LifecycleTransaction.getFiles(getBackupsDirectory(location).toPath(), getFilter(), onTxnErr);
            }

            filtered = true;
        }

        private BiFunction<File, FileType, Boolean> getFilter()
        {
            // This function always return false since it adds to the components map
            return (file, type) ->
            {
                switch (type)
                {
                    case TXN_LOG:
                        return false;
                    case TEMPORARY:
                        if (skipTemporary)
                            return false;

                    case FINAL:
                        Pair<Descriptor, Component> pair = SSTable.tryComponentFromFilename(file.getParentFile(), file.getName());
                        if (pair == null)
                            return false;

                        // we are only interested in the SSTable files that belong to the specific ColumnFamily
                        if (!pair.left.ksname.equals(metadata.ksName) || !pair.left.cfname.equals(metadata.cfName))
                            return false;

                        Set<Component> previous = components.get(pair.left);
                        if (previous == null)
                        {
                            previous = new HashSet<>();
                            components.put(pair.left, previous);
                        }
                        else if (pair.right.type == Component.Type.DIGEST)
                        {
                            if (pair.right != pair.left.digestComponent)
                            {
                                // Need to update the DIGEST component as it might be set to another
                                // digest type as a guess. This may happen if the first component is
                                // not the DIGEST (but the Data component for example), so the digest
                                // type is _guessed_ from the Version.
                                // Although the Version explicitly defines the digest type, it doesn't
                                // seem to be true under all circumstances. Generated sstables from a
                                // post 2.1.8 snapshot produced Digest.sha1 files although Version
                                // defines Adler32.
                                // TL;DR this piece of code updates the digest component to be "correct".
                                components.remove(pair.left);
                                Descriptor updated = pair.left.withDigestComponent(pair.right);
                                components.put(updated, previous);
                            }
                        }
                        previous.add(pair.right);
                        nbFiles++;
                        return false;

                    default:
                        throw new AssertionError();
                }
            };
        }
    }

    
Returns:
 Return a map of all snapshots to space being used
The pair for a snapshot has size on disk and true size./**
     *
     * @return  Return a map of all snapshots to space being used
     * The pair for a snapshot has size on disk and true size.
     */
    public Map<String, Pair<Long, Long>> getSnapshotDetails()
    {
        final Map<String, Pair<Long, Long>> snapshotSpaceMap = new HashMap<>();
        for (File snapshot : listSnapshots())
        {
            final long sizeOnDisk = FileUtils.folderSize(snapshot);
            final long trueSize = getTrueAllocatedSizeIn(snapshot);
            Pair<Long, Long> spaceUsed = snapshotSpaceMap.get(snapshot.getName());
            if (spaceUsed == null)
                spaceUsed =  Pair.create(sizeOnDisk,trueSize);
            else
                spaceUsed = Pair.create(spaceUsed.left + sizeOnDisk, spaceUsed.right + trueSize);
            snapshotSpaceMap.put(snapshot.getName(), spaceUsed);
        }
        return snapshotSpaceMap;
    }

    public List<String> listEphemeralSnapshots()
    {
        final List<String> ephemeralSnapshots = new LinkedList<>();
        for (File snapshot : listSnapshots())
        {
            if (getEphemeralSnapshotMarkerFile(snapshot).exists())
                ephemeralSnapshots.add(snapshot.getName());
        }
        return ephemeralSnapshots;
    }

    private List<File> listSnapshots()
    {
        final List<File> snapshots = new LinkedList<>();
        for (final File dir : dataPaths)
        {
            File snapshotDir = dir.getName().startsWith(SECONDARY_INDEX_NAME_SEPARATOR) ?
                                       new File(dir.getParent(), SNAPSHOT_SUBDIR) :
                                       new File(dir, SNAPSHOT_SUBDIR);
            if (snapshotDir.exists() && snapshotDir.isDirectory())
            {
                final File[] snapshotDirs  = snapshotDir.listFiles();
                if (snapshotDirs != null)
                {
                    for (final File snapshot : snapshotDirs)
                    {
                        if (snapshot.isDirectory())
                            snapshots.add(snapshot);
                    }
                }
            }
        }

        return snapshots;
    }

    public boolean snapshotExists(String snapshotName)
    {
        for (File dir : dataPaths)
        {
            File snapshotDir;
            if (dir.getName().startsWith(SECONDARY_INDEX_NAME_SEPARATOR))
            {
                snapshotDir = new File(dir.getParentFile(), join(SNAPSHOT_SUBDIR, snapshotName, dir.getName()));
            }
            else
            {
                snapshotDir = new File(dir, join(SNAPSHOT_SUBDIR, snapshotName));
            }
            if (snapshotDir.exists())
                return true;
        }
        return false;
    }

    public static void clearSnapshot(String snapshotName, List<File> snapshotDirectories)
    {
        // If snapshotName is empty or null, we will delete the entire snapshot directory
        String tag = snapshotName == null ? "" : snapshotName;
        for (File dir : snapshotDirectories)
        {
            File snapshotDir = new File(dir, join(SNAPSHOT_SUBDIR, tag));
            if (snapshotDir.exists())
            {
                logger.trace("Removing snapshot directory {}", snapshotDir);
                try
                {
                    FileUtils.deleteRecursive(snapshotDir);
                }
                catch (FSWriteError e)
                {
                    if (FBUtilities.isWindows)
                        SnapshotDeletingTask.addFailedSnapshot(snapshotDir);
                    else
                        throw e;
                }
            }
        }
    }

    // The snapshot must exist
    public long snapshotCreationTime(String snapshotName)
    {
        for (File dir : dataPaths)
        {
            File snapshotDir = getSnapshotDirectory(dir, snapshotName);
            if (snapshotDir.exists())
                return snapshotDir.lastModified();
        }
        throw new RuntimeException("Snapshot " + snapshotName + " doesn't exist");
    }

    
Returns:
total snapshot size in byte for all snapshots./**
     * @return total snapshot size in byte for all snapshots.
     */
    public long trueSnapshotsSize()
    {
        long result = 0L;
        for (File dir : dataPaths)
        {
            File snapshotDir = dir.getName().startsWith(SECONDARY_INDEX_NAME_SEPARATOR) ?
                                       new File(dir.getParent(), SNAPSHOT_SUBDIR) :
                                       new File(dir, SNAPSHOT_SUBDIR);
            result += getTrueAllocatedSizeIn(snapshotDir);
        }
        return result;
    }

    
Returns:
Raw size on disk for all directories/**
     * @return Raw size on disk for all directories
     */
    public long getRawDiretoriesSize()
    {
        long totalAllocatedSize = 0L;

        for (File path : dataPaths)
            totalAllocatedSize += FileUtils.folderSize(path);

        return totalAllocatedSize;
    }

    public long getTrueAllocatedSizeIn(File input)
    {
        if (!input.isDirectory())
            return 0;

        SSTableSizeSummer visitor = new SSTableSizeSummer(input, sstableLister(Directories.OnTxnErr.THROW).listFiles());
        try
        {
            Files.walkFileTree(input.toPath(), visitor);
        }
        catch (IOException e)
        {
            logger.error("Could not calculate the size of {}. {}", input, e);
        }

        return visitor.getAllocatedSize();
    }

    public static List<File> getKSChildDirectories(String ksName)
    {
        return getKSChildDirectories(ksName, dataDirectories);

    }

    // Recursively finds all the sub directories in the KS directory.
    public static List<File> getKSChildDirectories(String ksName, DataDirectory[] directories)
    {
        List<File> result = new ArrayList<>();
        for (DataDirectory dataDirectory : directories)
        {
            File ksDir = new File(dataDirectory.location, ksName);
            File[] cfDirs = ksDir.listFiles();
            if (cfDirs == null)
                continue;
            for (File cfDir : cfDirs)
            {
                if (cfDir.isDirectory())
                    result.add(cfDir);
            }
        }
        return result;
    }

    public List<File> getCFDirectories()
    {
        List<File> result = new ArrayList<>();
        for (File dataDirectory : dataPaths)
        {
            if (dataDirectory.isDirectory())
                result.add(dataDirectory);
        }
        return result;
    }

    private static File getOrCreate(File base, String... subdirs)
    {
        File dir = subdirs == null || subdirs.length == 0 ? base : new File(base, join(subdirs));
        if (dir.exists())
        {
            if (!dir.isDirectory())
                throw new AssertionError(String.format("Invalid directory path %s: path exists but is not a directory", dir));
        }
        else if (!dir.mkdirs() && !(dir.exists() && dir.isDirectory()))
        {
            throw new FSWriteError(new IOException("Unable to create directory " + dir), dir);
        }
        return dir;
    }

    private static String join(String... s)
    {
        return StringUtils.join(s, File.separator);
    }

    @VisibleForTesting
    static void overrideDataDirectoriesForTest(String loc)
    {
        for (int i = 0; i < dataDirectories.length; ++i)
            dataDirectories[i] = new DataDirectory(new File(loc));
    }

    @VisibleForTesting
    static void resetDataDirectoriesAfterTest()
    {
        String[] locations = DatabaseDescriptor.getAllDataFileLocations();
        for (int i = 0; i < locations.length; ++i)
            dataDirectories[i] = new DataDirectory(new File(locations[i]));
    }

    private class SSTableSizeSummer extends DirectorySizeCalculator
    {
        private final HashSet<File> toSkip;
        SSTableSizeSummer(File path, List<File> files)
        {
            super(path);
            toSkip = new HashSet<>(files);
        }

        @Override
        public boolean isAcceptable(Path path)
        {
            File file = path.toFile();
            Pair<Descriptor, Component> pair = SSTable.tryComponentFromFilename(path.getParent().toFile(), file.getName());
            return pair != null
                    && pair.left.ksname.equals(metadata.ksName)
                    && pair.left.cfname.equals(metadata.cfName)
                    && !toSkip.contains(file);
        }
    }
}