/**
    * 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.hadoop.hbase.snapshot;
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorCompletionService;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.io.HFileLink;
  import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription;
  import org.apache.hadoop.hbase.protobuf.generated.SnapshotProtos.SnapshotRegionManifest;
  import org.apache.hadoop.hbase.regionserver.StoreFileInfo;
  
  /**
   * Utility methods for interacting with the snapshot referenced files.
   */
  @InterfaceAudience.Private
  public final class SnapshotReferenceUtil {
    private static final Log LOG = LogFactory.getLog(SnapshotReferenceUtil.class);
  
    public interface StoreFileVisitor {
      void storeFile(final HRegionInfo regionInfo, final String familyName,
         final SnapshotRegionManifest.StoreFile storeFile) throws IOException;
    }
  
    public interface SnapshotVisitor extends StoreFileVisitor {
    }
  
    private SnapshotReferenceUtil() {
      // private constructor for utility class
    }
  
    /**
     * Iterate over the snapshot store files
     *
     * @param conf The current {@link Configuration} instance.
     * @param fs {@link FileSystem}
     * @param snapshotDir {@link Path} to the Snapshot directory
     * @param visitor callback object to get the referenced files
     * @throws IOException if an error occurred while scanning the directory
     */
    public static void visitReferencedFiles(final Configuration conf, final FileSystem fs,
        final Path snapshotDir, final SnapshotVisitor visitor)
        throws IOException {
      SnapshotDescription desc = SnapshotDescriptionUtils.readSnapshotInfo(fs, snapshotDir);
      visitReferencedFiles(conf, fs, snapshotDir, desc, visitor);
    }
  
    /**
     * Iterate over the snapshot store files, restored.edits and logs
     *
     * @param conf The current {@link Configuration} instance.
     * @param fs {@link FileSystem}
     * @param snapshotDir {@link Path} to the Snapshot directory
     * @param desc the {@link SnapshotDescription} of the snapshot to verify
     * @param visitor callback object to get the referenced files
     * @throws IOException if an error occurred while scanning the directory
     */
    public static void visitReferencedFiles(final Configuration conf, final FileSystem fs,
        final Path snapshotDir, final SnapshotDescription desc, final SnapshotVisitor visitor)
        throws IOException {
      visitTableStoreFiles(conf, fs, snapshotDir, desc, visitor);
    }
  
    /**©
     * Iterate over the snapshot store files
     *
    * @param conf The current {@link Configuration} instance.
    * @param fs {@link FileSystem}
    * @param snapshotDir {@link Path} to the Snapshot directory
    * @param desc the {@link SnapshotDescription} of the snapshot to verify
    * @param visitor callback object to get the store files
    * @throws IOException if an error occurred while scanning the directory
    */
   static void visitTableStoreFiles(final Configuration conf, final FileSystem fs,
       final Path snapshotDir, final SnapshotDescription desc, final StoreFileVisitor visitor)
       throws IOException {
     SnapshotManifest manifest = SnapshotManifest.open(conf, fs, snapshotDir, desc);
     List<SnapshotRegionManifest> regionManifests = manifest.getRegionManifests();
     if (regionManifests == null || regionManifests.size() == 0) {
       LOG.debug("No manifest files present: " + snapshotDir);
       return;
     }
 
     for (SnapshotRegionManifest regionManifest: regionManifests) {
       visitRegionStoreFiles(regionManifest, visitor);
     }
   }
 
   /**
    * Iterate over the snapshot store files in the specified region
    *
    * @param manifest snapshot manifest to inspect
    * @param visitor callback object to get the store files
    * @throws IOException if an error occurred while scanning the directory
    */
   static void visitRegionStoreFiles(final SnapshotRegionManifest manifest,
       final StoreFileVisitor visitor) throws IOException {
     HRegionInfo regionInfo = HRegionInfo.convert(manifest.getRegionInfo());
     for (SnapshotRegionManifest.FamilyFiles familyFiles: manifest.getFamilyFilesList()) {
       String familyName = familyFiles.getFamilyName().toStringUtf8();
       for (SnapshotRegionManifest.StoreFile storeFile: familyFiles.getStoreFilesList()) {
         visitor.storeFile(regionInfo, familyName, storeFile);
       }
     }
   }
 
   /**
    * Verify the validity of the snapshot
    *
    * @param conf The current {@link Configuration} instance.
    * @param fs {@link FileSystem}
    * @param snapshotDir {@link Path} to the Snapshot directory of the snapshot to verify
    * @param snapshotDesc the {@link SnapshotDescription} of the snapshot to verify
    * @throws CorruptedSnapshotException if the snapshot is corrupted
    * @throws IOException if an error occurred while scanning the directory
    */
   public static void verifySnapshot(final Configuration conf, final FileSystem fs,
       final Path snapshotDir, final SnapshotDescription snapshotDesc) throws IOException {
     SnapshotManifest manifest = SnapshotManifest.open(conf, fs, snapshotDir, snapshotDesc);
     verifySnapshot(conf, fs, manifest);
   }
 
   /**
    * Verify the validity of the snapshot
    *
    * @param conf The current {@link Configuration} instance.
    * @param fs {@link FileSystem}
    * @param manifest snapshot manifest to inspect
    * @throws CorruptedSnapshotException if the snapshot is corrupted
    * @throws IOException if an error occurred while scanning the directory
    */
   public static void verifySnapshot(final Configuration conf, final FileSystem fs,
       final SnapshotManifest manifest) throws IOException {
     final SnapshotDescription snapshotDesc = manifest.getSnapshotDescription();
     final Path snapshotDir = manifest.getSnapshotDir();
     concurrentVisitReferencedFiles(conf, fs, manifest, "VerifySnapshot", new StoreFileVisitor() {
       @Override
       public void storeFile(final HRegionInfo regionInfo, final String family,
           final SnapshotRegionManifest.StoreFile storeFile) throws IOException {
         verifyStoreFile(conf, fs, snapshotDir, snapshotDesc, regionInfo, family, storeFile);
       }
     });
   }
 
   public static void concurrentVisitReferencedFiles(final Configuration conf, final FileSystem fs,
       final SnapshotManifest manifest, final String desc, final StoreFileVisitor visitor)
       throws IOException {
 
     final Path snapshotDir = manifest.getSnapshotDir();
     List<SnapshotRegionManifest> regionManifests = manifest.getRegionManifests();
     if (regionManifests == null || regionManifests.size() == 0) {
       LOG.debug("No manifest files present: " + snapshotDir);
       return;
     }
 
     ExecutorService exec = SnapshotManifest.createExecutor(conf, desc);
 
     try {
       concurrentVisitReferencedFiles(conf, fs, manifest, exec, visitor);
     } finally {
       exec.shutdown();
     }
   }
 
   public static void concurrentVisitReferencedFiles(final Configuration conf, final FileSystem fs,
       final SnapshotManifest manifest, final ExecutorService exec, final StoreFileVisitor visitor)
       throws IOException {
     final SnapshotDescription snapshotDesc = manifest.getSnapshotDescription();
     final Path snapshotDir = manifest.getSnapshotDir();
 
     List<SnapshotRegionManifest> regionManifests = manifest.getRegionManifests();
     if (regionManifests == null || regionManifests.size() == 0) {
       LOG.debug("No manifest files present: " + snapshotDir);
       return;
     }
 
     final ExecutorCompletionService<Void> completionService =
       new ExecutorCompletionService<Void>(exec);
 
     for (final SnapshotRegionManifest regionManifest : regionManifests) {
       completionService.submit(new Callable<Void>() {
         @Override public Void call() throws IOException {
           visitRegionStoreFiles(regionManifest, visitor);
           return null;
         }
       });
     }
     try {
       for (int i = 0; i < regionManifests.size(); ++i) {
         completionService.take().get();
       }
     } catch (InterruptedException e) {
       throw new InterruptedIOException(e.getMessage());
     } catch (ExecutionException e) {
       if (e.getCause() instanceof CorruptedSnapshotException) {
         throw new CorruptedSnapshotException(e.getCause().getMessage(), snapshotDesc);
       } else {
         throw new IOException(e.getCause());
       }
     }
   }
 
   /**
    * Verify the validity of the snapshot store file
    *
    * @param conf The current {@link Configuration} instance.
    * @param fs {@link FileSystem}
    * @param snapshotDir {@link Path} to the Snapshot directory of the snapshot to verify
    * @param snapshot the {@link SnapshotDescription} of the snapshot to verify
    * @param regionInfo {@link HRegionInfo} of the region that contains the store file
    * @param family family that contains the store file
    * @param storeFile the store file to verify
    * @throws CorruptedSnapshotException if the snapshot is corrupted
    * @throws IOException if an error occurred while scanning the directory
    */
   private static void verifyStoreFile(final Configuration conf, final FileSystem fs,
       final Path snapshotDir, final SnapshotDescription snapshot, final HRegionInfo regionInfo,
       final String family, final SnapshotRegionManifest.StoreFile storeFile) throws IOException {
     TableName table = TableName.valueOf(snapshot.getTable());
     String fileName = storeFile.getName();
 
     Path refPath = null;
     if (StoreFileInfo.isReference(fileName)) {
       // If is a reference file check if the parent file is present in the snapshot
       refPath = new Path(new Path(regionInfo.getEncodedName(), family), fileName);
       refPath = StoreFileInfo.getReferredToFile(refPath);
       String refRegion = refPath.getParent().getParent().getName();
       refPath = HFileLink.createPath(table, refRegion, family, refPath.getName());
       if (!HFileLink.buildFromHFileLinkPattern(conf, refPath).exists(fs)) {
         throw new CorruptedSnapshotException("Missing parent hfile for: " + fileName +
           " path=" + refPath, snapshot);
       }
 
       if (storeFile.hasReference()) {
         // We don't really need to look for the file on-disk
         // we already have the Reference information embedded here.
         return;
       }
     }
 
     Path linkPath;
     if (refPath != null && HFileLink.isHFileLink(refPath)) {
       linkPath = new Path(family, refPath.getName());
     } else if (HFileLink.isHFileLink(fileName)) {
       linkPath = new Path(family, fileName);
     } else {
       linkPath = new Path(family, HFileLink.createHFileLinkName(
               table, regionInfo.getEncodedName(), fileName));
     }
 
     // check if the linked file exists (in the archive, or in the table dir)
     HFileLink link = HFileLink.buildFromHFileLinkPattern(conf, linkPath);
     try {
       FileStatus fstat = link.getFileStatus(fs);
       if (storeFile.hasFileSize() && storeFile.getFileSize() != fstat.getLen()) {
         String msg = "hfile: " + fileName + " size does not match with the expected one. " +
           " found=" + fstat.getLen() + " expected=" + storeFile.getFileSize();
         LOG.error(msg);
         throw new CorruptedSnapshotException(msg, snapshot);
       }
     } catch (FileNotFoundException e) {
       String msg = "Can't find hfile: " + fileName + " in the real (" +
           link.getOriginPath() + ") or archive (" + link.getArchivePath()
           + ") directory for the primary table.";
       LOG.error(msg);
       throw new CorruptedSnapshotException(msg, snapshot);
     }
   }
 
   /**
    * Returns the store file names in the snapshot.
    *
    * @param conf The current {@link Configuration} instance.
    * @param fs {@link FileSystem}
    * @param snapshotDir {@link Path} to the Snapshot directory
    * @throws IOException if an error occurred while scanning the directory
    * @return the names of hfiles in the specified snaphot
    */
   public static Set<String> getHFileNames(final Configuration conf, final FileSystem fs,
       final Path snapshotDir) throws IOException {
     SnapshotDescription desc = SnapshotDescriptionUtils.readSnapshotInfo(fs, snapshotDir);
     return getHFileNames(conf, fs, snapshotDir, desc);
   }
 
   /**
    * Returns the store file names in the snapshot.
    *
    * @param conf The current {@link Configuration} instance.
    * @param fs {@link FileSystem}
    * @param snapshotDir {@link Path} to the Snapshot directory
    * @param snapshotDesc the {@link SnapshotDescription} of the snapshot to inspect
    * @throws IOException if an error occurred while scanning the directory
    * @return the names of hfiles in the specified snaphot
    */
   private static Set<String> getHFileNames(final Configuration conf, final FileSystem fs,
       final Path snapshotDir, final SnapshotDescription snapshotDesc)
       throws IOException {
     final Set<String> names = new HashSet<String>();
     visitTableStoreFiles(conf, fs, snapshotDir, snapshotDesc, new StoreFileVisitor() {
       @Override
       public void storeFile(final HRegionInfo regionInfo, final String family,
             final SnapshotRegionManifest.StoreFile storeFile) throws IOException {
         String hfile = storeFile.getName();
         if (HFileLink.isHFileLink(hfile)) {
           names.add(HFileLink.getReferencedHFileName(hfile));
         } else {
           names.add(hfile);
         }
       }
     });
     return names;
   }
 }