/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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.opencastproject.assetmanager.storage.impl.fs;
  
  import static org.apache.commons.io.FilenameUtils.EXTENSION_SEPARATOR;
  import static org.apache.commons.io.FilenameUtils.getExtension;
  import static org.apache.commons.lang3.exception.ExceptionUtils.getMessage;
  import static org.opencastproject.util.FileSupport.link;
  import static org.opencastproject.util.IoSupport.file;
  import static org.opencastproject.util.PathSupport.path;
  import static org.opencastproject.util.data.functions.Strings.trimToNone;
  
  import org.opencastproject.assetmanager.api.storage.AssetStore;
  import org.opencastproject.assetmanager.api.storage.AssetStoreException;
  import org.opencastproject.assetmanager.api.storage.DeletionSelector;
  import org.opencastproject.assetmanager.api.storage.Source;
  import org.opencastproject.assetmanager.api.storage.StoragePath;
  import org.opencastproject.util.FileSupport;
  import org.opencastproject.util.NotFoundException;
  import org.opencastproject.workspace.api.Workspace;
  
  import org.apache.commons.io.FileUtils;
  import org.apache.commons.io.FilenameUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FilenameFilter;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.MalformedURLException;
  import java.net.URI;
  import java.util.Optional;
  
  public abstract class AbstractFileSystemAssetStore implements AssetStore {
    /** Log facility */
    private static final Logger logger = LoggerFactory.getLogger(AbstractFileSystemAssetStore.class);
  
    /** The store type e.g. filesystem (short-term), aws (long-term), other implementations */
    protected String storeType = null;
  
    protected abstract Workspace getWorkspace();
  
    protected abstract String getRootDirectory();
    protected abstract String getRootDirectory(String orgId, String mpId);
  
    /**
     * Optional further handling of the complete deletion of mediapackage from the local store.
     * This method will be called after the deletion of the mediapackage directory.
     * @param orgId Organization ID
     * @param mpId Mediapackage ID
     */
    protected abstract void onDeleteMediaPackage(String orgId, String mpId);
  
    @Override
    public void put(StoragePath storagePath, Source source) throws AssetStoreException {
      // Retrieving the file from the workspace has the advantage that in most cases the file already exists in the local
      // working file repository. In the very few cases where the file is not in the working file repository,
      // this strategy leads to a minor overhead because the file not only gets downloaded and stored in the file system
      // but also a hard link needs to be created (or if that's not possible, a copy of the file.
      final File origin = getUniqueFileFromWorkspace(source);
      final File destination = createFile(storagePath, source);
      try {
        mkParent(destination);
        link(origin, destination);
      } catch (IOException e) {
        logger.error("Error while linking/copying file {} to {}: {}", origin, destination, getMessage(e));
        throw new AssetStoreException(e);
      } finally {
        if (origin != null) {
          FileUtils.deleteQuietly(origin);
        }
      }
    }
  
    private File getUniqueFileFromWorkspace(Source source) {
      try {
        return getWorkspace().get(source.getUri(), true);
      } catch (NotFoundException e) {
       logger.error("Source file '{}' does not exist", source.getUri());
       throw new AssetStoreException(e);
     } catch (IOException e) {
       logger.error("Error while getting file '{}' from workspace: {}", source.getUri(), getMessage(e));
       throw new AssetStoreException(e);
     }
   }
 
   @Override
   public boolean copy(final StoragePath from, final StoragePath to) throws AssetStoreException {
     var file = findStoragePathFile(from);
     if (file.isPresent()) {
       var f = file.get();
 
       final File t = createFile(to, f);
       mkParent(t);
       logger.debug("Copying {} to {}", f.getAbsolutePath(), t.getAbsolutePath());
       try {
         link(f, t, true);
       } catch (IOException e) {
         logger.error("Error copying archive file {} to {}", f, t);
         throw new AssetStoreException(e);
       }
       return true;
     }
     return false;
   }
 
   @Override
   public Optional<InputStream> get(final StoragePath path) throws AssetStoreException {
     var file = findStoragePathFile(path);
     if (file.isPresent()) {
       try {
         return Optional.of(new FileInputStream(file.get()));
       } catch (FileNotFoundException e) {
         logger.error("Error getting archive file {}", file);
         throw new AssetStoreException(e);
       }
     }
     return Optional.empty();
   }
 
   @Override
   public boolean contains(StoragePath path) throws AssetStoreException {
     return findStoragePathFile(path).isPresent();
   }
 
   @Override
   public boolean delete(DeletionSelector sel) throws AssetStoreException {
     File dir = getDeletionSelectorDir(sel);
     if (dir == null) {
       // MediaPackage could not be found locally. This could mean
       //   - all snapshots live in a remote asset store
       //   - mount failed and files are temporary not available
       //   - file was deleted out-of-band
       //   - other fs problem
       // In any case, we cannot continue and return "false" to indicate that the files could not be found.
       return false;
     }
     try {
       FileUtils.deleteDirectory(dir);
       // also delete the media package directory if all versions have been deleted
       boolean mpDirDeleted = FileSupport.deleteHierarchyIfEmpty(file(path(
               getRootDirectory(sel.getOrganizationId(), sel.getMediaPackageId()), sel.getOrganizationId())),
               dir.getParentFile());
       if (mpDirDeleted) {
         onDeleteMediaPackage(sel.getOrganizationId(), sel.getMediaPackageId());
       }
       return true;
     } catch (IOException e) {
       logger.error("Error deleting directory from archive {}", dir);
       throw new AssetStoreException(e);
     }
   }
 
   /**
    * Returns the directory file from a deletion selector
    *
    * @param sel
    *          the deletion selector
    * @return the directory file or null if it does not exist (e.g. MediaPackage does not exist locally)
    */
   private File getDeletionSelectorDir(DeletionSelector sel) {
     final String rootPath = getRootDirectory(sel.getOrganizationId(), sel.getMediaPackageId());
     if (rootPath == null) {
       return null;
     }
     final String basePath = path(rootPath, sel.getOrganizationId(), sel.getMediaPackageId());
     if (sel.getVersion().isPresent()) {
       return file(basePath, sel.getVersion().get().toString());
     }
     return file(basePath);
   }
 
   /** Create all parent directories of a file. */
   private void mkParent(File f) {
     mkDirs(f.getParentFile());
   }
 
   /** Create this directory and all of its parents. */
   protected void mkDirs(File d) {
     if (d == null) {
       return;
     }
     // mkdirs *may* not have succeeded if it returns false, so check if the directory exists in that case
     if (!d.mkdirs() && !d.exists()) {
       final String msg = "Cannot create directory " + d;
       logger.error(msg);
       throw new AssetStoreException(msg);
     }
   }
 
   /** Return the extension of a file. */
   private Optional<String> extension(File f) {
     Optional<String> opt = trimToNone(getExtension(f.getAbsolutePath()));
     return opt.isPresent()
         ? Optional.of(opt.get())
         : Optional.empty();
   }
 
   /** Return the extension of a URI, i.e. the extension of its path. */
   private Optional<String> extension(URI uri) {
     try {
       Optional<String> opt = trimToNone(getExtension(uri.toURL().getPath()));
       return opt.isPresent()
           ? Optional.of(opt.get())
           : Optional.empty();
     } catch (MalformedURLException e) {
       throw new Error(e);
     }
   }
 
   /** Create a file from a storage path and the extension of file <code>f</code>. */
   private File createFile(StoragePath p, File f) {
     return createFile(p, extension(f));
   }
 
   /** Create a file from a storage path and the extension of the URI of <code>s</code>. */
   private File createFile(StoragePath p, Source s) {
     return createFile(p, extension(s.getUri()));
   }
 
   /** Create a file from a storage path and an optional extension. */
   private File createFile(StoragePath p, Optional<String> extension) {
     String rootDirectory = getRootDirectory(p.getOrganizationId(), p.getMediaPackageId());
     if (rootDirectory == null) {
       rootDirectory = getRootDirectory();
     }
     return file(
             rootDirectory,
             p.getOrganizationId(),
             p.getMediaPackageId(),
             p.getVersion().toString(),
             extension.isPresent() ? p.getMediaPackageElementId() + EXTENSION_SEPARATOR + extension.get() : p
                     .getMediaPackageElementId());
   }
 
   /** Returns a file from a storage path if it exists, null otherwise */
   private File getExistingFile(StoragePath p, Optional<String> extension) {
     String rootDirectory = getRootDirectory(p.getOrganizationId(), p.getMediaPackageId());
     if (rootDirectory == null) {
       return null;
     }
     return file(
             rootDirectory,
             p.getOrganizationId(),
             p.getMediaPackageId(),
             p.getVersion().toString(),
             extension.isPresent() ? p.getMediaPackageElementId() + EXTENSION_SEPARATOR + extension.get() : p
                     .getMediaPackageElementId());
   }
 
   /**
    * Returns a file {@link Optional} from a storage path if one is found or an empty {@link Optional}
    *
    * @param storagePath
    *          the storage path
    * @return the file {@link Optional}
    */
   private Optional<File> findStoragePathFile(final StoragePath storagePath) {
     final FilenameFilter filter = new FilenameFilter() {
       @Override
       public boolean accept(File dir, String name) {
         return FilenameUtils.getBaseName(name).equals(storagePath.getMediaPackageElementId());
       }
     };
     final File containerDir = getExistingFile(storagePath, Optional.empty()).getParentFile();
 
     var files = containerDir.listFiles(filter);
     if (files == null) {
       return Optional.empty();
     }
     switch (files.length) {
       case 0:
         return Optional.empty();
       case 1:
         return Optional.of(files[0]);
       default:
         throw new AssetStoreException("Storage path " + files[0].getParent()
             + "contains multiple files with the same element id!: " + storagePath.getMediaPackageElementId());
     }
   }
 
   @Override
   public String getStoreType() {
     return storeType;
   }
 
 }