/*
    * 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.opencastproject.util.IoSupport.file;
  
  import org.opencastproject.assetmanager.api.storage.AssetStore;
  import org.opencastproject.storage.StorageUsage;
  import org.opencastproject.workspace.api.Workspace;
  
  import com.google.common.cache.CacheBuilder;
  import com.google.common.cache.CacheLoader;
  import com.google.common.cache.LoadingCache;
  import com.google.common.util.concurrent.ExecutionError;
  import com.google.common.util.concurrent.UncheckedExecutionException;
  
  import org.apache.commons.io.FileUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.osgi.service.component.ComponentContext;
  import org.osgi.service.component.annotations.Activate;
  import org.osgi.service.component.annotations.Component;
  import org.osgi.service.component.annotations.Reference;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.io.IOException;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Optional;
  import java.util.concurrent.TimeUnit;
  
  import javax.naming.ConfigurationException;
  
  @Component(
      property = {
      "service.description=File system based asset store",
      "store.type=local-filesystem"
      },
      immediate = true,
      service = { AssetStore.class, StorageUsage.class }
  )
  public class OsgiFileSystemAssetStore extends AbstractFileSystemAssetStore {
    /** Log facility */
    private static final Logger logger = LoggerFactory.getLogger(OsgiFileSystemAssetStore.class);
  
    /** A cache of mediapckage ids and their associated storages */
    private LoadingCache<String, Optional<String>> cache = null;
    private int cacheSize = 1000;
    private int cacheExpiration = 1;
  
    /** Configuration key for the default Opencast storage directory. A value is optional. */
    public static final String CFG_OPT_STORAGE_DIR = "org.opencastproject.storage.dir";
  
    /**
     * The default store directory name.
     * Will be used in conjunction with {@link #CFG_OPT_STORAGE_DIR} if {@link #CFG_OPT_STORAGE_DIR} is not set.
     */
    private static final String DEFAULT_STORE_DIRECTORY = "archive";
  
    /** Configuration key for the archive root directory. */
    public static final String CONFIG_STORE_ROOT_DIR = "org.opencastproject.episode.rootdir";
  
    /** The root directories for storing files (typically one) */
    private List<String> rootDirectories;
  
    /** The workspace */
    private Workspace workspace;
  
    @Override protected Workspace getWorkspace() {
      return workspace;
    }
  
    @Override
    /**
     * Returns the root directory with the most usable space left
     * @return The root directory path
    */
   protected String getRootDirectory() {
     // Determine which storage to return by amount of remaining usable space
     long usableSpace = 0;
     String mostUsableDirectory = null;
     for (String path : rootDirectories) {
       Optional<Long> maybeUsableSpace = Optional.of(new File(path).getUsableSpace());
       if (maybeUsableSpace.isEmpty()) {
         continue;
       }
       if (maybeUsableSpace.get() > usableSpace) {
         usableSpace = maybeUsableSpace.get();
         mostUsableDirectory = path;
       }
     }
 
     return mostUsableDirectory;
   }
 
   /**
    * Looks for the root directory of the given mediapackage id
    * @param orgId the organization which the mediapackage belongs to
    * @param mpId the mediapackage id
    * @return The root directory path of the given mediapackage, or null if the mediapackage could not be found anywhere
    */
   protected String getRootDirectory(String orgId, String mpId) {
     try {
       String cacheKey = Paths.get(orgId, mpId).toString();
       Optional<String> pathOpt = cache.getUnchecked(cacheKey);
       if (pathOpt.isPresent()) {
         logger.debug("Root directory for mediapackage {} is {}", mpId, pathOpt.get());
         return pathOpt.get();
       } else {
         logger.debug("Root directory for mediapackage {} could not be found, returning null.", mpId);
         cache.invalidate(cacheKey);
         return null;
       }
     } catch (ExecutionError e) {
       logger.warn("Exception while getting path for mediapackage {}", mpId, e);
       return null;
     } catch (UncheckedExecutionException e) {
       logger.warn("Exception while getting path for  mediapackage {}", mpId, e);
       return null;
     }
   }
 
   /**
    * Looks for the root directory that contains the given mediapackage id.
    * Used by the cache.
    * @param orgAndMpId The part of the path that contains the organization id and mediapacakge id
    * @return The root directory path of the given mediapackage
    */
   private String getRootDirectoryForMediaPackage(String orgAndMpId) {
     // Search the mediapackage on all storages
     for (String path : rootDirectories) {
       Path dirPath = Path.of(path, orgAndMpId);
       if (Files.exists(dirPath) && Files.isDirectory(dirPath)) {
         return path;
       }
     }
 
     return null;
   }
 
   private List<String> getRootDirectories() {
     return Collections.unmodifiableList(rootDirectories);
   }
 
   protected void setupCache() {
     cache = CacheBuilder.newBuilder().maximumSize(cacheSize).expireAfterWrite(cacheExpiration, TimeUnit.MINUTES)
             .build(new CacheLoader<String, Optional<String>>() {
               @Override
               public Optional<String> load(String orgAndMpId) throws Exception {
                 String rootDirectory = getRootDirectoryForMediaPackage(orgAndMpId);
                 return rootDirectory == null ? Optional.empty() : Optional.of(rootDirectory);
               }
             });
   }
 
   protected void onDeleteMediaPackage(String orgId, String mpId) {
     String cacheKey = Paths.get(orgId, mpId).toString();
     cache.invalidate(cacheKey);
   }
 
   /**
    * OSGi DI.
    */
   @Reference
   public void setWorkspace(Workspace workspace) {
     this.workspace = workspace;
   }
 
   /**
    * Service activator, called via declarative services configuration.
    *
    * @param cc
    *          the component context
    */
   @Activate
   public void activate(final ComponentContext cc) throws IllegalStateException, IOException, ConfigurationException {
     storeType = (String) cc.getProperties().get(AssetStore.STORE_TYPE_PROPERTY);
     logger.info("{} is: {}", AssetStore.STORE_TYPE_PROPERTY, storeType);
 
     rootDirectories = new ArrayList<>();
 
     // Read in single directory
     String rootDirectory = StringUtils.trimToNull(cc.getBundleContext().getProperty(CONFIG_STORE_ROOT_DIR));
     if (rootDirectory == null) {
       final String storageDir = StringUtils.trimToNull(cc.getBundleContext().getProperty(CFG_OPT_STORAGE_DIR));
       if (storageDir == null) {
         throw new IllegalArgumentException("Storage directory must be set");
       }
       rootDirectory = Paths.get(storageDir, DEFAULT_STORE_DIRECTORY).toFile().getAbsolutePath();
     }
     mkDirs(file(rootDirectory));
     rootDirectories.add(rootDirectory);
 
     // Read in multiple directories
     int index = 1;
     boolean isRootDirectory = true;
     while (isRootDirectory) {
       String directory = StringUtils.trimToNull(cc.getBundleContext().getProperty(CONFIG_STORE_ROOT_DIR + "." + index));
 
       if (directory != null) {
         rootDirectories.add(directory);
       } else {
         isRootDirectory = false;
       }
       index++;
     }
     // Check for bad configuration
     for (int i = 0; i < rootDirectories.size(); i++) {
       for (int j = 0; j < rootDirectories.size(); j++) {
         if (i == j) {
           continue;
         }
         if (isChild(rootDirectories.get(j), rootDirectories.get(i))) {
           throw new ConfigurationException("Storage directory " + rootDirectories.get(j) + " is a subdirectory of "
               + rootDirectories.get(i) + ". This is not allowed.");
         }
       }
     }
     // Create
     for (String directory: rootDirectories) {
       mkDirs(file(directory));
     }
     // Check for write access
     for (String directory : rootDirectories) {
       File tmp = new File(directory + "/tobedeleted.tmp");
       tmp.createNewFile();
       tmp.delete();
     }
 
     logger.info("Start asset manager files system store at {}", rootDirectories);
 
     // Setup rootDirectory cache
     // Remembers the root directory for a given mediapackage
     setupCache();
   }
 
   private static boolean isChild(String childText, String parentText) {
     Path parent = Paths.get(parentText).toAbsolutePath();
     Path child = Paths.get(childText).toAbsolutePath();
     if (child.startsWith(parent)) {
       return true;
     }
     return false;
   }
 
   // Depending on how these functions are used, it may not make sense to just sum over all root directories.
   // It would likely be more proper to return the individual values for each directory in a collection.
   // However, that would require a major rewrite of the StorageUsage interface, which is a lot of work for some
   // functions that seem to see no use anyhow.
   @Override
   public Optional<Long> getUsedSpace() {
     long usedSpace = 0;
     for (String path : rootDirectories) {
       usedSpace += FileUtils.sizeOfDirectory(new File(path));
     }
     return Optional.of(usedSpace);
   }
 
   @Override
   public Optional<Long> getUsableSpace() {
     long usableSpace = 0;
     for (String path : rootDirectories) {
       usableSpace += new File(path).getUsableSpace();
     }
     return Optional.of(usableSpace);
   }
 
   @Override
   public Optional<Long> getTotalSpace() {
     long totalSpace = 0;
     for (String path : rootDirectories) {
       totalSpace += new File(path).getTotalSpace();
     }
     return Optional.of(totalSpace);
   }
 
   @Override
   public String getStorageName() {
     return "File System Asset Store";
   }
 }