/*
 * 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.jackrabbit.oak.plugins.blob;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.serialization.ValidatingObjectInputStream;
import org.apache.jackrabbit.oak.commons.io.FileTreeTraverser;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static org.apache.jackrabbit.oak.plugins.blob.DataStoreCacheUtils.recursiveDelete;

/**
 * Utility methods to upgrade Old DataStore cache
 * {@link org.apache.jackrabbit.core.data.CachingDataStore}.
 */
public class DataStoreCacheUpgradeUtils {
    private static final Logger LOG = LoggerFactory.getLogger(DataStoreCacheUpgradeUtils.class);

    static final String UPLOAD_MAP = "async-pending-uploads.ser";
    static final String UPLOAD_STAGING_DIR = UploadStagingCache.UPLOAD_STAGING_DIR;
    static final String DOWNLOAD_DIR = FileCache.DOWNLOAD_DIR;

    /**
     * De-serialize the pending uploads map from {@link org.apache.jackrabbit.core.data.AsyncUploadCache}.
     *
     * @param homeDir the directory where the serialized file is maintained
     * @return the de-serialized map
     */
    private static Map<String, Long> deSerializeUploadMap(File homeDir) {
        Map<String, Long> asyncUploadMap = new HashMap<>();

        File asyncUploadMapFile = new File(homeDir, UPLOAD_MAP);
        if (asyncUploadMapFile.exists()) {
            String path = asyncUploadMapFile.getAbsolutePath();

            InputStream fis = null;
            try {
                fis = (new FileInputStream(path));
                ValidatingObjectInputStream input = new ValidatingObjectInputStream(fis);
                input.accept(HashMap.class, Map.class, Number.class, Long.class, String.class);
                asyncUploadMap = (Map<String, Long>) input.readObject();
            } catch (Exception e) {
                LOG.error("Error in reading pending uploads map [{}] from location [{}]", UPLOAD_MAP,
                    homeDir, e);
            } finally {
                IOUtils.closeQuietly(fis);
            }
            LOG.debug("AsyncUploadMap read [{}]", asyncUploadMap);
        }
        return asyncUploadMap;
    }

    /**
     * Delete the serialized pending uploads map from the file system.
     *
     * @param homeDir the repository home directory
     */
    private static void deleteSerializedUploadMap(File homeDir) {
        File uploadMap = new File(homeDir, UPLOAD_MAP);
        FileUtils.deleteQuietly(uploadMap);
        LOG.info("Deleted asyncUploadMap [{}] from [{}]", UPLOAD_MAP, homeDir);
    }

    private static boolean notInExceptions(File file, List<String> exceptions) {
        String parent = file.getParent();
        for (String exception : exceptions) {
            if (parent.contains(exception)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Move the DataStore downloaded cache files to the appropriate folder used by the new cache
     * {@link FileCache}
     * @param path the root of the datastore
     */
    public static void moveDownloadCache(final File path) {
        final List<String> exceptions = List.of("tmp", UPLOAD_STAGING_DIR, DOWNLOAD_DIR);
        File newDownloadDir = new File(path, DOWNLOAD_DIR);

        FileTreeTraverser.depthFirstPostOrder(path)
                .filter(file -> file.isFile()
                        && !file.getParentFile().equals(path)
                        && !notInExceptions(file, exceptions))
                .forEach(download -> {
                    LOG.trace("Download cache file absolute pre-upgrade path {}", download);

                    File newDownload = new File(newDownloadDir,
                            download.getAbsolutePath().substring(path.getAbsolutePath().length()));
                    newDownload.getParentFile().mkdirs();
                    LOG.trace("Downloaded cache file absolute post-upgrade path {}", newDownload);

                    try {
                        FileUtils.moveFile(download, newDownload);
                        LOG.info("Download cache file [{}] moved to [{}]", download, newDownload);
                        recursiveDelete(download, path);
                    } catch (Exception e) {
                        LOG.warn("Unable to move download cache file [{}] to [{}]", download, newDownload);
                    }
                });
    }

    /**
     * Move the pending uploads read from the de-serialized map to the appropriate directory
     * used by the {@link UploadStagingCache}.
     *
     * @param homeDir the repository home directory
     * @param path the root of the datastore
     * @param deleteMap flag indicating whether to delete the pending upload map after upgrade
     */
    public static void movePendingUploadsToStaging(File homeDir, File path, boolean deleteMap) {
        File newUploadDir = new File(path, UPLOAD_STAGING_DIR);
        if (homeDir != null && homeDir.exists()) {
            Map<String, Long> pendingUploads = deSerializeUploadMap(homeDir);
            Iterator<String> pendingFileIter = pendingUploads.keySet().iterator();

            while (pendingFileIter.hasNext()) {
                String file = pendingFileIter.next();
                File upload = new File(path, file);
                LOG.trace("Pending upload absolute path " + upload.getAbsolutePath());

                File newUpload = new File(newUploadDir, file);
                LOG.trace("Pending upload upgrade absolute path " + newUpload.getAbsolutePath());

                newUpload.getParentFile().mkdirs();

                if (upload.exists()) {
                    LOG.trace(upload + " File exists");
                    try {
                        FileUtils.moveFile(upload, newUpload);
                        LOG.info("Pending upload file [{}] moved to [{}]", upload, newUpload);
                        recursiveDelete(upload, path);
                    } catch (Exception e) {
                        LOG.warn("Unable to move pending upload file [{}] to [{}]", upload,
                            newUpload);
                    }
                } else {
                    LOG.warn("File [{}] does not exist", upload);
                }
            }

            if (deleteMap) {
                deleteSerializedUploadMap(homeDir);
            }
        }
    }

    /**
     * Upgrades the {@link org.apache.jackrabbit.core.data.CachingDataStore}.
     *
     * @param homeDir the repository home directory
     * @param path the root of the datastore
     * @param moveCache flag whether to move the downloaded cache files
     * @param deleteMap flag indicating whether to delete the pending upload map after upgrade
     */
    public static void upgrade(File homeDir, File path, boolean moveCache, boolean deleteMap) {
        movePendingUploadsToStaging(homeDir, path, deleteMap);

        if (moveCache) {
            moveDownloadCache(path);
        }
    }
}
