/*
 * Copyright (c) 2017, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
 *
 * WSO2 Inc. 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.wso2.carbon.stream.processor.core.persistence;

import com.google.common.io.Files;
import org.apache.log4j.Logger;
import org.wso2.carbon.stream.processor.core.ha.util.CompressionUtil;
import org.wso2.carbon.stream.processor.core.persistence.util.PersistenceConstants;
import org.wso2.siddhi.core.util.persistence.IncrementalPersistenceStore;
import org.wso2.siddhi.core.util.persistence.util.IncrementalSnapshotInfo;
import org.wso2.siddhi.core.util.persistence.util.PersistenceHelper;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Implementation of Persistence Store that would persist snapshots to the file system
 */
public class IncrementalFileSystemPersistenceStore implements IncrementalPersistenceStore {

    private static final Logger log = Logger.getLogger(IncrementalFileSystemPersistenceStore.class);
    private String folder;

    public IncrementalFileSystemPersistenceStore(){
    }
    
    public IncrementalFileSystemPersistenceStore(String storageFilePath) {
        folder = storageFilePath;
    }

    @Override
    public void save(IncrementalSnapshotInfo snapshotInfo, byte[] snapshot) {
        File file = new File(folder + File.separator + snapshotInfo.getSiddhiAppId() + File.separator +
                snapshotInfo.getRevision());
        byte[] compressedSnapshot;
        try {
            compressedSnapshot = CompressionUtil.compressGZIP(snapshot);
        } catch (IOException e) {
            log.error("Error occurred while trying to compress the snapshot. Failed to " +
                    "persist revision: " + snapshotInfo.getRevision() + " of Siddhi app: " +
                    snapshotInfo.getSiddhiAppId());
            return;
        }
        try {
            Files.createParentDirs(file);
            Files.write(compressedSnapshot, file);
            if (snapshotInfo.getType() == IncrementalSnapshotInfo.SnapshotType.BASE) {
                cleanOldRevisions(snapshotInfo);
            }
            if (log.isDebugEnabled()) {
                log.debug("Incremental persistence of '" + snapshotInfo.getSiddhiAppId() +
                        "' with revision '" + snapshotInfo.getRevision() + "' persisted successfully.");
            }
        } catch (IOException e) {
            log.error("Cannot save the revision '" + snapshotInfo.getRevision() + "' of SiddhiApp: '" +
                    snapshotInfo.getSiddhiAppId() + "' to the file system.", e);
        }
    }

    @Override
    public void setProperties(Map properties) {
        Map configurationMap = (Map) properties.get(PersistenceConstants.STATE_PERSISTENCE_CONFIGS);

        if (configurationMap != null) {
            Object folderObject = configurationMap.get("location");
            if (folderObject == null || !(folderObject instanceof String)) {
                folder = PersistenceConstants.DEFAULT_FILE_PERSISTENCE_FOLDER;
                if (log.isDebugEnabled()) {
                    log.debug("File system persistence location not set. Default persistence location will be used.");
                }
            } else {
                folder = String.valueOf(folderObject);
            }

        } else {
            folder = PersistenceConstants.DEFAULT_FILE_PERSISTENCE_FOLDER;
            if (log.isDebugEnabled()) {
                log.debug("File system persistence config not set. Default persistence location will be used.");
            }
        }
    }

    @Override
    public byte[] load(IncrementalSnapshotInfo snapshotInfo) {
        File file = new File(folder + File.separator + snapshotInfo.getSiddhiAppId() + File.separator +
                snapshotInfo.getRevision());
        byte[] bytes = null;
        try {
            bytes = Files.toByteArray(file);
            if (log.isDebugEnabled()) {
                log.debug("State loaded for SiddhiApp '" + snapshotInfo.getSiddhiAppId() + "' revision '" +
                        snapshotInfo.getRevision() + "' from file system.");
            }
        } catch (IOException e) {
            log.error("Cannot load the revision '" + snapshotInfo.getRevision() + "' of SiddhiApp '" +
                    snapshotInfo.getSiddhiAppId() + "' from file system.", e);
        }
        byte[] decompressedSnapshot;
        try {
            decompressedSnapshot = CompressionUtil.decompressGZIP(bytes);
        } catch (IOException e) {
            throw new RuntimeException("Error occurred while trying to decompress the snapshot. Failed to " +
                    "load revision: " + snapshotInfo.getRevision() + " of Siddhi app: " + snapshotInfo.getSiddhiAppId(), e);
        }
        return decompressedSnapshot;
    }

    @Override
    public List<IncrementalSnapshotInfo> getListOfRevisionsToLoad (long restoreTime, String siddhiAppName) {

        File dir = new File(folder + File.separator + siddhiAppName);
        File[] files = dir.listFiles();
        if (files == null || files.length == 0) {
            return null;
        }
        List<IncrementalSnapshotInfo> results = new ArrayList<>();
        for (File file : files) {
            String fileName = file.getName();
            IncrementalSnapshotInfo snapshotInfo = PersistenceHelper.convertRevision(fileName);
            if (snapshotInfo.getTime() <= restoreTime &&
                    siddhiAppName.equals(snapshotInfo.getSiddhiAppId()) &&
                    snapshotInfo.getElementId() != null &&
                    snapshotInfo.getQueryName() != null) {
                //Note: Here we discard the (items.length == 2) scenario which is handled
                // by the full snapshot handling
                if (log.isDebugEnabled()) {
                    log.debug("List of revisions to load : " + fileName);
                }
                results.add(snapshotInfo);
            }
        }
        return results;
    }

    @Override
    public String getLastRevision(String siddhiAppName) {
        long restoreTime = -1;
        File dir = new File(folder + File.separator + siddhiAppName);
        File[] files = dir.listFiles();
        if (files == null || files.length == 0) {
            return null;
        }
        for (File file : files) {
            String fileName = file.getName();
            IncrementalSnapshotInfo snapshotInfo = PersistenceHelper.convertRevision(fileName);
            if (snapshotInfo.getTime() > restoreTime &&
                    siddhiAppName.equals(snapshotInfo.getSiddhiAppId()) &&
                    snapshotInfo.getElementId() != null &&
                    snapshotInfo.getQueryName() != null) {
                //Note: Here we discard the (items.length == 2) scenario which is handled
                // by the full snapshot handling
                restoreTime = snapshotInfo.getTime();
            }
        }
        if (restoreTime != -1) {
            if (log.isDebugEnabled()) {
                log.debug("Latest revision to load: " + restoreTime + PersistenceConstants.REVISION_SEPARATOR +
                        siddhiAppName);
            }
            return restoreTime + PersistenceConstants.REVISION_SEPARATOR + siddhiAppName;
        }
        return null;
    }

    private void cleanOldRevisions(IncrementalSnapshotInfo incrementalSnapshotInfo) {
        if (incrementalSnapshotInfo.getType() == IncrementalSnapshotInfo.SnapshotType.BASE) {
            File dir = new File(folder + File.separator + incrementalSnapshotInfo.getSiddhiAppId());
            File[] files = dir.listFiles();
            if (files != null) {
                long baseTimeStamp = (incrementalSnapshotInfo.getTime());
                for (File file : files) {
                    String fileName = file.getName();
                    IncrementalSnapshotInfo snapshotInfo = PersistenceHelper.convertRevision(fileName);
                    if (snapshotInfo.getTime() < baseTimeStamp &&
                            incrementalSnapshotInfo.getSiddhiAppId().equals(snapshotInfo.getSiddhiAppId()) &&
                            incrementalSnapshotInfo.getQueryName().equals(snapshotInfo.getQueryName()) &&
                            incrementalSnapshotInfo.getElementId().equals(snapshotInfo.getElementId())) {
                        if (file.exists()) {
                            Boolean isDeleted = file.delete();
                            if (!isDeleted) {
                                log.error("Error deleting old revision " + fileName);
                            }
                        }
                    }
                }
            }
        }
    }
}
