jnidzwetzki/bboxdb

/*******************************************************************************
 *
 *    Copyright (C) 2015-2022 the BBoxDB project
 *  
 *    Licensed 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.bboxdb.distribution;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.bboxdb.storage.entity.DistributionGroupMetadata;
import org.bboxdb.storage.sstable.SSTableHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.yaml.snakeyaml.Yaml;

public class DistributionGroupMetadataHelper {
    
    /**
     * The Logger
     */
    private final static Logger logger = LoggerFactory.getLogger(DistributionGroupMetadataHelper.class);
    
    /**
     * Write new metadata for a distribution group
     * @param distributionGroupName
     * @param distributionGroupMetadata
     * @throws IOException 
     */
    public static void writeMedatadataForGroup(final String basedir, 
            final String distributionGroupName, 
            final DistributionGroupMetadata distributionGroupMetadata) throws IOException {
        
        final Map<String, Object> data = new HashMap<>();
        data.put("version", distributionGroupMetadata.getVersion());
        
        final String filename = getFilename(basedir, distributionGroupName);
        final File metadataFile = new File(filename);
        
        logger.info("Writing metadata to {} ", metadataFile);
        
        final FileWriter writer = new FileWriter(metadataFile);
        
        final Yaml yaml = new Yaml();
        yaml.dump(data, writer);
        writer.close();
    }

    /**
     * Get the filename of the meta data
     * @param distributionGroupName
     * @return
     */
    private static String getFilename(final String basedir, final String distributionGroupName) {
        return SSTableHelper.getDistributionGroupMedatadaFile(basedir, distributionGroupName);
    }

    /**
     * Read the metadata data of a distribution group
     * @param distributionGroupName
     * @return
     */
    public static DistributionGroupMetadata getMedatadaForGroup(final String basedir, 
            final String distributionGroupName) {
        
        final Yaml yaml = new Yaml(); 
        final String filename = getFilename(basedir, distributionGroupName);

        final File file = new File(filename);
        
        if(! file.exists()) {
            return null;
        }
        
        FileReader reader;
        try {
            reader = new FileReader(filename);
        } catch (FileNotFoundException e) {
            logger.warn("Unable to load file: " + filename, e);
            return null;
        }

        return yaml.loadAs(reader, DistributionGroupMetadata.class);
    }
}