/*
 * 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.pig.backend.hadoop.executionengine.mapReduceLayer;

import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POStore;
import org.apache.pig.impl.util.UriUtil;

/**
 * Class that computes the size of output for file-based systems.
 */
public class FileBasedOutputSizeReader implements PigStatsOutputSizeReader {

    private static final Log log = LogFactory.getLog(FileBasedOutputSizeReader.class);

    /**
     * Returns whether the given POStore is supported by this output size reader
     * or not. We check whether the uri scheme of output file is one of hdfs,
     * local, and s3.
     * @param sto POStore
     */
    @Override
    public boolean supports(POStore sto, Configuration conf) {
        boolean nullOrSupportedScheme = UriUtil.isHDFSFileOrLocalOrS3N(getLocationUri(sto), conf);
        if (nullOrSupportedScheme) {
            // Some store functions that do not have scheme
            // do not support file-based output reader (e.g.HCatStorer),
            // so they should be excluded.
            String unsupported = conf.get(
                    PigStatsOutputSizeReader.OUTPUT_SIZE_READER_UNSUPPORTED);
            if (unsupported != null) {
                String storeFuncName = sto.getStoreFunc().getClass().getCanonicalName();
                for (String s : unsupported.split(",")) {
                    if (s.equalsIgnoreCase(storeFuncName)) {
                        return false;
                    }
                }
            }
        }
        return nullOrSupportedScheme;
    }

    /**
     * Returns the total size of output files in bytes
     * @param sto POStore
     * @param conf configuration
     */
    @Override
    public long getOutputSize(POStore sto, Configuration conf) throws IOException {
        if (!supports(sto, conf)) {
            log.warn("'" + sto.getStoreFunc().getClass().getCanonicalName()
                    + "' is not supported by " + getClass().getCanonicalName());
            return -1;
        }

        Path p = new Path(getLocationUri(sto));
        return getPathSize(p, p.getFileSystem(conf));
    }

    private long getPathSize(Path storePath, FileSystem fs) throws IOException {
        long bytes = 0;
        FileStatus[] lst = fs.listStatus(storePath);
        if (lst != null) {
            for (FileStatus status : lst) {
                if (status.isFile()) {
                    if (status.getLen() > 0)
                        bytes += status.getLen();
                }
                else { // recursively count nested leaves' (files) sizes
                    bytes += getPathSize(status.getPath(), fs);
                }
            }
        }
        return bytes;
    }

    /**
     * Returns the uri of output file in string
     * @param sto POStore
     */
    private static String getLocationUri(POStore sto) {
        return sto.getSFile().getFileName();
    }
}