/*
 * 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.wayang.profiler.util;

import java.io.IOException;
import java.util.Arrays;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.rrd4j.ConsolFun;
import org.rrd4j.core.FetchData;
import org.rrd4j.core.FetchRequest;
import org.rrd4j.core.RrdBackendFactory;
import org.rrd4j.core.RrdDb;

/**
 * Utility to read from an RRD file.
 */
public class RrdAccessor implements AutoCloseable {

    private final Logger logger = LogManager.getLogger(this.getClass());

    private final RrdDb rrdDb;

    private RrdAccessor(RrdDb rrdDb) {
        this.rrdDb = rrdDb;
        try {
            this.logger.info("Opened RRD with {} archives and data sources {}.", rrdDb.getArcCount(), Arrays.toString(rrdDb.getDsNames()));
        } catch (Throwable t) {
            throw new RuntimeException(t);
        }
    }

    public static RrdAccessor open(String rrdPath) {
        try {
            final RrdDb rrdDb = new RrdDb("", "rrdtool:/" + rrdPath, RrdBackendFactory.getFactory("MEMORY"));
            rrdDb.getLastUpdateTime();
            return new RrdAccessor(rrdDb);
        } catch (IOException e) {
            throw new RuntimeException("Could not open RRD.", e);
        }
    }

    public double query(String dsName, long startTimestamp, long endTimestamp, ConsolFun consolidationFunction) {
        long tStart = convertToUnixTimestamp(startTimestamp);
        long tEnd = convertToUnixTimestamp(endTimestamp);
        if (tStart == tEnd) {
            this.logger.warn("Shifting end time by 1 second because it is identical with the start time.");
            tEnd++;
        }
        try {
            final FetchRequest request = this.rrdDb.createFetchRequest(consolidationFunction, tStart, tEnd);
            final FetchData fetchData = request.fetchData();
            return fetchData.getAggregate(dsName, consolidationFunction);
        } catch (IOException e) {
            e.printStackTrace();
            return Double.NaN;
        }
    }

    public long getLastUpdateMillis() {
        try {
            return convertToJavaTimestamp(this.rrdDb.getLastUpdateTime());
        } catch (IOException e) {
            e.printStackTrace();
            return -1;
        }
    }

    public static long convertToUnixTimestamp(long javaTimestamp) {
        return (javaTimestamp + 500) / 1000;
    }

    public static long convertToJavaTimestamp(long unixTimestamp) {
        return unixTimestamp * 1000 + 500;
    }

    @Override
    public void close() {
        if (this.rrdDb != null) {
            try {
                this.rrdDb.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}