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package com.opower.hadoop.conf;

import org.apache.hadoop.conf.Configuration;
import org.joda.time.DateTimeZone;
import org.joda.time.Interval;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Utility methods for the hadoop {@link Configuration}
 *
 * @author oren.benjamin
 */
public final class ConfigurationUtils {

    /**
     * Add an interval to the configuration
     * 
     * Stored as three configuration values:
     * 

     *   <key>.start: interval start (millis since epoch set with {@link Configuration#setLong})
     *   <key>.end  : interval end (millis since epoch set with {@link Configuration#setLong})
     *   <key>.zone : time zone ID
     * 
     * 

     * @param key      the configuration key
     * @param interval the configuration value
     */
    public static void setInterval(Configuration configuration, String key, Interval interval) {
        checkNotNull(configuration, "configuration");
        checkNotNull(key, "key");
        checkNotNull(interval, "interval");

        configuration.setLong(key + ".start", interval.getStartMillis());
        configuration.setLong(key + ".end", interval.getEndMillis());
        configuration.set(key + ".zone", interval.getChronology().getZone().getID());
    }

    /**
     * Get an interval from the hadoop configuration
     *
     * @param configuration the hadoop configuration
     * @param key           the configuration key
     * @return the interval value configured for {@code key}
     * @see #setInterval
     */
    public static Interval getInterval(Configuration configuration, String key) {
        checkNotNull(configuration, "configuration");
        checkNotNull(key, "key");

        long start = getRequiredLong(configuration, key + ".start");
        long end = getRequiredLong(configuration, key + ".end");
        String zoneID = getRequiredValue(configuration, key + ".zone");
        return new Interval(start, end, DateTimeZone.forID(zoneID));
    }

    /**
     * Get a long value from a hadoop configuration
     * @param configuration the hadoop configuration
     * @param key           the configuration key
     * @return the long value configured for {@code key}
     * @throws NumberFormatException if the configuration value is not a parseable long
     * @throws NullPointerException if no configuration value is set
     */
    public static long getRequiredLong(Configuration configuration, String key) {
        checkNotNull(configuration, "configuration");
        checkNotNull(key, "key");

        return Long.parseLong(getRequiredValue(configuration, key));
    }

    /**
     * Get a required value from a hadoop configuration
     *
     * @param configuration the hadoop configuration
     * @param key           the configuration key
     * @return the configuration value
     * @throws NullPointerException if no configuration value is set for {@code key}
     */
    public static String getRequiredValue(Configuration configuration, String key) {
        checkNotNull(configuration, "configuration");
        checkNotNull(key, "key");

        return checkNotNull(configuration.get(key), "No configuration value corresponding to key: %s", key);
    }

    private ConfigurationUtils() {}
}