/*
 * 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.piggybank.evaluation.datetime.diff;

import org.apache.pig.EvalFunc;
import org.apache.pig.FuncSpec;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.impl.logicalLayer.schema.Schema;
import org.joda.time.*;

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

/**
 * <p>ISOSecondsBetween returns the number of seconds between two ISO8601 datetimes as a Long</p>
 * <ul>
 * <li>Jodatime: http://joda-time.sourceforge.net/</li>
 * <li>ISO8601 Date Format: http://en.wikipedia.org/wiki/ISO_8601</li>
 * </ul>
 * <br />
 * <pre>
 * Example usage:
 * 
 * REGISTER /Users/me/commiter/piggybank/java/piggybank.jar ;
 * REGISTER /Users/me/commiter/piggybank/java/lib/joda-time-1.6.jar ;
 *
 * DEFINE ISOYearsBetween org.apache.pig.piggybank.evaluation.datetime.diff.ISOYearsBetween();
 * DEFINE ISOMonthsBetween org.apache.pig.piggybank.evaluation.datetime.diff.ISOMonthsBetween();
 * DEFINE ISODaysBetween org.apache.pig.piggybank.evaluation.datetime.diff.ISODaysBetween();
 * DEFINE ISOHoursBetween org.apache.pig.piggybank.evaluation.datetime.diff.ISOHoursBetween();
 * DEFINE ISOMinutesBetween org.apache.pig.piggybank.evaluation.datetime.diff.ISOMinutesBetween();
 * DEFINE ISOSecondsBetween org.apache.pig.piggybank.evaluation.datetime.diff.ISOSecondsBetween();
 *
 * ISOin = LOAD 'test.tsv' USING PigStorage('\t') AS (dt:chararray, dt2:chararray);
 *
 * DESCRIBE ISOin;
 * ISOin: {dt: chararray,dt2: chararray}
 *
 * DUMP ISOin;
 *
 * (2009-01-07T01:07:01.000Z,2008-02-01T00:00:00.000Z)
 * (2008-02-06T02:06:02.000Z,2008-02-01T00:00:00.000Z)
 * (2007-03-05T03:05:03.000Z,2008-02-01T00:00:00.000Z)
 * ...
 *
 * diffs = FOREACH ISOin GENERATE ISOYearsBetween(dt, dt2) AS years,
 *     ISOMonthsBetween(dt, dt2) AS months,
 *     ISODaysBetween(dt, dt2) AS days,
 * 	   ISOHoursBetween(dt, dt2) AS hours,
 * 	   ISOMinutesBetween(dt, dt2) AS mins,
 * 	   ISOSecondsBetween(dt, dt2) AS secs;
 *
 * DESCRIBE diffs;
 * diffs: {years: long,months: long,days: long,hours: long,mins: long,secs: long}
 *
 * DUMP diffs;
 *
 * (0L,11L,341,8185L,491107L,29466421L)
 * (0L,0L,5,122L,7326L,439562L)
 * (0L,-10L,-332,-7988L,-479334L,-28760097L)
 * </pre>
 */

public class ISOSecondsBetween extends EvalFunc<Long> {

    @Override
    public Long exec(Tuple input) throws IOException
    {
        if (input == null || input.size() < 2) {
            return null;
        }

        if (input.get(0) == null || input.get(1) == null) {
            return null;
        }

        DateTime startDate = new DateTime(input.get(0).toString());
        DateTime endDate = new DateTime(input.get(1).toString());

        // Larger date first
        Seconds s = Seconds.secondsBetween(endDate, startDate);
        long seconds = s.getSeconds();

        return seconds;
    }

	@Override
	public Schema outputSchema(Schema input) {
        return new Schema(new Schema.FieldSchema(getSchemaName(this.getClass().getName().toLowerCase(), input), DataType.LONG));
	}

    @Override
    public List<FuncSpec> getArgToFuncMapping() throws FrontendException {
        List<FuncSpec> funcList = new ArrayList<FuncSpec>();
        Schema s = new Schema();
        s.add(new Schema.FieldSchema(null, DataType.CHARARRAY));
        s.add(new Schema.FieldSchema(null, DataType.CHARARRAY));
        funcList.add(new FuncSpec(this.getClass().getName(), s));
        return funcList;
    }
}
