/*
 * Copyright 2013 Eediom Inc.
 * 
 * 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.araqne.logdb.query.expr;

import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.araqne.logdb.QueryContext;
import org.araqne.logdb.QueryParseException;
import org.araqne.logdb.Row;

/**
 * @since 1.7.2
 * @author xeraph
 * 
 */
public class DateDiff implements Expression {
	private final List<Expression> exprs;
	private final Expression start;
	private final Expression end;
	private final int calField;

	private static final long YEAR_DIV = 31536000000L;
	private static final long MON_DIV = 2592000000L;
	private static final long DAY_DIV = 86400000L;
	private static final long HOUR_DIV = 3600000L;
	private static final long MIN_DIV = 60000L;
	private static final long SEC_DIV = 1000L;

	public DateDiff(QueryContext ctx, List<Expression> exprs) {
		this.exprs = exprs;

		if (exprs.size() != 3)
//			throw new QueryParseException("invalid-datediff-args", -1);
			throw new QueryParseException("90630", -1, -1  , null);

		start = exprs.get(0);
		end = exprs.get(1);

		String s = exprs.get(2).eval(null).toString();
		if (s.equals("day"))
			calField = Calendar.DAY_OF_YEAR;
		else if (s.equals("mon"))
			calField = Calendar.MONTH;
		else if (s.equals("year"))
			calField = Calendar.YEAR;
		else if (s.equals("hour"))
			calField = Calendar.HOUR;
		else if (s.equals("min"))
			calField = Calendar.MINUTE;
		else if (s.equals("sec"))
			calField = Calendar.SECOND;
		else if (s.equals("msec"))
			calField = Calendar.MILLISECOND;
		else{
		//	throw new QueryParseException("invalid-datediff-unit", -1);
			Map<String, String> params = new HashMap<String, String> ();
			params.put("field", s);
			throw new QueryParseException("90631", -1, -1  , params);
		}
	}

	@Override
	public Object eval(Row map) {
		Object o1 = start.eval(map);
		if (o1 == null)
			return null;

		Object o2 = end.eval(map);
		if (o2 == null)
			return null;

		if (o1 instanceof Date && o2 instanceof Date) {
			Date d1 = (Date) o1;
			Date d2 = (Date) o2;

			long interval = d2.getTime() - d1.getTime();
			switch (calField) {
			case Calendar.YEAR:
				return interval / YEAR_DIV;
			case Calendar.MONTH:
				return interval / MON_DIV;
			case Calendar.DAY_OF_YEAR:
				return interval / DAY_DIV;
			case Calendar.HOUR:
				return interval / HOUR_DIV;
			case Calendar.MINUTE:
				return interval / MIN_DIV;
			case Calendar.SECOND:
				return interval / SEC_DIV;
			case Calendar.MILLISECOND:
				return interval;
			}
		}

		return null;
	}

	@Override
	public String toString() {
		return "datediff(" + start + "," + end + "," + exprs.get(2) + ")";
	}
}