/*
 * Copyright (c) 2011-2015 EPFL DATA Laboratory
 * Copyright (c) 2014-2015 The Squall Collaboration (see NOTICE)
 *
 * All rights reserved.
 *
 * 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 ch.epfl.data.squall.expressions;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import ch.epfl.data.squall.types.DateType;
import ch.epfl.data.squall.types.IntegerType;
import ch.epfl.data.squall.types.Type;
import ch.epfl.data.squall.visitors.ValueExpressionVisitor;

public class DateDiff implements ValueExpression<Integer> {
    private static final long serialVersionUID = 1L;

    private final Type<Date> _dc = new DateType();
    private final Type<Integer> _ic = new IntegerType();

    private final ValueExpression<Date> _ve1, _ve2;

    public DateDiff(ValueExpression<Date> ve1, ValueExpression<Date> ve2) {
	_ve1 = ve1;
	_ve2 = ve2;
    }

    @Override
    public void accept(ValueExpressionVisitor vev) {
	vev.visit(this);
    }

    @Override
    public void changeValues(int i, ValueExpression<Integer> newExpr) {
	// nothing
    }

    @Override
    public Integer eval(List<String> tuple) {
	Date dateObj1 = _ve1.eval(tuple);
	Date dateObj2 = _ve2.eval(tuple);

	long diff = dateObj2.getTime() - dateObj1.getTime();
	int diffDays = (int) (diff / (24 * 1000 * 60 * 60));

	return diffDays;
    }

    @Override
    public String evalString(List<String> tuple) {
	return _ic.toString(eval(tuple));
    }

    @Override
    public List<ValueExpression> getInnerExpressions() {
	final List<ValueExpression> result = new ArrayList<ValueExpression>();
	result.add(_ve1);
	result.add(_ve2);
	return result;
    }

    @Override
    public Type getType() {
	return _ic;
    }

    @Override
    public void inverseNumber() {
	// nothing
    }

    @Override
    public boolean isNegative() {
	// nothing
	return false;
    }

    @Override
    public String toString() {
	final StringBuilder sb = new StringBuilder();
	sb.append("DateDiff ");
	sb.append("First Exp: ").append(_ve1.toString()).append("\n");
	sb.append("Second Exp: ").append(_ve2.toString()).append("\n");
	return sb.toString();
    }
}