/*
 * Copyright 1999-2012 Alibaba Group.
 *  
 * 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.
 */
/**
 * (created at 2011-1-21)
 */
package com.alibaba.cobar.parser.ast.expression.primary.literal;

import java.util.HashMap;
import java.util.Map;

import com.alibaba.cobar.parser.ast.expression.Expression;
import com.alibaba.cobar.parser.visitor.SQLASTVisitor;

/**
 * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
 */
public class IntervalPrimary extends Literal {
    public static enum Unit {
        MICROSECOND,
        SECOND,
        MINUTE,
        HOUR,
        DAY,
        WEEK,
        MONTH,
        QUARTER,
        YEAR,
        SECOND_MICROSECOND,
        MINUTE_MICROSECOND,
        MINUTE_SECOND,
        HOUR_MICROSECOND,
        HOUR_SECOND,
        HOUR_MINUTE,
        DAY_MICROSECOND,
        DAY_SECOND,
        DAY_MINUTE,
        DAY_HOUR,
        YEAR_MONTH
    }

    private static final Map<String, Unit> unitMap = initUnitMap();

    private static Map<String, Unit> initUnitMap() {
        Unit[] units = Unit.class.getEnumConstants();
        Map<String, Unit> map = new HashMap<String, IntervalPrimary.Unit>(units.length);
        for (Unit unit : units) {
            map.put(unit.name(), unit);
        }
        return map;
    }

    /**
     * @param unitString must be upper case, null is forbidden
     */
    public static Unit getIntervalUnit(String unitString) {
        return unitMap.get(unitString);
    }

    private final Unit unit;
    private final Expression quantity;

    public IntervalPrimary(Expression quantity, Unit unit) {
        super();
        if (quantity == null)
            throw new IllegalArgumentException("quantity expression is null");
        if (unit == null)
            throw new IllegalArgumentException("unit of time is null");
        this.quantity = quantity;
        this.unit = unit;
    }

    /**
     * @return never null
     */
    public Unit getUnit() {
        return unit;
    }

    /**
     * @return never null
     */
    public Expression getQuantity() {
        return quantity;
    }

    @Override
    public void accept(SQLASTVisitor visitor) {
        visitor.visit(this);
    }
}