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/**
 * Copyright (c) 1997-2013, www.tinygroup.org ([email protected]).
 * 
 * Licensed under the GPL, Version 3.0 (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.gnu.org/licenses/gpl.html
 * 

 * 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.tinygroup.tinysqldsl.expression;

import org.tinygroup.tinysqldsl.base.StatementSqlBuilder;
import org.tinygroup.tinysqldsl.util.DslUtil;

import java.util.List;

/**
 * CASE/WHEN expression.
 *
 * Syntax: 
 * CASE
 * WHEN condition THEN expression
 * [WHEN condition THEN expression]...
 * [ELSE expression]
 * END
 * 
 *
 * 

 * or 

 * 

 *
 *  * CASE expression
 * WHEN condition THEN expression
 * [WHEN condition THEN expression]...
 * [ELSE expression]
 * END
 * 
 *
 * See also: https://aurora.vcu.edu/db2help/db2s0/frame3.htm#casexp
 * http://sybooks.sybase.com/onlinebooks/group-as/asg1251e /commands/
 *
 * @ebt-link;pt=5954?target=%25N%15_52628_START_RESTART_N%25
 *
 *
 */
public class CaseExpression implements Expression {

    private Expression switchExpression;
    private List whenClauses;
    private Expression elseExpression;

    /**
     * @return Returns the switchExpression.
     */
    public Expression getSwitchExpression() {
        return switchExpression;
    }

    /**
     * @param switchExpression The switchExpression to set.
     */
    public void setSwitchExpression(Expression switchExpression) {
        this.switchExpression = switchExpression;
    }

    /**
     * @return Returns the elseExpression.
     */
    public Expression getElseExpression() {
        return elseExpression;
    }

    /**
     * @param elseExpression
     *            The elseExpression to set.
     */
    public void setElseExpression(Expression elseExpression) {
        this.elseExpression = elseExpression;
    }

    /**
     * @return Returns the whenClauses.
     */
    public List getWhenClauses() {
        return whenClauses;
    }

    /**
     * @param whenClauses
     *            The whenClauses to set.
     */
    public void setWhenClauses(List whenClauses) {
        this.whenClauses = whenClauses;
    }

    public String toString() {
        return "CASE "
                + ((switchExpression != null) ? switchExpression + " " : "")
                + DslUtil.getStringList(whenClauses, false, false)
                + " "
                + ((elseExpression != null) ? "ELSE " + elseExpression + " "
                : "") + "END";
    }

    public void builderExpression(StatementSqlBuilder builder) {
        StringBuilder buffer = builder.getStringBuilder();
        buffer.append("CASE ");
        Expression switchExp = getSwitchExpression();
        if (switchExp != null) {
            switchExp.builderExpression(builder);
            buffer.append(" ");
        }

        for (Expression exp : getWhenClauses()) {
            exp.builderExpression(builder);
        }

        Expression elseExp = getElseExpression();
        if (elseExp != null) {
            buffer.append("ELSE ");
            elseExp.builderExpression(builder);
            buffer.append(" ");
        }

        buffer.append("END");
    }
}