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/*
 * JasperReports - Free Java Reporting Library.
 * Copyright (C) 2001 - 2011 Jaspersoft Corporation. All rights reserved.
 * http://www.jaspersoft.com
 *
 * Unless you have purchased a commercial license agreement from Jaspersoft,
 * the following license terms apply:
 *
 * This program is part of JasperReports.
 *
 * JasperReports is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * JasperReports is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with JasperReports. If not, see .
 */
package net.sf.jasperreports.engine.query;

import net.sf.jasperreports.engine.JRRuntimeException;


/**
 * Base BETWEEN clause function for SQL queries. 
 * 
 * The purpose of this clause function is to find that a given 
 * value can be found in a given A...B interval.
 * 
 * 
 * The first token in the $X{...} syntax is the function ID token. Possible values for 
 * the BETWEEN clause function ID token are:
 * 

 * BETWEEN - in this case the A...B interval will be considered open: (A,B)
 * [BETWEEN - in this case the A...B interval will be considered right-open: [A,B)
 * BETWEEN] - in this case the A...B interval will be considered left-open: (A,B]
 * [BETWEEN] - in this case the A...B interval will be considered closed: [A,B]
 *  
 * 
 * 
 * @author sanda zaharia ([email protected])
 * @version $Id: JRSqlBetweenClause.java 5180 2012-03-29 13:23:12Z teodord $
 */
public class JRSqlBetweenClause implements JRClauseFunction
{
	
	protected static final int POSITION_CLAUSE_ID = 0;
	protected static final int POSITION_DB_COLUMN = 1;
	protected static final int POSITION_LEFT_PARAMETER = 2;
	protected static final int POSITION_RIGHT_PARAMETER = 3;

	protected static final String CLAUSE_TRUISM = "0 = 0";

	protected static final JRSqlBetweenClause singleton = new JRSqlBetweenClause();
	
	/**
	 * Returns the singleton function instance.
	 * 
	 * @return the singleton function instance
	 */
	public static JRSqlBetweenClause instance()
	{
		return singleton;
	}


	/**
	 * Creates a BETWEEN-like SQL clause, depending on the clause ID.
	 * 
	 * 
	 * The method expects three clause tokens (after the ID token):
	 * 

	 * 	The first token is the SQL column (or column combination) to be used in the clause.
	 * 	The second token is the name of the parameter that contains the left member value.
	 * 	The second token is the name of the parameter that contains the right member value.
	 * 
	 * 
	 * 
	 * The method constructs one of the following clauses:
	 * 

	 * (column > ? AND column < ?) if the clause ID is BETWEEN
	 * (column >= ? AND column < ?) if the clause ID is [BETWEEN
	 * (column > ? AND column <= ?) if the clause ID is BETWEEN]
	 * (column >= ? AND column <= ?) if the clause ID is [BETWEEN]
	 *  
	 * If the left member value is null, one of the following clauses will be generated:
	 * 
	 * column < ? if the clause ID is BETWEEN or BETWEEN
	 * column <= ? if the clause ID is BETWEEN] or [BETWEEN]
	 *  
	 * If the right member value is null, one of the following clauses will be generated:
	 * 
	 * column > ? if the clause ID is BETWEEN or BETWEEN]
	 * column >= ? if the clause ID is [BETWEEN or [BETWEEN]
	 *  
	 * If the both left and right member values are null, the method generates a SQL clause that 
	 * will always evaluate to true (e.g. 0 = 0).
	 * 
	 * @param clauseTokens
	 * @param queryContext
	 */
	public void apply(JRClauseTokens clauseTokens, JRQueryClauseContext queryContext)
	{
		String clauseId = clauseTokens.getToken(POSITION_CLAUSE_ID);
		String col = clauseTokens.getToken(POSITION_DB_COLUMN);
		String leftParam = clauseTokens.getToken(POSITION_LEFT_PARAMETER);
		String rightParam = clauseTokens.getToken(POSITION_RIGHT_PARAMETER);

		if (clauseId == null)
		{
			throw new JRRuntimeException("Missing clause name token");
		}
		
		if (col == null)
		{
			throw new JRRuntimeException("SQL LESS/GREATER clause missing DB column token");
		}
		
		if (leftParam == null)
		{
			throw new JRRuntimeException("SQL LESS/GREATER clause missing left parameter token");
		}
		
		if (rightParam == null)
		{
			throw new JRRuntimeException("SQL LESS/GREATER clause missing right parameter token");
		}
		
		Object leftParamValue = queryContext.getValueParameter(leftParam).getValue();
		Object rightParamValue = queryContext.getValueParameter(rightParam).getValue();
		StringBuffer sbuffer = queryContext.queryBuffer();
		
		if(leftParamValue != null && rightParamValue != null)
		{
			sbuffer.append("( ");
			handleGreaterClause(sbuffer, clauseId, col, leftParam, queryContext);
			sbuffer.append(" AND ");
			handleLessClause(sbuffer, clauseId, col, rightParam, queryContext);
			sbuffer.append(" )");
		}
		else if(leftParamValue == null)
		{
			if(rightParamValue == null)
			{
				sbuffer.append(CLAUSE_TRUISM);
			}
			else
			{
				handleLessClause(sbuffer, clauseId, col, rightParam, queryContext);
			}
		}
		else 
		{
			handleGreaterClause(sbuffer, clauseId, col, leftParam, queryContext);
		}
	}
	
	/**
	 * 
	 * @param clauseId the clause ID
	 * @return the '>' or '>=' sign
	 */
	protected String getGreaterOperator(String clauseId)
	{
		return clauseId.startsWith("[") ? ">=" : ">";
	}
	
	/**
	 * 
	 * @param clauseId the clause ID
	 * @return the '<' or '<=' sign
	 */
	protected String getLessOperator(String clauseId)
	{
		return clauseId.endsWith("]") ? "<=" : "<";
	}
	
	/**
	 * Generates either a 'column > ?' or a 'column >= ?' clause
	 * 
	 * @param sbuffer the StringBuffer that contains the generated query
	 * @param clauseId the clause ID
	 * @param col the name of the column, or a column names combination  
	 * @param leftParam the name of the parameter that contains the left member value
	 * @param queryContext the query context
	 */
	protected void handleGreaterClause(
			StringBuffer sbuffer, 
			String clauseId, 
			String col, 
			String leftParam, 
			JRQueryClauseContext queryContext
			)
	{
		sbuffer.append(col);
		sbuffer.append(' ');
		sbuffer.append(getGreaterOperator(clauseId));
		sbuffer.append(' ');
		sbuffer.append('?');
		
		queryContext.addQueryParameter(leftParam);
		
	}
	
	/**
	 * Generates either a 'column < ?' or a 'column <= ?' clause
	 * 
	 * @param sbuffer the StringBuffer that contains the generated query
	 * @param clauseId the clause ID
	 * @param col the name of the column, or a column names combination  
	 * @param rightParam the name of the parameter that contains the right member value
	 * @param queryContext the query context
	 */
	protected void handleLessClause(
			StringBuffer sbuffer, 
			String clauseId, 
			String col, 
			String rightParam, 
			JRQueryClauseContext queryContext
			)
	{
		sbuffer.append(col);
		sbuffer.append(' ');
		sbuffer.append(getLessOperator(clauseId));
		sbuffer.append(' ');
		sbuffer.append('?');
		
		queryContext.addQueryParameter(rightParam);
		
	}
}