package adql.query.constraint;
/*
* This file is part of ADQLLibrary.
*
* ADQLLibrary 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.
*
* ADQLLibrary 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 ADQLLibrary. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright 2012-2015 - UDS/Centre de Données astronomiques de Strasbourg (CDS),
* Astronomisches Rechen Institute (ARI)
*/
import java.util.NoSuchElementException;
import adql.query.ADQLIterator;
import adql.query.ADQLObject;
import adql.query.TextPosition;
import adql.query.operand.ADQLColumn;
/**
* Represents a comparison between a column to the NULL value.
*
* @author Grégory Mantelet (CDS;ARI)
* @version 1.4 (06/2015)
*/
public class IsNull implements ADQLConstraint {
/** The column whose the value must be compared to <i>null</i>. */
private ADQLColumn column;
/** Indicates whether the predicate IS NOT NULL must be used rather than IS NULL. */
private boolean isNotNull = false;
/** Position of this {@link IsNull} in the given ADQL query string.
* @since 1.4 */
private TextPosition position = null;
/**
* Builds a comparison between the given column and NULL.
*
* @param column The column whose the value must be compared to NULL.
* @throws NullPointerException If the given column is <i>null</i>.
*/
public IsNull(ADQLColumn column) throws NullPointerException{
this(column, false);
}
/**
* Builds a comparison between the column and NULL.
*
* @param column The column whose the value must be compared to NULL.
* @param isNot <i>true</i> means IS NOT NULL, <i>false</i> means IS NULL.
* @throws NullPointerException If the given column is <i>null</i>.
*/
public IsNull(ADQLColumn column, boolean isNot) throws NullPointerException{
setColumn(column);
isNotNull = isNot;
}
/**
* Builds a IsNull constraint by copying the given one.
*
* @param toCopy The IsNull to copy.
* @throws Exception If there is an error during the copy.
*/
public IsNull(IsNull toCopy) throws Exception{
column = (ADQLColumn)toCopy.column.getCopy();
isNotNull = toCopy.isNotNull;
position = (toCopy.position == null) ? null : new TextPosition(toCopy.position);
}
/**
* Gets the column whose the value is compared to <i>NULL</i>.
*
* @return The column compared to <i>NULL</i>.
*/
public final ADQLColumn getColumn(){
return column;
}
/**
* Lets changing the column whose the value must be compared to <i>NULL</i>.
*
* @param column The new column to compare to <i>NULL</i>.
* @throws NullPointerException If the given column is <i>null</i>.
*/
public final void setColumn(ADQLColumn column) throws NullPointerException{
if (column == null)
throw new NullPointerException("Impossible to compare nothing to NULL: no column has been given to build a IsNull constraint !");
else{
this.column = column;
position = null;
}
}
/**
* Tells whether the predicate is IS NULL or IS NOT NULL.
*
* @return <i>true</i> for IS NOT NULL, <i>false</i> for IS NULL.
*/
public final boolean isNotNull(){
return isNotNull;
}
/**
* Lets indicating which predicate must be used (IS NULL or IS NOT NULL).
*
* @param notNull <i>true</i> for IS NOT NULL, <i>false</i> for IS NULL.
*/
public final void setNotNull(boolean notNull){
isNotNull = notNull;
position = null;
}
@Override
public final TextPosition getPosition(){
return position;
}
/**
* Set the position of this {@link IsNull} in the given ADQL query string.
*
* @param position New position of this {@link IsNull}.
* @since 1.4
*/
public final void setPosition(final TextPosition position){
this.position = position;
}
@Override
public ADQLObject getCopy() throws Exception{
return new IsNull(this);
}
@Override
public String getName(){
return "IS" + (isNotNull ? " NOT " : " ") + "NULL";
}
@Override
public ADQLIterator adqlIterator(){
return new ADQLIterator(){
private boolean columnGot = (column == null);
@Override
public ADQLObject next(){
if (columnGot)
throw new NoSuchElementException();
columnGot = true;
return column;
}
@Override
public boolean hasNext(){
return !columnGot;
}
@Override
public void replace(ADQLObject replacer) throws UnsupportedOperationException, IllegalStateException{
if (!columnGot)
throw new IllegalStateException("replace(ADQLObject) impossible: next() has not yet been called !");
if (replacer == null)
remove();
else if (replacer instanceof ADQLColumn){
column = (ADQLColumn)replacer;
position = null;
}else
throw new UnsupportedOperationException("Impossible to replace a column (" + column.toADQL() + ") by a " + replacer.getClass().getName() + " (" + replacer.toADQL() + ") in a IsNull constraint (" + toADQL() + ") !");
}
@Override
public void remove(){
if (!columnGot)
throw new IllegalStateException("remove() impossible: next() has not yet been called !");
else
throw new UnsupportedOperationException("Impossible to remove the only column (" + column.toADQL() + ") of a constraint IsNull (" + toADQL() + ") !");
}
};
}
@Override
public String toADQL(){
return column.toADQL() + " " + getName();
}
}