package org.geotools.tutorial.function;
import java.util.List;
import org.geotools.filter.capability.FunctionNameImpl;
import org.geotools.util.Converters;
import org.opengis.filter.capability.FunctionName;
import org.opengis.filter.expression.Expression;
import org.opengis.filter.expression.ExpressionVisitor;
import org.opengis.filter.expression.Function;
import org.opengis.filter.expression.Literal;
import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.Point;
import com.vividsolutions.jts.linearref.LinearLocation;
import com.vividsolutions.jts.linearref.LocationIndexedLine;
/**
* Quick function that illustrates snapping to a line.
*
* @author jody
*/
public class SnapFunction implements Function {
static FunctionName NAME = new FunctionNameImpl("snap", Point.class,
FunctionNameImpl.parameter("point",Point.class),
FunctionNameImpl.parameter("line",Geometry.class));
private final List<Expression> parameters;
private final Literal fallback;
public SnapFunction(List<Expression> parameters, Literal fallback) {
if (parameters == null) {
throw new NullPointerException("parameters required");
}
if (parameters.size() != 2) {
throw new IllegalArgumentException(
"snap( point, line) requires two parameters only");
}
this.parameters = parameters;
this.fallback = fallback;
}
public Object evaluate(Object object) {
return evaluate(object, Point.class);
}
public <T> T evaluate(Object object, Class<T> context) {
Expression pointExpression = parameters.get(0);
Point point = pointExpression.evaluate(object, Point.class);
Expression lineExpression = parameters.get(1);
Geometry line = lineExpression.evaluate(object, Geometry.class);
LocationIndexedLine index = new LocationIndexedLine(line);
LinearLocation location = index.project(point.getCoordinate());
Coordinate snap = index.extractPoint(location);
Point pt = point.getFactory().createPoint(snap);
return Converters.convert(pt, context); // convert to requested format
}
public Object accept(ExpressionVisitor visitor, Object extraData) {
return visitor.visit(this, extraData);
}
public String getName() {
return NAME.getName();
}
public FunctionName getFunctionName() {
return NAME;
}
public List<Expression> getParameters() {
return parameters;
}
public Literal getFallbackValue() {
return fallback;
}
}