/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
package org.apache.jena.sparql.engine;
import java.util.Collection ;
import java.util.HashMap ;
import java.util.Map ;
import java.util.Set ;
import org.apache.jena.graph.Node ;
import org.apache.jena.sparql.ARQConstants ;
import org.apache.jena.sparql.algebra.Op ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.expr.Expr ;
import org.apache.jena.sparql.expr.ExprList ;
import org.apache.jena.sparql.graph.NodeTransform;
import org.apache.jena.sparql.graph.NodeTransformLib ;
/** Support for renaming all the variables in an algebra expession
* except for a fixed set to leave alone */
public class Rename
{
/** Given an old name, and some names already in use, pick a fresh, new name*/
public static Var chooseVarName(Var var, Collection<Var> inUse, String prefix)
{
Var var2 = var ;
do {
var2 = Var.alloc(prefix+var2.getName()) ;
} while (inUse.contains(var2)) ;
return var2 ;
}
/** Rename one node to another */
public static Op renameNode(Op op, Node oldName, Node newName)
{
NodeTransform renamer = new RenameNode(oldName, newName) ;
return NodeTransformLib.transform(renamer, op) ;
}
/** Rename one variable to another */
public static Op renameVar(Op op, Var oldName, Var newName)
{
NodeTransform renamer = new RenameNode(oldName, newName) ;
return NodeTransformLib.transform(renamer, op) ;
}
// See also OpVar, VarFinder and VarLib - needs to be pulled together really.
// Also need renaming support for renames where only a
// certain set are mapped (for (assign (?x ?.0)))
private static final String prefix = ARQConstants.allocVarScopeHiding ;
/** Rename all variables in a pattern, EXCEPT for those named as constant */
public static Op renameVars(Op op, Collection<Var> constants)
{
return NodeTransformLib.transform(new RenameAnyVars(constants, prefix), op) ;
}
/** Rename all variables in an expression, EXCEPT for those named as constant */
public static ExprList renameVars(ExprList exprList, Set<Var> constants)
{
NodeTransform renamer = new RenameAnyVars(constants, prefix) ;
return NodeTransformLib.transform(renamer, exprList) ;
}
public static Expr renameVars(Expr expr, Set<Var> constants)
{
NodeTransform renamer = new RenameAnyVars(constants, prefix) ;
return NodeTransformLib.transform(renamer, expr) ;
}
/** Undo the effect of the rename operation, once or repeatedly.
* This assumes the op was renamed by VarRename.rename */
public static Op reverseVarRename(Op op, boolean repeatedly)
{
NodeTransform renamer = new UnrenameAnyVars(prefix, repeatedly) ;
return NodeTransformLib.transform(renamer, op) ;
}
// ---- Transforms that do the renaming and unrenaming.
static class RenameNode implements NodeTransform
{
private final Node oldName ;
private final Node newName ;
public RenameNode (Node oldName, Node newName)
{
this.oldName = oldName ;
this.newName = newName ;
}
@Override
public Node apply(Node node)
{
if ( node.equals(oldName) )
return newName ;
return node ;
}
}
static class RenameAnyVars implements NodeTransform
{
private final Map<Var, Var> aliases = new HashMap<>() ;
private final Collection<Var> constants ;
private final String varPrefix ;
public RenameAnyVars(Collection<Var> constants, String varPrefix)
{
this.constants = constants ;
this.varPrefix = varPrefix ;
}
@Override
public final Node apply(Node node)
{
if ( ! Var.isVar(node) ) return node ;
if ( constants.contains(node) ) return node ;
Var var = (Var)node ;
Var var2 = aliases.get(var) ;
if ( var2 != null )
return var2 ;
// The new name is the old name with a "/" - clashes?
// Provided the old name isn't a constant as well, this is safe
// if renaming is bottom up and done once.
// Really safe - use the global allocator.
//var2 = allocator.allocVar() ;
var2 = Rename.chooseVarName(var, constants, prefix) ;
aliases.put(var, var2) ;
return var2 ;
}
}
/** Reverse a renaming (assuming renaming was done by prefixing variable names) */
static class UnrenameAnyVars implements NodeTransform
{
private final String varPrefix ;
private final boolean repeatedly ;
public UnrenameAnyVars(String varPrefix, boolean repeatedly)
{
this.varPrefix = varPrefix ;
this.repeatedly = repeatedly ;
}
@Override
public Node apply(Node node)
{
if ( ! Var.isVar(node) )
return node ;
Var var = (Var)node ;
String varName = var.getName() ;
if ( repeatedly )
{
while ( varName.startsWith(varPrefix) )
varName = varName.substring(varPrefix.length()) ;
}
else
{
if ( varName.startsWith(varPrefix) )
varName = varName.substring(varPrefix.length()) ;
}
if ( varName == var.getName() )
return node ;
return Var.alloc(varName) ;
}
}
}