/*
* Copyright 2008 Google Inc.
*
* Licensed 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 com.google.gwt.resources.css.ast;
import java.util.List;
/**
* The base class for visiting a CSS tree. Traversal is initiated with a call to
* one of the <code>accept</code> methods. The default behavior of the
* <code>visit</code> methods is to return <code>true</code> to indicate that
* the calling node should traverse its descendant nodes.
*/
public class CssVisitor {
protected static final Context UNMODIFIABLE_CONTEXT = new Context() {
public boolean canInsert() {
return false;
}
public boolean canRemove() {
return false;
}
public void insertAfter(CssNode node) {
throw new UnsupportedOperationException();
}
public void insertBefore(CssNode node) {
throw new UnsupportedOperationException();
}
public void removeMe() {
throw new UnsupportedOperationException();
}
public void replaceMe(CssNode node) {
throw new UnsupportedOperationException();
}
};
public final void accept(List<? extends CssNode> nodes) {
doAccept(nodes);
}
public final <T extends CssNode> T accept(T node) {
return doAccept(node);
}
public final void acceptWithInsertRemove(List<? extends CssNode> nodes) {
doAcceptWithInsertRemove(nodes);
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssDef x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssEval x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssExternalSelectors x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssIf x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssMediaRule x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssNoFlip x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssPageRule x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssProperty x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssRule x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssSelector x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssSprite x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssStylesheet x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssUrl x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public void endVisit(CssUnknownAtRule x, Context ctx) {
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssDef x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssEval x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssExternalSelectors x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssIf x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssMediaRule x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssNoFlip x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssPageRule x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssProperty x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssRule x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssSelector x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssSprite x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssStylesheet x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssUrl x, Context ctx) {
return true;
}
/**
* @param x the node being visited
* @param ctx the context for the visit
*/
public boolean visit(CssUnknownAtRule x, Context ctx) {
return true;
}
protected void doAccept(List<? extends CssNode> list) {
for (CssNode node : list) {
doTraverse(node, UNMODIFIABLE_CONTEXT);
}
}
protected <T extends CssNode> T doAccept(T node) {
doTraverse(node, UNMODIFIABLE_CONTEXT);
return node;
}
protected void doAcceptWithInsertRemove(List<? extends CssNode> list) {
for (CssNode node : list) {
doTraverse(node, UNMODIFIABLE_CONTEXT);
}
}
protected final void doTraverse(CssNode node, Context ctx) {
try {
node.traverse(this, ctx);
} catch (Throwable e) {
throw translateException(node, e);
}
}
private CssCompilerException translateException(CssNode node, Throwable e) {
CssCompilerException ex;
if (e instanceof CssCompilerException) {
ex = (CssCompilerException) e;
} else {
ex = new CssCompilerException("Unexpected error during visit.", e);
}
ex.addNode(node);
return ex;
}
}