AbstractNodeItemVisitor.java
/*
* Portions of this software was developed by employees of the National Institute
* of Standards and Technology (NIST), an agency of the Federal Government and is
* being made available as a public service. Pursuant to title 17 United States
* Code Section 105, works of NIST employees are not subject to copyright
* protection in the United States. This software may be subject to foreign
* copyright. Permission in the United States and in foreign countries, to the
* extent that NIST may hold copyright, to use, copy, modify, create derivative
* works, and distribute this software and its documentation without fee is hereby
* granted on a non-exclusive basis, provided that this notice and disclaimer
* of warranty appears in all copies.
*
* THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
* EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
* THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
* INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
* SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE. IN NO EVENT
* SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
* INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
* OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
* CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
* PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
* OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
*/
package gov.nist.secauto.metaschema.core.metapath.item.node;
import java.util.List;
import edu.umd.cs.findbugs.annotations.NonNull;
/**
* Used by implementations of this class to visit a sequence of node items in a
* directed graph, using depth-first ordering.
*
* @param <RESULT>
* the type of result produced by visitation
* @param <CONTEXT>
* the type of data to pass to each visited node
*/
public abstract class AbstractNodeItemVisitor<RESULT, CONTEXT> implements INodeItemVisitor<RESULT, CONTEXT> {
/**
* Visit the provided {@code item}.
*
* @param item
* the item to visit
* @param context
* provides contextual information for use by the visitor
* @return the result produced by visiting the item
*/
public final RESULT visit(@NonNull INodeItemVisitable item, CONTEXT context) {
return item.accept(this, context);
}
/**
* Visit any child flags associated with the provided {@code item}.
*
* @param item
* the item to visit
* @param context
* provides contextual information for use by the visitor
* @return the result produced by visiting the item's flags
*/
protected RESULT visitFlags(@NonNull INodeItem item, CONTEXT context) {
RESULT result = defaultResult();
for (IFlagNodeItem flag : item.getFlags()) {
assert flag != null;
if (!shouldVisitNextChild(item, flag, result, context)) {
break;
}
RESULT childResult = flag.accept(this, context);
result = aggregateResult(result, childResult, context);
}
return result;
}
/**
* Visit any child model items associated with the provided {@code item}.
*
* @param item
* the item to visit
* @param context
* provides contextual information for use by the visitor
* @return the result produced by visiting the item's child model items
*/
protected RESULT visitModelChildren(@NonNull INodeItem item, CONTEXT context) {
RESULT result = defaultResult();
for (List<? extends IModelNodeItem<?, ?>> childItems : item.getModelItems()) {
for (IModelNodeItem<?, ?> childItem : childItems) {
assert childItem != null;
if (!shouldVisitNextChild(item, childItem, result, context)) {
break;
}
RESULT childResult = childItem.accept(this, context);
result = aggregateResult(result, childResult, context);
}
}
return result;
}
/**
* Determine if the child should be visited next, or skipped.
*
* @param parent
* the parent of the child to visit next
* @param child
* the next child to visit
* @param result
* the current visitation result
* @param context
* provides contextual information for use by the visitor
* @return {@code true} if the child should be visited, or {@code false} if the
* child should be skipped
*/
protected boolean shouldVisitNextChild(
@NonNull INodeItem parent,
@NonNull INodeItem child,
RESULT result,
CONTEXT context) {
// this is the default behavior, which can be overridden
return true;
}
/**
* Determine if the child should be visited next, or skipped.
*
* @param parent
* the parent of the child to visit next
* @param child
* the next child to visit
* @param result
* the current visitation result
* @param context
* provides contextual information for use by the visitor
* @return {@code true} if the child should be visited, or {@code false} if the
* child should be skipped
*/
protected boolean shouldVisitNextChild(
@NonNull INodeItem parent,
@NonNull IModelNodeItem<?, ?> child,
RESULT result,
CONTEXT context) {
// this is the default behavior, which can be overridden
return true;
}
/**
* The initial, default visitation result, which will be used as the basis for
* aggregating results produced when visiting.
*
* @return the default result
* @see #aggregateResult(Object, Object, Object)
*/
protected abstract RESULT defaultResult();
/**
* Combine two results into a single, aggregate result.
*
* @param first
* the original result
* @param second
* the new result to combine with the original result
* @param context
* provides contextual information for use by the visitor
* @return the combined result
*/
protected RESULT aggregateResult(RESULT first, RESULT second, CONTEXT context) {
// this is the default behavior, which can be overridden
return second;
}
@Override
public RESULT visitDocument(IDocumentNodeItem item, CONTEXT context) {
// this is the default behavior, which can be overridden
return visitModelChildren(item, context);
// return visitAssembly(item.getRootAssemblyNodeItem(), context);
}
@Override
public RESULT visitFlag(IFlagNodeItem item, CONTEXT context) {
// this is the default behavior, which can be overridden
return defaultResult();
}
@Override
public RESULT visitField(IFieldNodeItem item, CONTEXT context) {
// this is the default behavior, which can be overridden
return visitFlags(item, context);
}
@Override
public RESULT visitAssembly(IAssemblyNodeItem item, CONTEXT context) {
// this is the default behavior, which can be overridden
return aggregateResult(visitFlags(item, context), visitModelChildren(item, context), context);
}
@Override
public RESULT visitMetaschema(IModuleNodeItem item, CONTEXT context) {
// this is the default behavior, which can be overridden
return aggregateResult(visitFlags(item, context), visitModelChildren(item, context), context);
}
}