package com.getperka.flatpack.util;
/*
* #%L
* FlatPack serialization code
* %%
* Copyright (C) 2012 - 2013 Perka 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.
* #L%
*/
import java.util.HashSet;
import java.util.Set;
import com.getperka.flatpack.FlatPackVisitor;
import com.getperka.flatpack.HasUuid;
import com.getperka.flatpack.codexes.EntityCodex;
import com.getperka.flatpack.ext.VisitorContext;
/**
* A {@link FlatPackVisitor} that breaks graph cycles by recording which entities have been
* traversed.
*/
public class AcyclicVisitor extends FlatPackVisitor {
private final Set<HasUuid> ended = new HashSet<HasUuid>();
private final Set<HasUuid> visited = new HashSet<HasUuid>();
/**
* Delegates to {@link #endVisitOnce} if {@code entity} has not been visited previously.
*/
@Override
public final <T extends HasUuid> void endVisit(T entity, EntityCodex<T> codex,
VisitorContext<T> ctx) {
if (ended.add(entity)) {
endVisitOnce(entity, codex, ctx);
}
}
public Set<HasUuid> getVisited() {
return visited;
}
/**
* Delegates to {@link #visitOnce} if {@code entity} has not been visited previously.
*/
@Override
public final <T extends HasUuid> boolean visit(T entity, EntityCodex<T> codex,
VisitorContext<T> ctx) {
if (visited.add(entity)) {
return visitOnce(entity, codex, ctx);
}
return false;
}
protected <T extends HasUuid> void endVisitOnce(T entity, EntityCodex<T> codex,
VisitorContext<T> ctx) {}
/**
* Returns {@link #isGreedy()}.
*/
protected <T extends HasUuid> boolean visitOnce(T entity, EntityCodex<T> codex,
VisitorContext<T> ctx) {
return isGreedy();
}
}