/*
* Copyright 2010 the original author or authors.
*
* 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 org.gradle.internal.graph;
import java.util.*;
/**
* Groups the nodes of a graph based on their reachability from a set of starting nodes.
*/
public class GraphAggregator<N> {
private final CachingDirectedGraphWalker<N, N> graphWalker;
public GraphAggregator(DirectedGraph<N, ?> graph) {
graphWalker = new CachingDirectedGraphWalker<N, N>(new ConnectedNodesAsValuesDirectedGraph<N>(graph));
}
public Result<N> group(Collection<? extends N> startNodes, Collection<? extends N> allNodes) {
Map<N, Set<N>> reachableByNode = new HashMap<N, Set<N>>();
Set<N> topLevelNodes = new LinkedHashSet<N>(allNodes);
for (N node : allNodes) {
Set<N> reachableNodes = graphWalker.add(node).findValues();
reachableByNode.put(node, reachableNodes);
topLevelNodes.removeAll(reachableNodes);
}
topLevelNodes.addAll(startNodes);
Map<N, Set<N>> nodes = new HashMap<N, Set<N>>();
for (N node : topLevelNodes) {
nodes.put(node, calculateReachableNodes(reachableByNode, node, topLevelNodes));
}
return new Result<N>(nodes, topLevelNodes);
}
private Set<N> calculateReachableNodes(Map<N, Set<N>> nodes, N node, Set<N> topLevelNodes) {
Set<N> reachableNodes = nodes.get(node);
reachableNodes.add(node);
Set<N> reachableStartNodes = new LinkedHashSet<N>(topLevelNodes);
reachableStartNodes.retainAll(reachableNodes);
reachableStartNodes.remove(node);
for (N startNode : reachableStartNodes) {
reachableNodes.removeAll(calculateReachableNodes(nodes, startNode, topLevelNodes));
}
return reachableNodes;
}
public static class Result<N> {
private final Map<N, Set<N>> nodes;
private final Set<N> topLevelNodes;
public Result(Map<N, Set<N>> nodes, Set<N> topLevelNodes) {
this.nodes = nodes;
this.topLevelNodes = topLevelNodes;
}
public Set<N> getNodes(N startNode) {
return nodes.get(startNode);
}
public Set<N> getTopLevelNodes() {
return topLevelNodes;
}
}
private static class ConnectedNodesAsValuesDirectedGraph<N> implements DirectedGraph<N, N> {
private final DirectedGraph<N, ?> graph;
private ConnectedNodesAsValuesDirectedGraph(DirectedGraph<N, ?> graph) {
this.graph = graph;
}
public void getNodeValues(N node, Collection<? super N> values, Collection<? super N> connectedNodes) {
Set<N> edges = new LinkedHashSet<N>();
graph.getNodeValues(node, new ArrayList(), edges);
values.addAll(edges);
connectedNodes.addAll(edges);
}
}
}