1 files changed, 146 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime-rete/src/main/java/tools/refinery/viatra/runtime/rete/itc/alg/misc/DFSPathFinder.java b/subprojects/viatra-runtime-rete/src/main/java/tools/refinery/viatra/runtime/rete/itc/alg/misc/DFSPathFinder.java
new file mode 100644
index 00000000..2cec33a2
--- /dev/null
+++ b/subprojects/viatra-runtime-rete/src/main/java/tools/refinery/viatra/runtime/rete/itc/alg/misc/DFSPathFinder.java
@@ -0,0 +1,146 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2016, Abel Hegedus and IncQueryLabs Ltd.
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.viatra.runtime.rete.itc.alg.misc;
+
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Set;
+
+import tools.refinery.viatra.runtime.rete.itc.igraph.IGraphDataSource;
+import tools.refinery.viatra.runtime.rete.itc.igraph.ITcDataSource;
+import tools.refinery.viatra.runtime.matchers.util.IMemoryView;
+
+/**
+ * A depth-first search implementation of the {@link IGraphPathFinder}.
+ *
+ * TODO use ITC to filter nodes that must be traversed, instead of checks
+ *
+ * @author Abel Hegedus
+ *
+ * @param <V>
+ *            the node type of the graph
+ */
+public class DFSPathFinder<V> implements IGraphPathFinder<V> {
+
+    private IGraphDataSource<V> graph;
+    private ITcDataSource<V> itc;
+
+    public DFSPathFinder(IGraphDataSource<V> graph, ITcDataSource<V> itc) {
+        this.graph = graph;
+        this.itc = itc;
+    }
+
+    @Override
+    public Iterable<Deque<V>> getAllPaths(V sourceNode, V targetNode) {
+        Set<V> endNodes = new HashSet<V>();
+        endNodes.add(targetNode);
+        return getAllPathsToTargets(sourceNode, endNodes);
+    }
+
+    @Override
+    public Iterable<Deque<V>> getAllPathsToTargets(V sourceNode, Set<V> targetNodes) {
+        List<Deque<V>> paths = new ArrayList<Deque<V>>();
+        Deque<V> visited = new LinkedList<V>();
+        Set<V> reachableTargets = new HashSet<V>();
+        for (V targetNode : targetNodes) {
+            if (itc.isReachable(sourceNode, targetNode)) {
+                reachableTargets.add(targetNode);
+            }
+        }
+        if (!reachableTargets.isEmpty()) {
+            return paths;
+        }
+        visited.add(sourceNode);
+        return getPaths(paths, visited, reachableTargets);
+    }
+
+    protected Iterable<Deque<V>> getPaths(List<Deque<V>> paths, Deque<V> visited, Set<V> targetNodes) {
+        IMemoryView<V> nodes = graph.getTargetNodes(visited.getLast());
+        // examine adjacent nodes
+        for (V node : nodes.distinctValues()) {
+            if (visited.contains(node)) {
+                continue;
+            }
+            if (targetNodes.contains(node)) {
+                visited.add(node);
+                // clone visited LinkedList
+                Deque<V> visitedClone = new LinkedList<V>(visited);
+                paths.add(visitedClone);
+                visited.removeLast();
+                break;
+            }
+        }
+
+        // in breadth-first, recursion needs to come after visiting connected nodes
+        for (V node : nodes.distinctValues()) {
+            if (visited.contains(node) || targetNodes.contains(node)) {
+                continue;
+            }
+            boolean canReachTarget = false;
+            for (V target : targetNodes) {
+                if (itc.isReachable(node, target)) {
+                    canReachTarget = true;
+                    break;
+                }
+            }
+            if (canReachTarget) {
+                visited.addLast(node);
+                getPaths(paths, visited, targetNodes);
+                visited.removeLast();
+            }
+        }
+
+        return paths;
+    }
+
+    public String printPaths(List<Deque<V>> paths) {
+        StringBuilder sb = new StringBuilder();
+        for (Deque<V> visited : paths) {
+            sb.append("Path: ");
+            for (V node : visited) {
+                sb.append(node);
+                sb.append(" --> ");
+            }
+            sb.append("\n");
+        }
+        return sb.toString();
+    }
+
+    @Override
+    public Deque<V> getPath(V sourceNode, V targetNode) {
+        // TODO optimize
+        Iterable<Deque<V>> allPaths = getAllPaths(sourceNode, targetNode);
+        Iterator<Deque<V>> pathIterator = allPaths.iterator();
+        return pathIterator.hasNext() ? pathIterator.next() : new LinkedList<V>();
+    }
+
+    @Override
+    public Iterable<Deque<V>> getShortestPaths(V sourceNode, V targetNode) {
+        // TODO optimize
+        Iterable<Deque<V>> allPaths = getAllPaths(sourceNode, targetNode);
+        List<Deque<V>> shortestPaths = new ArrayList<Deque<V>>();
+        int shortestPathLength = -1;
+        for (Deque<V> path : allPaths) {
+            int pathLength = path.size();
+            if (shortestPathLength == -1 || pathLength < shortestPathLength) {
+                shortestPaths.clear();
+                shortestPathLength = pathLength;
+            }
+            if (pathLength == shortestPathLength) {
+                shortestPaths.add(path);
+            }
+        }
+        return shortestPaths;
+    }
+
+}