1 files changed, 69 insertions, 0 deletions
diff --git a/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/YangDAG.java b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/YangDAG.java
new file mode 100644
index 000000000..2269adbff
--- /dev/null
+++ b/infra/translate-utils/src/main/java/io/fd/honeycomb/translate/util/YangDAG.java
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2017 Cisco and/or its affiliates.
+ *
+ * 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 io.fd.honeycomb.translate.util;
+
+import java.util.Iterator;
+import org.jgrapht.experimental.dag.DirectedAcyclicGraph;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+/**
+ * Directed acyclic graph representing ordering relationships between schema nodes represented as wildcarded
+ * InstanceIdentifiers. Maintains topological order of vertices. Feature is used by translation layer if more nodes are
+ * affected in single read/write transaction.
+ */
+public final class YangDAG {
+
+    private final DirectedAcyclicGraph<InstanceIdentifier<?>, Edge>
+        dag = new DirectedAcyclicGraph<>((sourceVertex, targetVertex) -> new Edge());
+
+    /**
+     * Adds the vertex if it wasn't already in the graph.
+     *
+     * @param vertex vertex to be added
+     */
+    public void addVertex(final InstanceIdentifier<?> vertex) {
+        dag.addVertex(vertex);
+    }
+
+    /**
+     * Adds edge between source and target vertices.
+     *
+     * @param source source vertex of the edge
+     * @param target target vertex of the edge
+     * @throws IllegalArgumentException if the edge would induce a cycle in the graph
+     */
+    public void addEdge(final InstanceIdentifier<?> source, final InstanceIdentifier<?> target) {
+        try {
+            dag.addDagEdge(source, target);
+        } catch (DirectedAcyclicGraph.CycleFoundException e) {
+            throw new IllegalArgumentException(String.format(
+                "Unable to add writer with relation: %s -> %s. Loop detected", source, target), e);
+        }
+    }
+
+    /**
+     * Traverses schema nodes in topological order.
+     *
+     * @return an iterator that will traverse the graph in topological order.
+     */
+    public Iterator<InstanceIdentifier<?>> iterator() {
+        return dag.iterator();
+    }
+
+    private static final class Edge {
+    }
+}