Allow listening to changes of topology

3 files changed, 85 insertions, 2 deletions

diff --git a/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/AdjacencyList.kt b/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/AdjacencyList.kt
index e2824f5d..ef9e0396 100644
--- a/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/AdjacencyList.kt
+++ b/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/AdjacencyList.kt
@@ -75,6 +75,11 @@ internal class AdjacencyListTopology : MutableTopology {
 	// Topology
 
 	/**
+	 * The listeners of this topology.
+	 */
+	override val listeners: MutableSet<TopologyListener> = HashSet()
+
+	/**
 	 * A unique identifier of this node within the topology.
 	 */
 	override val Entity<*>.id: Int
@@ -109,6 +114,7 @@ internal class AdjacencyListTopology : MutableTopology {
 		val edge = Edge(label, tag, from, to)
 		from.outgoingEdges.add(edge)
 		to.ingoingEdges.add(edge)
+		listeners.forEach { it.run { this@AdjacencyListTopology.onEdgeAdded(edge) } }
 		return edge
 	}
 
@@ -156,7 +162,13 @@ internal class AdjacencyListTopology : MutableTopology {
 	 * @param element The element to add to this graph.
 	 * @return `true` if the graph has changed, `false` otherwise.
 	 */
-	override fun add(element: Entity<*>): Boolean = nodes.putIfAbsent(element, Node(nextId.getAndIncrement())) == null
+	override fun add(element: Entity<*>): Boolean {
+		if (nodes.putIfAbsent(element, Node(nextId.getAndIncrement())) == null) {
+			listeners.forEach { it.run { this@AdjacencyListTopology.onNodeAdded(element) } }
+			return true
+		}
+		return false
+	}
 
 	/**
 	 * Add all nodes in the specified collection to the graph.
@@ -184,7 +196,11 @@ internal class AdjacencyListTopology : MutableTopology {
 		nodes[element]?.outgoingEdges?.forEach {
 			it.to.ingoingEdges.remove(it)
 		}
-		return nodes.keys.remove(element)
+		if (nodes.keys.remove(element)) {
+			listeners.forEach { it.run { this@AdjacencyListTopology.onNodeRemoved(element) } }
+			return true
+		}
+		return false
 	}
 
 
diff --git a/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/Topology.kt b/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/Topology.kt
index 5b697bfb..27c1c889 100644
--- a/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/Topology.kt
+++ b/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/Topology.kt
@@ -34,9 +34,15 @@ package nl.atlarge.opendc.topology
  */
 interface Topology : TopologyContext, Cloneable, Set<Entity<*>> {
 	/**
+	 * The listeners of this topology.
+	 */
+	val listeners: MutableSet<TopologyListener>
+
+	/**
 	 * Create a copy of the topology.
 	 *
 	 * @return A new [Topology] with a copy of the graph.
 	 */
 	public override fun clone(): Topology
 }
+
diff --git a/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/TopologyListener.kt b/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/TopologyListener.kt
new file mode 100644
index 00000000..b5062709
--- /dev/null
+++ b/opendc-core/src/main/kotlin/nl/atlarge/opendc/topology/TopologyListener.kt
@@ -0,0 +1,61 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2017 atlarge-research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package nl.atlarge.opendc.topology;
+
+/**
+ * A listener interface for [Topology] instances. The methods of this interface are invoked on
+ * mutation of the topology the listener is listening to.
+ *
+ * @author Fabian Mastenbroek (f.s.mastenbroek@student.tudelft.nl)
+ */
+interface TopologyListener {
+	/**
+	 * This method is invoked when an [Entity] is added to the [Topology].
+	 *
+	 * @param node The entity that has been added to the [Topology].
+	 */
+	fun Topology.onNodeAdded(node: Entity<*>) {}
+
+	/**
+	 * This method is invoked when an [Entity] is removed from the [Topology].
+	 *
+	 * @param node The entity that has been removed from the [Topology].
+	 */
+	fun Topology.onNodeRemoved(node: Entity<*>) {}
+
+	/**
+	 * This method is invoked when an [Edge] is added to the [Topology].
+	 *
+	 * @param edge The edge that has been added to the [Topology].
+	 */
+	fun Topology.onEdgeAdded(edge: Edge<*>) {}
+
+	/**
+	 * This method is invoked when an [Edge] is removed from the [Topology].
+	 *
+	 * @param edge The entity that has been removed from the [Topology].
+	 */
+	fun Topology.onEdgeRemoved(edge: Edge<*>) {}
+}