Moving Multicast subsystem into app and refactoring APIs to support multihomed sources and sinks

Change-Id: I95d07b163c619b018ff106159b134ff214aa2ffd
diff --git a/apps/mcast/api/src/main/java/org/onosproject/mcast/api/McastEvent.java b/apps/mcast/api/src/main/java/org/onosproject/mcast/api/McastEvent.java
new file mode 100644
index 0000000..9230736
--- /dev/null
+++ b/apps/mcast/api/src/main/java/org/onosproject/mcast/api/McastEvent.java
@@ -0,0 +1,121 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * 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.onosproject.mcast.api;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.event.AbstractEvent;
+
+import java.util.Objects;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
+/**
+ * An entity representing a multicast event. Event either add or remove
+ * sinks or sources.
+ */
+@Beta
+public class McastEvent extends AbstractEvent<McastEvent.Type, McastRouteUpdate> {
+
+    /**
+     * Mcast Event type enum.
+     */
+    public enum Type {
+        /**
+         * A new mcast route has been added.
+         */
+        ROUTE_ADDED,
+
+        /**
+         * A mcast route has been removed.
+         */
+        ROUTE_REMOVED,
+
+        /**
+         * A set of sources for a mcast route (ie. the subject) has been added.
+         */
+        SOURCES_ADDED,
+
+        /**
+         * A set of sources for a mcast route has been removed.
+         */
+        SOURCES_REMOVED,
+
+        /**
+         * A set of sinks for a mcast route (ie. the subject) has been added.
+         */
+        SINKS_ADDED,
+
+        /**
+         * A set of sinks for a mcast route (ie. the subject) has been removed.
+         */
+        SINKS_REMOVED
+    }
+
+    private McastRouteUpdate prevSubject;
+
+    /**
+     * Creates a McastEvent of a given type using the subject.
+     *
+     * @param type        the event type
+     * @param prevSubject the previous mcast information
+     * @param subject     the current mcast information
+     */
+    public McastEvent(McastEvent.Type type, McastRouteUpdate prevSubject, McastRouteUpdate subject) {
+        super(type, subject);
+        this.prevSubject = prevSubject;
+    }
+
+    /**
+     * Gets the previous subject in this Mcast event.
+     *
+     * @return the previous subject, or null if previous subject is not
+     * specified.
+     */
+    public McastRouteUpdate prevSubject() {
+        return this.prevSubject;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type(), subject(), prevSubject());
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (this == other) {
+            return true;
+        }
+
+        if (!(other instanceof McastEvent)) {
+            return false;
+        }
+
+        McastEvent that = (McastEvent) other;
+
+        return Objects.equals(this.subject(), that.subject()) &&
+                Objects.equals(this.type(), that.type()) &&
+                Objects.equals(this.prevSubject(), that.prevSubject());
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this)
+                .add("type", type())
+                .add("prevSubject", prevSubject())
+                .add("subject", subject())
+                .toString();
+    }
+}