REST API support for DHCP Relay

Change-Id: Icfefebd15ff43718493e5223254b23ec02ee0bab
diff --git a/apps/dhcprelay/web/src/main/java/org/onosproject/dhcprelay/rest/DhcpRelayWebResource.java b/apps/dhcprelay/web/src/main/java/org/onosproject/dhcprelay/rest/DhcpRelayWebResource.java
new file mode 100644
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--- /dev/null
+++ b/apps/dhcprelay/web/src/main/java/org/onosproject/dhcprelay/rest/DhcpRelayWebResource.java
@@ -0,0 +1,78 @@
+/*
+ * 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.dhcprelay.rest;
+
+import org.onlab.packet.IpAddress;
+import org.onlab.packet.IpPrefix;
+import org.onosproject.dhcprelay.api.DhcpRelayService;
+import org.onosproject.rest.AbstractWebResource;
+import org.onosproject.routeservice.Route;
+import org.onosproject.routeservice.RouteStore;
+import org.onosproject.routing.fpm.api.FpmRecord;
+import org.slf4j.Logger;
+
+import javax.ws.rs.DELETE;
+import javax.ws.rs.Path;
+import javax.ws.rs.PathParam;
+import javax.ws.rs.core.Response;
+
+import java.io.IOException;
+import java.util.Optional;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * DHCP Relay agent REST API.
+ */
+@Path("fpm-delete")
+public class DhcpRelayWebResource extends AbstractWebResource {
+    private static final Logger LOG = getLogger(DhcpRelayWebResource.class);
+
+    /**
+     * Deletes the fpm route from fpm record.
+     * Corresponding route from the route store
+     *
+     * @param prefix IpPrefix
+     * @return 204 NO CONTENT
+     * @throws IOException to signify bad request
+     */
+    @DELETE
+    @Path("{prefix}")
+    public Response dhcpFpmDelete(@PathParam("prefix") String prefix) {
+        DhcpRelayService dhcpRelayService = get(DhcpRelayService.class);
+        RouteStore routeStore = get(RouteStore.class);
+
+        try {
+            // removes fpm route from fpm record
+            Optional<FpmRecord> fpmRecord = dhcpRelayService.removeFpmRecord(IpPrefix.valueOf(prefix));
+            if (fpmRecord.isPresent()) {
+                IpAddress nextHop = fpmRecord.get().nextHop();
+                Route route = new Route(Route.Source.DHCP, IpPrefix.valueOf(prefix), nextHop);
+                // removes DHCP route from route store
+                routeStore.removeRoute(route);
+            } else {
+                LOG.warn("fpmRecord is not present");
+            }
+        } catch (IllegalArgumentException ex) {
+            throw new IllegalArgumentException(ex);
+        }
+
+        return Response.noContent().build();
+    }
+
+}