[ONOS-6163] (vnet) revise intent service for vnets

Revise intent service for virtual networks.

Change-Id: I4955cde2296e58d8f0e356d19483e84f51193318
diff --git a/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/intent/phase/VirtualIntentCompiling.java b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/intent/phase/VirtualIntentCompiling.java
new file mode 100644
index 0000000..639c04c
--- /dev/null
+++ b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/intent/phase/VirtualIntentCompiling.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2017-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.incubator.net.virtual.impl.intent.phase;
+
+import org.onosproject.incubator.net.virtual.NetworkId;
+import org.onosproject.incubator.net.virtual.impl.intent.VirtualIntentProcessor;
+import org.onosproject.net.intent.Intent;
+import org.onosproject.net.intent.IntentData;
+import org.onosproject.net.intent.IntentException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+import java.util.Optional;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Represents a phase where an intent is being compiled or recompiled
+ * for virtual networks.
+ */
+public class VirtualIntentCompiling implements VirtualIntentProcessPhase {
+    private static final Logger log = LoggerFactory.getLogger(VirtualIntentCompiling.class);
+
+    private final NetworkId networkId;
+    private final VirtualIntentProcessor processor;
+    private final IntentData data;
+    private final Optional<IntentData> stored;
+
+    /**
+     * Creates a intent recompiling phase.
+     *
+     * @param networkId virtual network identifier
+     * @param processor intent processor that does work for recompiling
+     * @param data      intent data containing an intent to be recompiled
+     * @param stored    intent data stored in the store
+     */
+    VirtualIntentCompiling(NetworkId networkId, VirtualIntentProcessor processor,
+                           IntentData data, Optional<IntentData> stored) {
+        this.networkId = checkNotNull(networkId);
+        this.processor = checkNotNull(processor);
+        this.data = checkNotNull(data);
+        this.stored = checkNotNull(stored);
+    }
+
+    @Override
+    public Optional<VirtualIntentProcessPhase> execute() {
+        try {
+            List<Intent> compiled = processor
+                    .compile(networkId, data.intent(),
+                             //TODO consider passing an optional here in the future
+                             stored.map(IntentData::installables).orElse(null));
+            return Optional.of(new VirtualIntentInstalling(networkId, processor,
+                                                           IntentData.compiled(data, compiled), stored));
+        } catch (IntentException e) {
+            log.warn("Unable to compile intent {} due to:", data.intent(), e);
+            if (stored.filter(x -> !x.installables().isEmpty()).isPresent()) {
+                // removing orphaned flows and deallocating resources
+                return Optional.of(
+                        new VirtualIntentWithdrawing(networkId, processor,
+                                                     new IntentData(data, stored.get().installables())));
+            } else {
+                return Optional.of(new VirtualIntentFailed(data));
+            }
+        }
+    }
+}