CORD-61 Dynamic XConnect support

- Add new XConnectConfig with unit test
- Gather XConnect features into XConnectHandler
- Introduce ObjectiveError.Type.GROUPREMOVALFAILED
- Rename
    - NetworkConfigEventHandler -> AppConfigHandler
    - XConnectNextObjectiveStoreKey -> XConnectStoreKey
    - Test json file
- Refactor

Change-Id: I8ca3176ed976c71ce9e28b7f3722ce80d49c816f
diff --git a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/config/XConnectConfig.java b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/config/XConnectConfig.java
new file mode 100644
index 0000000..089f8b0
--- /dev/null
+++ b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/config/XConnectConfig.java
@@ -0,0 +1,111 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * 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.segmentrouting.config;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.google.common.collect.ImmutableSet;
+import org.onlab.packet.VlanId;
+import org.onosproject.core.ApplicationId;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.PortNumber;
+import org.onosproject.net.config.Config;
+import org.onosproject.segmentrouting.storekey.XConnectStoreKey;
+
+import java.util.Set;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * Configuration object for cross-connect.
+ */
+public class XConnectConfig extends Config<ApplicationId> {
+    private static final String VLAN = "vlan";
+    private static final String PORTS = "ports";
+    private static final String NAME = "name"; // dummy field for naming
+
+    private static final String UNEXPECTED_FIELD_NAME = "Unexpected field name";
+
+    @Override
+    public boolean isValid() {
+        try {
+            getXconnects().forEach(this::getPorts);
+        } catch (IllegalArgumentException e) {
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Returns all xconnect keys.
+     *
+     * @return all keys (device/vlan pairs)
+     * @throws IllegalArgumentException if wrong format
+     */
+    public Set<XConnectStoreKey> getXconnects() {
+        ImmutableSet.Builder<XConnectStoreKey> builder = ImmutableSet.builder();
+        object.fields().forEachRemaining(entry -> {
+            DeviceId deviceId = DeviceId.deviceId(entry.getKey());
+            builder.addAll(getXconnects(deviceId));
+        });
+        return builder.build();
+    }
+
+    /**
+     * Returns xconnect keys of given device.
+     *
+     * @param deviceId ID of the device from which we want to get XConnect info
+     * @return xconnect keys (device/vlan pairs) of given device
+     * @throws IllegalArgumentException if wrong format
+     */
+    public Set<XConnectStoreKey> getXconnects(DeviceId deviceId) {
+        ImmutableSet.Builder<XConnectStoreKey> builder = ImmutableSet.builder();
+        JsonNode vlanPortPair = object.get(deviceId.toString());
+        if (vlanPortPair != null) {
+            vlanPortPair.forEach(jsonNode -> {
+                if (!hasOnlyFields((ObjectNode) jsonNode, VLAN, PORTS, NAME)) {
+                    throw new IllegalArgumentException(UNEXPECTED_FIELD_NAME);
+                }
+                VlanId vlanId = VlanId.vlanId((short) jsonNode.get(VLAN).asInt());
+                builder.add(new XConnectStoreKey(deviceId, vlanId));
+            });
+        }
+        return builder.build();
+    }
+
+    /**
+     * Returns ports of given xconnect key.
+     *
+     * @param xconnect xconnect key
+     * @return set of two ports associated with given xconnect key
+     * @throws IllegalArgumentException if wrong format
+     */
+    public Set<PortNumber> getPorts(XConnectStoreKey xconnect) {
+        ImmutableSet.Builder<PortNumber> builder = ImmutableSet.builder();
+        object.get(xconnect.deviceId().toString()).forEach(vlanPortsPair -> {
+            if (xconnect.vlanId().toShort() == vlanPortsPair.get(VLAN).asInt()) {
+                int portCount = vlanPortsPair.get(PORTS).size();
+                checkArgument(portCount == 2,
+                        "Expect 2 ports but found " + portCount + " on " + xconnect);
+                vlanPortsPair.get(PORTS).forEach(portNode -> {
+                    builder.add(PortNumber.portNumber(portNode.asInt()));
+                });
+            }
+        });
+        return builder.build();
+    }
+}