Separate ResourceStore into stores for discrete and continuous type

This is a preliminary work for ONOS-4281.

Change-Id: Ifed9c761eb16f6a249a9d069948edc7421301617
diff --git a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/TransactionalDiscreteResourceStore.java b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/TransactionalDiscreteResourceStore.java
new file mode 100644
index 0000000..8275ac6
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/TransactionalDiscreteResourceStore.java
@@ -0,0 +1,126 @@
+/*
+ * 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.store.resource.impl;
+
+import com.google.common.collect.Sets;
+import org.onosproject.net.resource.DiscreteResource;
+import org.onosproject.net.resource.DiscreteResourceId;
+import org.onosproject.net.resource.Resource;
+import org.onosproject.net.resource.ResourceConsumer;
+import org.onosproject.net.resource.Resources;
+import org.onosproject.store.service.TransactionContext;
+import org.onosproject.store.service.TransactionalMap;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+
+import static org.onosproject.store.resource.impl.ConsistentResourceStore.SERIALIZER;
+
+class TransactionalDiscreteResourceStore {
+    private final Logger log = LoggerFactory.getLogger(getClass());
+    private final TransactionalMap<DiscreteResourceId, Set<DiscreteResource>> childMap;
+    private final TransactionalMap<DiscreteResourceId, ResourceConsumer> consumers;
+
+    TransactionalDiscreteResourceStore(TransactionContext tx) {
+        this.childMap = tx.getTransactionalMap(MapNames.DISCRETE_CHILD_MAP, SERIALIZER);
+        this.consumers = tx.getTransactionalMap(MapNames.DISCRETE_CONSUMER_MAP, SERIALIZER);
+    }
+
+    // check the existence in the set: O(1) operation
+    Optional<Resource> lookup(DiscreteResourceId id) {
+        if (!id.parent().isPresent()) {
+            return Optional.of(Resource.ROOT);
+        }
+
+        Set<DiscreteResource> values = childMap.get(id.parent().get());
+        if (values == null) {
+            return Optional.empty();
+        }
+
+        DiscreteResource resource = Resources.discrete(id).resource();
+        if (values.contains(resource)) {
+            return Optional.of(resource);
+        } else {
+            return Optional.empty();
+        }
+    }
+
+    boolean appendValues(DiscreteResourceId key, List<DiscreteResource> values) {
+        Set<DiscreteResource> requested = new LinkedHashSet<>(values);
+        Set<DiscreteResource> oldValues = childMap.putIfAbsent(key, requested);
+        if (oldValues == null) {
+            return true;
+        }
+
+        Set<DiscreteResource> addedValues = Sets.difference(requested, oldValues);
+        // no new value, then no-op
+        if (addedValues.isEmpty()) {
+            // don't write to map because all values are already stored
+            return true;
+        }
+
+        Set<DiscreteResource> newValues = new LinkedHashSet<>(oldValues);
+        newValues.addAll(addedValues);
+        return childMap.replace(key, oldValues, newValues);
+    }
+
+    boolean removeValues(DiscreteResourceId key, List<DiscreteResource> values) {
+        Set<DiscreteResource> oldValues = childMap.putIfAbsent(key, new LinkedHashSet<>());
+        if (oldValues == null) {
+            log.trace("No-Op removing values. key {} did not exist", key);
+            return true;
+        }
+
+        if (values.stream().allMatch(x -> !oldValues.contains(x))) {
+            // don't write map because none of the values are stored
+            log.trace("No-Op removing values. key {} did not contain {}", key, values);
+            return true;
+        }
+
+        LinkedHashSet<DiscreteResource> newValues = new LinkedHashSet<>(oldValues);
+        newValues.removeAll(values);
+        return childMap.replace(key, oldValues, newValues);
+    }
+
+    boolean isAllocated(DiscreteResourceId id) {
+        return consumers.get(id) != null;
+    }
+
+    boolean allocate(ResourceConsumer consumer, DiscreteResource resource) {
+        // if the resource is not registered, then abort
+        Optional<Resource> lookedUp = lookup(resource.id());
+        if (!lookedUp.isPresent()) {
+            return false;
+        }
+
+        ResourceConsumer oldValue = consumers.put(resource.id(), consumer);
+        return oldValue == null;
+    }
+
+    boolean release(DiscreteResource resource, ResourceConsumer consumer) {
+        // if this single release fails (because the resource is allocated to another consumer)
+        // the whole release fails
+        if (!consumers.remove(resource.id(), consumer)) {
+            return false;
+        }
+
+        return true;
+    }
+}