Implement kubevirt loadbalancer service with unit tests

Change-Id: I1c29e75aa5196b497f8f12f1d182788e3d173244
(cherry picked from commit 870abf8c7a7904c5953e20807ee7c681d8b5cd0b)
diff --git a/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/DefaultKubevirtLoadBalancer.java b/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/DefaultKubevirtLoadBalancer.java
new file mode 100644
index 0000000..bf4a21d
--- /dev/null
+++ b/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/DefaultKubevirtLoadBalancer.java
@@ -0,0 +1,193 @@
+/*
+ * Copyright 2021-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.kubevirtnetworking.api;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.collect.ImmutableSet;
+import org.onlab.packet.IpAddress;
+
+import java.util.Objects;
+import java.util.Set;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * Default implementation of kubevirt load balancer.
+ */
+public final class DefaultKubevirtLoadBalancer implements KubevirtLoadBalancer {
+
+    private static final String NOT_NULL_MSG = "Loadbalancer % cannot be null";
+
+    private final String name;
+    private final String description;
+    private final String networkId;
+    private final IpAddress vip;
+    private final Set<IpAddress> members;
+    private final Set<KubevirtLoadBalancerRule> rules;
+
+    /**
+     * Default constructor.
+     *
+     * @param name              load balancer name
+     * @param description       load balancer description
+     * @param networkId         load balancer network identifier
+     * @param vip               load balancer virtual IP address
+     * @param members           load balancer members
+     * @param rules             load balancer rules
+     */
+    public DefaultKubevirtLoadBalancer(String name, String description, String networkId,
+                                       IpAddress vip, Set<IpAddress> members,
+                                       Set<KubevirtLoadBalancerRule> rules) {
+        this.name = name;
+        this.description = description;
+        this.networkId = networkId;
+        this.vip = vip;
+        this.members = members;
+        this.rules = rules;
+    }
+
+    @Override
+    public String name() {
+        return name;
+    }
+
+    @Override
+    public String description() {
+        return description;
+    }
+
+    @Override
+    public String networkId() {
+        return networkId;
+    }
+
+    @Override
+    public IpAddress vip() {
+        return vip;
+    }
+
+    @Override
+    public Set<IpAddress> members() {
+        if (members == null) {
+            return ImmutableSet.of();
+        } else {
+            return ImmutableSet.copyOf(members);
+        }
+    }
+
+    @Override
+    public Set<KubevirtLoadBalancerRule> rules() {
+        if (rules == null) {
+            return ImmutableSet.of();
+        } else {
+            return ImmutableSet.copyOf(rules);
+        }
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        DefaultKubevirtLoadBalancer that = (DefaultKubevirtLoadBalancer) o;
+        return name.equals(that.name) && Objects.equals(description, that.description) &&
+                networkId.equals(that.networkId) && vip.equals(that.vip) &&
+                Objects.equals(members, that.members) && Objects.equals(rules, that.rules);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(name, description, networkId, vip, members, rules);
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(this)
+                .add("name", name)
+                .add("description", description)
+                .add("networkId", networkId)
+                .add("vip", vip)
+                .add("members", members)
+                .add("rules", rules)
+                .toString();
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static final class Builder implements KubevirtLoadBalancer.Builder {
+
+        private String name;
+        private String description;
+        private String networkId;
+        private IpAddress vip;
+        private Set<IpAddress> members;
+        private Set<KubevirtLoadBalancerRule> rules;
+
+        // private constructor not intended to use from external
+        private Builder() {
+        }
+
+        @Override
+        public KubevirtLoadBalancer build() {
+            checkArgument(networkId != null, NOT_NULL_MSG, "networkId");
+            checkArgument(name != null, NOT_NULL_MSG, "name");
+            checkArgument(vip != null, NOT_NULL_MSG, "vip");
+
+            return new DefaultKubevirtLoadBalancer(name, description, networkId, vip, members, rules);
+        }
+
+        @Override
+        public Builder name(String name) {
+            this.name = name;
+            return this;
+        }
+
+        @Override
+        public Builder description(String description) {
+            this.description = description;
+            return this;
+        }
+
+        @Override
+        public Builder networkId(String networkId) {
+            this.networkId = networkId;
+            return this;
+        }
+
+        @Override
+        public Builder vip(IpAddress vip) {
+            this.vip = vip;
+            return this;
+        }
+
+        @Override
+        public Builder members(Set<IpAddress> members) {
+            this.members = members;
+            return this;
+        }
+
+        @Override
+        public Builder rules(Set<KubevirtLoadBalancerRule> rules) {
+            this.rules = rules;
+            return this;
+        }
+    }
+}