add variableIdToLiveVariableUsageInstanceMap to Varaitions.

Author: wangjoshuah

core-api/src/main/java/com/optimizely/ab/config/LiveVariableUsageInstance.java

@@ -24,7 +24,7 @@
  * Represents the value of a live variable for a variation
  */
 @JsonIgnoreProperties(ignoreUnknown = true)
-public class LiveVariableUsageInstance {
+public class LiveVariableUsageInstance implements IdMapped {
 
     private final String id;
     private final String value;

core-api/src/main/java/com/optimizely/ab/config/Variation.java

@@ -24,6 +24,7 @@
 import javax.annotation.Nullable;
 
 import java.util.List;
+import java.util.Map;
 
 /**
  * Represents the Optimizely Variation configuration.
@@ -36,6 +37,7 @@ public class Variation implements IdKeyMapped {
     private final String id;
     private final String key;
     private final List<LiveVariableUsageInstance> liveVariableUsageInstances;
+    private final Map<String, LiveVariableUsageInstance> variableIdToLiveVariableUsageInstanceMap;
 
     public Variation(String id, String key) {
         this(id, key, null);
@@ -48,6 +50,7 @@ public Variation(@JsonProperty("id") String id,
         this.id = id;
         this.key = key;
         this.liveVariableUsageInstances = liveVariableUsageInstances;
+        this.variableIdToLiveVariableUsageInstanceMap = ProjectConfigUtils.generateIdMapping(liveVariableUsageInstances);
     }
 
     public @Nonnull String getId() {
@@ -62,6 +65,10 @@ public Variation(@JsonProperty("id") String id,
         return liveVariableUsageInstances;
     }
 
+    public Map<String, LiveVariableUsageInstance> getVariableIdToLiveVariableUsageInstanceMap() {
+        return variableIdToLiveVariableUsageInstanceMap;
+    }
+
     public boolean is(String otherKey) {
         return key.equals(otherKey);
     }