feat: getOptimizelyConfig API to get static experiments and features data (#348)

## Summary
Added `OptimizelyConfigService` which generates `OptimizelyConfig` Object containing experiments and features data. This is the first step in the development of `getOptimizelyConfig` api. This service always generates a new `OptimzelyConfig` object for now. Next PR will contain caching implementation for `OptimizelyConfig` object.

## Test plan
Added Unit Tests

Author: fayyazarshad

core-api/src/main/java/com/optimizely/ab/Optimizely.java

@@ -1,5 +1,5 @@
 /****************************************************************************
- * Copyright 2016-2019, Optimizely, Inc. and contributors                   *
+ * Copyright 2016-2020, Optimizely, Inc. and contributors                   *
  *                                                                          *
  * Licensed under the Apache License, Version 2.0 (the "License");          *
  * you may not use this file except in compliance with the License.         *
@@ -28,6 +28,8 @@
 import com.optimizely.ab.event.internal.*;
 import com.optimizely.ab.event.internal.payload.EventBatch;
 import com.optimizely.ab.notification.*;
+import com.optimizely.ab.optimizelyconfig.OptimizelyConfig;
+import com.optimizely.ab.optimizelyconfig.OptimizelyConfigService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -882,6 +884,20 @@ public Variation getForcedVariation(@Nonnull String experimentKey,
         return decisionService.getForcedVariation(experiment, userId);
     }
 
+    /**
+     * Get {@link OptimizelyConfig} containing experiments and features map
+     *
+     * @return {@link OptimizelyConfig}
+     */
+    public OptimizelyConfig getOptimizelyConfig() {
+        ProjectConfig projectConfig = getProjectConfig();
+        if (projectConfig == null) {
+            logger.error("Optimizely instance is not valid, failing getOptimizelyConfig call.");
+            return null;
+        }
+        return new OptimizelyConfigService(projectConfig).getConfig();
+    }
+
     /**
      * @return the current {@link ProjectConfig} instance.
      */

core-api/src/main/java/com/optimizely/ab/optimizelyconfig/OptimizelyConfig.java

@@ -0,0 +1,48 @@
+/****************************************************************************
+ * Copyright 2020, Optimizely, Inc. and contributors                        *
+ *                                                                          *
+ * 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 com.optimizely.ab.optimizelyconfig;
+
+import java.util.*;
+
+/**
+ * Interface for OptimizleyConfig
+ */
+public class OptimizelyConfig {
+    
+    private Map<String, OptimizelyExperiment> experimentsMap;
+    private Map<String, OptimizelyFeature> featuresMap;
+    private String revision;
+
+    public OptimizelyConfig(Map<String, OptimizelyExperiment> experimentsMap, 
+                            Map<String, OptimizelyFeature> featuresMap,
+                            String revision) {
+        this.experimentsMap = experimentsMap;
+        this.featuresMap = featuresMap;
+        this.revision = revision;                          
+    }
+
+    public Map<String, OptimizelyExperiment> getExperimentsMap() {
+        return experimentsMap;
+    }
+
+    public Map<String, OptimizelyFeature> getFeaturesMap() {
+        return featuresMap;
+    }
+
+    public String getRevision() {
+        return revision;
+    }
+}

core-api/src/main/java/com/optimizely/ab/optimizelyconfig/OptimizelyConfigService.java

@@ -0,0 +1,182 @@
+/****************************************************************************
+ * Copyright 2020, Optimizely, Inc. and contributors                        *
+ *                                                                          *
+ * 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 com.optimizely.ab.optimizelyconfig;
+
+import com.optimizely.ab.annotations.VisibleForTesting;
+import com.optimizely.ab.config.*;
+import java.util.*;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class OptimizelyConfigService {
+
+    private ProjectConfig projectConfig;
+    private OptimizelyConfig optimizelyConfig;
+
+    public OptimizelyConfigService(ProjectConfig projectConfig) {
+        this.projectConfig = projectConfig;
+
+        Map<String, OptimizelyExperiment> experimentsMap = getExperimentsMap();
+        optimizelyConfig = new OptimizelyConfig(
+            experimentsMap,
+            getFeaturesMap(experimentsMap),
+            projectConfig.getRevision()
+        );
+    }
+
+    /**
+     * returns maps for experiment and features to be returned as one object
+     *
+     * @return {@link OptimizelyConfig} containing experiments and features
+     */
+    public OptimizelyConfig getConfig() {
+        return optimizelyConfig;
+    }
+
+    /**
+     * Generates a Map which contains list of variables for each feature key.
+     * This map is used for merging variation and feature variables.
+     */
+    @VisibleForTesting
+    Map<String, List<FeatureVariable>> generateFeatureKeyToVariablesMap() {
+        List<FeatureFlag> featureFlags = projectConfig.getFeatureFlags();
+        if (featureFlags == null) {
+            return Collections.emptyMap();
+        }
+        return featureFlags.stream().collect(Collectors.toMap(FeatureFlag::getKey, featureFlag -> featureFlag.getVariables()));
+    }
+
+    @VisibleForTesting
+    String getExperimentFeatureKey(String experimentId) {
+        List<String> featureKeys = projectConfig.getExperimentFeatureKeyMapping().get(experimentId);
+        return featureKeys != null ? featureKeys.get(0) : null;
+    }
+
+    @VisibleForTesting
+    Map<String, OptimizelyExperiment> getExperimentsMap() {
+        List<Experiment> experiments = projectConfig.getExperiments();
+        if(experiments == null) {
+            return Collections.emptyMap();
+        }
+        return experiments.stream().collect(Collectors.toMap(Experiment::getKey, experiment -> new OptimizelyExperiment(
+            experiment.getId(),
+            experiment.getKey(),
+            getVariationsMap(experiment.getVariations(), experiment.getId())
+        )));
+    }
+
+    @VisibleForTesting
+    Map<String, OptimizelyVariation> getVariationsMap(List<Variation> variations, String experimentId) {
+        if(variations == null) {
+            return Collections.emptyMap();
+        }
+        Boolean isFeatureExperiment = this.getExperimentFeatureKey(experimentId) != null;
+        return variations.stream().collect(Collectors.toMap(Variation::getKey, variation -> new OptimizelyVariation(
+            variation.getId(),
+            variation.getKey(),
+            isFeatureExperiment ? variation.getFeatureEnabled() : null,
+            getMergedVariablesMap(variation, experimentId)
+        )));
+    }
+
+    /**
+     * Merges Additional information from variables in feature flag with variation variables as per the following logic.
+     * 1. If Variation has variables and feature is enabled, then only `type` and `key` are merged from feature variable.
+     * 2. If Variation has variables and feature is disabled, then `type` and `key` are merged and `defaultValue` of feature variable is merged as `value` of variation variable.
+     * 3. If Variation does not contain a variable, then all `id`, `key`, `type` and defaultValue as `value` is used from feature varaible and added to variation.
+     */
+    @VisibleForTesting
+    Map<String, OptimizelyVariable> getMergedVariablesMap(Variation variation, String experimentId) {
+        String featureKey = this.getExperimentFeatureKey(experimentId);
+        if (featureKey != null) {
+            // Map containing variables list for every feature key used for merging variation and feature variables.
+            Map<String, List<FeatureVariable>> featureKeyToVariablesMap = generateFeatureKeyToVariablesMap();
+
+            // Generate temp map of all the available variable values from variation.
+            Map<String, OptimizelyVariable> tempVariableIdMap = getFeatureVariableUsageInstanceMap(variation.getFeatureVariableUsageInstances());
+
+            // Iterate over all the variables available in associated feature.
+            // Use value from variation variable if variable is available in variation and feature is enabled, otherwise use defaultValue from feature variable.
+            List<FeatureVariable> featureVariables = featureKeyToVariablesMap.get(featureKey);
+            if (featureVariables == null) {
+                return Collections.emptyMap();
+            }
+
+            return featureVariables.stream().collect(Collectors.toMap(FeatureVariable::getKey, featureVariable -> new OptimizelyVariable(
+                featureVariable.getId(),
+                featureVariable.getKey(),
+                featureVariable.getType().getVariableType().toLowerCase(),
+                variation.getFeatureEnabled() && tempVariableIdMap.get(featureVariable.getId()) != null
+                    ? tempVariableIdMap.get(featureVariable.getId()).getValue()
+                    : featureVariable.getDefaultValue()
+            )));
+        }
+        return Collections.emptyMap();
+    }
+
+    @VisibleForTesting
+    Map<String, OptimizelyVariable> getFeatureVariableUsageInstanceMap(List<FeatureVariableUsageInstance> featureVariableUsageInstances) {
+        if(featureVariableUsageInstances == null) {
+            return Collections.emptyMap();
+        }
+        return featureVariableUsageInstances.stream().collect(Collectors.toMap(FeatureVariableUsageInstance::getId, variable -> new OptimizelyVariable(
+            variable.getId(),
+            null,
+            null,
+            variable.getValue()
+        )));
+    }
+
+    @VisibleForTesting
+    Map<String, OptimizelyFeature> getFeaturesMap(Map<String, OptimizelyExperiment> allExperimentsMap) {
+        List<FeatureFlag> featureFlags = projectConfig.getFeatureFlags();
+        if(featureFlags == null) {
+            return Collections.emptyMap();
+        }
+        return featureFlags.stream().collect(Collectors.toMap(FeatureFlag::getKey, featureFlag -> new OptimizelyFeature(
+            featureFlag.getId(),
+            featureFlag.getKey(),
+            getExperimentsMapForFeature(featureFlag.getExperimentIds(), allExperimentsMap),
+            getFeatureVariablesMap(featureFlag.getVariables())
+        )));
+    }
+
+    @VisibleForTesting
+    Map<String, OptimizelyExperiment> getExperimentsMapForFeature(List<String> experimentIds, Map<String, OptimizelyExperiment> allExperimentsMap) {
+        if (experimentIds == null) {
+            return Collections.emptyMap();
+        }
+
+        List<String> experimentKeys = experimentIds.stream()
+            .map(experimentId -> projectConfig.getExperimentIdMapping().get(experimentId).getKey())
+            .collect(Collectors.toList());
+
+        return experimentKeys.stream().collect(Collectors.toMap(Function.identity(), key -> allExperimentsMap.get(key)));
+    }
+
+    @VisibleForTesting
+    Map<String, OptimizelyVariable> getFeatureVariablesMap(List<FeatureVariable> featureVariables) {
+        if (featureVariables == null) {
+            return Collections.emptyMap();
+        }
+        return featureVariables.stream().collect(Collectors.toMap(FeatureVariable::getKey, featureVariable -> new OptimizelyVariable(
+            featureVariable.getId(),
+            featureVariable.getKey(),
+            featureVariable.getType().getVariableType().toLowerCase(),
+            featureVariable.getDefaultValue()
+        )));
+    }
+}

core-api/src/main/java/com/optimizely/ab/optimizelyconfig/OptimizelyExperiment.java

@@ -0,0 +1,65 @@
+/****************************************************************************
+ * Copyright 2020, Optimizely, Inc. and contributors                        *
+ *                                                                          *
+ * 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 com.optimizely.ab.optimizelyconfig;
+
+import com.optimizely.ab.config.IdKeyMapped;
+
+import java.util.Map;
+
+/**
+ * Represents the experiment's map in {@link OptimizelyConfig}
+ */
+public class OptimizelyExperiment implements IdKeyMapped {
+
+    private String id;
+    private String key;
+    private Map<String, OptimizelyVariation> variationsMap;
+
+    public OptimizelyExperiment(String id, String key, Map<String, OptimizelyVariation> variationsMap) {
+        this.id = id;
+        this.key = key;
+        this.variationsMap = variationsMap;
+    }
+
+    public String getId() {
+        return id;
+    }
+
+    public String getKey() {
+        return key;
+    }
+
+    public Map<String, OptimizelyVariation> getVariationsMap() {
+        return variationsMap;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == null || getClass() != obj.getClass()) return false;
+        if (obj == this) return true;
+        OptimizelyExperiment optimizelyExperiment = (OptimizelyExperiment) obj;
+        return id.equals(optimizelyExperiment.getId()) &&
+            key.equals(optimizelyExperiment.getKey()) &&
+            variationsMap.equals(optimizelyExperiment.getVariationsMap());
+    }
+
+    @Override
+    public int hashCode() {
+        int hash = id.hashCode();
+        hash = 31 * hash + variationsMap.hashCode();
+        return hash;
+    }
+}