[FFM-11845]: Extend relevant constructors to enable storing previous and current FeatureConfig

examples/build.gradle

@@ -18,3 +18,13 @@ tasks.register('GettingStarted', JavaExec) {
     classpath = sourceSets.main.runtimeClasspath
     mainClass = "io.harness.ff.examples.GettingStarted"
 }
+
+tasks.register('EventExample', JavaExec) {
+    classpath = sourceSets.main.runtimeClasspath
+    mainClass = "io.harness.ff.examples.EventExample"
+}
+
+tasks.register('EventExampleWithFeatureSnapshot', JavaExec) {
+    classpath = sourceSets.main.runtimeClasspath
+    mainClass = "io.harness.ff.examples.EventExampleWithFeatureSnapshot"
+}

examples/src/main/java/io/harness/ff/examples/EventExampleWithFeatureSnapshot.java

@@ -0,0 +1,106 @@
+package io.harness.ff.examples;
+
+import io.harness.cf.client.api.BaseConfig;
+import io.harness.cf.client.api.CfClient;
+import io.harness.cf.client.api.Event;
+import io.harness.cf.client.api.XmlFileMapStore;
+import io.harness.cf.client.connector.HarnessConfig;
+import io.harness.cf.client.connector.HarnessConnector;
+import io.harness.cf.client.dto.Target;
+import io.harness.cf.model.FeatureSnapshot;
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.List;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+@Slf4j
+public class EventExamplePoC {
+    private static final String SDK_KEY = "";
+    private static final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
+
+    private static CfClient client;
+
+    public static void main(String... args) {
+
+        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+            scheduler.shutdown();
+            client.close();
+        }));
+
+        final XmlFileMapStore fileStore = new XmlFileMapStore("Non-Freemium");
+        // this is one way of initialising config.
+        final HarnessConnector hc = new HarnessConnector(SDK_KEY, HarnessConfig.builder().build());
+
+        BaseConfig bc = BaseConfig.builder().
+                enableFeatureSnapshot(true).build();
+
+        // initialise the client.
+        client = new CfClient(hc, bc);
+
+        client.on(Event.READY, result -> log.info("READY"));
+
+        // example: specified prefix we can filter on.
+        final String FLAG_PREFIX = "FFM_";
+        // example:  given flag change event - get both previous and current feature if prefix is matched.
+        client.on(Event.CHANGED, identifier -> {
+            if (identifier.startsWith(FLAG_PREFIX)) {
+                getSnapshot(identifier);
+            } else {
+                log.info("We had an event change but flag did not have required prefix");
+            }
+        });
+
+        // example : given flag change event - get all snapshots.
+        client.on(Event.CHANGED, identifier -> {
+            getAllSnapshots();
+        });
+
+        // example : given flag change event - get all snapshots with given prefix.
+        client.on(Event.CHANGED, identifier -> {
+            getAllSnapshotsWithPrefix();
+        });
+
+        final Target target = Target.builder().identifier("target1").attribute("testKey", "TestValue").name("target1").build();
+
+        scheduler.scheduleAtFixedRate(() -> {
+            log.info("ticking...");
+        }, 0, 10, TimeUnit.SECONDS);
+
+    }
+
+
+    // example method to extract a single snapshot.
+    private static void getSnapshot(String identifier) {
+        log.info("We had a chang event and prefix matched, lets inspect the diff");
+        // fetch current and previous version of the feature
+        FeatureSnapshot snapshot = client.getFeatureSnapshot(identifier);
+        log.info("Previous flag config: {}, {}", identifier, snapshot.getPrevious());
+        log.info("Current flag config: {}, {}", identifier, snapshot.getCurrent());
+    }
+
+
+    // example method to extract and print all the snapshots.
+    private static void getAllSnapshots() {
+        // get all snapshots
+        List<FeatureSnapshot> snapshots = client.getAllFeatureSnapshots();
+        int counter = 0;
+        for (FeatureSnapshot snapshot : snapshots) {
+            log.info("snapshots {} {}", ++counter, snapshot);
+        }
+    }
+
+    // example method to extract and print all the snapshots.
+    private static void getAllSnapshotsWithPrefix() {
+        // get all snapshots
+        String prefix = "FFM_";
+        List<FeatureSnapshot> snapshots = client.getAllFeatureSnapshots(prefix);
+        int counter = 0;
+        for (FeatureSnapshot snapshot : snapshots) {
+            log.info("snapshots {} {}", ++counter, snapshot);
+        }
+    }
+}
+
+

src/main/java/io/harness/cf/client/api/BaseConfig.java

@@ -42,6 +42,9 @@ public class BaseConfig {
   /** If metrics service POST call is taking > this time, we need to know about it */
   @Builder.Default private final long metricsServiceAcceptableDuration = 10000;
 
+  /** store previous and current version of the FeatureConfig */
+  @Builder.Default private final boolean enableFeatureSnapshot = false;
+
   /** Get metrics post frequency in seconds */
   public int getFrequency() {
     return Math.max(frequency, Config.MIN_FREQUENCY);

src/main/java/io/harness/cf/client/api/CfClient.java

@@ -5,6 +5,8 @@
 import io.harness.cf.client.dto.Message;
 import io.harness.cf.client.dto.Target;
 import io.harness.cf.client.logger.LogUtil;
+import io.harness.cf.model.FeatureSnapshot;
+import java.util.List;
 import java.util.function.Consumer;
 import lombok.NonNull;
 
@@ -83,6 +85,18 @@ public void on(@NonNull final Event event, @NonNull final Consumer<String> consu
     client.on(event, consumer);
   }
 
+  public List<FeatureSnapshot> getAllFeatureSnapshots(String prefix) {
+    return client.getFeatureSnapshots(prefix);
+  }
+
+  public List<FeatureSnapshot> getAllFeatureSnapshots() {
+    return client.getFeatureSnapshots();
+  }
+
+  public FeatureSnapshot getFeatureSnapshot(@NonNull String identifier) {
+    return client.getFeatureSnapshot(identifier);
+  }
+
   public void off() {
     client.off();
   }

src/main/java/io/harness/cf/client/api/InnerClient.java

@@ -91,7 +91,9 @@ protected void setUp(@NonNull final Connector connector, @NonNull final BaseConf
     this.connector.setOnUnauthorized(this::onUnauthorized);
 
     // initialization
-    repository = new StorageRepository(options.getCache(), options.getStore(), this, false);
+    repository =
+        new StorageRepository(
+            options.getCache(), options.getStore(), this, options.isEnableFeatureSnapshot());
     evaluator = new Evaluator(repository, options);
     authService = new AuthService(this.connector, options.getPollIntervalInSeconds(), this);
     pollProcessor =
@@ -313,12 +315,13 @@ public synchronized void waitForInitialization()
   }
 
   public List<FeatureSnapshot> getFeatureSnapshots() {
-    // TODO return null/empty list if snapshot is not enabled in config.
     return getFeatureSnapshots("");
   }
 
   public List<FeatureSnapshot> getFeatureSnapshots(String prefix) {
-    // TODO return null/empty list if snapshot is not enabled in config.
+    if (!options.isEnableFeatureSnapshot()){
+      log.debug("FeatureSnapshot disabled, snapshot will contain only current version.");
+    }
     List<String> identifiers = repository.getAllFeatureIdentifiers(prefix);
     List<FeatureSnapshot> snapshots = new LinkedList<>();
 
@@ -331,7 +334,9 @@ public List<FeatureSnapshot> getFeatureSnapshots(String prefix) {
   }
 
   public FeatureSnapshot getFeatureSnapshot(@NonNull String identifier) {
-    // TODO return null/empty list if snapshot is not enabled in config.
+    if (!options.isEnableFeatureSnapshot()){
+      log.debug("FeatureSnapshot disabled, snapshot will contain only current version.");
+    }
     Optional<FeatureConfig[]> ofc = repository.getCurrentAndPreviousFeatureConfig(identifier);
     FeatureSnapshot result = new FeatureSnapshot();
     if (ofc.isPresent()) {