add rank search result step

Signed-off-by: Jackie Han <[email protected]>

src/main/java/org/opensearch/flowframework/FlowFrameworkPlugin.java

@@ -60,6 +60,7 @@
 import org.opensearch.ml.client.MachineLearningNodeClient;
 import org.opensearch.plugins.ActionPlugin;
 import org.opensearch.plugins.Plugin;
+import org.opensearch.plugins.SearchPipelinePlugin;
 import org.opensearch.repositories.RepositoriesService;
 import org.opensearch.rest.RestController;
 import org.opensearch.rest.RestHandler;

src/main/java/org/opensearch/flowframework/workflow/RankSearchResultStep.java

@@ -0,0 +1,40 @@
+package org.opensearch.flowframework.workflow;
+
+import org.opensearch.action.support.PlainActionFuture;
+
+import java.util.Map;
+
+public class RankSearchResultStep implements WorkflowStep {
+
+    public RankSearchResultStep() {}
+
+    public static final String NAME = "rank_search_result";
+    /**
+     * Triggers the actual processing of the building block.
+     *
+     * @param currentNodeId      The id of the node executing this step
+     * @param currentNodeInputs  Input params and content for this node, from workflow parsing
+     * @param outputs            WorkflowData content of previous steps.
+     * @param previousNodeInputs Input params for this node that come from previous steps
+     * @return A CompletableFuture of the building block. This block should return immediately, but not be completed until the step executes, containing either the step's output data or {@link WorkflowData#EMPTY} which may be passed to follow-on steps.
+     */
+    @Override
+    public PlainActionFuture<WorkflowData> execute(String currentNodeId,
+                                                   WorkflowData currentNodeInputs,
+                                                   Map<String, WorkflowData> outputs,
+                                                   Map<String, String> previousNodeInputs) {
+        PlainActionFuture<WorkflowData> future = PlainActionFuture.newFuture();
+        future.onResponse(WorkflowData.EMPTY);
+        return future;
+    }
+
+    /**
+     * Gets the name of the workflow step.
+     *
+     * @return the name of this workflow step.
+     */
+    @Override
+    public String getName() {
+        return NAME;
+    }
+}

src/main/java/org/opensearch/flowframework/workflow/WorkflowStepFactory.java

@@ -73,6 +73,7 @@ public WorkflowStepFactory(
         stepMap.put(ToolStep.NAME, ToolStep::new);
         stepMap.put(RegisterAgentStep.NAME, () -> new RegisterAgentStep(mlClient, flowFrameworkIndicesHandler));
         stepMap.put(DeleteAgentStep.NAME, () -> new DeleteAgentStep(mlClient));
+        stepMap.put(RankSearchResultStep.NAME, RankSearchResultStep::new);
     }
 
     /**