Partial merge from vachaPOC

Signed-off-by: Finn Carroll <carrofin@amazon.com>

libs/core/src/main/java/org/opensearch/core/common/io/stream/ProtobufWriteable.java

@@ -0,0 +1,70 @@
+/*
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+package org.opensearch.core.common.io.stream;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * Implementers can be written to write to output and read from input using Protobuf.
+*
+* @opensearch.internal
+*/
+public interface ProtobufWriteable {
+
+    /**
+     * Write this into the stream output.
+    */
+    public void writeTo(OutputStream out) throws IOException;
+
+    /**
+     * Reference to a method that can write some object to a {@link OutputStream}.
+     * Most classes should implement {@link ProtobufWriteable} and the {@link ProtobufWriteable#writeTo(OutputStream)} method should <em>use</em>
+     * {@link OutputStream} methods directly or this indirectly:
+     * <pre><code>
+     * public void writeTo(OutputStream out) throws IOException {
+     *     out.writeVInt(someValue);
+     * }
+     * </code></pre>
+     */
+    @FunctionalInterface
+    interface Writer<V> {
+
+        /**
+         * Write {@code V}-type {@code value} to the {@code out}put stream.
+        *
+        * @param out Output to write the {@code value} too
+        * @param value The value to add
+        */
+        void write(OutputStream out, V value) throws IOException;
+
+    }
+
+    /**
+     * Reference to a method that can read some object from a stream. By convention this is a constructor that takes
+     * {@linkplain byte[]} as an argument for most classes and a static method for things like enums.
+     * <pre><code>
+     * public MyClass(final byte[] in) throws IOException {
+     *     this.someValue = in.readVInt();
+     * }
+     * </code></pre>
+     */
+    @FunctionalInterface
+    interface Reader<V> {
+
+        /**
+         * Read {@code V}-type value from a stream.
+        *
+        * @param in Input to read the value from
+        */
+        V read(byte[] in) throws IOException;
+
+    }
+
+}

server/src/main/java/org/opensearch/action/ProtobufActionListenerResponseHandler.java

@@ -0,0 +1,77 @@
+/*
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+package org.opensearch.action;
+
+import org.opensearch.core.common.io.stream.ProtobufWriteable;
+import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.threadpool.ThreadPool;
+import org.opensearch.transport.TransportResponseHandler;
+import org.opensearch.transport.TransportException;
+import org.opensearch.core.transport.TransportResponse;
+
+import java.io.IOException;
+import java.util.Objects;
+
+/**
+ * A simple base class for action response listeners, defaulting to using the SAME executor (as its
+* very common on response handlers).
+*
+* @opensearch.api
+*/
+public class ProtobufActionListenerResponseHandler<Response extends TransportResponse> implements TransportResponseHandler<Response> {
+
+    private final ActionListener<? super Response> listener;
+    private final ProtobufWriteable.Reader<Response> reader;
+    private final String executor;
+
+    public ProtobufActionListenerResponseHandler(
+        ActionListener<? super Response> listener,
+        ProtobufWriteable.Reader<Response> reader,
+        String executor
+    ) {
+        this.listener = Objects.requireNonNull(listener);
+        this.reader = Objects.requireNonNull(reader);
+        this.executor = Objects.requireNonNull(executor);
+    }
+
+    public ProtobufActionListenerResponseHandler(ActionListener<? super Response> listener, ProtobufWriteable.Reader<Response> reader) {
+        this(listener, reader, ThreadPool.Names.SAME);
+    }
+
+    @Override
+    public void handleResponse(Response response) {
+        listener.onResponse(response);
+    }
+
+    @Override
+    public void handleException(TransportException e) {
+        listener.onFailure(e);
+    }
+
+    @Override
+    public String executor() {
+        return executor;
+    }
+
+    @Override
+    public String toString() {
+        return super.toString() + "/" + listener;
+    }
+
+    @Override
+    public Response read(StreamInput in) throws IOException {
+        // TODO Auto-generated method stub
+        throw new UnsupportedOperationException("Unimplemented method 'read'");
+    }
+
+    @Override
+    public Response read(byte[] in) throws IOException {
+        return reader.read(in);
+    }
+}

server/src/main/java/org/opensearch/action/ProtobufActionRequest.java

@@ -0,0 +1,47 @@
+/*
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+package org.opensearch.action;
+
+import org.opensearch.transport.TransportRequest;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * Base action request implemented by plugins.
+*
+* @opensearch.api
+*/
+public abstract class ProtobufActionRequest extends TransportRequest {
+
+    public ProtobufActionRequest() {
+        super();
+        // this does not set the listenerThreaded API, if needed, its up to the caller to set it
+        // since most times, we actually want it to not be threaded...
+        // this.listenerThreaded = request.listenerThreaded();
+    }
+
+    public ProtobufActionRequest(byte[] in) throws IOException {
+        super(in);
+    }
+
+    public abstract ActionRequestValidationException validate();
+
+    /**
+     * Should this task store its result after it has finished?
+    */
+    public boolean getShouldStoreResult() {
+        return false;
+    }
+
+    @Override
+    public void writeTo(OutputStream out) throws IOException {
+        super.writeTo(out);
+    }
+}

server/src/main/java/org/opensearch/action/ProtobufActionRequestBuilder.java

@@ -0,0 +1,66 @@
+/*
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+package org.opensearch.action;
+
+import org.opensearch.client.ProtobufOpenSearchClient;
+import org.opensearch.common.unit.TimeValue;
+
+import java.util.Objects;
+
+/**
+ * Base Action Request Builder
+*
+* @opensearch.api
+*/
+public abstract class ProtobufActionRequestBuilder<Request extends ProtobufActionRequest, Response extends ProtobufActionResponse> {
+
+    protected final ProtobufActionType<Response> action;
+    protected final Request request;
+    protected final ProtobufOpenSearchClient client;
+
+    protected ProtobufActionRequestBuilder(ProtobufOpenSearchClient client, ProtobufActionType<Response> action, Request request) {
+        Objects.requireNonNull(action, "action must not be null");
+        this.action = action;
+        this.request = request;
+        this.client = client;
+    }
+
+    public Request request() {
+        return this.request;
+    }
+
+    public ActionFuture<Response> execute() {
+        return client.execute(action, request);
+    }
+
+    /**
+     * Short version of execute().actionGet().
+    */
+    public Response get() {
+        return execute().actionGet();
+    }
+
+    /**
+     * Short version of execute().actionGet().
+    */
+    public Response get(TimeValue timeout) {
+        return execute().actionGet(timeout);
+    }
+
+    /**
+     * Short version of execute().actionGet().
+    */
+    public Response get(String timeout) {
+        return execute().actionGet(timeout);
+    }
+
+    public void execute(ActionListener<Response> listener) {
+        client.execute(action, request, listener);
+    }
+}

server/src/main/java/org/opensearch/action/ProtobufActionResponse.java

@@ -0,0 +1,27 @@
+/*
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+package org.opensearch.action;
+
+import org.opensearch.core.transport.TransportResponse;
+
+import java.io.IOException;
+
+/**
+ * Base class for responses to action requests implemented by plugins.
+*
+* @opensearch.api
+*/
+public abstract class ProtobufActionResponse extends TransportResponse {
+
+    public ProtobufActionResponse() {}
+
+    public ProtobufActionResponse(byte[] in) throws IOException {
+        super(in);
+    }
+}

server/src/main/java/org/opensearch/action/ProtobufActionType.java

@@ -0,0 +1,64 @@
+/*
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+package org.opensearch.action;
+
+import org.opensearch.common.settings.Settings;
+import org.opensearch.core.common.io.stream.ProtobufWriteable;
+import org.opensearch.transport.TransportRequestOptions;
+
+/**
+ * A generic action. Should strive to make it a singleton.
+*
+* @opensearch.api
+*/
+public class ProtobufActionType<Response extends ProtobufActionResponse> {
+
+    private final String name;
+    private final ProtobufWriteable.Reader<Response> responseReader;
+
+    /**
+     * @param name The name of the action, must be unique across actions.
+    * @param responseReader A reader for the response type
+    */
+    public ProtobufActionType(String name, ProtobufWriteable.Reader<Response> responseReader) {
+        this.name = name;
+        this.responseReader = responseReader;
+    }
+
+    /**
+     * The name of the action. Must be unique across actions.
+    */
+    public String name() {
+        return this.name;
+    }
+
+    /**
+     * Get a reader that can create a new instance of the class from a {@link byte[]}
+    */
+    public ProtobufWriteable.Reader<Response> getResponseReaderTry() {
+        return responseReader;
+    }
+
+    /**
+     * Optional request options for the action.
+    */
+    public TransportRequestOptions transportOptions(Settings settings) {
+        return TransportRequestOptions.EMPTY;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        return o instanceof ProtobufActionType && name.equals(((ProtobufActionType<?>) o).name());
+    }
+
+    @Override
+    public int hashCode() {
+        return name.hashCode();
+    }
+}