In process RPC service (#40)

Signed-off-by: Fabio Di Fabio <fabio.difabio@consensys.net>

datatypes/src/main/java/org/hyperledger/besu/datatypes/rpc/JsonRpcResponse.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright ConsenSys AG.
+ *
+ * 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.hyperledger.besu.datatypes.rpc;
+
+import com.fasterxml.jackson.annotation.JsonGetter;
+
+/** Represent a Json RPC response */
+public interface JsonRpcResponse {
+
+  /**
+   * The JsonRPC version
+   *
+   * @return the version
+   */
+  @JsonGetter("jsonrpc")
+  default String getVersion() {
+    return "2.0";
+  }
+
+  /**
+   * Get the response type
+   *
+   * @return the response type
+   */
+  JsonRpcResponseType getType();
+}

datatypes/src/main/java/org/hyperledger/besu/datatypes/rpc/JsonRpcResponseType.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright ConsenSys AG.
+ *
+ * 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.hyperledger.besu.datatypes.rpc;
+
+/** Various types of responses that the JSON-RPC component may produce. */
+public enum JsonRpcResponseType {
+  /** no response */
+  NONE,
+  /** Successful response */
+  SUCCESS,
+  /** Error response */
+  ERROR,
+  /** Not authorized response */
+  UNAUTHORIZED
+}

datatypes/src/main/java/org/hyperledger/besu/datatypes/rpc/RpcMethodError.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright contributors to Hyperledger Besu.
+ *
+ * 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.hyperledger.besu.datatypes.rpc;
+
+import java.util.Optional;
+
+/**
+ * The {@code RpcMethodError} interface defines the structure for RPC error handling within the
+ * context of plugins. It provides methods to retrieve error code, message, and an optional data
+ * decoder function.
+ */
+public interface RpcMethodError {
+
+  /**
+   * Retrieves the error code associated with the RPC error.
+   *
+   * @return An integer representing the error code.
+   */
+  int getCode();
+
+  /**
+   * Retrieves the message associated with the RPC error.
+   *
+   * @return A {@code String} containing the error message.
+   */
+  String getMessage();
+
+  /**
+   * Some errors have additional data associated with them, that is possible to decode to provide a
+   * more detailed error response.
+   *
+   * @param data the additional data to decode
+   * @return an optional containing the decoded data if the error has it and the decoding is
+   *     successful, otherwise empty.
+   */
+  default Optional<String> decodeData(final String data) {
+    return Optional.empty();
+  }
+}