GH-711 Add initial support for source/target types determination

Resoves #711

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/message/MessageUtils.java

@@ -44,6 +44,11 @@ public abstract class MessageUtils {
 	 */
 	public static String TARGET_PROTOCOL = "target-protocol";
 
+	/**
+	 * Value for 'target-protocol' typically use as header key.
+	 */
+	public static String SOURCE_TYPE = "source-type";
+
 	/**
 	 * Create a message for the handler. If the handler is a wrapper for a function in an
 	 * isolated class loader, then the message will be created with the target class

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/utils/FunctionMessageUtils.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2021-2021 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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 org.springframework.cloud.function.utils;
+
+import org.springframework.cloud.function.context.message.MessageUtils;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHeaders;
+
+/**
+ *
+ * !!! INTERNAL ONLY !!!
+ *
+ * @author Oleg Zhurakousky
+ *
+ */
+public final class FunctionMessageUtils {
+
+	private FunctionMessageUtils() {
+
+	}
+
+	public static String getSourceType(String functionDefinition, Message<?> message) {
+		return determineSourceFromHeaders(message.getHeaders());
+	}
+
+	public static String getTargetType(String functionDefinition, Message<?> message) {
+		return message.getHeaders().containsKey(MessageUtils.TARGET_PROTOCOL) ? (String) message.getHeaders().get(MessageUtils.TARGET_PROTOCOL) : "unknown";
+	}
+
+	private static String determineSourceFromHeaders(MessageHeaders headers) {
+		for (String key : headers.keySet()) {
+			if (key.equals(MessageUtils.SOURCE_TYPE)) {
+				return (String) headers.get(MessageUtils.SOURCE_TYPE);
+			}
+			else if (key.startsWith("amqp_")) {
+				return "amqp";
+			}
+			else if (key.startsWith("kafka_")) {
+				return "kafka";
+			}
+			else if (key.startsWith("aws_")) {
+				return "aws";
+			}
+			else if (key.startsWith("solace_")) {
+				return "solace";
+			}
+			else if (key.toLowerCase().equals("user-agent") || key.toLowerCase().equals("accept-encoding") || key.toLowerCase().equals("host")) {
+				return "http";
+			}
+			// add rsocket
+		}
+		return "origin";
+	}
+}