Remove or hide unneeded constructors, use Message.user() etc. instead

Author: Jonas-Isr

orchestration/src/main/java/com/sap/ai/sdk/orchestration/AssistantMessage.java

@@ -25,8 +25,4 @@ public MessageContent content() {
   public AssistantMessage(String singleMessage) {
     content = new MessageContentSingle(singleMessage);
   }
-
-  public AssistantMessage(MessageContentSingle messageContent) {
-    content = messageContent;
-  }
 }

orchestration/src/main/java/com/sap/ai/sdk/orchestration/Message.java

@@ -23,6 +23,20 @@ static UserMessage user(@Nonnull final String msg) {
     return new UserMessage(msg);
   }
 
+  /**
+   * A convenience method to create a user message.
+   *
+   * @param msg the message content.
+   * @return the user message.
+   */
+  @Nonnull
+  static UserMessage user(@Nonnull final MessageContent msg) {
+    return new UserMessage(msg);
+  }
+
+//  TODO: discuss whether we want a static AssistantMessage user(@Nonnull final MessageContent msg)
+//    pro: consistency
+//    con: Only works if exactly one string is in there
   /**
    * A convenience method to create an assistant message.
    *
@@ -45,6 +59,17 @@ static SystemMessage system(@Nonnull final String msg) {
     return new SystemMessage(msg);
   }
 
+  /**
+   * A convenience method to create a system message.
+   *
+   * @param msg the message content.
+   * @return the system message.
+   */
+  @Nonnull
+  static SystemMessage system(@Nonnull final MessageContent msg) {
+    return new SystemMessage(msg);
+  }
+
   /**
    * Converts the message to a serializable ChatMessage object.
    *

orchestration/src/main/java/com/sap/ai/sdk/orchestration/MessageContentMulti.java

@@ -13,7 +13,6 @@
 
 public record MessageContentMulti(List<MultiMessageContent> multiContentList)
     implements MessageContent {
-  public MessageContentMulti {}
 
   public MessageContentMulti(MultiChatMessageContent... multiChatContents) {
     this(convertIntoMultiMessageList(multiChatContents));

orchestration/src/main/java/com/sap/ai/sdk/orchestration/OrchestrationChatResponse.java

@@ -8,6 +8,7 @@
 import com.sap.ai.sdk.orchestration.model.LLMChoice;
 import com.sap.ai.sdk.orchestration.model.LLMModuleResultSynchronous;
 import com.sap.ai.sdk.orchestration.model.MultiChatMessage;
+import com.sap.ai.sdk.orchestration.model.MultiChatMessageContent;
 import com.sap.ai.sdk.orchestration.model.TokenUsage;
 import java.util.ArrayList;
 import java.util.List;
@@ -64,22 +65,32 @@ public List<Message> getAllMessages() throws IllegalArgumentException {
       if (chatMessage instanceof ChatMessage simpleMsg) {
         final var message =
             switch (simpleMsg.getRole()) {
-              case "user" -> new UserMessage(simpleMsg.getContent());
-              case "assistant" -> new AssistantMessage(simpleMsg.getContent());
-              case "system" -> new SystemMessage(simpleMsg.getContent());
+              case "user" -> Message.user(simpleMsg.getContent());
+              case "assistant" -> Message.assistant(simpleMsg.getContent());
+              case "system" -> Message.system(simpleMsg.getContent());
               default ->
-                  throw new IllegalArgumentException("Unexpected role: " + simpleMsg.getRole());
+                  throw new IllegalArgumentException(
+                      "Unexpected role: "
+                          + simpleMsg.getRole()
+                          + ". Only 'user', 'assistant' and 'system' are supported.");
             };
         messages.add(message);
       } else if (chatMessage instanceof MultiChatMessage mCMessage) {
-        messages.add(new UserMessage(mCMessage.getContent()));
+          messages.add(
+              switch (mCMessage.getRole()) {
+                case "user" -> Message.user(new MessageContentMulti(mCMessage.getContent().toArray(MultiChatMessageContent[]::new)));
+                case "system" -> Message.system(new MessageContentMulti(mCMessage.getContent().toArray(MultiChatMessageContent[]::new)));
+                default ->
+                    throw new IllegalArgumentException("Unexpected role using MultiChatMessage: " + mCMessage.getRole() + ". Only 'user' and 'system' are supported.");
+              }
+          );
       } else {
         throw new IllegalArgumentException(
             "Messages of type " + chatMessage.getClass() + " are not supported by convenience API");
       }
     }
 
-    messages.add(new AssistantMessage(getChoice().getMessage().getContent()));
+    messages.add(Message.assistant(getChoice().getMessage().getContent()));
     return messages;
   }
 

orchestration/src/main/java/com/sap/ai/sdk/orchestration/SystemMessage.java

@@ -18,8 +18,7 @@ public class SystemMessage implements Message {
   @Nonnull String role = "system";
 
   /** The content of the message. */
-  @Nonnull
-  MessageContent content;
+  @Nonnull MessageContent content;
 
   @Override
   @Nonnull
@@ -31,24 +30,18 @@ public SystemMessage(String singleMessage) {
     content = new MessageContentSingle(singleMessage);
   }
 
-  public SystemMessage(MessageContent messageContent) {
+  SystemMessage(MessageContent messageContent) {
+    if (!(messageContent instanceof MessageContentSingle)) {
+      ((MessageContentMulti) messageContent).multiContentList().stream()
+          .filter(mCMC -> !(mCMC instanceof MultiMessageTextContent))
+          .findAny()
+          .ifPresent(mCMC -> {
+            throw new IllegalArgumentException("Only TextContent is supported for SystemMessage");
+          });
+    }
     content = messageContent;
   }
 
-  public SystemMessage(List<MultiChatMessageContent> multiChatMessageContentList) {
-  var contentArray = multiChatMessageContentList.stream()
-      .map(mCMC -> {
-        if (mCMC instanceof TextContent) {
-          return (TextContent) mCMC;
-        } else {
-          throw new IllegalArgumentException("Only TextContent is supported for SystemMessage");
-        }
-      })
-      .toArray(TextContent[]::new);
-    content =
-        new MessageContentMulti(contentArray);
-  }
-
   @Nonnull
   public SystemMessage addText(@Nonnull String... messages) {
     return new SystemMessage(

orchestration/src/main/java/com/sap/ai/sdk/orchestration/UserMessage.java

@@ -28,16 +28,10 @@ public UserMessage(String singleMessage) {
     content = new MessageContentSingle(singleMessage);
   }
 
-  public UserMessage(MessageContent messageContent) {
+  UserMessage(MessageContent messageContent) {
     content = messageContent;
   }
 
-  public UserMessage(List<MultiChatMessageContent> multiChatMessageContentList) {
-    content =
-        new MessageContentMulti(
-            multiChatMessageContentList.toArray(MultiChatMessageContent[]::new));
-  }
-
   @Nonnull
   public UserMessage addText(@Nonnull String... messages) {
     return new UserMessage(