Implement access and retrieval of message_reference

src/main/java/net/dv8tion/jda/api/entities/Message.java

@@ -30,6 +30,7 @@
 import net.dv8tion.jda.api.requests.restaction.pagination.ReactionPaginationAction;
 import net.dv8tion.jda.api.utils.AttachmentOption;
 import net.dv8tion.jda.internal.JDAImpl;
+import net.dv8tion.jda.internal.entities.MessageReference;
 import net.dv8tion.jda.internal.requests.FunctionalCallback;
 import net.dv8tion.jda.internal.requests.Requester;
 import net.dv8tion.jda.internal.utils.Checks;
@@ -214,17 +215,29 @@ public interface Message extends ISnowflake, Formattable
             "(?:\\?\\S*)?(?:#\\S*)?",                                      // Useless query or URN appendix
             Pattern.CASE_INSENSITIVE);
 
+    @Nullable
+    MessageReference getMessageReference();
+
     /**
-     * Referenced message.
+     * This returns the id of the referenced message, never null
      *
-     * <p>This will have different meaning depending on the {@link #getType() type} of message.
-     * Usually, this is a {@link MessageType#INLINE_REPLY INLINE_REPLY} reference.
-     * This can be null even if the type is {@link MessageType#INLINE_REPLY INLINE_REPLY}, when the message it references doesn't exist or discord wasn't able to resolve it in time.
+     * @throws java.lang.IllegalStateException
+     *         If this message does not have a reference
      *
-     * @return The referenced message, or null
+     * @return The referenced message id
      */
-    @Nullable
-    Message getReferencedMessage();
+    long getReferencedMessageIdLong();
+
+    /**
+     * This returns the id of the referenced message, never null
+     *
+     * @throws java.lang.IllegalStateException
+     *         If this message does not have a reference
+     *
+     * @return The referenced message id
+     */
+    @Nonnull
+    String getReferencedMessageId();
 
     /**
      * An immutable list of all mentioned {@link net.dv8tion.jda.api.entities.User Users}.

src/main/java/net/dv8tion/jda/internal/entities/AbstractMessage.java

@@ -32,6 +32,9 @@
 import java.time.OffsetDateTime;
 import java.util.*;
 
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
 public abstract class AbstractMessage implements Message
 {
     protected static final String UNSUPPORTED = "This operation is not supported for Messages of this type!";
@@ -104,9 +107,27 @@ protected void appendFormat(Formatter formatter, int width, int precision, boole
         }
     }
 
+
+    @NotNull
+    @Override
+    public String getReferencedMessageId()
+    {
+        unsupported();
+        return null;
+    }
+
     @Override
-    public Message getReferencedMessage()
+    public long getReferencedMessageIdLong()
     {
+        unsupported();
+        return 0;
+    }
+
+    @Nullable
+    @Override
+    public MessageReference getMessageReference()
+    {
+        unsupported();
         return null;
     }
 

src/main/java/net/dv8tion/jda/internal/entities/EntityBuilder.java

@@ -1219,6 +1219,20 @@ else if (MISSING_CHANNEL.equals(ex.getMessage()))
             }
         }
 
+        MessageReference messageReference = null;
+
+        if (!jsonObject.isNull("message_reference")) // always contains the channel + message id for a referenced message
+        {                                                // used for when referenced_message is not provided
+            DataObject messageReferenceJson = jsonObject.getObject("message_reference");
+
+            messageReference = new MessageReference(
+                    messageReferenceJson.getLong("message_id"),
+                    messageReferenceJson.getLong("channel_id"),
+                    referencedMessage,
+                    api
+            );
+        }
+
         List<ActionRow> components = Collections.emptyList();
         Optional<DataArray> componentsArrayOpt = jsonObject.optArray("components");
         if (componentsArrayOpt.isPresent())
@@ -1232,15 +1246,16 @@ else if (MISSING_CHANNEL.equals(ex.getMessage()))
 
         if (type == MessageType.UNKNOWN)
             throw new IllegalArgumentException(UNKNOWN_MESSAGE_TYPE);
+
         if (!type.isSystem())
         {
-            message = new ReceivedMessage(id, channel, type, referencedMessage, fromWebhook,
+            message = new ReceivedMessage(id, channel, type, messageReference, fromWebhook,
                     mentionsEveryone, mentionedUsers, mentionedRoles, tts, pinned,
                     content, nonce, user, member, activity, editTime, reactions, attachments, embeds, stickers, components, flags);
         }
         else
         {
-            message = new SystemMessage(id, channel, type, fromWebhook,
+            message = new SystemMessage(id, channel, type, messageReference, fromWebhook,
                     mentionsEveryone, mentionedUsers, mentionedRoles, tts, pinned,
                     content, nonce, user, member, activity, editTime, reactions, attachments, embeds, stickers, flags);
             return message; // We don't need to parse mentions for system messages, they are always empty anyway

src/main/java/net/dv8tion/jda/internal/entities/MessageReference.java

@@ -0,0 +1,117 @@
+package net.dv8tion.jda.internal.entities;
+
+import net.dv8tion.jda.api.JDA;
+import net.dv8tion.jda.api.entities.Message;
+import net.dv8tion.jda.api.entities.MessageType;
+import net.dv8tion.jda.api.entities.TextChannel;
+import net.dv8tion.jda.api.requests.RestAction;
+import net.dv8tion.jda.internal.JDAImpl;
+import net.dv8tion.jda.internal.requests.RestActionImpl;
+import net.dv8tion.jda.internal.requests.Route;
+import org.jetbrains.annotations.Nullable;
+
+import javax.annotation.Nonnull;
+
+public class MessageReference
+{
+    private final long messageId;
+    private final long channelId;
+    private final Message referencedMessage;
+    private final JDA api;
+
+    public MessageReference(long messageId, long channelId, @Nullable Message referencedMessage, JDA api)
+    {
+        this.messageId = messageId;
+        this.channelId = channelId;
+        this.referencedMessage = referencedMessage;
+        this.api = api;
+    }
+
+    /**
+     * Retrieves the referenced message for this message. If one is already present, it will be returned.
+     *
+     * @throws java.lang.IllegalStateException
+     *         If this message does not have a reference
+     *
+     * @return {@link net.dv8tion.jda.api.requests.RestAction RestAction} - Type: {@link net.dv8tion.jda.api.entities.Message}
+     */
+    @Nonnull
+    public RestAction<Message> retrieveReferencedMessage() {
+        Route.CompiledRoute route = Route.Messages.GET_MESSAGE.compile(getChannelId(), getMessageId());
+        JDAImpl jda = (JDAImpl) getJDA();
+
+        return new RestActionImpl<>(jda, route,
+                (response, request) -> jda.getEntityBuilder().createMessage(response.getObject(), getChannel(), false));
+    }
+
+    /**
+     * Referenced message.
+     *
+     * <p>This will have different meaning depending on the {@link Message#getType() type} of message.
+     * Usually, this is a {@link MessageType#INLINE_REPLY INLINE_REPLY} reference.
+     * This can be null even if the type is {@link MessageType#INLINE_REPLY INLINE_REPLY}, when the message it references doesn't exist or discord wasn't able to resolve it in time.
+     *
+     * @return The referenced message, or null
+     */
+    @Nullable
+    public Message getReferencedMessage()
+    {
+        return referencedMessage;
+    }
+
+    /**
+     * This will return the channel from which this message originates.
+     * <br>
+     * Messages from other servers can be referenced, in which case JDA may not have the channel cached.
+     *
+     * @return The channel for this message reference, or null
+     */
+    @Nullable
+    public TextChannel getChannel() {
+        return api.getTextChannelById(getChannelIdLong());
+    }
+
+    /**
+     * Returns the message id for this reference.
+     * @return The message id
+     */
+    public long getMessageIdLong()
+    {
+        return messageId;
+    }
+
+    /**
+     * Returns the channel id for this reference.
+     * @return The channel id
+     */
+    public long getChannelIdLong()
+    {
+        return channelId;
+    }
+
+    /**
+     * Returns the message id for this reference.
+     * @return The message id
+     */
+    public String getMessageId()
+    {
+        return Long.toUnsignedString(getMessageIdLong());
+    }
+
+    /**
+     * Returns the channel id for this reference.
+     * @return The channel id
+     */
+    public String getChannelId()
+    {
+        return Long.toUnsignedString(getChannelIdLong());
+    }
+
+    /**
+     * Returns the JDA instance related to this message reference.
+     * @return The corresponding JDA instance
+     */
+    public JDA getJDA() {
+        return api;
+    }
+}

src/main/java/net/dv8tion/jda/internal/entities/ReceivedMessage.java

@@ -33,6 +33,7 @@
 import net.dv8tion.jda.api.utils.data.DataObject;
 import net.dv8tion.jda.internal.JDAImpl;
 import net.dv8tion.jda.internal.requests.CompletedRestAction;
+import net.dv8tion.jda.internal.requests.RestActionImpl;
 import net.dv8tion.jda.internal.requests.Route;
 import net.dv8tion.jda.internal.requests.restaction.AuditableRestActionImpl;
 import net.dv8tion.jda.internal.requests.restaction.MessageActionImpl;
@@ -57,7 +58,7 @@ public class ReceivedMessage extends AbstractMessage
     protected final long id;
     protected final MessageType type;
     protected final MessageChannel channel;
-    protected final Message referencedMessage;
+    protected final MessageReference messageReference;
     protected final boolean fromWebhook;
     protected final boolean mentionsEveryone;
     protected final boolean pinned;
@@ -88,15 +89,16 @@ public class ReceivedMessage extends AbstractMessage
     protected List<String> invites = null;
 
     public ReceivedMessage(
-        long id, MessageChannel channel, MessageType type, Message referencedMessage,
+        long id, MessageChannel channel, MessageType type, MessageReference messageReference,
         boolean fromWebhook, boolean mentionsEveryone, TLongSet mentionedUsers, TLongSet mentionedRoles, boolean tts, boolean pinned,
         String content, String nonce, User author, Member member, MessageActivity activity, OffsetDateTime editTime,
         List<MessageReaction> reactions, List<Attachment> attachments, List<MessageEmbed> embeds, List<MessageSticker> stickers, List<ActionRow> components, int flags)
     {
         super(content, nonce, tts);
         this.id = id;
         this.channel = channel;
-        this.referencedMessage = referencedMessage;
+        this.messageReference = messageReference;
+
         this.type = type;
         this.api = (channel != null) ? (JDAImpl) channel.getJDA() : null;
         this.fromWebhook = fromWebhook;
@@ -129,10 +131,15 @@ public JDA getJDA()
         return api;
     }
 
+    /**
+     * Returns the {@link MessageReference} for this Message. This will be null if this Message has no reference.
+     * @return The message reference.
+     */
+    @Nullable
     @Override
-    public Message getReferencedMessage()
+    public MessageReference getMessageReference()
     {
-        return referencedMessage;
+        return messageReference;
     }
 
     @Override

src/main/java/net/dv8tion/jda/internal/entities/SystemMessage.java

@@ -29,16 +29,17 @@
 public class SystemMessage extends ReceivedMessage
 {
     public SystemMessage(
-        long id, MessageChannel channel, MessageType type,
+        long id, MessageChannel channel, MessageType type, MessageReference messageReference,
         boolean fromWebhook, boolean mentionsEveryone, TLongSet mentionedUsers, TLongSet mentionedRoles,
         boolean tts, boolean pinned,
         String content, String nonce, User author, Member member, MessageActivity activity, OffsetDateTime editTime,
         List<MessageReaction> reactions, List<Attachment> attachments, List<MessageEmbed> embeds, List<MessageSticker> stickers, int flags)
     {
-        super(id, channel, type, null, fromWebhook, mentionsEveryone, mentionedUsers, mentionedRoles,
+        super(id, channel, type, messageReference, fromWebhook, mentionsEveryone, mentionedUsers, mentionedRoles,
             tts, pinned, content, nonce, author, member, activity, editTime, reactions, attachments, embeds, stickers, Collections.emptyList(), flags);
     }
 
+
     @Nonnull
     @Override
     public RestAction<Void> pin()