Add private message visitor.

briar-api/src/main/java/org/briarproject/briar/api/blog/BlogInvitationRequest.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.messaging.PrivateMessageVisitor;
 import org.briarproject.briar.api.sharing.InvitationRequest;
 
 import javax.annotation.Nullable;
@@ -19,4 +20,8 @@ public class BlogInvitationRequest extends InvitationRequest<Blog> {
 				message, available, canBeOpened);
 	}
 
+	@Override
+	public void accept(PrivateMessageVisitor v) {
+		v.visitBlogInvitatioRequest(this);
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/blog/BlogInvitationResponse.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.messaging.PrivateMessageVisitor;
 import org.briarproject.briar.api.sharing.InvitationResponse;
 
 @NotNullByDefault
@@ -16,4 +17,8 @@ public class BlogInvitationResponse extends InvitationResponse {
 				accept, shareableId);
 	}
 
+	@Override
+	public void accept(PrivateMessageVisitor v) {
+		v.visitBlogInvitationResponse(this);
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/forum/ForumInvitationRequest.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.messaging.PrivateMessageVisitor;
 import org.briarproject.briar.api.sharing.InvitationRequest;
 
 import javax.annotation.Nullable;
@@ -21,4 +22,8 @@ public class ForumInvitationRequest extends InvitationRequest<Forum> {
 				message, available, canBeOpened);
 	}
 
+	@Override
+	public void accept(PrivateMessageVisitor v) {
+		v.visitForumInvitationRequest(this);
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/forum/ForumInvitationResponse.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.messaging.PrivateMessageVisitor;
 import org.briarproject.briar.api.sharing.InvitationResponse;
 
 import javax.annotation.concurrent.Immutable;
@@ -19,4 +20,8 @@ public class ForumInvitationResponse extends InvitationResponse {
 				accept, shareableId);
 	}
 
+	@Override
+	public void accept(PrivateMessageVisitor v) {
+		v.visitForumInvitationResponse(this);
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionRequest.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.messaging.PrivateMessageVisitor;
 import org.briarproject.briar.api.messaging.PrivateRequest;
 
 import javax.annotation.Nullable;
@@ -28,4 +29,9 @@ public class IntroductionRequest extends PrivateRequest<Author> {
 	public boolean isContact() {
 		return contact;
 	}
+
+	@Override
+	public void accept(PrivateMessageVisitor v) {
+		v.visitIntroductionRequest(this);
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionResponse.java

@@ -5,6 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.messaging.PrivateMessageVisitor;
 import org.briarproject.briar.api.messaging.PrivateResponse;
 
 import javax.annotation.concurrent.Immutable;
@@ -35,4 +36,8 @@ public class IntroductionResponse extends PrivateResponse {
 		return ourRole == INTRODUCER;
 	}
 
+	@Override
+	public void accept(PrivateMessageVisitor v) {
+		v.visitIntroductionResponse(this);
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/messaging/PrivateMessageHeader.java

@@ -54,4 +54,7 @@ public class PrivateMessageHeader {
 		return read;
 	}
 
+	public void accept(PrivateMessageVisitor v) {
+		v.visitPrivateMessageHeader(this);
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/messaging/PrivateMessageVisitor.java

+package org.briarproject.briar.api.messaging;
+
+import org.briarproject.briar.api.blog.BlogInvitationRequest;
+import org.briarproject.briar.api.blog.BlogInvitationResponse;
+import org.briarproject.briar.api.forum.ForumInvitationRequest;
+import org.briarproject.briar.api.forum.ForumInvitationResponse;
+import org.briarproject.briar.api.introduction.IntroductionRequest;
+import org.briarproject.briar.api.introduction.IntroductionResponse;
+import org.briarproject.briar.api.privategroup.invitation.GroupInvitationRequest;
+import org.briarproject.briar.api.privategroup.invitation.GroupInvitationResponse;
+
+public interface PrivateMessageVisitor {
+
+	void visitPrivateMessageHeader(PrivateMessageHeader h);
+
+	void visitBlogInvitatioRequest(BlogInvitationRequest r);
+
+	void visitBlogInvitationResponse(BlogInvitationResponse r);
+
+	void visitForumInvitationRequest(ForumInvitationRequest r);
+
+	void visitForumInvitationResponse(ForumInvitationResponse r);
+
+	void visitGroupInvitationRequest(GroupInvitationRequest r);
+
+	void visitGroupInvitationResponse(GroupInvitationResponse r);
+
+	void visitIntroductionRequest(IntroductionRequest r);
+
+	void visitIntroductionResponse(IntroductionResponse r);
+}

briar-api/src/main/java/org/briarproject/briar/api/privategroup/invitation/GroupInvitationRequest.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.messaging.PrivateMessageVisitor;
 import org.briarproject.briar.api.privategroup.PrivateGroup;
 import org.briarproject.briar.api.sharing.InvitationRequest;
 
@@ -22,4 +23,8 @@ public class GroupInvitationRequest extends InvitationRequest<PrivateGroup> {
 				message, available, canBeOpened);
 	}
 
+	@Override
+	public void accept(PrivateMessageVisitor v) {
+		v.visitGroupInvitationRequest(this);
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/privategroup/invitation/GroupInvitationResponse.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.messaging.PrivateMessageVisitor;
 import org.briarproject.briar.api.sharing.InvitationResponse;
 
 import javax.annotation.concurrent.Immutable;
@@ -19,4 +20,8 @@ public class GroupInvitationResponse extends InvitationResponse {
 				accept, shareableId);
 	}
 
+	@Override
+	public void accept(PrivateMessageVisitor v) {
+		v.visitGroupInvitationResponse(this);
+	}
 }