Introducing JsonBuffer type

Signed-off-by: Michael X. Grey <[email protected]>

Author: mxgrey

src/buffer.rs

@@ -52,6 +52,9 @@ pub use bufferable::*;
 mod manage_buffer;
 pub use manage_buffer::*;
 
+#[cfg(feature = "diagram")]
+mod json_buffer;
+
 /// A buffer is a special type of node within a workflow that is able to store
 /// and release data. When a session is finished, the buffered data from the
 /// session will be automatically cleared.

src/buffer/json_buffer.rs

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2025 Open Source Robotics Foundation
+ *
+ * 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.
+ *
+*/
+
+use bevy_ecs::prelude::Entity;
+
+use schemars::schema::Schema;
+
+#[derive(Clone, Copy, Debug)]
+pub struct JsonBuffer {
+    pub(crate) scope: Entity,
+    pub(crate) source: Entity,
+    pub(crate) interface: &'static dyn JsonInterface,
+}
+
+pub(crate) trait JsonInterface {
+    fn message_type(&self) -> &str;
+    fn schema(&self) -> &Schema;
+}
+
+impl<'a> std::fmt::Debug for &'a dyn JsonInterface {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f
+            .debug_struct("Message Properties")
+            .field("type", &self.message_type())
+            .field("schema", self.schema())
+            .finish()
+    }
+}