registry: add backend/frontend registries and plugin loader

examples/trx-plugin-example/src/lib.rs

@@ -0,0 +1,42 @@
+// SPDX-FileCopyrightText: 2025 Stanislaw Grams <stanislawgrams@gmail.com>
+//
+// SPDX-License-Identifier: BSD-2-Clause
+
+use std::net::SocketAddr;
+
+use tokio::sync::{mpsc, watch};
+use tokio::task::JoinHandle;
+use tracing::info;
+
+use trx_backend::{register_backend, RigAccess};
+use trx_core::{DynResult, RigRequest, RigState};
+use trx_frontend::{register_frontend, FrontendSpawner};
+
+const BACKEND_NAME: &str = "example";
+const FRONTEND_NAME: &str = "example-frontend";
+
+/// Entry point called by trx-bin when the plugin is loaded.
+#[no_mangle]
+pub extern "C" fn trx_register() {
+    register_backend(BACKEND_NAME, example_backend_factory);
+    register_frontend(FRONTEND_NAME, ExampleFrontend::spawn_frontend);
+}
+
+fn example_backend_factory(_access: RigAccess) -> DynResult<Box<dyn trx_core::rig::RigCat>> {
+    Err("example plugin backend not implemented".into())
+}
+
+struct ExampleFrontend;
+
+impl FrontendSpawner for ExampleFrontend {
+    fn spawn_frontend(
+        _state_rx: watch::Receiver<RigState>,
+        _rig_tx: mpsc::Sender<RigRequest>,
+        _callsign: Option<String>,
+        listen_addr: SocketAddr,
+    ) -> JoinHandle<()> {
+        tokio::spawn(async move {
+            info!("example frontend loaded at {} (no-op)", listen_addr);
+        })
+    }
+}