wip(inventory-agent): local presence advertisement and discovery using mdns almost working

harmony_inventory_agent/src/local_presence/advertise.rs

@@ -0,0 +1,73 @@
+use log::{error, info, warn};
+use mdns_sd::{ServiceDaemon, ServiceInfo};
+use std::collections::HashMap;
+
+use crate::{hwinfo::PhysicalHost, local_presence::{PresenceError, SERVICE_NAME, VERSION}};
+
+/// Advertises the agent's presence on the local network.
+///
+/// This function is synchronous and non-blocking. It spawns a background Tokio task
+/// to handle the mDNS advertisement for the lifetime of the application.
+pub fn advertise(service_port: u16) -> Result<(), PresenceError> {
+    let host_id = match PhysicalHost::gather() {
+        Ok(host) => Some(host.host_uuid),
+        Err(e) => {
+            error!("Could not build physical host, harmony presence id will be unavailable : {e}");
+            None
+        }
+    };
+
+    let instance_name = format!("inventory-agent-{}", host_id.clone().unwrap_or("unknown".to_string()));
+
+    let spawned_msg = format!("Spawned local presence advertisement task for '{instance_name}'.");
+
+    tokio::spawn(async move {
+        info!(
+            "Local presence task started. Advertising as '{}'.",
+            instance_name
+        );
+
+        // The ServiceDaemon must live for the entire duration of the advertisement.
+        // If it's dropped, the advertisement stops.
+        let mdns = match ServiceDaemon::new() {
+            Ok(daemon) => daemon,
+            Err(e) => {
+                warn!("Failed to create mDNS daemon: {}. Task shutting down.", e);
+                return;
+            }
+        };
+
+        let mut props = HashMap::new();
+        if let Some(host_id) = host_id {
+            props.insert("id".to_string(), host_id);
+        }
+        props.insert("version".to_string(), VERSION.to_string());
+
+        let service_info = ServiceInfo::new(
+            SERVICE_NAME,
+            &instance_name,
+            &format!("{}.local.", instance_name),
+            (), // Let the daemon determine the host IPs
+            service_port,
+            Some(props),
+        )
+        .expect("ServiceInfo creation should not fail with valid inputs");
+
+        // The registration handle must also be kept alive.
+        let _registration_handle = match mdns.register(service_info) {
+            Ok(handle) => {
+                info!("Service successfully registered on the local network.");
+                handle
+            }
+            Err(e) => {
+                warn!("Failed to register service: {}. Task shutting down.", e);
+                return;
+            }
+        };
+
+    });
+
+    info!("{spawned_msg}");
+
+    Ok(())
+}