hive-c0re: in-memory broker + per-agent sockets + coordinator state

hive-c0re/src/broker.rs

@@ -0,0 +1,30 @@
+//! In-memory message broker. Phase 3 replaces this with a sqlite-backed store.
+
+use std::collections::{HashMap, VecDeque};
+use std::sync::Mutex;
+
+use hive_sh4re::Message;
+
+#[derive(Default)]
+pub struct Broker {
+    queues: Mutex<HashMap<String, VecDeque<Message>>>,
+}
+
+impl Broker {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn send(&self, message: Message) {
+        let mut queues = self.queues.lock().unwrap();
+        queues
+            .entry(message.to.clone())
+            .or_default()
+            .push_back(message);
+    }
+
+    pub fn recv(&self, recipient: &str) -> Option<Message> {
+        let mut queues = self.queues.lock().unwrap();
+        queues.get_mut(recipient).and_then(|q| q.pop_front())
+    }
+}