From c7f3c21fd04d8f407b36633afa05bc46736ffb41 Mon Sep 17 00:00:00 2001
From: Joe Ardent <code@ardent.nebcorp.com>
Date: Wed, 17 Sep 2025 12:55:23 -0700
Subject: [PATCH] Add function for parsing topology messages.

---
 src/lib.rs | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 4fcd203..aa3c747 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,5 +1,5 @@
 use std::{
-    collections::HashMap,
+    collections::{BTreeMap, HashMap},
     io::{BufRead, Write},
     sync::{
         Arc, Mutex, OnceLock,
@@ -20,6 +20,7 @@ pub type NodeyNodeFace = Arc<Mutex<dyn Node>>;
 pub type OnInit = Box<dyn Fn(&Runner)>;
 pub type RpcFuture = Receiver<Message>;
 pub type RpcResult = std::result::Result<Option<Value>, ErrorCode>;
+pub type Topology = BTreeMap<String, Vec<String>>;
 
 pub trait Node {
     fn handle(&mut self, runner: &Runner, msg: Message);
@@ -224,9 +225,43 @@ pub fn check_err(msg: &Message) -> RpcResult {
     Ok(None)
 }
 
+/// Convenience function for turning a list of `(&str, serde::Value)` pairs into
+/// a Payload.
 pub fn mk_payload(payload: &[(&str, Value)]) -> Payload {
     payload
         .iter()
         .map(|p| (p.0.to_string(), p.1.clone()))
         .collect()
 }
+
+/// Convenience function for turning a `topology` message into a map of node ->
+/// neighbors (String -> Vec<String>).
+pub fn parse_toplogy(msg: &Message) -> Option<Topology> {
+    if msg.typ() != "topology" {
+        return None;
+    }
+    let topology = msg
+        .body
+        .payload
+        .get("topology")
+        .unwrap()
+        .as_object()
+        .cloned()
+        .unwrap();
+    Some(
+        topology
+            .into_iter()
+            .map(|(node, neighbors)| {
+                (
+                    node,
+                    neighbors
+                        .as_array()
+                        .unwrap()
+                        .iter()
+                        .map(|neighbor| neighbor.as_str().unwrap().to_string())
+                        .collect(),
+                )
+            })
+            .collect(),
+    )
+}