feat: add GET /api/v1/metagraph endpoint exposing all subnet neurons (UID + hotkey + stake)

Author: echobt

crates/platform-server/src/api/metagraph.rs

@@ -0,0 +1,59 @@
+//! Metagraph API handler
+//!
+//! Exposes all registered neurons (miners + validators) from the cached metagraph.
+
+use crate::state::AppState;
+use axum::{extract::State, Json};
+use serde::Serialize;
+use sp_core::crypto::Ss58Codec;
+use std::sync::Arc;
+
+#[derive(Debug, Serialize)]
+pub struct NeuronInfo {
+    pub uid: u64,
+    pub hotkey: String,
+    pub stake: u64,
+}
+
+/// GET /api/v1/metagraph - Get all registered neurons
+pub async fn get_metagraph(State(state): State<Arc<AppState>>) -> Json<Vec<NeuronInfo>> {
+    let mg = state.metagraph.read();
+    let neurons = match *mg {
+        Some(ref metagraph) => metagraph
+            .neurons
+            .iter()
+            .map(|(uid, neuron)| NeuronInfo {
+                uid: *uid,
+                hotkey: neuron.hotkey.to_ss58check(),
+                stake: neuron.stake.min(u64::MAX as u128) as u64,
+            })
+            .collect(),
+        None => vec![],
+    };
+    Json(neurons)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_neuron_info_serialize() {
+        let info = NeuronInfo {
+            uid: 42,
+            hotkey: "5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY".to_string(),
+            stake: 10_000_000_000_000,
+        };
+        let json = serde_json::to_string(&info).unwrap();
+        assert!(json.contains("42"));
+        assert!(json.contains("5GrwvaEF"));
+        assert!(json.contains("10000000000000"));
+    }
+
+    #[test]
+    fn test_neuron_info_empty_vec_serialize() {
+        let neurons: Vec<NeuronInfo> = vec![];
+        let json = serde_json::to_string(&neurons).unwrap();
+        assert_eq!(json, "[]");
+    }
+}

crates/platform-server/src/api/mod.rs

@@ -6,5 +6,6 @@ pub mod challenges;
 pub mod evaluations;
 pub mod events;
 pub mod leaderboard;
+pub mod metagraph;
 pub mod submissions;
 pub mod validators;

crates/platform-server/src/main.rs

@@ -216,6 +216,7 @@ async fn main() -> anyhow::Result<()> {
         .route("/ws/challenge", get(challenge_ws_handler))
         // === CONTROL PLANE API ===
         .route("/api/v1/auth", post(api::auth::authenticate))
+        .route("/api/v1/metagraph", get(api::metagraph::get_metagraph))
         .route("/api/v1/validators", get(api::validators::list_validators))
         .route(
             "/api/v1/validators",