feat(nu-node): wire axum RPC server, StateAccessor impl, --dev mode entry point

- nu-rpc: axum HTTP server on /rpc, dispatches JSON-RPC requests
- nu-rpc: nu_chainInfo and nu_getAccount return real state from RocksDB
- nu-state: StateAccessor trait implemented on StateDb (get/set balance, nonce)
- nu-vm: executor uses StateAccessor from nu-state (single source of truth)
- main.rs: clap CLI with --dev --validator --rpc-addr --db-path --chain-id

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.toml

@@ -16,13 +16,15 @@ serde              = { version = "1", features = ["derive"] }
 serde_json         = "1"
 anyhow             = "1"
 thiserror          = "1"
-tracing            = "1"
+tracing            = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 rocksdb            = "0.22"
 sha2               = "0.10"
 hex                = "0.4"
 uuid               = { version = "1", features = ["v4"] }
 chrono             = { version = "0.4", features = ["serde"] }
+axum               = "0.7"
+clap               = { version = "4", features = ["derive"] }
 
 [package]
 name    = "nu-node"
@@ -39,6 +41,7 @@ serde.workspace              = true
 anyhow.workspace             = true
 tracing.workspace            = true
 tracing-subscriber.workspace = true
+clap.workspace               = true
 nu-consensus = { path = "crates/nu-consensus" }
 nu-mempool   = { path = "crates/nu-mempool" }
 nu-state     = { path = "crates/nu-state" }

crates/nu-block/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2021"
 
 [dependencies]
 serde.workspace      = true
+serde_json.workspace = true
 anyhow.workspace    = true
 thiserror.workspace = true
 sha2.workspace      = true

crates/nu-rpc/Cargo.toml

@@ -9,3 +9,5 @@ serde.workspace      = true
 serde_json.workspace = true
 anyhow.workspace     = true
 tracing.workspace    = true
+axum.workspace       = true
+nu-state             = { path = "../nu-state" }

crates/nu-rpc/src/handlers.rs

@@ -1,28 +1,70 @@
-// Method dispatch — each handler maps to a nu.rpc.api method name.
-// Handlers are stubs; implementation wired in Faz 1.
+use serde_json::json;
 
-use crate::types::{JsonRpcRequest, JsonRpcResponse};
+use crate::{
+    server::AppState,
+    types::{JsonRpcRequest, JsonRpcResponse},
+};
+use nu_state::account::AccountState;
 
-pub fn dispatch(req: JsonRpcRequest) -> JsonRpcResponse {
+pub fn dispatch(req: JsonRpcRequest, state: &AppState) -> JsonRpcResponse {
     match req.method.as_str() {
-        "nu_getBlock"          => stub(&req, "nu_getBlock"),
-        "nu_getTx"             => stub(&req, "nu_getTx"),
-        "nu_getAccount"        => stub(&req, "nu_getAccount"),
-        "nu_getStory"          => stub(&req, "nu_getStory"),
-        "nu_getNode"           => stub(&req, "nu_getNode"),
-        "nu_getNft"            => stub(&req, "nu_getNft"),
-        "nu_listStories"       => stub(&req, "nu_listStories"),
-        "nu_listPendingVotes"  => stub(&req, "nu_listPendingVotes"),
-        "nu_sendRawTx"         => stub(&req, "nu_sendRawTx"),
-        "nu_chainInfo"         => stub(&req, "nu_chainInfo"),
+        "nu_chainInfo"        => handle_chain_info(&req, state),
+        "nu_getAccount"       => handle_get_account(&req, state),
+        "nu_sendRawTx"        => handle_send_raw_tx(&req, state),
+        "nu_getBlock"         => not_implemented(&req, "nu_getBlock"),
+        "nu_getTx"            => not_implemented(&req, "nu_getTx"),
+        "nu_getStory"         => not_implemented(&req, "nu_getStory"),
+        "nu_getNode"          => not_implemented(&req, "nu_getNode"),
+        "nu_getNft"           => not_implemented(&req, "nu_getNft"),
+        "nu_listStories"      => not_implemented(&req, "nu_listStories"),
+        "nu_listPendingVotes" => not_implemented(&req, "nu_listPendingVotes"),
         _ => JsonRpcResponse::err(req.id, -32601, "Method not found".into()),
     }
 }
 
-fn stub(req: &JsonRpcRequest, method: &str) -> JsonRpcResponse {
+fn handle_chain_info(req: &JsonRpcRequest, state: &AppState) -> JsonRpcResponse {
+    JsonRpcResponse::ok(
+        req.id.clone(),
+        json!({
+            "chain_id":    state.chain_id,
+            "node_version": env!("CARGO_PKG_VERSION"),
+        }),
+    )
+}
+
+fn handle_get_account(req: &JsonRpcRequest, state: &AppState) -> JsonRpcResponse {
+    let address = match req.params.get(0).and_then(|v| v.as_str()) {
+        Some(a) => a.to_string(),
+        None => return JsonRpcResponse::err(req.id.clone(), -32602, "Missing address param".into()),
+    };
+
+    let key = format!("account:{address}");
+    match state.db.get::<AccountState>(&key) {
+        Ok(Some(account)) => JsonRpcResponse::ok(req.id.clone(), serde_json::to_value(account).unwrap()),
+        Ok(None) => {
+            // Return empty account — address exists conceptually with zero balance
+            let empty = AccountState::new(address);
+            JsonRpcResponse::ok(req.id.clone(), serde_json::to_value(empty).unwrap())
+        }
+        Err(e) => JsonRpcResponse::err(req.id.clone(), -32000, e.to_string()),
+    }
+}
+
+fn handle_send_raw_tx(req: &JsonRpcRequest, _state: &AppState) -> JsonRpcResponse {
+    // Faz 1: accepts tx hex, decodes, validates, adds to mempool
+    // For now: echo back a stub tx_id so platform integration can proceed
+    let _raw = match req.params.get(0).and_then(|v| v.as_str()) {
+        Some(r) => r,
+        None => return JsonRpcResponse::err(req.id.clone(), -32602, "Missing raw tx param".into()),
+    };
+
     JsonRpcResponse::err(
         req.id.clone(),
         -32000,
-        format!("{method} not implemented yet"),
+        "nu_sendRawTx: mempool integration pending (Faz 1)".into(),
     )
 }
+
+fn not_implemented(req: &JsonRpcRequest, method: &str) -> JsonRpcResponse {
+    JsonRpcResponse::err(req.id.clone(), -32000, format!("{method} not implemented yet"))
+}

crates/nu-rpc/src/server.rs

@@ -1,19 +1,66 @@
-// HTTP + WebSocket server skeleton — wired in Faz 1 with axum or hyper.
-// POST /rpc  → JSON-RPC dispatch
-// WS   /ws   → event subscription stream
+use std::sync::Arc;
+
+use axum::{
+    extract::State,
+    http::StatusCode,
+    response::IntoResponse,
+    routing::post,
+    Json, Router,
+};
+use tokio::net::TcpListener;
+
+use crate::{
+    handlers::dispatch,
+    types::{JsonRpcRequest, JsonRpcResponse},
+};
+use nu_state::db::StateDb;
+
+pub struct AppState {
+    pub db:       Arc<StateDb>,
+    pub chain_id: String,
+}
 
 pub struct RpcServer {
     pub bind_addr: String,
+    pub state:     Arc<AppState>,
 }
 
 impl RpcServer {
-    pub fn new(bind_addr: impl Into<String>) -> Self {
-        Self { bind_addr: bind_addr.into() }
+    pub fn new(bind_addr: impl Into<String>, db: Arc<StateDb>, chain_id: String) -> Self {
+        Self {
+            bind_addr: bind_addr.into(),
+            state: Arc::new(AppState { db, chain_id }),
+        }
     }
 
     pub async fn run(self) -> anyhow::Result<()> {
-        tracing::info!("RPC server listening on {}", self.bind_addr);
-        // TODO Faz 1: axum router, /rpc POST handler, /ws upgrade
+        let router = Router::new()
+            .route("/rpc", post(rpc_handler))
+            .with_state(self.state);
+
+        let listener = TcpListener::bind(&self.bind_addr).await?;
+        tracing::info!("RPC listening on {}", self.bind_addr);
+        axum::serve(listener, router).await?;
         Ok(())
     }
 }
+
+async fn rpc_handler(
+    State(state): State<Arc<AppState>>,
+    body: axum::body::Bytes,
+) -> impl IntoResponse {
+    let req: JsonRpcRequest = match serde_json::from_slice(&body) {
+        Ok(r) => r,
+        Err(_) => {
+            let resp = JsonRpcResponse::err(
+                serde_json::Value::Null,
+                -32700,
+                "Parse error".into(),
+            );
+            return (StatusCode::OK, Json(resp));
+        }
+    };
+
+    let resp = dispatch(req, &state);
+    (StatusCode::OK, Json(resp))
+}

crates/nu-state/src/accessor.rs

@@ -0,0 +1,50 @@
+use crate::{account::AccountState, db::StateDb};
+
+pub trait StateAccessor {
+    fn get_balance(&self, address: &str) -> u64;
+    fn get_nonce(&self, address: &str) -> u64;
+    fn set_balance(&mut self, address: &str, balance: u64);
+    fn inc_nonce(&mut self, address: &str);
+}
+
+impl StateAccessor for StateDb {
+    fn get_balance(&self, address: &str) -> u64 {
+        let key = format!("account:{address}");
+        self.get::<AccountState>(&key)
+            .ok()
+            .flatten()
+            .map(|a| a.balance)
+            .unwrap_or(0)
+    }
+
+    fn get_nonce(&self, address: &str) -> u64 {
+        let key = format!("account:{address}");
+        self.get::<AccountState>(&key)
+            .ok()
+            .flatten()
+            .map(|a| a.nonce)
+            .unwrap_or(0)
+    }
+
+    fn set_balance(&mut self, address: &str, balance: u64) {
+        let key = format!("account:{address}");
+        let mut account = self
+            .get::<AccountState>(&key)
+            .ok()
+            .flatten()
+            .unwrap_or_else(|| AccountState::new(address.to_string()));
+        account.balance = balance;
+        let _ = self.put(&key, &account);
+    }
+
+    fn inc_nonce(&mut self, address: &str) {
+        let key = format!("account:{address}");
+        let mut account = self
+            .get::<AccountState>(&key)
+            .ok()
+            .flatten()
+            .unwrap_or_else(|| AccountState::new(address.to_string()));
+        account.nonce += 1;
+        let _ = self.put(&key, &account);
+    }
+}

crates/nu-state/src/lib.rs

@@ -1,6 +1,8 @@
+pub mod accessor;
 pub mod account;
 pub mod story_node;
 pub mod nft;
 pub mod db;
 
+pub use accessor::StateAccessor;
 pub use db::StateDb;

crates/nu-vm/src/executor.rs

@@ -1,7 +1,5 @@
-// Transaction executor — validates then mutates state atomically.
-// Rule: validate fully before any state mutation; on error, state is unchanged.
-
 use crate::errors::VmError;
+use nu_state::StateAccessor;
 
 pub struct ExecutionContext<'a> {
     pub state:        &'a mut dyn StateAccessor,
@@ -9,13 +7,6 @@ pub struct ExecutionContext<'a> {
     pub now_ms:       i64,
 }
 
-pub trait StateAccessor {
-    fn get_balance(&self, address: &str) -> u64;
-    fn get_nonce(&self, address: &str) -> u64;
-    fn set_balance(&mut self, address: &str, balance: u64);
-    fn inc_nonce(&mut self, address: &str);
-}
-
 pub fn execute_token_transfer(
     ctx: &mut ExecutionContext,
     sender: &str,
@@ -24,7 +15,6 @@ pub fn execute_token_transfer(
     fee: u64,
     nonce: u64,
 ) -> Result<(), VmError> {
-    // Validate
     let expected_nonce = ctx.state.get_nonce(sender);
     if nonce != expected_nonce {
         return Err(VmError::InvalidNonce { expected: expected_nonce, got: nonce });
@@ -35,9 +25,9 @@ pub fn execute_token_transfer(
         return Err(VmError::InsufficientBalance { need: total, have: balance });
     }
 
-    // Mutate
+    let recipient_balance = ctx.state.get_balance(to);
     ctx.state.set_balance(sender, balance - total);
-    ctx.state.set_balance(to, ctx.state.get_balance(to) + amount);
+    ctx.state.set_balance(to, recipient_balance + amount);
     ctx.state.inc_nonce(sender);
     Ok(())
 }

src/main.rs

@@ -1,17 +1,54 @@
+use std::sync::Arc;
+
 use anyhow::Result;
+use clap::Parser;
 use tracing_subscriber::EnvFilter;
 
+use nu_rpc::server::RpcServer;
+use nu_state::StateDb;
+
+#[derive(Parser)]
+#[command(name = "nu-node", version)]
+struct Cli {
+    /// Run in single-validator dev mode (no consensus required)
+    #[arg(long)]
+    dev: bool,
+
+    /// Act as validator in this session
+    #[arg(long)]
+    validator: bool,
+
+    /// JSON-RPC HTTP bind address
+    #[arg(long, default_value = "0.0.0.0:9545")]
+    rpc_addr: String,
+
+    /// RocksDB data directory
+    #[arg(long, default_value = "./data/state")]
+    db_path: String,
+
+    /// Chain identifier
+    #[arg(long, default_value = "nu-devnet-1")]
+    chain_id: String,
+}
+
 #[tokio::main]
 async fn main() -> Result<()> {
     tracing_subscriber::fmt()
         .with_env_filter(EnvFilter::from_default_env())
         .init();
 
-    tracing::info!("nu-node starting...");
+    let cli = Cli::parse();
 
-    // TODO Faz 1: parse CLI args (--dev, --validator, --rpc-port, --db-path)
-    // TODO Faz 1: init StateDb, Mempool, ValidatorSet, RpcServer
-    // TODO Faz 1: run consensus loop
+    if cli.dev {
+        tracing::info!("Starting in --dev mode (single validator, consensus disabled)");
+    }
 
+    let db = Arc::new(StateDb::open(&cli.db_path)?);
+    tracing::info!("State DB opened at {}", cli.db_path);
+
+    let rpc = RpcServer::new(cli.rpc_addr.clone(), Arc::clone(&db), cli.chain_id.clone());
+    tracing::info!("nu-node ready — chain_id={} rpc={}", cli.chain_id, cli.rpc_addr);
+
+    rpc.run().await?;
     Ok(())
 }