From d950bce3f5a5ec3e619bcf4115cddebc892a5126 Mon Sep 17 00:00:00 2001
From: Oliver Nordbjerg <onbjerg@users.noreply.github.com>
Date: Fri, 12 Apr 2024 17:11:14 +0200
Subject: [PATCH] refactor: use async fns in minimal example (#7600)

---
 Cargo.toml                        | 13 +++++--
 examples/exex/minimal/src/main.rs | 65 +++++++++++++------------------
 2 files changed, 38 insertions(+), 40 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 98b18dd6d..df9416813 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -260,8 +260,13 @@ reth-trie = { path = "crates/trie" }
 reth-trie-parallel = { path = "crates/trie-parallel" }
 
 # revm
-revm = { version = "8.0.0", features = ["std", "secp256k1"], default-features = false }
-revm-primitives = { version = "3.1.0", features = ["std"], default-features = false }
+revm = { version = "8.0.0", features = [
+    "std",
+    "secp256k1",
+], default-features = false }
+revm-primitives = { version = "3.1.0", features = [
+    "std",
+], default-features = false }
 revm-inspectors = { git = "https://github.com/paradigmxyz/evm-inspectors", rev = "21f8f3d" }
 
 # eth
@@ -276,7 +281,9 @@ alloy-rpc-types-trace = { git = "https://github.com/alloy-rs/alloy", rev = "987b
 alloy-rpc-types-engine = { git = "https://github.com/alloy-rs/alloy", rev = "987b393" }
 alloy-genesis = { git = "https://github.com/alloy-rs/alloy", rev = "987b393" }
 alloy-node-bindings = { git = "https://github.com/alloy-rs/alloy", rev = "987b393" }
-alloy-provider = { git = "https://github.com/alloy-rs/alloy", rev = "987b393", default-features = false, features = ["reqwest"] }
+alloy-provider = { git = "https://github.com/alloy-rs/alloy", rev = "987b393", default-features = false, features = [
+    "reqwest",
+] }
 alloy-eips = { git = "https://github.com/alloy-rs/alloy", rev = "987b393" }
 alloy-signer = { git = "https://github.com/alloy-rs/alloy", rev = "987b393" }
 alloy-signer-wallet = { git = "https://github.com/alloy-rs/alloy", rev = "987b393" }
diff --git a/examples/exex/minimal/src/main.rs b/examples/exex/minimal/src/main.rs
index 3cc8c6b06..410a4a4ea 100644
--- a/examples/exex/minimal/src/main.rs
+++ b/examples/exex/minimal/src/main.rs
@@ -1,55 +1,46 @@
-use std::{
-    pin::Pin,
-    task::{ready, Context, Poll},
-};
-
 use futures::Future;
 use reth::builder::FullNodeTypes;
-use reth_exex::{ExExContext, ExExEvent};
+use reth_exex::ExExContext;
 use reth_node_ethereum::EthereumNode;
 use reth_provider::CanonStateNotification;
 
-/// A minimal example of an ExEx that simply prints out commit and reorg notifications.
-struct MinimalExEx<Node: FullNodeTypes> {
+/// The initialization logic of the ExEx is just an async function.
+///
+/// During initialization you can wait for resources you need to be up for the ExEx to function,
+/// like a database connection.
+async fn exex_init<Node: FullNodeTypes>(
     ctx: ExExContext<Node>,
+) -> eyre::Result<impl Future<Output = eyre::Result<()>>> {
+    Ok(exex(ctx))
 }
 
-impl<Node: FullNodeTypes> Future for MinimalExEx<Node> {
-    type Output = eyre::Result<()>;
-
-    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        let this = self.get_mut();
-
-        // Process all new chain state notifications until there are no more
-        while let Some(notification) = ready!(this.ctx.notifications.poll_recv(cx)) {
-            // Process one notification
-            match &notification {
-                CanonStateNotification::Commit { new } => {
-                    println!("Received commit: {:?}", new.first().number..=new.tip().number);
-                }
-                CanonStateNotification::Reorg { old, new } => {
-                    println!(
-                        "Received reorg: {:?} -> {:?}",
-                        old.first().number..=old.tip().number,
-                        new.first().number..=new.tip().number
-                    );
-                }
-            };
-
-            // Send a finished height event, signaling the node that we don't need any blocks below
-            // this height anymore
-            this.ctx.events.send(ExExEvent::FinishedHeight(notification.tip().number))?;
-        }
-
-        Poll::Pending
+/// An ExEx is just a future, which means you can implement all of it in an async function!
+///
+/// This ExEx just prints out whenever a state transition happens, either a new chain segment being
+/// added, or a chain segment being re-orged.
+async fn exex<Node: FullNodeTypes>(mut ctx: ExExContext<Node>) -> eyre::Result<()> {
+    while let Some(notification) = ctx.notifications.recv().await {
+        match &notification {
+            CanonStateNotification::Commit { new } => {
+                println!("Received commit: {:?}", new.first().number..=new.tip().number);
+            }
+            CanonStateNotification::Reorg { old, new } => {
+                println!(
+                    "Received reorg: {:?} -> {:?}",
+                    old.first().number..=old.tip().number,
+                    new.first().number..=new.tip().number
+                );
+            }
+        };
     }
+    Ok(())
 }
 
 fn main() -> eyre::Result<()> {
     reth::cli::Cli::parse_args().run(|builder, _| async move {
         let handle = builder
             .node(EthereumNode::default())
-            .install_exex("Minimal", move |ctx| async { Ok(MinimalExEx { ctx }) })
+            .install_exex("Minimal", exex_init)
             .launch()
             .await?;