Return header information

Cargo.toml

@@ -6,3 +6,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+actix-web = "4"
+log = "0.4.17"
+env_logger = "0.9.0"
+clap = { version = "3.1.15", features = ["derive", "env"] }

src/main.rs

@@ -1,3 +1,48 @@
-fn main() {
-    println!("Hello, world!");
+use actix_web::{App, HttpRequest, HttpResponse, HttpServer, Responder, web};
+use clap::Parser;
+
+/// Simple HTTP responder
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+struct Args {
+    /// Listen address
+    #[clap(short, long, env, default_value = "0.0.0.0:8000")]
+    listen_address: String,
+}
+
+async fn handler(req: HttpRequest) -> impl Responder {
+    let mut headers = req.headers().iter()
+        .map(|h| format!("{}: {}", h.0.as_str(), h.1.to_str().unwrap_or_default()))
+        .collect::<Vec<_>>();
+    headers.sort();
+
+    let body = format!(
+        "Remote Peer: {}\nVerb: {}\nPath: {}\nQuery: {}\n\n=== Headers ===\n{}",
+        req.peer_addr().expect("Missing remote peer address!"),
+        req.head().method,
+        req.uri().path(),
+        req.uri().query().unwrap_or_default(),
+        headers.join("\n")
+    );
+
+    HttpResponse::Ok()
+        .content_type("text/plain")
+        .body(body)
+}
+
+#[actix_web::main]
+async fn main() -> std::io::Result<()> {
+    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));
+
+    let args: Args = Args::parse();
+
+    log::info!("Will listen on {}...", args.listen_address);
+
+    HttpServer::new(|| {
+        App::new()
+            .route("{tail:.*}", web::route().to(handler))
+    })
+        .bind(args.listen_address)?
+        .run()
+        .await
 }