make SERVER_ADDR env variable override the listening address

src/main.rs

@@ -1,7 +1,17 @@
 use db::N_STATEMENTS;
-use rocket::{futures::lock::Mutex, get, fs::FileServer, http::Status, response::Redirect, response::content::RawHtml, routes, State};
+use rocket::{
+    fs::FileServer, futures::lock::Mutex, get, http::Status, response::content::RawHtml,
+    response::Redirect, routes, State,
+};
+use std::{
+    env,
+    fs::File,
+    net::{Ipv4Addr, SocketAddr, SocketAddrV4},
+    str::FromStr,
+    sync::Arc,
+    time::Duration,
+};
 use tokio_postgres::{Client, NoTls, Statement};
-use std::{fs::File, sync::Arc, time::Duration};
 
 mod db;
 mod linkgen;
@@ -16,7 +26,8 @@ pub struct GlobalState {
 }
 #[tokio::main]
 async fn main() {
-    let postgres_config = "host=localhost user=shortener password=".to_owned() + include_str!("../postgres_password.txt").trim();
+    let postgres_config = "host=localhost user=shortener password=".to_owned()
+        + include_str!("../postgres_password.txt").trim();
     let (client, conn) = match tokio_postgres::connect(&postgres_config, NoTls).await {
         Ok((client, conn)) => (client, conn),
         Err(e) => {
@@ -31,9 +42,21 @@ async fn main() {
     });
     db::prepare_tables(&client).await.unwrap();
     let statements = db::prepare_statements(&client).await.unwrap();
+
+    let default_listen_addr = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 3020).into();
+    let listen_addr = env::var("SERVER_ADDR")
+        .ok()
+        .map(|v| SocketAddr::from_str(&v).ok())
+        .flatten()
+        .unwrap_or(default_listen_addr);
     let mut config = rocket::Config::default();
-    config.port = 3020;
+    config.address = listen_addr.ip();
-    let state = GlobalState { db_client: client, statements };
+    config.port = listen_addr.port();
+
+    let state = GlobalState {
+        db_client: client,
+        statements,
+    };
     let state_mutex = Arc::new(Mutex::new(state));
     {
         let state_mutex = state_mutex.clone();
@@ -68,7 +91,11 @@ async fn create(state: &State<Mutex<GlobalState>>, url: &str, secret: Option<&st
             custom_link = true;
         }
     }
-    let actual_len = if allow_secret_options && length.is_some() { length.unwrap() } else { DEFAULT_LINK_LENGTH };
+    let actual_len = if allow_secret_options && length.is_some() {
+        length.unwrap()
+    } else {
+        DEFAULT_LINK_LENGTH
+    };
     if actual_len < 1 || actual_len > 64 {
         return (Status::BadRequest, "invalid length".to_owned());
     }
@@ -86,7 +113,7 @@ async fn create(state: &State<Mutex<GlobalState>>, url: &str, secret: Option<&st
                     if custom_link {
                         return (Status::BadRequest, "link already exists".to_owned());
                     }
-                },
+                }
                 None => {
                     actual_link = Some(link_id.clone());
                     break;
@@ -101,7 +128,7 @@ async fn create(state: &State<Mutex<GlobalState>>, url: &str, secret: Option<&st
 
     let res = match ttl {
         Some(ttl) => db::add_temporary_link(&state, actual_link.as_ref().unwrap(), url, ttl).await,
-        None => db::add_link(&state, actual_link.as_ref().unwrap(), url).await
+        None => db::add_link(&state, actual_link.as_ref().unwrap(), url).await,
     };
     match res {
         Ok(_) => (),
@@ -116,7 +143,10 @@ async fn create(state: &State<Mutex<GlobalState>>, url: &str, secret: Option<&st
 }
 
 #[get("/<link>")]
-pub async fn go_to_link(state: &State<Mutex<GlobalState>>, link: &str) -> Result<Option<Redirect>, Status> {
+pub async fn go_to_link(
+    state: &State<Arc<Mutex<GlobalState>>>,
+    link: &str,
+) -> Result<Option<Redirect>, Status> {
     match db::get_link(&state, link).await {
         Ok(url) => match url {
             Some(url) => Ok(Some(Redirect::to(url))),