Use per-env application settings

configuration.yaml → configuration/base.yaml

@@ -1,5 +1,5 @@
-application_host: localhost
-application_port: 8000
+application:
+  port: 8000
 database:
   host: localhost
   port: 5432

configuration/local.yaml

@@ -0,0 +1,2 @@
+application:
+  host: localhost

configuration/production.yaml

@@ -0,0 +1,2 @@
+application:
+  host: ::0

src/configuration.rs

@@ -3,9 +3,14 @@ use serde::Deserialize;
 
 #[derive(Deserialize)]
 pub struct Settings {
+    pub application: ApplicationSettings,
     pub database: DatabaseSettings,
-    pub application_host: String,
-    pub application_port: u16,
+}
+
+#[derive(Deserialize)]
+pub struct ApplicationSettings {
+    pub host: String,
+    pub port: u16,
 }
 
 #[derive(Deserialize)]
@@ -38,12 +43,49 @@ impl DatabaseSettings {
 }
 
 pub fn get_configuration() -> Result<Settings, config::ConfigError> {
+    let config_dir = std::env::current_dir()
+        .and_then(|dir| Ok(dir.join("configuration")))
+        .expect("Failed to determine the current directory");
+
+    let environment: Environment = std::env::var("APP_ENVIRONMENT")
+        .unwrap_or_else(|_| "local".into())
+        .try_into()
+        .expect("Failed to parse app environment");
+
+    let env_config = format!("{}.yaml", environment.as_str());
+
     let settings = config::Config::builder()
-        .add_source(config::File::new(
-            "configuration.yaml",
-            config::FileFormat::Yaml,
-        ))
+        .add_source(config::File::from(config_dir.join("base.yaml")))
+        .add_source(config::File::from(config_dir.join(env_config)))
         .build()?;
 
     settings.try_deserialize()
 }
+
+pub enum Environment {
+    Local,
+    Production,
+}
+
+impl Environment {
+    fn as_str(&self) -> &'static str {
+        match self {
+            Environment::Local => "local",
+            Environment::Production => "production",
+        }
+    }
+}
+
+impl TryFrom<String> for Environment {
+    type Error = String;
+
+    fn try_from(s: String) -> Result<Self, Self::Error> {
+        match s.to_lowercase().as_str() {
+            "local" => Ok(Environment::Local),
+            "production" => Ok(Environment::Production),
+            other => Err(format!(
+                "{other} is not a supported environment. Use either `local` or `production`."
+            )),
+        }
+    }
+}

src/main.rs

@@ -13,7 +13,7 @@ async fn main() -> Result<(), std::io::Error> {
     init_subscriber(subscriber);
 
     let config = get_configuration().expect("Failed to read configuration");
-    let address = format!("{}:{}", config.application_host, config.application_port);
+    let address = format!("{}:{}", config.application.host, config.application.port);
 
     let listener = TcpListener::bind(address)
         .await