feat(rust): add configuration parsing and an error type

rust/Cargo.toml

@@ -6,7 +6,13 @@ edition = "2024"
 [dependencies]
 tokio = { version = "*", features = ["full"] }
 serde = { version = "*", features = ["derive"] }
+either = { version = "*", features = ["serde"] }
+
 thiserror = "*"
-clap = { version = "*", features = ["derive"] }
+anyhow = "*"
 tracing = "*"
 tracing-subscriber = "*"
+
+clap = { version = "*", features = ["derive"] }
+figment = { version = "*", features = ["toml", "env", "json"] }
+

rust/src/config.rs

@@ -1,4 +1,27 @@
+use either::{Either, Either::Left};
 use serde::Deserialize;
 
-#[derive(Deserialize)]
+#[derive(Deserialize, Clone, Debug)]
-struct CommandConfig {}
+pub struct CommandConfig {
+    /// The port(s) to listen on.
+    ///
+    /// If you are using Docker, don't change this, you'll need to map an
+    /// external port to this.
+    ///
+    /// To listen on multiple ports, specify a vector e.g. [8080, 8448]
+    ///
+    /// default: 8008
+    #[serde(default = "default_port")]
+    pub port: ListeningPort,
+}
+
+#[derive(Deserialize, Clone, Debug)]
+#[serde(transparent)]
+pub struct ListeningPort {
+    #[serde(with = "either::serde_untagged")]
+    pub ports: Either<u16, Vec<u16>>,
+}
+
+fn default_port() -> ListeningPort {
+    ListeningPort { ports: Left(8008) }
+}

rust/src/error.rs

@@ -0,0 +1,21 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum CommandError {
+    #[error("the configuration is invalid")]
+    InvalidConfig(#[from] Box<figment::Error>),
+
+    #[error(transparent)]
+    Unknown(#[from] anyhow::Error),
+    // examples
+    // #[error("the data for key `{0}` is not available")]
+    // Redaction(String),
+    // #[error("invalid header (expected {expected:?}, found {found:?})")]
+    // InvalidHeader { expected: String, found: String },
+}
+
+impl From<figment::Error> for CommandError {
+    fn from(error: figment::Error) -> Self {
+        CommandError::InvalidConfig(Box::new(error))
+    }
+}

rust/src/main.rs

@@ -1,4 +1,8 @@
 use clap::Parser;
+use figment::{
+    Figment,
+    providers::{Env, Format, Json, Toml},
+};
 use tracing::{Level, event};
 
 mod args;
@@ -6,10 +10,19 @@ use args::{ActionType, CommandArgs};
 
 mod config;
 
+mod error;
+use error::CommandError;
+
 #[tokio::main]
-async fn main() {
+async fn main() -> Result<(), CommandError> {
     let args = CommandArgs::parse();
 
+    let config: config::CommandConfig = Figment::new()
+        .admerge(Json::file("config.json"))
+        .admerge(Toml::file("config.toml"))
+        .admerge(Env::prefixed("APP_"))
+        .extract()?;
+
     match &args.action {
         ActionType::Serve(serve_args) => {
             tracing_subscriber::fmt()
@@ -24,7 +37,11 @@ async fn main() {
 
             println!("{:#?}", args);
 
-            // println!("{:#?}", config);
+            println!("{:#?}", config);
+
+            println!("{:#?}", config.port.ports);
         }
     }
+
+    Ok(())
 }