Add CLI args and env var support

- Added `clap` dependency to `ldk-server` to
  support passing essential node config via CLI arguments and environment
  variables.
- Implemented layered config loading: config file (full set of options) +
  environment variables + CLI arguments. Env vars and CLI args override
  values from the config file when present.
- Added tests for the new config loading logic.
- Updated README with usage instructions and explanation of config precedence.

Close #42

Author: moisesPompilio

Cargo.lock

@@ -38,19 +38,60 @@ We welcome your feedback and contributions to help shape the future of LDK Serve
 ### Configuration
 Refer `./ldk-server/ldk-server-config.toml` to see available configuration options.
 
+You can configure the node via a TOML file, environment variables, or CLI arguments. All options are optional — values provided via CLI override environment variables, which override the values in the TOML file.
+
 ### Building
 ```
 git clone https://github.com/lightningdevkit/ldk-server.git
 cargo build
 ```
 
 ### Running
+- Using a config file:
 ```
 cargo run --bin ldk-server ./ldk-server/ldk-server-config.toml
 ```
 
-Interact with the node using CLI:
+- Using environment variables (all optional):
+```
+export LDK_SERVER_NODE_NETWORK=regtest
+export LDK_SERVER_NODE_LISTENING_ADDRESS=localhost:3001
+export LDK_SERVER_NODE_REST_SERVICE_ADDRESS=127.0.0.1:3002
+export LDK_SERVER_NODE_ALIAS=LDK-Server
+export LDK_SERVER_BITCOIND_RPC_ADDRESS=127.0.0.1:18443
+export LDK_SERVER_BITCOIND_RPC_USER=your-rpc-user
+export LDK_SERVER_BITCOIND_RPC_PASSWORD=your-rpc-password
+export LDK_SERVER_STORAGE_DIR_PATH=/path/to/storage
+cargo run --bin ldk-server
+```
+
+- Using CLI arguments (all optional):
+```
+cargo run --bin ldk-server -- \
+  --node-network regtest \
+  --node-listening-address localhost:3001 \
+  --node-rest-service-address 127.0.0.1:3002 \
+  --node-alias LDK-Server \
+  --bitcoind-rpc-address 127.0.0.1:18443 \
+  --bitcoind-rpc-user your-rpc-user \
+  --bitcoind-rpc-password your-rpc-password \
+  --storage-dir-path /path/to/storage
+```
+
+- Mixed configuration example (config file + overrides):
+```
+# config file sets listening_address = "localhost:3001"
+cargo run --bin ldk-server ./ldk-server/ldk-server-config.toml  --node-listening-address localhost:3009
+# Result: `localhost:3009` will be used because CLI overrides the config file
+```
+
+### Interacting with the Node
+
+Once running, use the CLI client:
 ```
-./target/debug/ldk-server-cli -b localhost:3002 onchain-receive # To generate onchain-receive address.
-./target/debug/ldk-server-cli -b localhost:3002 help # To print help/available commands.
+# Generate an on-chain receive address
+./target/debug/ldk-server-cli -b localhost:3002 onchain-receive
+
+# View commands
+./target/debug/ldk-server-cli -b localhost:3002 help
 ```

README.md

@@ -18,6 +18,7 @@ rusqlite = { version = "0.31.0", features = ["bundled"] }
 rand = { version = "0.8.5", default-features = false }
 async-trait = { version = "0.1.85", default-features = false }
 toml = { version = "0.8.9", default-features = false, features = ["parse"] }
+clap = { version = "4.0.5", default-features = false, features = ["derive", "std", "error-context", "suggestions", "help", "env"] }
 
 # Required for RabittMQ based EventPublisher. Only enabled for `events-rabbitmq` feature.
 lapin = { version = "2.4.0", features = ["rustls"], default-features = false, optional = true }

ldk-server/Cargo.toml

@@ -13,6 +13,8 @@ use tokio::signal::unix::SignalKind;
 use hyper::server::conn::http1;
 use hyper_util::rt::TokioIo;
 
+use clap::Parser;
+
 use crate::io::events::event_publisher::{EventPublisher, NoopEventPublisher};
 use crate::io::events::get_event_name;
 #[cfg(feature = "events-rabbitmq")]
@@ -24,7 +26,7 @@ use crate::io::persist::{
 	FORWARDED_PAYMENTS_PERSISTENCE_SECONDARY_NAMESPACE, PAYMENTS_PERSISTENCE_PRIMARY_NAMESPACE,
 	PAYMENTS_PERSISTENCE_SECONDARY_NAMESPACE,
 };
-use crate::util::config::load_config;
+use crate::util::config::{load_config, ArgsConfig};
 use crate::util::proto_adapter::{forwarded_payment_to_proto, payment_to_proto};
 use hex::DisplayHex;
 use ldk_node::config::Config;
@@ -36,38 +38,19 @@ use ldk_server_protos::events::{event_envelope, EventEnvelope};
 use ldk_server_protos::types::Payment;
 use prost::Message;
 use rand::Rng;
-use std::fs;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::{SystemTime, UNIX_EPOCH};
 use tokio::select;
 
-const USAGE_GUIDE: &str = "Usage: ldk-server <config_path>";
-
 fn main() {
-	let args: Vec<String> = std::env::args().collect();
-
-	if args.len() < 2 {
-		eprintln!("{USAGE_GUIDE}");
-		std::process::exit(-1);
-	}
-
-	let arg = args[1].as_str();
-	if arg == "-h" || arg == "--help" {
-		println!("{}", USAGE_GUIDE);
-		std::process::exit(0);
-	}
-
-	if fs::File::open(arg).is_err() {
-		eprintln!("Unable to access configuration file.");
-		std::process::exit(-1);
-	}
+	let args_config = ArgsConfig::parse();
 
 	let mut ldk_node_config = Config::default();
-	let config_file = match load_config(Path::new(arg)) {
+	let config_file = match load_config(&args_config) {
 		Ok(config) => config,
 		Err(e) => {
-			eprintln!("Invalid configuration file: {}", e);
+			eprintln!("Invalid configuration: {}", e);
 			std::process::exit(-1);
 		},
 	};