Add lightning address support for Cashu via npub.cash

Implement get_lightning_address and register_lightning_address for the
Cashu wallet using CDK's built-in npub.cash integration. When configured
with a npubcash_url, the wallet enables npub.cash during init, starts
background polling for incoming quotes, and returns deterministic
lightning addresses derived from the wallet's Nostr keys.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: benthecarman

examples/cli/Cargo.toml

@@ -8,7 +8,7 @@ name = "orange-cli"
 path = "src/main.rs"
 
 [dependencies]
-orange-sdk = { path = "../../orange-sdk" }
+orange-sdk = { path = "../../orange-sdk", features = ["cashu"] }
 tokio = { version = "1.0", features = ["full"] }
 clap = { version = "4.0", features = ["derive"] }
 anyhow = "1.0"

examples/cli/src/main.rs

@@ -6,8 +6,8 @@ use rustyline::error::ReadlineError;
 
 use orange_sdk::bitcoin_payment_instructions::amount::Amount;
 use orange_sdk::{
-	ChainSource, Event, ExtraConfig, LoggerType, Mnemonic, PaymentInfo, Seed, SparkWalletConfig,
-	StorageConfig, Tunables, Wallet, WalletConfig, bitcoin::Network,
+	CashuConfig, ChainSource, CurrencyUnit, Event, ExtraConfig, LoggerType, Mnemonic, PaymentInfo,
+	Seed, SparkWalletConfig, StorageConfig, Tunables, Wallet, WalletConfig, bitcoin::Network,
 };
 use rand::RngCore;
 use std::fs;
@@ -23,6 +23,15 @@ const NETWORK: Network = Network::Bitcoin; // Supports Bitcoin and Regtest
 #[derive(Parser)]
 #[command(author, version, about, long_about = None)]
 struct Cli {
+	/// Use Cashu wallet instead of Spark
+	#[arg(long)]
+	cashu: bool,
+	/// Cashu mint URL (requires --cashu)
+	#[arg(long, requires = "cashu")]
+	mint_url: String,
+	/// npub.cash URL for lightning address support (requires --cashu)
+	#[arg(long, requires = "cashu")]
+	npubcash_url: Option<String>,
 	#[command(subcommand)]
 	command: Option<Commands>,
 }
@@ -74,12 +83,22 @@ struct WalletState {
 	shutdown: Arc<AtomicBool>,
 }
 
-fn get_config(network: Network) -> Result<WalletConfig> {
+fn get_config(network: Network, cli: &Cli) -> Result<WalletConfig> {
 	let storage_path = format!("./wallet_data/{network}");
 
 	// Generate or load seed
 	let seed = generate_or_load_seed(&storage_path)?;
 
+	let extra_config = if cli.cashu {
+		ExtraConfig::Cashu(CashuConfig {
+			mint_url: cli.mint_url.clone(),
+			unit: CurrencyUnit::Sat,
+			npubcash_url: cli.npubcash_url.clone(),
+		})
+	} else {
+		ExtraConfig::Spark(SparkWalletConfig::default())
+	};
+
 	match network {
 		Network::Regtest => {
 			let lsp_address = "185.150.162.100:3551"
@@ -103,7 +122,7 @@ fn get_config(network: Network) -> Result<WalletConfig> {
 				network,
 				seed,
 				tunables: Tunables::default(),
-				extra_config: ExtraConfig::Spark(SparkWalletConfig::default()),
+				extra_config,
 			})
 		},
 		Network::Bitcoin => {
@@ -132,17 +151,17 @@ fn get_config(network: Network) -> Result<WalletConfig> {
 				network,
 				seed,
 				tunables: Tunables::default(),
-				extra_config: ExtraConfig::Spark(SparkWalletConfig::default()),
+				extra_config,
 			})
 		},
 		_ => Err(anyhow::anyhow!("Unsupported network: {network:?}")),
 	}
 }
 
 impl WalletState {
-	async fn new() -> Result<Self> {
+	async fn new(cli: &Cli) -> Result<Self> {
 		let shutdown = Arc::new(AtomicBool::new(false));
-		let config = get_config(NETWORK)
+		let config = get_config(NETWORK, cli)
 			.with_context(|| format!("Failed to get wallet config for network: {NETWORK:?}"))?;
 
 		println!("{} Initializing wallet...", "⚡".bright_yellow());
@@ -241,7 +260,7 @@ async fn main() -> Result<()> {
 	println!();
 
 	// Initialize wallet once at startup
-	let mut state = WalletState::new().await?;
+	let mut state = WalletState::new(&cli).await?;
 
 	// Set up signal handling for graceful shutdown
 	let shutdown_state = state.shutdown.clone();

justfile

@@ -16,6 +16,9 @@ test-cashu *args:
 cli:
     cd examples/cli && cargo run
 
+cli-cashu *args:
+    cd examples/cli && cargo run -- --cashu --npubcash-url https://npubx.cash --mint-url {{ args }}
+
 cli-logs:
     tail -n 50 -f examples/cli/wallet_data/bitcoin/wallet.log
 

orange-sdk/Cargo.toml

@@ -16,7 +16,7 @@ name = "orange_sdk"
 default = ["spark"]
 uniffi = ["dep:uniffi", "spark", "cashu", "rand", "pin-project-lite"]
 spark = ["breez-sdk-spark", "uuid", "serde_json"]
-cashu = ["cdk", "serde_json"]
+cashu = ["cdk", "cdk/npubcash", "serde_json"]
 _test-utils = ["corepc-node", 'electrsd', "cashu", "uuid/v7", "rand"]
 _cashu-tests = ["_test-utils", "cdk-ldk-node", "cdk/mint", "cdk-sqlite", "cdk-axum", "axum"]
 

orange-sdk/src/ffi/cashu.rs

@@ -45,24 +45,34 @@ pub struct CashuConfig {
 	pub mint_url: String,
 	/// The currency unit to use (typically Sat)
 	pub unit: CurrencyUnit,
+	/// Optional npub.cash URL for lightning address support
+	pub npubcash_url: Option<String>,
 }
 
 #[uniffi::export]
 impl CashuConfig {
 	#[uniffi::constructor]
-	pub fn new(mint_url: String, unit: CurrencyUnit) -> Self {
-		CashuConfig { mint_url, unit }
+	pub fn new(mint_url: String, unit: CurrencyUnit, npubcash_url: Option<String>) -> Self {
+		CashuConfig { mint_url, unit, npubcash_url }
 	}
 }
 
 impl From<CashuConfig> for OrangeCashuConfig {
 	fn from(config: CashuConfig) -> Self {
-		OrangeCashuConfig { mint_url: config.mint_url, unit: config.unit.into() }
+		OrangeCashuConfig {
+			mint_url: config.mint_url,
+			unit: config.unit.into(),
+			npubcash_url: config.npubcash_url,
+		}
 	}
 }
 
 impl From<OrangeCashuConfig> for CashuConfig {
 	fn from(config: OrangeCashuConfig) -> Self {
-		CashuConfig { mint_url: config.mint_url, unit: config.unit.into() }
+		CashuConfig {
+			mint_url: config.mint_url,
+			unit: config.unit.into(),
+			npubcash_url: config.npubcash_url,
+		}
 	}
 }

orange-sdk/src/lib.rs

@@ -529,6 +529,27 @@ impl Wallet {
 
 		let tx_metadata = TxMetadataStore::new(Arc::clone(&store)).await;
 
+		// Cashu must init before LDK Node because CashuKvDatabase does
+		// synchronous SQLite reads that deadlock with LDK Node's background
+		// store writes. Other backends can init concurrently.
+		#[cfg(feature = "cashu")]
+		let cashu_wallet = if let ExtraConfig::Cashu(cashu) = &config.extra_config {
+			Some(
+				Cashu::init(
+					&config,
+					cashu.clone(),
+					Arc::clone(&store),
+					Arc::clone(&event_queue),
+					tx_metadata.clone(),
+					Arc::clone(&logger),
+					Arc::clone(&runtime),
+				)
+				.await?,
+			)
+		} else {
+			None
+		};
+
 		let (trusted, ln_wallet) = tokio::join!(
 			async {
 				let trusted: Arc<Box<DynTrustedWalletInterface>> = match &config.extra_config {
@@ -546,18 +567,9 @@ impl Wallet {
 						.await?,
 					)),
 					#[cfg(feature = "cashu")]
-					ExtraConfig::Cashu(cashu) => Arc::new(Box::new(
-						Cashu::init(
-							&config,
-							cashu.clone(),
-							Arc::clone(&store),
-							Arc::clone(&event_queue),
-							tx_metadata.clone(),
-							Arc::clone(&logger),
-							Arc::clone(&runtime),
-						)
-						.await?,
-					)),
+					ExtraConfig::Cashu(_) => {
+						Arc::new(Box::new(cashu_wallet.expect("initialized above")))
+					},
 					#[cfg(feature = "_test-utils")]
 					ExtraConfig::Dummy(cfg) => Arc::new(Box::new(
 						DummyTrustedWallet::new(