feat: drain on-chain wallet

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- Allow to drain on-chain wallet by sending amount `0`.
+
 ## [1.4.4] - 2023-10-28
 
 - Improve collab revert

crates/ln-dlc-node/src/ldk_node_wallet.rs

@@ -183,22 +183,22 @@ where
 
     /// Send funds to the given address.
     ///
-    /// If `amount_sat_or_drain` is `None` the wallet will be drained, i.e., all available funds
+    /// If `amount_sat_or_drain` is `0` the wallet will be drained, i.e., all available funds
     /// will be spent.
     pub(crate) fn send_to_address(
         &self,
         address: &bitcoin::Address,
-        amount_sat_or_drain: Option<u64>,
+        amount_sat_or_drain: u64,
     ) -> Result<Txid> {
         let fee_rate = self.fee_rate_estimator.estimate(ConfirmationTarget::Normal);
 
         let tx = {
             let locked_wallet = self.bdk_lock();
             let mut tx_builder = locked_wallet.build_tx();
 
-            if let Some(amount_sats) = amount_sat_or_drain {
+            if amount_sat_or_drain > 0 {
                 tx_builder
-                    .add_recipient(address.script_pubkey(), amount_sats)
+                    .add_recipient(address.script_pubkey(), amount_sat_or_drain)
                     .fee_rate(fee_rate)
                     .enable_rbf();
             } else {
@@ -234,11 +234,11 @@ where
 
         let txid = self.broadcast_transaction(&tx)?;
 
-        if let Some(amount_sats) = amount_sat_or_drain {
+        if amount_sat_or_drain > 0 {
             tracing::info!(
                 "Created new transaction {} sending {}sats on-chain to address {}",
                 txid,
-                amount_sats,
+                amount_sat_or_drain,
                 address
             );
         } else {

crates/ln-dlc-node/src/node/mod.rs

@@ -560,7 +560,7 @@ where
     pub fn send_to_address(&self, address: &bitcoin::Address, amount_sats: u64) -> Result<Txid> {
         self.wallet
             .ldk_wallet()
-            .send_to_address(address, Some(amount_sats))
+            .send_to_address(address, amount_sats)
     }
 }
 

crates/tests-e2e/tests/collaborative_revert_position.rs

@@ -27,9 +27,9 @@ async fn can_revert_channel() {
     let wallet_info = app.rx.wallet_info().expect("To be able to get wallet info");
     assert_eq!(wallet_info.balances.on_chain, 0);
 
-    let split: Vec<_> = channel.original_funding_txo.split(":").collect();
-    let txid = Txid::from_str(&split[0]).expect("To have a channel id");
-    let vout = u32::from_str(&split[1]).expect("To have valid vout");
+    let split: Vec<_> = channel.original_funding_txo.split(':').collect();
+    let txid = Txid::from_str(split[0]).expect("To have a channel id");
+    let vout = u32::from_str(split[1]).expect("To have valid vout");
 
     coordinator
         .sync_wallet()

mobile/lib/features/wallet/send/send_screen.dart

@@ -38,7 +38,7 @@ class _SendScreenState extends State<SendScreen> {
   ChannelInfo? channelInfo;
 
   Destination? _destination;
-  Amount? _amount;
+  Amount _amount = Amount.zero();
 
   final TextEditingController _controller = TextEditingController();
 
@@ -64,7 +64,7 @@ class _SendScreenState extends State<SendScreen> {
         if (destination != null) {
           _destination = destination;
           _amount = destination.amount;
-          _controller.text = _amount!.formatted();
+          _controller.text = _amount.formatted();
 
           _invalidDestination = false;
           _valid = _formKey.currentState?.validate() ?? false;
@@ -103,7 +103,7 @@ class _SendScreenState extends State<SendScreen> {
                           setState(() {
                             _destination = destination;
                             _amount = destination.amount;
-                            _controller.text = _amount!.formatted();
+                            _controller.text = _amount.formatted();
 
                             _invalidDestination = false;
                             _valid = _formKey.currentState?.validate() ?? false;
@@ -176,12 +176,13 @@ class _SendScreenState extends State<SendScreen> {
                     ),
                   )),
               const SizedBox(height: 20),
-              const Text("Amount in sats", style: TextStyle(fontWeight: FontWeight.bold)),
+              const Text("Amount in sats (0 to drain the wallet)",
+                  style: TextStyle(fontWeight: FontWeight.bold)),
               const SizedBox(height: 2),
               AmountInputField(
                 controller: _controller,
                 label: "",
-                value: _amount ?? Amount.zero(),
+                value: _amount,
                 enabled: _destination != null && _destination!.amount.sats == 0,
                 onChanged: (value) {
                   setState(() {
@@ -196,8 +197,12 @@ class _SendScreenState extends State<SendScreen> {
 
                   final amount = Amount.parseAmount(value);
 
-                  if (amount.sats <= 0) {
-                    return "Amount is mandatory";
+                  if (amount.sats <= 0 && _destination!.getWalletType() == WalletType.lightning) {
+                    return "Amount cannot be 0";
+                  }
+
+                  if (amount.sats < 0) {
+                    return "Amount cannot be negative";
                   }
 
                   if (_destination == null) {