Merge #493

493: Add checks to max_giveable amount. r=da-kami a=bonomat

We need to check two things:
- balance to be higher than dust amount (546).
- balance to be higher than min-relay fee.

Additionally, the tx_builder might fail if not enough funds are in the wallet to pay for the overall transaction fees. In both cases, we return 0. 

fixes #487 

Co-authored-by: Philipp Hoenisch <philipp@hoenisch.at>

swap/src/bin/swap.rs

@@ -97,7 +97,6 @@ async fn main() -> Result<()> {
             let max_givable = || bitcoin_wallet.max_giveable(TxLock::script_size());
             let (send_bitcoin, fees) = determine_btc_to_swap(
                 event_loop_handle.request_quote(),
-                max_givable().await?,
                 bitcoin_wallet.new_address(),
                 || bitcoin_wallet.balance(),
                 max_givable,
@@ -329,7 +328,6 @@ async fn init_monero_wallet(
 
 async fn determine_btc_to_swap<FB, TB, FMG, TMG, FS, TS>(
     bid_quote: impl Future<Output = Result<BidQuote>>,
-    mut current_maximum_giveable: bitcoin::Amount,
     get_new_address: impl Future<Output = Result<bitcoin::Address>>,
     balance: FB,
     max_giveable: FMG,
@@ -345,7 +343,14 @@ where
 {
     debug!("Requesting quote");
     let bid_quote = bid_quote.await?;
-    info!("Received quote: 1 XMR ~ {}", bid_quote.price);
+    info!(
+        minimum_amount = %bid_quote.min_quantity,
+        maximum_amount = %bid_quote.max_quantity,
+        "Received quote: 1 XMR ~ {}",
+        bid_quote.price
+    );
+
+    let mut current_maximum_giveable = max_giveable().await?;
 
     let max_giveable = if current_maximum_giveable == bitcoin::Amount::ZERO
         || current_maximum_giveable < bid_quote.min_quantity
@@ -411,18 +416,47 @@ mod tests {
     use super::*;
     use crate::determine_btc_to_swap;
     use ::bitcoin::Amount;
+    use std::sync::Mutex;
     use tracing::subscriber;
 
+    struct MaxGiveable {
+        amounts: Vec<Amount>,
+        call_counter: usize,
+    }
+
+    impl MaxGiveable {
+        fn new(amounts: Vec<Amount>) -> Self {
+            Self {
+                amounts,
+                call_counter: 0,
+            }
+        }
+        fn give(&mut self) -> Result<Amount> {
+            let amount = self
+                .amounts
+                .get(self.call_counter)
+                .ok_or_else(|| anyhow::anyhow!("No more balances available"))?;
+            self.call_counter += 1;
+            Ok(*amount)
+        }
+    }
+
     #[tokio::test]
     async fn given_no_balance_and_transfers_less_than_max_swaps_max_giveable() {
         let _guard = subscriber::set_default(tracing_subscriber::fmt().with_test_writer().finish());
+        let givable = Arc::new(Mutex::new(MaxGiveable::new(vec![
+            Amount::ZERO,
+            Amount::from_btc(0.0009).unwrap(),
+        ])));
 
         let (amount, fees) = determine_btc_to_swap(
             async { Ok(quote_with_max(0.01)) },
-            Amount::ZERO,
             get_dummy_address(),
             || async { Ok(Amount::from_btc(0.001)?) },
-            || async { Ok(Amount::from_btc(0.0009)?) },
+            || async {
+                let mut result = givable.lock().unwrap();
+                result.give()
+            },
             || async { Ok(()) },
         )
         .await
@@ -433,17 +467,22 @@ mod tests {
 
         assert_eq!((amount, fees), (expected_amount, expected_fees))
     }
-
     #[tokio::test]
     async fn given_no_balance_and_transfers_more_then_swaps_max_quantity_from_quote() {
         let _guard = subscriber::set_default(tracing_subscriber::fmt().with_test_writer().finish());
+        let givable = Arc::new(Mutex::new(MaxGiveable::new(vec![
+            Amount::ZERO,
+            Amount::from_btc(0.1).unwrap(),
+        ])));
 
         let (amount, fees) = determine_btc_to_swap(
             async { Ok(quote_with_max(0.01)) },
-            Amount::ZERO,
             get_dummy_address(),
             || async { Ok(Amount::from_btc(0.1001)?) },
-            || async { Ok(Amount::from_btc(0.1)?) },
+            || async {
+                let mut result = givable.lock().unwrap();
+                result.give()
+            },
             || async { Ok(()) },
         )
         .await
@@ -458,13 +497,19 @@ mod tests {
     #[tokio::test]
     async fn given_initial_balance_below_max_quantity_swaps_max_givable() {
         let _guard = subscriber::set_default(tracing_subscriber::fmt().with_test_writer().finish());
+        let givable = Arc::new(Mutex::new(MaxGiveable::new(vec![
+            Amount::from_btc(0.0049).unwrap(),
+            Amount::from_btc(99.9).unwrap(),
+        ])));
 
         let (amount, fees) = determine_btc_to_swap(
             async { Ok(quote_with_max(0.01)) },
-            Amount::from_btc(0.0049).unwrap(),
-            async { panic!("should not request new address when initial balance is > 0") },
+            async { panic!("should not request new address when initial balance  is > 0") },
             || async { Ok(Amount::from_btc(0.005)?) },
-            || async { panic!("should not wait for deposit when initial balance > 0") },
+            || async {
+                let mut result = givable.lock().unwrap();
+                result.give()
+            },
             || async { Ok(()) },
         )
         .await
@@ -479,13 +524,19 @@ mod tests {
     #[tokio::test]
     async fn given_initial_balance_above_max_quantity_swaps_max_quantity() {
         let _guard = subscriber::set_default(tracing_subscriber::fmt().with_test_writer().finish());
+        let givable = Arc::new(Mutex::new(MaxGiveable::new(vec![
+            Amount::from_btc(0.1).unwrap(),
+            Amount::from_btc(99.9).unwrap(),
+        ])));
 
         let (amount, fees) = determine_btc_to_swap(
             async { Ok(quote_with_max(0.01)) },
-            Amount::from_btc(0.1).unwrap(),
             async { panic!("should not request new address when initial balance is > 0") },
             || async { Ok(Amount::from_btc(0.1001)?) },
-            || async { panic!("should not wait for deposit when initial balance > 0") },
+            || async {
+                let mut result = givable.lock().unwrap();
+                result.give()
+            },
             || async { Ok(()) },
         )
         .await
@@ -500,13 +551,19 @@ mod tests {
     #[tokio::test]
     async fn given_no_initial_balance_then_min_wait_for_sufficient_deposit() {
         let _guard = subscriber::set_default(tracing_subscriber::fmt().with_test_writer().finish());
+        let givable = Arc::new(Mutex::new(MaxGiveable::new(vec![
+            Amount::ZERO,
+            Amount::from_btc(0.01).unwrap(),
+        ])));
 
         let (amount, fees) = determine_btc_to_swap(
             async { Ok(quote_with_min(0.01)) },
-            Amount::ZERO,
             get_dummy_address(),
             || async { Ok(Amount::from_btc(0.0101)?) },
-            || async { Ok(Amount::from_btc(0.01)?) },
+            || async {
+                let mut result = givable.lock().unwrap();
+                result.give()
+            },
             || async { Ok(()) },
         )
         .await
@@ -521,13 +578,19 @@ mod tests {
     #[tokio::test]
     async fn given_balance_less_then_min_wait_for_sufficient_deposit() {
         let _guard = subscriber::set_default(tracing_subscriber::fmt().with_test_writer().finish());
+        let givable = Arc::new(Mutex::new(MaxGiveable::new(vec![
+            Amount::from_btc(0.0001).unwrap(),
+            Amount::from_btc(0.01).unwrap(),
+        ])));
 
         let (amount, fees) = determine_btc_to_swap(
             async { Ok(quote_with_min(0.01)) },
-            Amount::from_btc(0.0001).unwrap(),
             get_dummy_address(),
             || async { Ok(Amount::from_btc(0.0101)?) },
-            || async { Ok(Amount::from_btc(0.01)?) },
+            || async {
+                let mut result = givable.lock().unwrap();
+                result.give()
+            },
             || async { Ok(()) },
         )
         .await
@@ -542,15 +605,24 @@ mod tests {
     #[tokio::test]
     async fn given_no_initial_balance_and_transfers_less_than_min_keep_waiting() {
         let _guard = subscriber::set_default(tracing_subscriber::fmt().with_test_writer().finish());
+        let givable = Arc::new(Mutex::new(MaxGiveable::new(vec![
+            Amount::ZERO,
+            Amount::from_btc(0.01).unwrap(),
+            Amount::from_btc(0.01).unwrap(),
+            Amount::from_btc(0.01).unwrap(),
+            Amount::from_btc(0.01).unwrap(),
+        ])));
 
         let error = tokio::time::timeout(
             Duration::from_secs(1),
             determine_btc_to_swap(
                 async { Ok(quote_with_min(0.1)) },
-                Amount::ZERO,
                 get_dummy_address(),
                 || async { Ok(Amount::from_btc(0.0101)?) },
-                || async { Ok(Amount::from_btc(0.01)?) },
+                || async {
+                    let mut result = givable.lock().unwrap();
+                    result.give()
+                },
                 || async { Ok(()) },
             ),
         )

swap/src/bitcoin/wallet.rs

@@ -30,6 +30,7 @@ const SLED_TREE_NAME: &str = "default_tree";
 /// amount for tx fees.
 const MAX_RELATIVE_TX_FEE: Decimal = dec!(0.03);
 const MAX_ABSOLUTE_TX_FEE: Decimal = dec!(100_000);
+const DUST_AMOUNT: u64 = 546;
 
 pub struct Wallet<B = ElectrumBlockchain, D = bdk::sled::Tree, C = Client> {
     client: Arc<Mutex<C>>,
@@ -316,7 +317,17 @@ where
     /// transaction confirmed.
     pub async fn max_giveable(&self, locking_script_size: usize) -> Result<Amount> {
         let wallet = self.wallet.lock().await;
+        let balance = wallet.get_balance()?;
+        if balance < DUST_AMOUNT {
+            return Ok(Amount::ZERO);
+        }
         let client = self.client.lock().await;
+        let min_relay_fee = client.min_relay_fee()?.as_sat();
+
+        if balance < min_relay_fee {
+            return Ok(Amount::ZERO);
+        }
+
         let fee_rate = client.estimate_feerate(self.target_block)?;
 
         let mut tx_builder = wallet.build_tx();
@@ -325,11 +336,16 @@ where
         tx_builder.set_single_recipient(dummy_script);
         tx_builder.drain_wallet();
         tx_builder.fee_rate(fee_rate);
-        let (_, details) = tx_builder.finish().context("Failed to build transaction")?;
-
-        let max_giveable = details.sent - details.fees;
 
-        Ok(Amount::from_sat(max_giveable))
+        let response = tx_builder.finish();
+        match response {
+            Ok((_, details)) => {
+                let max_giveable = details.sent - details.fees;
+                Ok(Amount::from_sat(max_giveable))
+            }
+            Err(bdk::Error::InsufficientFunds { .. }) => Ok(Amount::ZERO),
+            Err(e) => bail!("Failed to build transaction. {:#}", e),
+        }
     }
 
     /// Estimate total tx fee for a pre-defined target block based on the
@@ -758,6 +774,7 @@ impl fmt::Display for ScriptStatus {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::bitcoin::TxLock;
     use proptest::prelude::*;
 
     #[test]
@@ -945,4 +962,46 @@ mod tests {
             assert!(estimate_fee(weight, amount, fee_rate, relay_fee).is_err());
         }
     }
+
+    struct StaticFeeRate {
+        min_relay_fee: u64,
+    }
+
+    impl EstimateFeeRate for StaticFeeRate {
+        fn estimate_feerate(&self, _target_block: usize) -> Result<FeeRate> {
+            Ok(FeeRate::default_min_relay_fee())
+        }
+
+        fn min_relay_fee(&self) -> Result<bitcoin::Amount> {
+            Ok(bitcoin::Amount::from_sat(self.min_relay_fee))
+        }
+    }
+
+    #[tokio::test]
+    async fn given_no_balance_returns_amount_0() {
+        let wallet = Wallet::new_funded(0, StaticFeeRate { min_relay_fee: 1 });
+        let amount = wallet.max_giveable(TxLock::script_size()).await.unwrap();
+
+        assert_eq!(amount, Amount::ZERO);
+    }
+
+    #[tokio::test]
+    async fn given_balance_below_min_relay_fee_returns_amount_0() {
+        let wallet = Wallet::new_funded(1000, StaticFeeRate {
+            min_relay_fee: 1001,
+        });
+        let amount = wallet.max_giveable(TxLock::script_size()).await.unwrap();
+
+        assert_eq!(amount, Amount::ZERO);
+    }
+
+    #[tokio::test]
+    async fn given_balance_above_relay_fee_returns_amount_greater_0() {
+        let wallet = Wallet::new_funded(10_000, StaticFeeRate {
+            min_relay_fee: 1000,
+        });
+        let amount = wallet.max_giveable(TxLock::script_size()).await.unwrap();
+
+        assert!(amount.as_sat() > 0);
+    }
 }