Inform user if cancel tx is has already been published

Alice and Bob can both submit cancel. A scenario exists where one of
them may try and manually cancel but the other party has already
published cancel. Log a message to notify the user this has happened.
Add reusable function to check error for bitcoin rpc error code

swap/src/asb/recovery/cancel.rs

@@ -1,4 +1,4 @@
-use crate::bitcoin::{Txid, Wallet};
+use crate::bitcoin::{parse_rpc_error_code, RpcErrorCode, Txid, Wallet};
 use crate::database::{Database, Swap};
 use crate::protocol::alice::AliceState;
 use anyhow::{bail, Result};
@@ -44,9 +44,11 @@ pub async fn cancel(
     let txid = match state3.submit_tx_cancel(bitcoin_wallet.as_ref()).await {
         Ok(txid) => txid,
         Err(err) => {
-            if let Some(bdk::Error::TransactionConfirmed) = err.downcast_ref::<bdk::Error>() {
-                tracing::info!("Cancel transaction has already been published and confirmed")
-            };
+            if let Ok(code) = parse_rpc_error_code(&err) {
+                if code == i64::from(RpcErrorCode::RpcVerifyAlreadyInChain) {
+                    tracing::info!("Cancel transaction has already been confirmed on chain")
+                }
+            }
             bail!(err);
         }
     };

swap/src/bitcoin.rs

@@ -249,6 +249,58 @@ pub fn current_epoch(
     ExpiredTimelocks::None
 }
 
+/// Bitcoin error codes: https://github.com/bitcoin/bitcoin/blob/97d3500601c1d28642347d014a6de1e38f53ae4e/src/rpc/protocol.h#L23
+pub enum RpcErrorCode {
+    /// Transaction or block was rejected by network rules. Error code -26.
+    RpcVerifyRejected,
+    /// Transaction or block was rejected by network rules. Error code -27.
+    RpcVerifyAlreadyInChain,
+    /// General error during transaction or block submission
+    RpcVerifyError,
+}
+
+impl From<RpcErrorCode> for i64 {
+    fn from(code: RpcErrorCode) -> Self {
+        match code {
+            RpcErrorCode::RpcVerifyError => -25,
+            RpcErrorCode::RpcVerifyRejected => -26,
+            RpcErrorCode::RpcVerifyAlreadyInChain => -27,
+        }
+    }
+}
+
+pub fn parse_rpc_error_code(error: &anyhow::Error) -> anyhow::Result<i64> {
+    let string = match error.downcast_ref::<bdk::Error>() {
+        Some(bdk::Error::Electrum(bdk::electrum_client::Error::Protocol(
+            serde_json::Value::String(string),
+        ))) => string,
+        _ => bail!("Error is of incorrect variant:{}", error),
+    };
+
+    let json = serde_json::from_str(&string.replace("sendrawtransaction RPC error:", ""))?;
+
+    let json_map = match json {
+        serde_json::Value::Object(map) => map,
+        _ => bail!("Json error is not json object "),
+    };
+
+    let error_code_value = match json_map.get("code") {
+        Some(val) => val,
+        None => bail!("No error code field"),
+    };
+
+    let error_code_number = match error_code_value {
+        serde_json::Value::Number(num) => num,
+        _ => bail!("Error code is not a number"),
+    };
+
+    if let Some(int) = error_code_number.as_i64() {
+        Ok(int)
+    } else {
+        bail!("Error code is not an unsigned integer")
+    }
+}
+
 #[derive(Clone, Copy, thiserror::Error, Debug)]
 #[error("transaction does not spend anything")]
 pub struct NoInputs;

swap/src/cli/cancel.rs

@@ -1,4 +1,4 @@
-use crate::bitcoin::{Txid, Wallet};
+use crate::bitcoin::{parse_rpc_error_code, RpcErrorCode, Txid, Wallet};
 use crate::database::{Database, Swap};
 use crate::protocol::bob::BobState;
 use anyhow::{bail, Result};
@@ -38,9 +38,11 @@ pub async fn cancel(
     let txid = match state6.submit_tx_cancel(bitcoin_wallet.as_ref()).await {
         Ok(txid) => txid,
         Err(err) => {
-            if let Some(bdk::Error::TransactionConfirmed) = err.downcast_ref::<bdk::Error>() {
-                tracing::info!("Cancel transaction has already been published and confirmed")
-            };
+            if let Ok(code) = parse_rpc_error_code(&err) {
+                if code == i64::from(RpcErrorCode::RpcVerifyAlreadyInChain) {
+                    tracing::info!("Cancel transaction has already been confirmed on chain")
+                }
+            }
             bail!(err);
         }
     };