Experimenting with two-party PSBT signing.

side-node/src/bitcoin/clients/esplora.rs

@@ -39,17 +39,45 @@ impl EsploraWallet {
         recipient: Address,
         amount: Amount,
     ) -> Result<bitcoin::Transaction, anyhow::Error> {
-        let mut tx_builder = self.wallet.build_tx();
+        let mut tx_builder = self.build_tx()?;
         tx_builder
             .add_recipient(recipient.script_pubkey(), amount)
             .enable_rbf();
         let mut psbt = tx_builder.finish()?;
-        let finalized = self.wallet.sign(&mut psbt, SignOptions::default())?;
-        assert!(finalized);
-        let tx = psbt.extract_tx()?;
+        let tx = self.sign(&mut psbt, true)?.extract_tx()?;
         Ok(tx)
     }
 
+    pub(crate) fn build_tx(
+        &mut self,
+    ) -> Result<
+        bdk_wallet::TxBuilder<bdk_wallet::wallet::coin_selection::BranchAndBoundCoinSelection>,
+        anyhow::Error,
+    > {
+        Ok(self.wallet.build_tx())
+    }
+
+    pub(crate) fn sign(
+        &self,
+        psbt: &mut bitcoin::Psbt,
+        finalize: bool,
+    ) -> Result<bitcoin::Psbt, anyhow::Error> {
+        tracing::info!("{} signing PSBT", self.name);
+
+        let options = SignOptions {
+            try_finalize: finalize,
+            ..Default::default()
+        };
+
+        let finalized = self.wallet.sign(psbt, options)?;
+
+        // make sure the PSBT is finalized if we asked for it
+        if finalize {
+            assert!(finalized)
+        }
+        Ok(psbt.to_owned())
+    }
+
     /// Syncs the wallet with the latest state of the Bitcoin blockchain
     pub(crate) async fn sync(&mut self) -> Result<(), anyhow::Error> {
         tracing::info!("{} full scan sync start", self.name);
@@ -105,6 +133,10 @@ impl EsploraWallet {
         );
         self.client.broadcast(tx).await
     }
+
+    pub(crate) fn wallet(&mut self) -> &Wallet {
+        &self.wallet
+    }
 }
 
 /// Creates a Bitcoin descriptor wallet with the mnemonic in the given user directory.