bitcoin-serai changes from next

Expands the NotEnoughFunds error and enables fetching the entire unsigned
transaction, not just the outputs it'll have.

networks/bitcoin/src/wallet/send.rs

@@ -44,7 +44,7 @@ pub enum TransactionError {
   #[error("fee was too low to pass the default minimum fee rate")]
   TooLowFee,
   #[error("not enough funds for these payments")]
-  NotEnoughFunds,
+  NotEnoughFunds { inputs: u64, payments: u64, fee: u64 },
   #[error("transaction was too large")]
   TooLargeTransaction,
 }
@@ -213,7 +213,11 @@ impl SignableTransaction {
     }
 
     if input_sat < (payment_sat + needed_fee) {
-      Err(TransactionError::NotEnoughFunds)?;
+      Err(TransactionError::NotEnoughFunds {
+        inputs: input_sat,
+        payments: payment_sat,
+        fee: needed_fee,
+      })?;
     }
 
     // If there's a change address, check if there's change to give it
@@ -258,9 +262,9 @@ impl SignableTransaction {
     res
   }
 
-  /// Returns the outputs this transaction will create.
-  pub fn outputs(&self) -> &[TxOut] {
-    &self.tx.output
+  /// Returns the transaction, sans witness, this will create if signed.
+  pub fn transaction(&self) -> &Transaction {
+    &self.tx
   }
 
   /// Create a multisig machine for this transaction.

networks/bitcoin/tests/wallet.rs

@@ -195,10 +195,10 @@ async_sequential! {
       Err(TransactionError::TooLowFee),
     );
 
-    assert_eq!(
+    assert!(matches!(
       SignableTransaction::new(inputs.clone(), &[(addr(), inputs[0].value() * 2)], None, None, FEE),
-      Err(TransactionError::NotEnoughFunds),
-    );
+      Err(TransactionError::NotEnoughFunds { .. }),
+    ));
 
     assert_eq!(
       SignableTransaction::new(inputs, &vec![(addr(), 1000); 10000], None, None, FEE),

processor/src/networks/bitcoin.rs

@@ -455,7 +455,7 @@ impl Bitcoin {
         panic!("trying to create a bitcoin transaction without inputs")
       }
       // No outputs left and the change isn't worth enough/not even enough funds to pay the fee
-      Err(TransactionError::NoOutputs | TransactionError::NotEnoughFunds) => Ok(None),
+      Err(TransactionError::NoOutputs | TransactionError::NotEnoughFunds { .. }) => Ok(None),
       // amortize_fee removes payments which fall below the dust threshold
       Err(TransactionError::DustPayment) => panic!("dust payment despite removing dust"),
       Err(TransactionError::TooMuchData) => {