add withdrawal on each payment transaction

We could make it slightly smarter here and requires that the withdrawal is only requested when the balance is somewhat sufficient.
Sufficient would mean, bigger than the cost of adding it. Indeed, adding a withdrawal would only make sense if the cost of adding it
isn't greater to its value.

lib/core/src/Cardano/Wallet.hs

@@ -1102,11 +1102,12 @@ selectCoinsForPayment
     => ctx
     -> WalletId
     -> NonEmpty TxOut
+    -> Quantity "lovelace" Word64
     -> ExceptT (ErrSelectForPayment e) IO CoinSelection
-selectCoinsForPayment ctx wid recipients = do
+selectCoinsForPayment ctx wid recipients withdrawal = do
     (utxo, txp) <- withExceptT ErrSelectForPaymentNoSuchWallet $
         selectCoinsSetup @ctx @s @k ctx wid
-    selectCoinsForPaymentFromUTxO @ctx @t @k @e ctx utxo txp recipients
+    selectCoinsForPaymentFromUTxO @ctx @t @k @e ctx utxo txp recipients withdrawal
 
 -- | Retrieve wallet data which is needed for all types of coin selections.
 selectCoinsSetup
@@ -1132,16 +1133,17 @@ selectCoinsForPaymentFromUTxO
     -> W.UTxO
     -> W.TxParameters
     -> NonEmpty TxOut
+    -> Quantity "lovelace" Word64
     -> ExceptT (ErrSelectForPayment e) IO CoinSelection
-selectCoinsForPaymentFromUTxO ctx utxo txp recipients = do
+selectCoinsForPaymentFromUTxO ctx utxo txp recipients (Quantity withdrawal) = do
     lift . traceWith tr $ MsgPaymentCoinSelectionStart utxo txp recipients
     (sel, utxo') <- withExceptT ErrSelectForPaymentCoinSelection $ do
         let opts = coinSelOpts tl (txp ^. #getTxMaxSize)
         CoinSelection.random opts recipients utxo
     lift . traceWith tr $ MsgPaymentCoinSelection sel
     let feePolicy = feeOpts tl Nothing (txp ^. #getFeePolicy)
     withExceptT ErrSelectForPaymentFee $ do
-        balancedSel <- adjustForFee feePolicy utxo' sel
+        balancedSel <- adjustForFee feePolicy utxo' (sel { withdrawal })
         lift . traceWith tr $ MsgPaymentCoinSelectionAdjusted balancedSel
         pure balancedSel
   where
@@ -1264,12 +1266,13 @@ estimateFeeForPayment
     => ctx
     -> WalletId
     -> NonEmpty TxOut
+    -> Quantity "lovelace" Word64
     -> ExceptT (ErrSelectForPayment e) IO FeeEstimation
-estimateFeeForPayment ctx wid recipients = do
+estimateFeeForPayment ctx wid recipients withdrawal = do
     (utxo, txp) <- withExceptT ErrSelectForPaymentNoSuchWallet $
         selectCoinsSetup @ctx @s @k ctx wid
     let selectCoins =
-            selectCoinsForPaymentFromUTxO @ctx @t @k @e ctx utxo txp recipients
+            selectCoinsForPaymentFromUTxO @ctx @t @k @e ctx utxo txp recipients withdrawal
     estimateFeeForCoinSelection $ (Fee . feeBalance <$> selectCoins)
         `catchE` handleCannotCover utxo recipients
 
@@ -1385,9 +1388,6 @@ signTx ctx wid pwd (UnsignedTx inpsNE outsNE) = db & \DBLayer{..} -> do
     outs = NE.toList outsNE
 
 -- | Makes a fully-resolved coin selection for the given set of payments.
---
--- TODO
--- This function completely disregard deposit and withdrawals.
 selectCoinsExternal
     :: forall ctx s t k e.
         ( GenChange s
@@ -1400,10 +1400,11 @@ selectCoinsExternal
     -> WalletId
     -> ArgGenChange s
     -> NonEmpty TxOut
+    -> Quantity "lovelace" Word64
     -> ExceptT (ErrSelectCoinsExternal e) IO UnsignedTx
-selectCoinsExternal ctx wid argGenChange payments = do
+selectCoinsExternal ctx wid argGenChange payments withdrawal = do
     cs <- withExceptT ErrSelectCoinsExternalUnableToMakeSelection $
-        selectCoinsForPayment @ctx @s @t @k @e ctx wid payments
+        selectCoinsForPayment @ctx @s @t @k @e ctx wid payments withdrawal
     cs' <- db & \DBLayer{..} ->
         withExceptT ErrSelectCoinsExternalNoSuchWallet $
             mapExceptT atomically $ do

lib/core/src/Cardano/Wallet/Api/Server.hs

@@ -1037,11 +1037,13 @@ selectCoins
     -> ApiT WalletId
     -> ApiSelectCoinsData n
     -> Handler (ApiCoinSelection n)
-selectCoins ctx genChange (ApiT wid) body =
+selectCoins ctx gen (ApiT wid) body =
     fmap mkApiCoinSelection
-        $ withWorkerCtx ctx wid liftE liftE
-        $ \wrk -> liftHandler $ W.selectCoinsExternal @_ @s @t @k wrk wid genChange
-        $ coerceCoin <$> body ^. #payments
+    $ withWorkerCtx ctx wid liftE liftE
+    $ \wrk -> do
+        withdrawal <- liftIO $ W.fetchRewardBalance @_ @s @k wrk wid
+        let outs = coerceCoin <$> body ^. #payments
+        liftHandler $ W.selectCoinsExternal @_ @s @t @k wrk wid gen outs withdrawal
 
 {-------------------------------------------------------------------------------
                                     Addresses
@@ -1126,8 +1128,9 @@ postTransaction ctx genChange (ApiT wid) body = do
     let outs = coerceCoin <$> (body ^. #payments)
     let pwd = coerce $ getApiT $ body ^. #passphrase
 
-    selection <- withWorkerCtx ctx wid liftE liftE $ \wrk -> liftHandler $
-        W.selectCoinsForPayment @_ @s @t wrk wid outs
+    selection <- withWorkerCtx ctx wid liftE liftE $ \wrk -> do
+        withdrawal <- liftIO $ W.fetchRewardBalance @_ @s @k wrk wid
+        liftHandler $ W.selectCoinsForPayment @_ @s @t wrk wid outs withdrawal
 
     (tx, meta, time, wit) <- withWorkerCtx ctx wid liftE liftE $ \wrk -> liftHandler $
         W.signPayment @_ @s @t @k wrk wid genChange pwd selection
@@ -1212,8 +1215,10 @@ postTransactionFee
     -> Handler ApiFee
 postTransactionFee ctx (ApiT wid) body = do
     let outs = coerceCoin <$> (body ^. #payments)
-    withWorkerCtx ctx wid liftE liftE $ \wrk -> liftHandler
-        (apiFee <$> W.estimateFeeForPayment @_ @s @t @k wrk wid outs)
+    withWorkerCtx ctx wid liftE liftE $ \wrk -> do
+        withdrawal <- liftIO $ W.fetchRewardBalance @_ @s @k wrk wid
+        fee <- liftHandler $ W.estimateFeeForPayment @_ @s @t @k wrk wid outs withdrawal
+        pure $ apiFee fee
 
 joinStakePool
     :: forall ctx s t n k.