Merge pull request input-output-hk/cardano-sl#3635 from input-output-hk/adinapoli/cbr-440

[CBR-440] Do not require the spending password for the estimation of the fees

Author: adinapoli-iohk

src/Cardano/Wallet/API/V1/Handlers/Transactions.hs

@@ -95,9 +95,7 @@ estimateFees :: ActiveWalletLayer IO
              -> Payment
              -> Handler (WalletResponse EstimatedFees)
 estimateFees aw payment@Payment{..} = do
-    let spendingPassword = maybe mempty coerce pmtSpendingPassword
-    res <- liftIO $ (WalletLayer.estimateFees aw) spendingPassword
-                                                  (toInputGrouping pmtGroupingPolicy)
+    res <- liftIO $ (WalletLayer.estimateFees aw) (toInputGrouping pmtGroupingPolicy)
                                                   SenderPaysFee
                                                   payment
     case res of

src/Cardano/Wallet/API/V1/Swagger.hs

@@ -1042,6 +1042,15 @@ endpoint is during API integration testing. Note also that this will fail by
 default unless the node is running in debug mode.
 |]
 
+estimateFeesDescription :: Text
+estimateFeesDescription = [text|
+Estimate the fees which would incur from the input payment. This endpoint
+**does not** require a _spending password_ to be supplied as it generates
+under the hood an unsigned transaction. Therefore, callers can simply set
+the `spendingPassword` field to `null` as that won't influence the fee
+calculation.
+|]
+
 
 --
 -- The API
@@ -1077,3 +1086,4 @@ api (compileInfo, curSoftwareVersion) walletAPI mkDescription = toSwagger wallet
   & paths %~ (POST, "/api/internal/apply-update") `setDescription` applyUpdateDescription
   & paths %~ (POST, "/api/internal/postpone-update") `setDescription` postponeUpdateDescription
   & paths %~ (DELETE, "/api/internal/reset-wallet-state") `setDescription` resetWalletStateDescription
+  & paths %~ (POST, "/api/v1/transactions/fees") `setDescription` estimateFeesDescription

src/Cardano/Wallet/Kernel/CoinSelection/FromGeneric.hs

@@ -12,7 +12,12 @@ module Cardano.Wallet.Kernel.CoinSelection.FromGeneric (
   , newOptions
     -- * Transaction building
   , CoinSelFinalResult(..)
+  , UnsignedTx -- opaque
+  , utxOwnedInputs
+  , utxOutputs
+  , utxChange
   , mkStdTx
+  , mkStdUnsignedTx
     -- * Coin selection policies
   , random
   , largestFirst
@@ -178,6 +183,27 @@ feeOptions CoinSelectionOptions{..} = FeeOptions{
   Building transactions
 -------------------------------------------------------------------------------}
 
+-- | Our notion of @unsigned transaction@. Unfortunately we cannot reuse
+-- directly the 'Tx' from @Core@ as that discards the information about
+-- "ownership" of inputs, which is instead required when dealing with the
+-- Core Txp.Util API.
+data UnsignedTx = UnsignedTx {
+    utxOwnedInputs :: NonEmpty (Core.TxIn, Core.TxOutAux)
+  , utxOutputs     :: NonEmpty Core.TxOutAux
+  , utxChange      :: [Core.Coin]
+}
+
+-- | Creates a "standard" unsigned transaction.
+mkStdUnsignedTx :: NonEmpty (Core.TxIn, Core.TxOutAux)
+                -- ^ Selected inputs
+                -> NonEmpty Core.TxOutAux
+                -- ^ Selected outputs
+                -> [Core.Coin]
+                -- ^ Change coins
+                -> UnsignedTx
+mkStdUnsignedTx inps outs change = UnsignedTx inps outs change
+
+
 -- | Build a transaction
 
 -- | Construct a standard transaction
@@ -200,11 +226,12 @@ mkStdTx :: Monad m
 mkStdTx pm shuffle hdwSigners inps outs change = do
     allOuts <- shuffle $ foldl' (flip NE.cons) outs change
     return $ CTxp.makeMPubKeyTxAddrs pm hdwSigners (fmap repack inps) allOuts
-  where
-    -- Repack a utxo-derived tuple into a format suitable for
-    -- 'TxOwnedInputs'.
-    repack :: (Core.TxIn, Core.TxOutAux) -> (Core.TxOut, Core.TxIn)
-    repack (txIn, aux) = (Core.toaOut aux, txIn)
+
+-- | Repacks a utxo-derived tuple into a format suitable for
+-- 'TxOwnedInputs'.
+repack :: (Core.TxIn, Core.TxOutAux) -> (Core.TxOut, Core.TxIn)
+repack (txIn, aux) = (Core.toaOut aux, txIn)
+
 
 {-------------------------------------------------------------------------------
   Coin selection policy top-level entry point