Add new Orchard spending key generation

src/C/Zcash.chs

@@ -133,3 +133,12 @@ import ZcashHaskell.Types
      }
   -> `()'
 #}
+
+{# fun unsafe rust_wrapper_derive_orchard_spending_key as rustWrapperGenOrchardSpendKey
+     { toBorshVar* `BS.ByteString'&
+     , `Word32'
+     , `Word32'
+     , getVarBuffer `Buffer (BS.ByteString)'&
+     }
+  -> `()'
+#}

src/ZcashHaskell/Orchard.hs

@@ -18,7 +18,8 @@
 module ZcashHaskell.Orchard where
 
 import C.Zcash
-  ( rustWrapperOrchardCheck
+  ( rustWrapperGenOrchardSpendKey
+  , rustWrapperOrchardCheck
   , rustWrapperOrchardNoteDecode
   , rustWrapperUADecode
   , rustWrapperUfvkDecode
@@ -32,6 +33,12 @@ import Foreign.Rust.Marshall.Variable
 import ZcashHaskell.Types
 import ZcashHaskell.Utils (encodeBech32m, f4Jumble)
 
+-- | Derives an Orchard spending key for the given seed and account ID
+genOrchardSpendingKey :: Seed -> CoinType -> AccountId -> BS.ByteString
+genOrchardSpendingKey s coinType accountId =
+  withPureBorshVarBuffer $
+  rustWrapperGenOrchardSpendKey s (getValue coinType) (fromIntegral accountId)
+
 -- | Checks if given bytestring is a valid encoded unified address
 isValidUnifiedAddress :: BS.ByteString -> Maybe UnifiedAddress
 isValidUnifiedAddress str =