From 7649fc29ace23e6142339177901237bfdcc71694 Mon Sep 17 00:00:00 2001
From: KtorZ <matthias.benkort@gmail.com>
Date: Wed, 6 Mar 2019 14:33:56 +0100
Subject: [PATCH] implement txId using CBOR encoders

---
 cardano-wallet.cabal                   |  2 ++
 src/Cardano/Wallet/Binary.hs           | 28 +++++++++++++++++++++++---
 test/unit/Cardano/Wallet/BinarySpec.hs | 27 ++++++++++++++++++++++++-
 3 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/cardano-wallet.cabal b/cardano-wallet.cabal
index acaa3c6d47b..f4860279623 100644
--- a/cardano-wallet.cabal
+++ b/cardano-wallet.cabal
@@ -35,9 +35,11 @@ library
     , bytestring
     , cborg
     , containers
+    , cryptonite
     , deepseq
     , digest
     , transformers
+    , memory
   hs-source-dirs:
       src
   exposed-modules:
diff --git a/src/Cardano/Wallet/Binary.hs b/src/Cardano/Wallet/Binary.hs
index 6a1e1f2797f..1857c4af9e3 100644
--- a/src/Cardano/Wallet/Binary.hs
+++ b/src/Cardano/Wallet/Binary.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE TypeApplications #-}
 
 -- |
 -- Copyright: © 2018-2019 IOHK
@@ -16,9 +17,11 @@ module Cardano.Wallet.Binary
     -- * Decoding
       decodeBlock
     , decodeBlockHeader
+    , decodeTx
 
     -- * Encoding
     , encodeTx
+    , txId
 
     -- * Helpers
     , inspectNextToken
@@ -40,6 +43,10 @@ import Cardano.Wallet.Primitive
     )
 import Control.Monad
     ( void )
+import Crypto.Hash
+    ( hash )
+import Crypto.Hash.Algorithms
+    ( Blake2b_256 )
 import Data.ByteString
     ( ByteString )
 import Data.Digest.CRC32
@@ -55,6 +62,7 @@ import qualified Codec.CBOR.Decoding as CBOR
 import qualified Codec.CBOR.Encoding as CBOR
 import qualified Codec.CBOR.Read as CBOR
 import qualified Codec.CBOR.Write as CBOR
+import qualified Data.ByteArray as BA
 import qualified Data.ByteString.Lazy as BL
 import qualified Data.Set as Set
 
@@ -319,6 +327,16 @@ decodeSignature = do
         2 -> decodeProxySignature decodeHeavyIndex
         _ -> fail $ "decodeSignature: unknown signature constructor: " <> show t
 
+decodeSignedTx :: CBOR.Decoder s Tx
+decodeSignedTx = do
+    _ <- CBOR.decodeListLenCanonicalOf 2
+    _ <- CBOR.decodeListLenCanonicalOf 3
+    ins <- decodeListIndef decodeTxIn
+    outs <- decodeListIndef decodeTxOut
+    _ <- decodeAttributes
+    _ <- decodeList decodeTxWitness
+    return $ Tx ins outs
+
 decodeSharesProof :: CBOR.Decoder s ()
 decodeSharesProof = do
     _ <- CBOR.decodeBytes -- Shares Hash
@@ -341,16 +359,14 @@ decodeSoftwareVersion = do
 
 decodeTx :: CBOR.Decoder s Tx
 decodeTx = do
-    _ <- CBOR.decodeListLenCanonicalOf 2
     _ <- CBOR.decodeListLenCanonicalOf 3
     ins <- decodeListIndef decodeTxIn
     outs <- decodeListIndef decodeTxOut
     _ <- decodeAttributes
-    _ <- decodeList decodeTxWitness
     return $ Tx ins outs
 
 decodeTxPayload :: CBOR.Decoder s (Set Tx)
-decodeTxPayload = Set.fromList <$> decodeListIndef decodeTx
+decodeTxPayload = Set.fromList <$> decodeListIndef decodeSignedTx
 
 {-# ANN decodeTxIn ("HLint: ignore Use <$>" :: String) #-}
 decodeTxIn :: CBOR.Decoder s TxIn
@@ -407,6 +423,12 @@ decodeUpdateProof = do
 
 -- * Encoding
 
+-- | Compute a transaction id; assumed to be effectively injective.
+-- It returns an hex-encoded 64-byte hash.
+txId :: Tx -> Hash "Tx"
+txId =
+    Hash . BA.convert . hash @_ @Blake2b_256 . CBOR.toStrictByteString . encodeTx
+
 encodeAddressPayload :: ByteString -> CBOR.Encoding
 encodeAddressPayload payload = mempty
     <> CBOR.encodeListLen 2
diff --git a/test/unit/Cardano/Wallet/BinarySpec.hs b/test/unit/Cardano/Wallet/BinarySpec.hs
index 3a0545b7350..171ecb9c77d 100644
--- a/test/unit/Cardano/Wallet/BinarySpec.hs
+++ b/test/unit/Cardano/Wallet/BinarySpec.hs
@@ -5,7 +5,7 @@ module Cardano.Wallet.BinarySpec (spec) where
 import Prelude
 
 import Cardano.Wallet.Binary
-    ( decodeBlock, decodeBlockHeader )
+    ( decodeBlock, decodeBlockHeader, decodeTx, encodeTx, txId )
 import Cardano.Wallet.Primitive
     ( Address (..)
     , Block (..)
@@ -27,11 +27,13 @@ import Test.Hspec
 
 import qualified Codec.CBOR.Decoding as CBOR
 import qualified Codec.CBOR.Read as CBOR
+import qualified Codec.CBOR.Write as CBOR
 import qualified Data.ByteString.Lazy as BL
 import qualified Data.ByteString.Lazy.Char8 as L8
 import qualified Data.Set as Set
 
 
+{-# ANN spec ("HLint: ignore Use head" :: String) #-}
 spec :: Spec
 spec = do
     describe "Decoding blocks" $ do
@@ -55,6 +57,29 @@ spec = do
             let decoded = unsafeDeserialiseFromBytes decodeBlock bs
             decoded `shouldBe` block3
 
+    describe "Encoding Tx" $ do
+        let txs = Set.toList (transactions block2 <> transactions block3)
+        let roundTripTx tx = do
+                let bytes = CBOR.toLazyByteString (encodeTx tx)
+                let tx' = unsafeDeserialiseFromBytes decodeTx bytes
+                tx `shouldBe` tx'
+
+        it "encode . decode = pure (1)" $ do
+            roundTripTx (txs !! 0)
+
+        it "encode . decode = pure (2)" $ do
+            roundTripTx (txs !! 1)
+
+        it "should compute correct txId (1)" $ do
+            let hash = txId (txs !! 0)
+            let hash' = hash16 "c470563001e448e61ff1268c2a6eb458ace1d04011a02cb262b6d709d66c23d0"
+            hash `shouldBe` hash'
+
+        it "should compute correct txId (2)" $ do
+            let hash = txId (txs !! 1)
+            let hash' = hash16 "d30d37f1f8674c6c33052826fdc5bc198e3e95c150364fd775d4bc663ae6a9e6"
+            hash `shouldBe` hash'
+
 
 -- A mainnet block header
 blockHeader1 :: BlockHeader