MimbleWimble(Tests): parse MWEB tx as part of LTC tx

Made MWEB transaction a part of LitecoinTransaction, as it
should be. Modified deserialization code to properly handle
reading and writing MimbleWimble transaction. Got rid of
hardcoded offsets.

Author: webwarrior-ws

src/NLitecoin/Litecoin.fs

@@ -50,10 +50,14 @@ module private TxListExtensions =
 type LitecoinTransaction() = 
     inherit Transaction()
 
+    static let mwebExtensionTxFlag = 8uy
+
+    member val MimbleWimbleTransaction: Option<MimbleWimble.Transaction> = None with get, set
+
     override self.GetConsensusFactory() = LitecoinConsensusFactory.Instance
 
     member private self.Read (stream: BitcoinStream) (witSupported: bool) =
-        let flags = 0uy
+        let mutable flags = 0uy
         self.nVersion <- stream.ReadWrite self.nVersion
         // Try to read the vin. In case the dummy is there, this will be read as an empty vector.
         stream.ReadWrite(&self.vin)
@@ -64,7 +68,7 @@ type LitecoinTransaction() =
 
         if self.vin.Count = 0 && witSupported && not hasNoDummy then
             // We read a dummy or an empty vin.
-            let flags = stream.ReadWrite flags
+            flags <- stream.ReadWrite flags
             if flags <> 0uy then
                 // Assume we read a dummy and a flag.
                 stream.ReadWrite(&self.vin)
@@ -79,22 +83,17 @@ type LitecoinTransaction() =
             stream.ReadWrite(&self.vout)
             self.vout <- self.vout.WithTransaction self
 
-        let flags =
-            if ((flags &&& 1uy) <> 0uy) && witSupported then
-                // The witness flag is present, and we support witnesses.
-                let wit = Witness self.Inputs
-                wit.ReadWrite stream
-                flags ^^^ 1uy
-            else
-                flags
-        let flags =
-            if (flags &&& 8uy) <> 0uy then //MWEB extension tx flag
-                (* The MWEB flag is present, but currently no MWEB data is supported. 
-                    * This fix just prevent from throwing exception bellow so cannonical litecoin transaction can be read
-                    *)
-                flags ^^^ 8uy
-            else
-                flags
+        if ((flags &&& 1uy) <> 0uy) && witSupported then
+            // The witness flag is present, and we support witnesses.
+            let wit = Witness self.Inputs
+            wit.ReadWrite stream
+            flags <- flags ^^^ 1uy
+        
+        if (flags &&& mwebExtensionTxFlag) <> 0uy then
+            let version = ref 0uy
+            stream.ReadWrite version
+            self.MimbleWimbleTransaction <- Some(MimbleWimble.Transaction.Read stream)
+            flags <- flags ^^^ 8uy
 
         if flags <> 0uy then
             // Unknown flag in the serialization
@@ -118,6 +117,12 @@ type LitecoinTransaction() =
             else
                 0uy
 
+        let flags = 
+            if self.MimbleWimbleTransaction.IsSome then 
+                flags ||| mwebExtensionTxFlag 
+            else 
+                flags 
+
         let flags = 
             if flags <> 0uy then
                 // Use extended format in case witnesses are to be serialized.
@@ -135,6 +140,12 @@ type LitecoinTransaction() =
             let wit = Witness self.Inputs
             wit.ReadWrite stream
 
+        match self.MimbleWimbleTransaction with
+        | Some mwebTransaction -> 
+            stream.ReadWrite MimbleWimble.Transaction.Version |> ignore
+            (mwebTransaction :> MimbleWimble.ISerializeable).Write stream
+        | None -> ()
+
     override self.ReadWrite(stream: BitcoinStream) =
         let witSupported = 
             (((uint32 stream.TransactionOptions) &&& (uint32 TransactionOptions.Witness)) <> 0u) &&

src/NLitecoin/MimbleWimble/Types.fs

@@ -705,10 +705,7 @@ type Transaction =
         // The transaction body.
         Body: TxBody
     }
-    /// see https://github.com/litecoin-project/lips/blob/master/lip-0003.mediawiki#user-content-PegIn_Transactions
-    static member RegularLTCPeginTranasctionSize = 200
-
-    static member RegularTransactionOffset = 9
+    static member Version = 1uy
 
     /// Parse hex-encoded MimbleWimble transaction
     static member ParseString(txString: string) : Transaction =

src/NLitecoin/NLitecoin.fsproj

@@ -12,13 +12,13 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Compile Include="Litecoin.fs" />
     <Compile Include="MimbleWimble\Types.fs" />
     <Compile Include="MimbleWimble\EC.fs" />
     <Compile Include="MimbleWimble\Pedersen.fs" />
     <Compile Include="MimbleWimble\Bulletproof.fs" />
     <Compile Include="MimbleWimble\TransactionBuilder.fs" />
     <Compile Include="MimbleWimble\Wallet.fs" />
+    <Compile Include="Litecoin.fs" />
   </ItemGroup>
 
   <ItemGroup>

tests/NLitecoin.MimbleWimble.Tests/TransactionTests.fs

@@ -14,8 +14,11 @@ let Setup () =
 let ParsePegInTransaction () =
     let rawTransaction = IO.File.ReadAllText "transaction1.txt"
 
-    let mimbleRawWimbleTransaction = rawTransaction[Transaction.RegularLTCPeginTranasctionSize *  2 ..]
-    let transaction = Transaction.ParseString mimbleRawWimbleTransaction
+    let litecoinTransaction = 
+        NBitcoin.Transaction.Parse(rawTransaction, NLitecoin.Litecoin.Instance.Mainnet)
+
+    let transaction = 
+        (litecoinTransaction :?> NLitecoin.LitecoinTransaction).MimbleWimbleTransaction.Value
 
     Assert.AreEqual(0, transaction.Body.Inputs.Length)
     Assert.AreEqual(1, transaction.Body.Kernels.Length)
@@ -31,8 +34,11 @@ let ParsePegInTransaction () =
 let ParseHogExTransaction () =
     let rawTransaction = IO.File.ReadAllText "transaction2.txt"
 
-    let mimbleRawWimbleTransaction = rawTransaction[Transaction.RegularTransactionOffset * 2 ..]
-    let transaction = Transaction.ParseString mimbleRawWimbleTransaction
+    let litecoinTransaction = 
+        NBitcoin.Transaction.Parse(rawTransaction, NLitecoin.Litecoin.Instance.Mainnet)
+
+    let transaction = 
+        (litecoinTransaction :?> NLitecoin.LitecoinTransaction).MimbleWimbleTransaction.Value
 
     Assert.GreaterOrEqual(transaction.Body.Inputs.Length, 1)
     Assert.AreEqual(1, transaction.Body.Kernels.Length)
@@ -48,8 +54,11 @@ let ParseHogExTransaction () =
 let ParsePegOutTransaction () =
     let rawTransaction = IO.File.ReadAllText "transaction3.txt"
 
-    let mimbleRawWimbleTransaction = rawTransaction[Transaction.RegularTransactionOffset * 2 ..]
-    let transaction = Transaction.ParseString mimbleRawWimbleTransaction
+    let litecoinTransaction = 
+        NBitcoin.Transaction.Parse(rawTransaction, NLitecoin.Litecoin.Instance.Mainnet)
+
+    let transaction = 
+        (litecoinTransaction :?> NLitecoin.LitecoinTransaction).MimbleWimbleTransaction.Value
 
     Assert.GreaterOrEqual(transaction.Body.Inputs.Length, 1)
     Assert.AreEqual(1, transaction.Body.Kernels.Length)