From 4f9601f8d8ce7859c362ccb6dab6d51977da0e81 Mon Sep 17 00:00:00 2001
From: Rene Vergara <rene@vergara.network>
Date: Tue, 9 Apr 2024 13:05:57 -0500
Subject: [PATCH 1/2] Add function to decode Orchard action with spending key

---
 librustzcash-wrapper/src/lib.rs | 41 +++++++++++++++++++++++++++++++++
 src/C/Zcash.chs                 |  8 +++++++
 src/ZcashHaskell/Orchard.hs     | 13 +++++++++++
 3 files changed, 62 insertions(+)

diff --git a/librustzcash-wrapper/src/lib.rs b/librustzcash-wrapper/src/lib.rs
index 623f001..d5533f5 100644
--- a/librustzcash-wrapper/src/lib.rs
+++ b/librustzcash-wrapper/src/lib.rs
@@ -852,6 +852,47 @@ pub extern "C" fn rust_wrapper_orchard_note_decrypt(
     }
 }
 
+#[no_mangle]
+pub extern "C" fn rust_wrapper_orchard_note_decrypt_sk(
+    key: *const u8,
+    key_len: usize,
+    note: *const u8,
+    note_len: usize,
+    external: bool,
+    out: *mut u8,
+    out_len: &mut usize
+    ){
+    let sk_input: Vec<u8> = marshall_from_haskell_var(key, key_len, RW);
+    let note_input: Haction = marshall_from_haskell_var(note, note_len, RW);
+    let action: Action<Signature<SpendAuth>> = Action::from_parts(
+        Nullifier::from_bytes(&to_array(note_input.nf.bytes)).unwrap(), 
+        VerificationKey::try_from(to_array(note_input.rk.bytes)).unwrap(), 
+        ExtractedNoteCommitment::from_bytes(&to_array(note_input.cmx.bytes)).unwrap(), 
+        TransmittedNoteCiphertext {epk_bytes: to_array(note_input.eph_key.bytes), enc_ciphertext: to_array(note_input.enc_txt.bytes), out_ciphertext: to_array(note_input.out_txt.bytes)}, 
+        ValueCommitment::from_bytes(&to_array(note_input.cv.bytes)).unwrap(), 
+        Signature::from(to_array(note_input.auth.bytes)));
+    let sk_array = to_array(sk_input);
+    let domain = OrchardDomain::for_nullifier(*action.nullifier());
+    let dec_sk = SpendingKey::from_bytes(sk_array).unwrap();
+    let fvk = FullViewingKey::from(&dec_sk);
+    let ivk = if external {
+        fvk.to_ivk(Scope::External)
+    } else {
+        fvk.to_ivk(Scope::Internal)
+    };
+    let pivk = PreparedIncomingViewingKey::new(&ivk);
+    let result = zcash_note_encryption::try_note_decryption(&domain, &pivk, &action);
+    match result {
+        Some((n, r, m)) => {
+            let hn = Hnote {note: n.value().inner(), recipient: r.to_raw_address_bytes().to_vec(), memo: m.to_vec()};
+            marshall_to_haskell_var(&hn, out, out_len, RW);
+        }
+        None => {
+            let hn0 = Hnote { note: 0, recipient: vec![0], memo: vec![0]};
+            marshall_to_haskell_var(&hn0, out, out_len, RW);
+        }
+    }
+}
 
 #[no_mangle]
 pub extern "C" fn rust_wrapper_tx_read(
diff --git a/src/C/Zcash.chs b/src/C/Zcash.chs
index c236b03..ea2f9ea 100644
--- a/src/C/Zcash.chs
+++ b/src/C/Zcash.chs
@@ -126,6 +126,14 @@ import ZcashHaskell.Types
   -> `()'
 #}
 
+{# fun unsafe rust_wrapper_orchard_note_decrypt_sk as rustWrapperOrchardNoteDecodeSK
+     { toBorshVar* `BS.ByteString'&
+     , toBorshVar* `OrchardAction'&
+     , `Bool'
+     , getVarBuffer `Buffer DecodedNote'&
+     }
+  -> `()'
+#}
 {# fun unsafe rust_wrapper_tx_parse as rustWrapperTxParse
      { toBorshVar* `BS.ByteString'&
      , getVarBuffer `Buffer [BS.ByteString]'&
diff --git a/src/ZcashHaskell/Orchard.hs b/src/ZcashHaskell/Orchard.hs
index a810114..b503da2 100644
--- a/src/ZcashHaskell/Orchard.hs
+++ b/src/ZcashHaskell/Orchard.hs
@@ -22,6 +22,7 @@ import C.Zcash
   , rustWrapperGenOrchardSpendKey
   , rustWrapperOrchardCheck
   , rustWrapperOrchardNoteDecode
+  , rustWrapperOrchardNoteDecodeSK
   , rustWrapperUADecode
   , rustWrapperUfvkDecode
   )
@@ -153,3 +154,15 @@ decryptOrchardAction key encAction =
     decodedAction =
       withPureBorshVarBuffer $
       rustWrapperOrchardNoteDecode (o_key key) encAction
+
+-- | Attemtps to decode the given @OrchardAction@ using the given @OrchardSpendingKey@
+decryptOrchardActionSK ::
+     OrchardSpendingKey -> Scope -> OrchardAction -> Maybe DecodedNote
+decryptOrchardActionSK sk scope oa =
+  case a_value decodedAction of
+    0 -> Nothing
+    _ -> Just decodedAction
+  where
+    decodedAction =
+      withPureBorshVarBuffer $
+      rustWrapperOrchardNoteDecodeSK (getBytes sk) oa (scope == External)

From 7c5d4cf99fa11961a27e3c9c954a73d4778f9640 Mon Sep 17 00:00:00 2001
From: Rene Vergara <rene@vergara.network>
Date: Tue, 9 Apr 2024 13:06:23 -0500
Subject: [PATCH 2/2] Update version

---
 CHANGELOG.md        | 4 ++++
 zcash-haskell.cabal | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ea99a3a..97a42c6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.5.4.0]
+
+- Function to decode Orchard actions with a spending key
+
 ## [0.5.3.0]
 
 ### Added
diff --git a/zcash-haskell.cabal b/zcash-haskell.cabal
index aa3c73f..2e0cae2 100644
--- a/zcash-haskell.cabal
+++ b/zcash-haskell.cabal
@@ -5,7 +5,7 @@ cabal-version: 3.0
 -- see: https://github.com/sol/hpack
 
 name:           zcash-haskell
-version:        0.5.3.0
+version:        0.5.4.0
 synopsis:       Utilities to interact with the Zcash blockchain
 description:    Please see the README on the repo at <https://git.vergara.tech/Vergara_Tech/zcash-haskell#readme>
 category:       Blockchain