From 8244ffa1cec822a6e0db108ec72ed5f268297eee Mon Sep 17 00:00:00 2001
From: Rene Vergara <rene@vergara.network>
Date: Thu, 7 Nov 2024 12:13:52 -0600
Subject: [PATCH] feat: add sapling merkle path test

---
 CHANGELOG.md                    |  1 +
 librustzcash-wrapper/src/lib.rs | 31 +++++++++++++++++++++++++++++++
 src/C/Zcash.chs                 |  8 ++++++++
 src/ZcashHaskell/Sapling.hs     |  5 +++++
 4 files changed, 45 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c817ca1..5c1328f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Sapling commitment node functions
+- Sapling Merkle path test
 
 ## [0.7.4.0]
 
diff --git a/librustzcash-wrapper/src/lib.rs b/librustzcash-wrapper/src/lib.rs
index 2c1b644..165b144 100644
--- a/librustzcash-wrapper/src/lib.rs
+++ b/librustzcash-wrapper/src/lib.rs
@@ -1683,6 +1683,37 @@ pub extern "C" fn rust_wrapper_read_sapling_tree_anchor(
     }
 }
 
+#[no_mangle]
+pub extern "C" fn rust_wrapper_read_sapling_path_anchor(
+    path: *const u8,
+    path_len: usize,
+    cmx: *const u8,
+    cmx_len: usize,
+    out: *mut u8,
+    out_len: &mut usize
+    ){
+    let path_in: Hpath = marshall_from_haskell_var(path, path_len, RW);
+    let cmx_in: Vec<u8> = marshall_from_haskell_var(cmx, cmx_len, RW);
+    let mk_path = sapling_crypto::MerklePath::from_parts(path_in.path.iter().map(|x| Node::from_bytes(to_array(x.bytes.clone())).unwrap()).collect(), Position::from(u64::from(path_in.position)));
+    match mk_path {
+        Ok(mp1) => {
+            let nc = SaplingNoteCommitment::from_bytes(&to_array(cmx_in));
+            if nc.is_some().into() {
+                let anchor = mp1.root(Node::from_cmu(&nc.unwrap()));
+                let h = Hhex { bytes: anchor.to_bytes().to_vec() };
+                marshall_to_haskell_var(&h, out, out_len, RW);
+            } else {
+                let h0 = Hhex { bytes: vec![0] };
+                marshall_to_haskell_var(&h0, out, out_len, RW);
+            }
+        },
+        Err(_e) =>{
+            let h0 = Hhex { bytes: vec![0] };
+            marshall_to_haskell_var(&h0, out, out_len, RW);
+        }
+    }
+}
+
 #[no_mangle]
 pub extern "C" fn rust_wrapper_read_orchard_frontier(
     tree: *const u8,
diff --git a/src/C/Zcash.chs b/src/C/Zcash.chs
index 6d915bb..fde4550 100644
--- a/src/C/Zcash.chs
+++ b/src/C/Zcash.chs
@@ -283,6 +283,14 @@ import ZcashHaskell.Types
   -> `()'
 #}
 
+{# fun unsafe rust_wrapper_read_sapling_path_anchor as rustWrapperReadSaplingPathAnchor
+     { toBorshVar* `MerklePath'&
+     , toBorshVar* `BS.ByteString'&
+     , getVarBuffer `Buffer HexString'&
+     }
+  -> `()'
+#}
+
 {# fun unsafe rust_wrapper_read_orchard_node as rustWrapperReadOrchardNode
      { toBorshVar* `BS.ByteString'&
      , getVarBuffer `Buffer HexString'&
diff --git a/src/ZcashHaskell/Sapling.hs b/src/ZcashHaskell/Sapling.hs
index 87b21f7..1347778 100644
--- a/src/ZcashHaskell/Sapling.hs
+++ b/src/ZcashHaskell/Sapling.hs
@@ -25,6 +25,7 @@ import C.Zcash
   , rustWrapperReadSaplingCommitmentTree
   , rustWrapperReadSaplingFrontier
   , rustWrapperReadSaplingNode
+  , rustWrapperReadSaplingPathAnchor
   , rustWrapperReadSaplingPosition
   , rustWrapperReadSaplingTreeAnchor
   , rustWrapperReadSaplingTreeParts
@@ -237,6 +238,10 @@ getSaplingTreeAnchor tree =
   withPureBorshVarBuffer $
   rustWrapperReadSaplingTreeAnchor $ toBytes $ sapTree tree
 
+getSaplingPathAnchor :: HexString -> MerklePath -> HexString
+getSaplingPathAnchor hex p =
+  withPureBorshVarBuffer $ rustWrapperReadSaplingPathAnchor p (hexBytes hex)
+
 getSaplingFrontier :: SaplingCommitmentTree -> Maybe SaplingFrontier
 getSaplingFrontier tree =
   if sf_pos updatedTree > 1