Fix merkle path

src/node/sv2_messages.cpp

@@ -3,6 +3,61 @@
 #include <node/sv2_messages.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
+#include <hash.h>
+#include <streams.h>
+#include <deque>
+#include <iostream>
+
+uint256 HashTwoTxIDs(const uint256& txid1, const uint256& txid2) {
+    CHashWriter hasher(SER_GETHASH, 0);
+    hasher << txid1 << txid2;
+    return hasher.GetHash();
+}
+std::vector<uint256> GetMerklePathForCoinbase(const CBlock& block) {
+    auto size = block.vtx.size();
+    // If we have only the coinbase tx, we don't have a merkle path
+    if (size == 1) {
+        return {};
+    // If we have coinbase tx and another tx the path is the second node id
+    } else if (size == 2) {
+        std::vector<uint256> path;
+        path.push_back(block.vtx[1]->GetHash());
+        return path;
+    // Otherwise we calculate the merkle path
+    } else {
+        std::deque<uint256> id_list;
+        for (const auto& tx : block.vtx) {
+            id_list.push_back(tx->GetHash());
+        }
+        // Last id must be dublicated when txs are odds
+        if (size % 2 == 1) {
+            id_list.push_back(block.vtx[size - 1]->GetHash());
+        }
+
+        // Remove coinbase
+        id_list.pop_front();
+
+        std::vector<uint256> path;
+
+        // First path element is always the second tx
+        path.push_back(id_list.front());
+        id_list.pop_front();
+
+        while (!id_list.empty()) {
+            for (size_t i = 0; i < id_list.size() / 2; ++i) {
+                id_list[i] = HashTwoTxIDs(id_list[i * 2], id_list[i * 2 + 1]);
+            }
+            id_list.resize(id_list.size()/2);
+            path.push_back(id_list.front());
+            id_list.pop_front();
+            if (id_list.size() % 2 == 1) {
+                id_list.push_back(id_list[id_list.size() - 1]);
+            }
+        }
+
+        return path;
+    }
+}
 
 node::Sv2NewTemplateMsg::Sv2NewTemplateMsg(const CBlock& block, uint64_t template_id, bool future_template)
     : m_template_id{template_id}, m_future_template{future_template}
@@ -28,11 +83,16 @@ node::Sv2NewTemplateMsg::Sv2NewTemplateMsg(const CBlock& block, uint64_t templat
 
     m_coinbase_tx_locktime = coinbase_tx->nLockTime;
 
-    // Skip the coinbase_tx hash from the merkle path since the downstream client
-    // will build their own coinbase tx.
-    for (auto it = block.vtx.begin() + 1; it != block.vtx.end(); ++it) {
-        m_merkle_path.push_back((*it)->GetHash());
+    std::vector<uint256> merklepath = GetMerklePathForCoinbase(block);
+
+    for (const auto& hash : merklepath) {
+        m_merkle_path.push_back(hash);
     }
+
+    //for (auto it = block.vtx.begin() + 1; it != block.vtx.end(); ++it) {
+    //    m_merkle_path.push_back((*it)->GetHash());
+    //}
+
 }
 
 node::Sv2SetNewPrevHashMsg::Sv2SetNewPrevHashMsg(const CBlock& block, uint64_t template_id) : m_template_id{template_id}
@@ -42,3 +102,4 @@ node::Sv2SetNewPrevHashMsg::Sv2SetNewPrevHashMsg(const CBlock& block, uint64_t t
     m_nBits = block.nBits;
     m_target = ArithToUint256(arith_uint256().SetCompact(block.nBits));
 }
+