From a4bf84039c00b196b87f969acf6369d72c56ab46 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter@wuille.net>
Date: Sun, 23 May 2021 17:38:40 -0700
Subject: Separate WitnessV1Taproot variant in CTxDestination

---
 src/key_io.cpp            | 15 +++++++++++++++
 src/rpc/util.cpp          | 10 ++++++++++
 src/script/descriptor.cpp |  1 +
 src/script/standard.cpp   | 15 ++++++++-------
 src/script/standard.h     | 13 ++++++++++---
 src/wallet/rpcwallet.cpp  |  1 +
 6 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/src/key_io.cpp b/src/key_io.cpp
index dbcbfa1f29..615f4c9312 100644
--- a/src/key_io.cpp
+++ b/src/key_io.cpp
@@ -54,6 +54,14 @@ public:
         return bech32::Encode(bech32::Encoding::BECH32, m_params.Bech32HRP(), data);
     }
 
+    std::string operator()(const WitnessV1Taproot& tap) const
+    {
+        std::vector<unsigned char> data = {1};
+        data.reserve(53);
+        ConvertBits<8, 5, true>([&](unsigned char c) { data.push_back(c); }, tap.begin(), tap.end());
+        return bech32::Encode(bech32::Encoding::BECH32M, m_params.Bech32HRP(), data);
+    }
+
     std::string operator()(const WitnessUnknown& id) const
     {
         if (id.version < 1 || id.version > 16 || id.length < 2 || id.length > 40) {
@@ -135,6 +143,13 @@ CTxDestination DecodeDestination(const std::string& str, const CChainParams& par
                 return CNoDestination();
             }
 
+            if (version == 1 && data.size() == WITNESS_V1_TAPROOT_SIZE) {
+                static_assert(WITNESS_V1_TAPROOT_SIZE == WitnessV1Taproot::size());
+                WitnessV1Taproot tap;
+                std::copy(data.begin(), data.end(), tap.begin());
+                return tap;
+            }
+
             if (version > 16) {
                 error_str = "Invalid Bech32 address witness version";
                 return CNoDestination();
diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index 7cf25e0c82..2059628b54 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -301,6 +301,16 @@ public:
         return obj;
     }
 
+    UniValue operator()(const WitnessV1Taproot& tap) const
+    {
+        UniValue obj(UniValue::VOBJ);
+        obj.pushKV("isscript", true);
+        obj.pushKV("iswitness", true);
+        obj.pushKV("witness_version", 1);
+        obj.pushKV("witness_program", HexStr(tap));
+        return obj;
+    }
+
     UniValue operator()(const WitnessUnknown& id) const
     {
         UniValue obj(UniValue::VOBJ);
diff --git a/src/script/descriptor.cpp b/src/script/descriptor.cpp
index 19fad1009e..d4b43932b9 100644
--- a/src/script/descriptor.cpp
+++ b/src/script/descriptor.cpp
@@ -645,6 +645,7 @@ static std::optional<OutputType> OutputTypeFromDestination(const CTxDestination&
     }
     if (std::holds_alternative<WitnessV0KeyHash>(dest) ||
         std::holds_alternative<WitnessV0ScriptHash>(dest) ||
+        std::holds_alternative<WitnessV1Taproot>(dest) ||
         std::holds_alternative<WitnessUnknown>(dest)) {
         return OutputType::BECH32;
     }
diff --git a/src/script/standard.cpp b/src/script/standard.cpp
index 540aa0f2d9..0a233b550a 100644
--- a/src/script/standard.cpp
+++ b/src/script/standard.cpp
@@ -242,13 +242,9 @@ bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
         return true;
     }
     case TxoutType::WITNESS_V1_TAPROOT: {
-        /* For now, no WitnessV1Taproot variant in CTxDestination exists, so map
-         * this to WitnessUnknown. */
-        WitnessUnknown unk;
-        unk.version = 1;
-        std::copy(vSolutions[0].begin(), vSolutions[0].end(), unk.program);
-        unk.length = vSolutions[0].size();
-        addressRet = unk;
+        WitnessV1Taproot tap;
+        std::copy(vSolutions[0].begin(), vSolutions[0].end(), tap.begin());
+        addressRet = tap;
         return true;
     }
     case TxoutType::WITNESS_UNKNOWN: {
@@ -337,6 +333,11 @@ public:
         return CScript() << OP_0 << ToByteVector(id);
     }
 
+    CScript operator()(const WitnessV1Taproot& tap) const
+    {
+        return CScript() << OP_1 << ToByteVector(tap);
+    }
+
     CScript operator()(const WitnessUnknown& id) const
     {
         return CScript() << CScript::EncodeOP_N(id.version) << std::vector<unsigned char>(id.program, id.program + id.length);
diff --git a/src/script/standard.h b/src/script/standard.h
index 12ab9979a8..a96b096fa7 100644
--- a/src/script/standard.h
+++ b/src/script/standard.h
@@ -6,6 +6,7 @@
 #ifndef BITCOIN_SCRIPT_STANDARD_H
 #define BITCOIN_SCRIPT_STANDARD_H
 
+#include <pubkey.h>
 #include <script/interpreter.h>
 #include <uint256.h>
 #include <util/hash_type.h>
@@ -113,6 +114,12 @@ struct WitnessV0KeyHash : public BaseHash<uint160>
 };
 CKeyID ToKeyID(const WitnessV0KeyHash& key_hash);
 
+struct WitnessV1Taproot : public XOnlyPubKey
+{
+    WitnessV1Taproot() : XOnlyPubKey() {}
+    explicit WitnessV1Taproot(const XOnlyPubKey& xpk) : XOnlyPubKey(xpk) {}
+};
+
 //! CTxDestination subtype to encode any future Witness version
 struct WitnessUnknown
 {
@@ -142,11 +149,11 @@ struct WitnessUnknown
  *  * ScriptHash: TxoutType::SCRIPTHASH destination (P2SH)
  *  * WitnessV0ScriptHash: TxoutType::WITNESS_V0_SCRIPTHASH destination (P2WSH)
  *  * WitnessV0KeyHash: TxoutType::WITNESS_V0_KEYHASH destination (P2WPKH)
- *  * WitnessUnknown: TxoutType::WITNESS_UNKNOWN/WITNESS_V1_TAPROOT destination (P2W???)
- *    (taproot outputs do not require their own type as long as no wallet support exists)
+ *  * WitnessV1Taproot: TxoutType::WITNESS_V1_TAPROOT destination (P2TR)
+ *  * WitnessUnknown: TxoutType::WITNESS_UNKNOWN destination (P2W???)
  *  A CTxDestination is the internal data type encoded in a bitcoin address
  */
-using CTxDestination = std::variant<CNoDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessUnknown>;
+using CTxDestination = std::variant<CNoDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>;
 
 /** Check whether a CTxDestination is a CNoDestination. */
 bool IsValidDestination(const CTxDestination& dest);
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 4e3c8ce49d..dd74d9f36b 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3737,6 +3737,7 @@ public:
         return obj;
     }
 
+    UniValue operator()(const WitnessV1Taproot& id) const { return UniValue(UniValue::VOBJ); }
     UniValue operator()(const WitnessUnknown& id) const { return UniValue(UniValue::VOBJ); }
 };
 
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