From 636fb820ea3a80df8ff46d7c476b2cf8caae962b Mon Sep 17 00:00:00 2001
From: sowle <crypto.sowle@gmail.com>
Date: Thu, 25 Aug 2022 04:22:38 +0200
Subject: [PATCH] explicit tx fee for zarcanum txs: get_tx_fee,
 add_tx_fee_amount_to_extra, process_type_in_variant_container

---
 src/currency_core/currency_format_utils.cpp   | 48 +++++++++++++++----
 src/currency_core/currency_format_utils.h     |  1 +
 .../currency_format_utils_abstract.h          | 21 +++++++-
 3 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/src/currency_core/currency_format_utils.cpp b/src/currency_core/currency_format_utils.cpp
index 97c0412f..b22683b3 100644
--- a/src/currency_core/currency_format_utils.cpp
+++ b/src/currency_core/currency_format_utils.cpp
@@ -418,18 +418,34 @@ namespace currency
     fee = 0;
     if (is_coinbase(tx))
       return true;
-    uint64_t amount_in = 0;
-    uint64_t amount_out = get_outs_money_amount(tx);
-   
-    BOOST_FOREACH(auto& in, tx.vin)
+
+    if (tx.version <= TRANSACTION_VERSION_PRE_HF4)
     {
-      amount_in += get_amount_from_variant(in);
+      // all amounts are open:  fee = sum(outputs) - sum(inputs)
+
+      uint64_t amount_in = 0;
+      uint64_t amount_out = get_outs_money_amount(tx);
+   
+      for(auto& in : tx.vin)
+        amount_in += get_amount_from_variant(in);
+
+      CHECK_AND_ASSERT_MES(amount_in >= amount_out, false, "transaction spends (" << print_money_brief(amount_in) << ") more than it has (" << print_money_brief(amount_out) << ")");
+      fee = amount_in - amount_out;
+      return true;
     }
 
+    // tx.version > TRANSACTION_VERSION_PRE_HF4
+    // all amounts are hidden with Pedersen commitments
+    // therefore fee should be explicitly stated in the extra
+    if (!process_type_in_variant_container<zarcanum_tx_data_v1>(tx.extra, [&](const zarcanum_tx_data_v1& ztd) -> bool {
+      fee += ztd.fee;
+      return true; // continue
+      }, false))
+    {
+      fee = 0;
+      return false;
+    }
 
-
-    CHECK_AND_ASSERT_MES(amount_in >= amount_out, false, "transaction spend (" << amount_in << ") more than it has (" << amount_out << ")");
-    fee = amount_in - amount_out;
     return true;
   }
   //---------------------------------------------------------------
@@ -555,6 +571,22 @@ namespace currency
     return true;
   }
   //---------------------------------------------------------------
+  // puts explicit fee amount to tx extra, should be used only for tx.verson > TRANSACTION_VERSION_PRE_HF4
+  bool add_tx_fee_amount_to_extra(transaction& tx, uint64_t fee, bool make_sure_its_unique /* = true */)
+  {
+    if (make_sure_its_unique)
+    {
+      if (count_type_in_variant_container<zarcanum_tx_data_v1>(tx.extra) != 0)
+        return false;
+    }
+
+    zarcanum_tx_data_v1 ztd = AUTO_VAL_INIT(ztd);
+    ztd.fee = fee;
+
+    tx.extra.push_back(ztd);
+    return true;
+  }
+  //---------------------------------------------------------------
   //---------------------------------------------------------------
 
   struct multisig_id_generator
diff --git a/src/currency_core/currency_format_utils.h b/src/currency_core/currency_format_utils.h
index d60f68d2..7084be7e 100644
--- a/src/currency_core/currency_format_utils.h
+++ b/src/currency_core/currency_format_utils.h
@@ -305,6 +305,7 @@ namespace currency
   bool parse_and_validate_tx_extra(const transaction& tx, crypto::public_key& tx_pub_key);
   crypto::public_key get_tx_pub_key_from_extra(const transaction& tx);
   bool add_tx_pub_key_to_extra(transaction& tx, const crypto::public_key& tx_pub_key);
+  bool add_tx_fee_amount_to_extra(transaction& tx, uint64_t fee, bool make_sure_its_unique = true);
   bool add_tx_extra_userdata(transaction& tx, const blobdata& extra_nonce);
 
   crypto::hash get_multisig_out_id(const transaction& tx, size_t n);
diff --git a/src/currency_core/currency_format_utils_abstract.h b/src/currency_core/currency_format_utils_abstract.h
index 5f3c6ed4..adddd8e5 100644
--- a/src/currency_core/currency_format_utils_abstract.h
+++ b/src/currency_core/currency_format_utils_abstract.h
@@ -94,7 +94,7 @@ namespace currency
   }
   //---------------------------------------------------------------
   template<typename specific_type_t, typename variant_t_container>
-  bool get_type_in_variant_container(const variant_t_container& av, specific_type_t& a)
+  bool get_type_in_variant_container(variant_t_container& av, specific_type_t& a)
   {
     for (auto& ai : av)
     {
@@ -107,6 +107,25 @@ namespace currency
     return false;
   }
   //---------------------------------------------------------------
+  // if cb returns true, it means "continue", false -- means "stop"
+  template<typename specific_type_t, typename variant_container_t, typename callback_t>
+  bool process_type_in_variant_container(variant_container_t& av, callback_t& cb, bool return_value_if_none_found = true)
+  {
+    bool found = false;
+    for (auto& ai : av)
+    {
+      if (ai.type() == typeid(specific_type_t))
+      {
+        found = true;
+        if (!cb(boost::get<specific_type_t>(ai)))
+          return false;
+      }
+    }
+    if (found)
+      return true;
+    return return_value_if_none_found;
+  }
+  //---------------------------------------------------------------
   // callback should return true to continue iterating through the container
   template <typename A, typename B, typename container_t, typename callback_t>
   bool handle_2_alternative_types_in_variant_container(const container_t& container, callback_t cb)