Introduce difficulty calculation in t8n

test/state/mpt_hash.hpp

@@ -9,6 +9,9 @@
 
 namespace evmone::state
 {
+static constexpr auto EmptyListHash =
+    0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347_bytes32;
+
 struct Account;
 struct Transaction;
 struct TransactionReceipt;

test/state/state.hpp

@@ -82,8 +82,12 @@ struct BlockInfo
 {
     int64_t number = 0;
     int64_t timestamp = 0;
+    int64_t parent_timestamp = 0;
     int64_t gas_limit = 0;
     address coinbase;
+    int64_t current_difficulty = 0;
+    int64_t parent_difficulty = 0;
+    hash256 parent_uncle_hash;
     bytes32 prev_randao;
     uint64_t base_fee = 0;
     std::vector<Withdrawal> withdrawals;

test/statetest/statetest_loader.cpp

@@ -150,16 +150,30 @@ inline uint64_t calculate_current_base_fee_eip1559(
 template <>
 state::BlockInfo from_json<state::BlockInfo>(const json::json& j)
 {
-    evmc::bytes32 difficulty;
+    evmc::bytes32 prev_randao;
+    int64_t current_difficulty = 0;
+    int64_t parent_difficulty = 0;
     const auto prev_randao_it = j.find("currentRandom");
     const auto current_difficulty_it = j.find("currentDifficulty");
     const auto parent_difficulty_it = j.find("parentDifficulty");
+
+    if (current_difficulty_it != j.end())
+        current_difficulty = from_json<int64_t>(*current_difficulty_it);
+    if (parent_difficulty_it != j.end())
+        parent_difficulty = from_json<int64_t>(*parent_difficulty_it);
+
+    // When it's not defined init it with difficulty value.
     if (prev_randao_it != j.end())
-        difficulty = from_json<bytes32>(*prev_randao_it);
+        prev_randao = from_json<bytes32>(*prev_randao_it);
     else if (current_difficulty_it != j.end())
-        difficulty = from_json<bytes32>(*current_difficulty_it);
+        prev_randao = from_json<bytes32>(*current_difficulty_it);
     else if (parent_difficulty_it != j.end())
-        difficulty = from_json<bytes32>(*parent_difficulty_it);
+        prev_randao = from_json<bytes32>(*parent_difficulty_it);
+
+    hash256 parent_uncle_hash;
+    const auto parent_uncle_hash_it = j.find("parentUncleHash");
+    if (parent_uncle_hash_it != j.end())
+        parent_uncle_hash = from_json<hash256>(*parent_uncle_hash_it);
 
     uint64_t base_fee = 0;
     if (j.contains("currentBaseFee"))
@@ -181,10 +195,15 @@ state::BlockInfo from_json<state::BlockInfo>(const json::json& j)
         }
     }
 
+    int64_t parent_timestamp = 0;
+    auto parent_timestamp_it = j.find("parentTimestamp");
+    if (parent_timestamp_it != j.end())
+        parent_timestamp = from_json<int64_t>(*parent_timestamp_it);
+
     return {from_json<int64_t>(j.at("currentNumber")), from_json<int64_t>(j.at("currentTimestamp")),
-        from_json<int64_t>(j.at("currentGasLimit")),
-        from_json<evmc::address>(j.at("currentCoinbase")), difficulty, base_fee,
-        std::move(withdrawals)};
+        parent_timestamp, from_json<int64_t>(j.at("currentGasLimit")),
+        from_json<evmc::address>(j.at("currentCoinbase")), current_difficulty, parent_difficulty,
+        parent_uncle_hash, prev_randao, base_fee, std::move(withdrawals)};
 }
 
 template <>

test/t8n/t8n.cpp

@@ -19,6 +19,61 @@ using namespace evmone;
 using namespace evmone::test;
 using namespace std::literals;
 
+namespace
+{
+using namespace intx;
+
+int64_t get_bomb_delay(evmc_revision rev)
+{
+    switch (rev)
+    {
+    case EVMC_BYZANTIUM:
+        return 3000000;
+    case EVMC_CONSTANTINOPLE:
+    case EVMC_PETERSBURG:
+    case EVMC_ISTANBUL:
+        return 5000000;
+    case EVMC_BERLIN:
+        return 9000000;
+    case EVMC_LONDON:
+        return 9700000;
+    default:
+        throw std::runtime_error("get_bomb_delay: Wrong rev");
+    }
+}
+
+int64_t calc_difficulty(const int64_t& parent_difficulty, const hash256& parent_uncle_hash,
+    const int64_t& parent_timestamp, const int64_t& current_timestamp, const int64_t& block_num,
+    evmc_revision rev)
+{
+    if (rev >= EVMC_PARIS)
+        return 0;
+
+    // TODO: Implement for older revisions
+    if (rev < EVMC_BYZANTIUM)
+        return 0x020000;
+
+    static constexpr auto min_difficulty = int64_t{1} << 17;
+
+    const auto kappa = get_bomb_delay(rev);
+
+    const auto H_i_prime = kappa >= block_num ? 0 : block_num - kappa;
+
+    const auto p = (H_i_prime / 100000) - 2;
+    assert(p < 63);
+
+    const auto epsilon = p < 0 ? 0 : int64_t{1} << p;
+
+    const auto y = parent_uncle_hash != state::EmptyListHash ? 2 : 1;
+
+    const auto sigma_2 = std::max(y - (current_timestamp - parent_timestamp) / 9, int64_t{-99});
+
+    const int64_t x = parent_difficulty / 2048;
+
+    return std::max(min_difficulty, (int64_t)parent_difficulty + x * sigma_2 + epsilon);
+}
+}  // namespace
+
 int main(int argc, const char* argv[])
 {
     evmc_revision rev = {};
@@ -80,8 +135,36 @@ int main(int argc, const char* argv[])
         }
 
         json::json j_result;
-        // FIXME: Calculate difficulty properly
-        j_result["currentDifficulty"] = "0x20000";
+
+        // Difficulty was received from upstream. No need to calc
+        // TODO: Check is it's needed by the blockchain test. If not remove if statement true branch
+        if (block.current_difficulty != 0)
+            j_result["currentDifficulty"] = hex0x(block.current_difficulty);
+        else
+        {
+            if (rev >= EVMC_SHANGHAI)
+                j_result["currentDifficulty"] = nullptr;
+            else
+            {
+                const auto current_difficulty =
+                    calc_difficulty(block.parent_difficulty, block.parent_uncle_hash,
+                        block.parent_timestamp, block.timestamp, block.number, rev);
+
+                j_result["currentDifficulty"] = hex0x(current_difficulty);
+                block.current_difficulty = current_difficulty;
+
+                // Override prev_randao with difficulty (swap bytes to BE) pre Merge
+                if (rev < EVMC_PARIS)
+                {
+                    std::memset(block.prev_randao.bytes, 0, 32);
+                    const auto s = sizeof(current_difficulty);
+                    const auto diff_ptr = reinterpret_cast<const uint8_t*>(&current_difficulty);
+                    for (size_t i = 0; i < s; ++i)
+                        block.prev_randao.bytes[24 + i] = diff_ptr[s - 1 - i];
+                }
+            }
+        };
+
         j_result["currentBaseFee"] = hex0x(block.base_fee);
 
         int64_t cumulative_gas_used = 0;

test/unittests/statetest_loader_block_info_test.cpp

@@ -131,7 +131,7 @@ TEST(statetest_loader, block_info_0_parent_difficulty)
         "parentBaseFee": "7",
         "parentGasUsed": "0",
         "parentGasLimit": "100000000000000000",
-        "parentTimstamp": "0",
+        "parentTimestamp": "253",
         "blockHashes": {
             "0": "0xc305d826e3784046a7e9d31128ef98d3e96133fe454c16ef630574d967dfdb1a"
         },
@@ -147,6 +147,7 @@ TEST(statetest_loader, block_info_0_parent_difficulty)
     EXPECT_EQ(bi.base_fee, 7);
     EXPECT_EQ(bi.timestamp, 1000);
     EXPECT_EQ(bi.number, 1);
+    EXPECT_EQ(bi.parent_timestamp, 253);
 }
 
 TEST(statetest_loader, block_info_0_random)