evm: Fix base fee calculation

lib/ain-cpp-imports/src/bridge.rs

@@ -16,5 +16,6 @@ pub mod ffi {
         fn getMinRelayTxFee() -> u64;
         fn getEthPrivKey(key_id: [u8; 20]) -> [u8; 32];
         fn getStateInputJSON() -> String;
+        fn pastChangiIntermediateHeight2() -> bool;
     }
 }

lib/ain-cpp-imports/src/lib.rs

@@ -49,6 +49,9 @@ mod ffi {
     pub fn getStateInputJSON() -> String {
         unimplemented!("{}", UNIMPL_MSG)
     }
+    pub fn pastChangiIntermediateHeight2() -> bool {
+        unimplemented!("{}", UNIMPL_MSG)
+    }
 }
 
 pub fn get_chain_id() -> Result<u64, Box<dyn Error>> {
@@ -119,5 +122,10 @@ pub fn get_state_input_json() -> Option<String> {
     }
 }
 
+pub fn past_changi_intermediate_height_2_height() -> Result<bool, Box<dyn Error>> {
+    let height = ffi::pastChangiIntermediateHeight2();
+    Ok(height)
+}
+
 #[cfg(test)]
 mod tests {}

lib/ain-evm/src/block.rs

@@ -47,6 +47,99 @@ impl BlockHandler {
         self.storage.set_base_fee(block.header.hash(), base_fee);
     }
 
+    fn pre_changi_intermediate_2_base_fee_calculation(
+        &self,
+        parent_gas_used: u64,
+        parent_gas_target: u64,
+        parent_base_fee: U256,
+        base_fee_max_change_denominator: U256,
+        initial_base_fee: U256,
+    ) -> U256 {
+        match parent_gas_used.cmp(&parent_gas_target) {
+            // TODO: incorrect calculation, remove before mainnet launch
+            Ordering::Less => parent_base_fee,
+            Ordering::Equal => {
+                let gas_used_delta = parent_gas_used - parent_gas_target;
+                let base_fee_per_gas_delta = max(
+                    parent_base_fee * gas_used_delta
+                        / parent_gas_target
+                        / base_fee_max_change_denominator,
+                    U256::one(),
+                );
+
+                max(parent_base_fee + base_fee_per_gas_delta, initial_base_fee)
+            }
+            Ordering::Greater => {
+                let gas_used_delta = parent_gas_target - parent_gas_used;
+                let base_fee_per_gas_delta = parent_base_fee * gas_used_delta
+                    / parent_gas_target
+                    / base_fee_max_change_denominator;
+
+                max(parent_base_fee - base_fee_per_gas_delta, initial_base_fee)
+            }
+        }
+    }
+
+    pub fn post_changi_intermediate_2_base_fee_calculation(
+        &self,
+        parent_gas_used: u64,
+        parent_gas_target: u64,
+        parent_base_fee: U256,
+        base_fee_max_change_denominator: U256,
+        initial_base_fee: U256,
+    ) -> U256 {
+        match parent_gas_used.cmp(&parent_gas_target) {
+            Ordering::Equal => parent_base_fee,
+            Ordering::Greater => {
+                let gas_used_delta = parent_gas_used - parent_gas_target;
+                let base_fee_per_gas_delta = max(
+                    parent_base_fee * gas_used_delta
+                        / parent_gas_target
+                        / base_fee_max_change_denominator,
+                    U256::one(),
+                );
+
+                max(parent_base_fee + base_fee_per_gas_delta, initial_base_fee)
+            }
+            Ordering::Less => {
+                let gas_used_delta = parent_gas_target - parent_gas_used;
+                let base_fee_per_gas_delta = parent_base_fee * gas_used_delta
+                    / parent_gas_target
+                    / base_fee_max_change_denominator;
+
+                max(parent_base_fee - base_fee_per_gas_delta, initial_base_fee)
+            }
+        }
+    }
+
+    pub fn get_base_fee(
+        &self,
+        parent_gas_used: u64,
+        parent_gas_target: u64,
+        parent_base_fee: U256,
+        base_fee_max_change_denominator: U256,
+        initial_base_fee: U256,
+    ) -> U256 {
+        match ain_cpp_imports::past_changi_intermediate_height_2_height()
+            .expect("Unable to get Changi intermediate height 2")
+        {
+            true => self.post_changi_intermediate_2_base_fee_calculation(
+                parent_gas_used,
+                parent_gas_target,
+                parent_base_fee,
+                base_fee_max_change_denominator,
+                initial_base_fee,
+            ),
+            false => self.pre_changi_intermediate_2_base_fee_calculation(
+                parent_gas_used,
+                parent_gas_target,
+                parent_base_fee,
+                base_fee_max_change_denominator,
+                initial_base_fee,
+            ),
+        }
+    }
+
     pub fn calculate_base_fee(&self, parent_hash: H256) -> U256 {
         // constants
         let initial_base_fee = U256::from(10_000_000_000u64); // wei
@@ -72,28 +165,13 @@ impl BlockHandler {
         let parent_gas_target =
             parent_block.header.gas_limit.as_u64() / elasticity_multiplier.as_u64();
 
-        match parent_gas_used.cmp(&parent_gas_target) {
-            Ordering::Less => parent_base_fee,
-            Ordering::Equal => {
-                let gas_used_delta = parent_gas_used - parent_gas_target;
-                let base_fee_per_gas_delta = max(
-                    parent_base_fee * gas_used_delta
-                        / parent_gas_target
-                        / base_fee_max_change_denominator,
-                    U256::one(),
-                );
-
-                max(parent_base_fee + base_fee_per_gas_delta, initial_base_fee)
-            }
-            Ordering::Greater => {
-                let gas_used_delta = parent_gas_target - parent_gas_used;
-                let base_fee_per_gas_delta = parent_base_fee * gas_used_delta
-                    / parent_gas_target
-                    / base_fee_max_change_denominator;
-
-                max(parent_base_fee - base_fee_per_gas_delta, initial_base_fee)
-            }
-        }
+        self.get_base_fee(
+            parent_gas_used,
+            parent_gas_target,
+            parent_base_fee,
+            base_fee_max_change_denominator,
+            initial_base_fee,
+        )
     }
 
     pub fn fee_history(
@@ -289,3 +367,83 @@ pub fn new_block_from_json(path: PathBuf, state_root: H256) -> Result<BlockAny,
         Vec::new(),
     ))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_base_fee_equal() {
+        let block = BlockHandler::new(Arc::new(Storage::new()));
+        assert_eq!(
+            U256::from(20_000_000_000u64),
+            block.post_changi_intermediate_2_base_fee_calculation(
+                15_000_000,
+                15_000_000,
+                U256::from(20_000_000_000u64),
+                U256::from(8),
+                U256::from(10_000_000_000u64)
+            )
+        )
+    }
+
+    #[test]
+    fn test_base_fee_max_increase() {
+        let block = BlockHandler::new(Arc::new(Storage::new()));
+        assert_eq!(
+            U256::from(22_500_000_000u64), // should increase by 12.5%
+            block.post_changi_intermediate_2_base_fee_calculation(
+                30_000_000,
+                15_000_000,
+                U256::from(20_000_000_000u64),
+                U256::from(8),
+                U256::from(10_000_000_000u64)
+            )
+        )
+    }
+
+    #[test]
+    fn test_base_fee_increase() {
+        let block = BlockHandler::new(Arc::new(Storage::new()));
+        assert_eq!(
+            U256::from(20_833_333_333u64), // should increase by ~4.15%
+            block.post_changi_intermediate_2_base_fee_calculation(
+                20_000_000,
+                15_000_000,
+                U256::from(20_000_000_000u64),
+                U256::from(8),
+                U256::from(10_000_000_000u64)
+            )
+        )
+    }
+
+    #[test]
+    fn test_base_fee_max_decrease() {
+        let block = BlockHandler::new(Arc::new(Storage::new()));
+        assert_eq!(
+            U256::from(17_500_000_000u64), // should decrease by 12.5%
+            block.post_changi_intermediate_2_base_fee_calculation(
+                0,
+                15_000_000,
+                U256::from(20_000_000_000u64),
+                U256::from(8),
+                U256::from(10_000_000_000u64)
+            )
+        )
+    }
+
+    #[test]
+    fn test_base_fee_decrease() {
+        let block = BlockHandler::new(Arc::new(Storage::new()));
+        assert_eq!(
+            U256::from(19_166_666_667u64), // should increase by ~4.15%
+            block.post_changi_intermediate_2_base_fee_calculation(
+                10_000_000,
+                15_000_000,
+                U256::from(20_000_000_000u64),
+                U256::from(8),
+                U256::from(10_000_000_000u64)
+            )
+        )
+    }
+}

src/chainparams.cpp

@@ -637,6 +637,7 @@ class CChangiParams : public CChainParams {
         consensus.GrandCentralEpilogueHeight = 1438200;
         consensus.NextNetworkUpgradeHeight = 1586750;
         consensus.ChangiIntermediateHeight = 1717800;
+        consensus.ChangiIntermediateHeight2 = 1717493;
 
         consensus.pos.diffLimit = uint256S("00000fffffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
         consensus.pos.nTargetTimespan = 5 * 60; // 5 min == 10 blocks

src/consensus/params.h

@@ -103,6 +103,7 @@ struct Params {
     int GrandCentralEpilogueHeight;
     int NextNetworkUpgradeHeight;
     int ChangiIntermediateHeight; // To be changed to NextNetworkUpgradeHeight on mainnet release
+    int ChangiIntermediateHeight2; // To be changed to NextNetworkUpgradeHeight on mainnet release
 
     /** Foundation share after AMK, normalized to COIN = 100% */
     CAmount foundationShareDFIP1;

src/ffi/ffiexports.cpp

@@ -201,3 +201,7 @@ std::array<uint8_t, 32> getEthPrivKey(std::array<uint8_t, 20> keyID) {
 rust::string getStateInputJSON() {
     return gArgs.GetArg("-ethstartstate", "");
 }
+
+bool pastChangiIntermediateHeight2() {
+    return ::ChainActive().Height() >= Params().GetConsensus().ChangiIntermediateHeight2;
+}

src/ffi/ffiexports.h

@@ -17,5 +17,6 @@ uint64_t getNativeTxSize(rust::Vec<uint8_t> rawTransaction);
 uint64_t getMinRelayTxFee();
 std::array<uint8_t, 32> getEthPrivKey(std::array<uint8_t, 20> keyID);
 rust::string getStateInputJSON();
+bool pastChangiIntermediateHeight2();
 
 #endif // DEFI_FFI_FFIEXPORTS_H