charge in postop, external mode uses off-chain estimations

contracts/interfaces/IBiconomyTokenPaymaster.sol

@@ -22,13 +22,11 @@ interface IBiconomyTokenPaymaster {
     event UpdatedVerifyingSigner(address indexed oldSigner, address indexed newSigner, address indexed actor);
     event UpdatedFeeCollector(address indexed oldFeeCollector, address indexed newFeeCollector, address indexed actor);
     event UpdatedPriceExpiryDuration(uint256 indexed oldValue, uint256 indexed newValue);
-    event TokensRefunded(
-        address indexed userOpSender, address indexed token, uint256 refundAmount, bytes32 indexed userOpHash
-    );
+
     event PaidGasInTokensIndependent(
         address indexed userOpSender,
         address indexed token,
-        uint256 nativeCharge,
+        uint256 gasCostBeforePostOpAndPenalty,
         uint256 tokenCharge,
         uint32 priceMarkup,
         uint256 tokenPrice,

contracts/token/BiconomyTokenPaymaster.sol

@@ -509,12 +509,14 @@ contract BiconomyTokenPaymaster is
                 revert InsufficientTokenBalance(userOp.sender, tokenAddress, estimatedTokenAmount, userOpHash);
             }
 
-            context = abi.encode(
-                mode,
-                userOp.sender,
-                tokenAddress,
-                estimatedTokenAmount,
-                userOpHash
+            context = abi.encodePacked(
+                PaymasterMode.EXTERNAL,
+                abi.encode(
+                    userOp.sender,
+                    tokenAddress,
+                    estimatedTokenAmount,
+                    userOpHash
+                )
             );
             validationData = _packValidationData(false, validUntil, validAfter);
 
@@ -529,7 +531,7 @@ contract BiconomyTokenPaymaster is
             (
                 uint128(uint256(userOp.accountGasLimits))
                     + uint128(bytes16(userOp.paymasterAndData[_PAYMASTER_POSTOP_GAS_OFFSET:_PAYMASTER_DATA_OFFSET]))
-                ) * 10 * userOp.unpackMaxFeePerGas()
+                ) * 10 //* userOp.unpackMaxFeePerGas()
             ) / 100;
 
             // Get address for token used to pay
@@ -555,16 +557,17 @@ contract BiconomyTokenPaymaster is
                 revert InsufficientTokenBalance(userOp.sender, tokenAddress, tokenAmount, userOpHash);
             }
 
-            context =
+            context = abi.encodePacked(
+                PaymasterMode.INDEPENDENT,
                 abi.encode(
-                    mode,
                     userOp.sender,
                     tokenAddress,
                     maxPenalty,
                     tokenPrice,
                     priceMarkup,
                     userOpHash
-                );
+                )
+            );
             validationData = 0; // Validation success and price is valid indefinetly
         }
     }
@@ -585,10 +588,8 @@ contract BiconomyTokenPaymaster is
         internal
         override
     {   
-
-        PaymasterMode mode = PaymasterMode(uint8(context[0]));
-
-        if (mode == PaymasterMode.EXTERNAL) {
+        PaymasterMode pmMode = PaymasterMode(uint8(context[0]));
+        if (pmMode == PaymasterMode.EXTERNAL) {
             // Decode context data
             (
                 address userOpSender,
@@ -603,7 +604,7 @@ contract BiconomyTokenPaymaster is
                 revert FailedToChargeTokens(userOpSender, tokenAddress, estimatedTokenAmount, userOpHash);
             }
 
-        } else if (mode == PaymasterMode.INDEPENDENT) {
+        } else if (pmMode == PaymasterMode.INDEPENDENT) {
             (
                 address userOpSender,
                 address tokenAddress,

test/base/TestBase.sol

@@ -14,6 +14,9 @@ import { Exec } from "account-abstraction/utils/Exec.sol";
 import { IPaymaster } from "account-abstraction/interfaces/IPaymaster.sol";
 
 import { Nexus } from "@nexus/contracts/Nexus.sol";
+import { INexus } from "@nexus/contracts/interfaces/INexus.sol";
+import { IERC7579Account } from "@nexus/contracts/interfaces/IERC7579Account.sol";
+import { IExecutionHelper } from "@nexus/contracts/interfaces/base/IExecutionHelper.sol";
 import { CheatCodes } from "@nexus/test/foundry/utils/CheatCodes.sol";
 import { BaseEventsAndErrors } from "./BaseEventsAndErrors.sol";
 import { MockToken } from "@nexus/contracts/mocks/MockToken.sol";
@@ -479,10 +482,10 @@ abstract contract TestBase is CheatCodes, TestHelper, BaseEventsAndErrors {
         // Assert we never undercharge
         assertGe(gasPaidBySAInNativeTokens, BUNDLER.addr.balance - initialBundlerBalance);
 
-        // Ensure that max 2% difference between what is should have been charged and what was charged
+        // Ensure that max 3% difference between what should have been charged and what was charged
         // this difference comes from difference of postop gas and estimated postop gas (paymaster.unaccountedGas)
         // and from estimation of real penalty which is not emitted by EP :(
-        assertApproxEqRel((totalGasFeePaid + maxPenalty - realPenalty) * priceMarkup / _PRICE_MARKUP_DENOMINATOR, gasPaidBySAInNativeTokens, 0.02e18, "If this fails, check the test case inline comments");
+        assertApproxEqRel((totalGasFeePaid + maxPenalty - realPenalty) * priceMarkup / _PRICE_MARKUP_DENOMINATOR, gasPaidBySAInNativeTokens, 0.03e18, "If this fails, check the test case inline comments");
     }
 
     function _toSingletonArray(address addr) internal pure returns (address[] memory) {

test/unit/concrete/TestTokenPaymaster.Base.t.sol

@@ -111,9 +111,6 @@ contract TestTokenPaymasterBase is TestBase {
         PackedUserOperation[] memory ops = new PackedUserOperation[](1);
         ops[0] = userOp;
 
-        vm.expectEmit(true, true, false, false, address(tokenPaymaster));
-        emit IBiconomyTokenPaymaster.TokensRefunded(address(ALICE_ACCOUNT), address(usdc), 0, bytes32(0));
-
         vm.expectEmit(true, true, false, false, address(tokenPaymaster));
         emit IBiconomyTokenPaymaster.PaidGasInTokensIndependent(address(ALICE_ACCOUNT), address(usdc), 0, 0, 1e6, 0, bytes32(0));
 

test/unit/concrete/TestTokenPaymaster.t.sol

@@ -407,7 +407,11 @@ contract TestTokenPaymaster is TestBase {
         uint256 initialPaymasterTokenBalance = testToken.balanceOf(address(tokenPaymaster));
 
         // Build the user operation for external mode
-        PackedUserOperation memory userOp = buildUserOpWithCalldata(ALICE, "", address(VALIDATOR_MODULE));
+        PackedUserOperation memory userOp = buildUserOpWithCalldata(
+            ALICE, 
+            abi.encodeWithSelector(IExecutionHelper.execute.selector, bytes32(0), abi.encodePacked(address(testToken), uint256(0), abi.encodeWithSelector(IERC20.approve.selector, address(tokenPaymaster), 1_000*1e18))), 
+            address(VALIDATOR_MODULE)
+        );
         uint48 validUntil = uint48(block.timestamp + 1 days);
         uint48 validAfter = uint48(block.timestamp);
         uint256 tokenPrice = 1e18; // Assume 1 token = 1 native token = 1 USD ?
@@ -420,7 +424,7 @@ contract TestTokenPaymaster is TestBase {
             validUntil: validUntil,
             validAfter: validAfter,
             tokenAddress: address(testToken),
-            estimatedTokenAmount: 1e18
+            estimatedTokenAmount: 3_000_000_000_000
         });
 
         // Generate and sign the token paymaster data
@@ -437,9 +441,6 @@ contract TestTokenPaymaster is TestBase {
         PackedUserOperation[] memory ops = new PackedUserOperation[](1);
         ops[0] = userOp;
 
-        vm.expectEmit(true, true, false, false, address(tokenPaymaster));
-        emit IBiconomyTokenPaymaster.TokensRefunded(address(ALICE_ACCOUNT), address(testToken), 0, bytes32(0));
-
         vm.expectEmit(true, true, false, false, address(tokenPaymaster));
         emit IBiconomyTokenPaymaster.PaidGasInTokensExternal(address(ALICE_ACCOUNT), address(testToken), 0, bytes32(0));
 
@@ -471,7 +472,7 @@ contract TestTokenPaymaster is TestBase {
         vm.stopPrank();
 
         vm.startPrank(PAYMASTER_OWNER.addr);
-        tokenPaymaster.setUnaccountedGas(20_000);
+        tokenPaymaster.setUnaccountedGas(40_000);
         vm.stopPrank();
 
         uint256 initialBundlerBalance = BUNDLER.addr.balance;
@@ -495,10 +496,10 @@ contract TestTokenPaymaster is TestBase {
 
         PackedUserOperation[] memory ops = new PackedUserOperation[](1);
         ops[0] = userOp;
-        vm.expectEmit(true, true, false, false, address(tokenPaymaster));
-        emit IBiconomyTokenPaymaster.TokensRefunded(address(ALICE_ACCOUNT), address(testToken), 0, bytes32(0));
+
         vm.expectEmit(true, true, false, false, address(tokenPaymaster));
         emit IBiconomyTokenPaymaster.PaidGasInTokensIndependent(address(ALICE_ACCOUNT), address(testToken), 0, 0, 1e6, 0, bytes32(0));
+
         startPrank(BUNDLER.addr);
         uint256 gasValue = gasleft();   
         ENTRYPOINT.handleOps(ops, payable(BUNDLER.addr));