Merge branch 'main' of github.com:connext/nxtp

connext · Oct 26, 2021 · 32d229b · 32d229b
2 parents a695bb1 + 855fde5
commit 32d229b
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Showing 2 changed files with 64 additions and 4 deletions.
diff --git a/packages/router/src/lib/helpers/shared.ts b/packages/router/src/lib/helpers/shared.ts
@@ -15,6 +15,7 @@ export const getNtpTimeSeconds = async () => {
 /**
  * Helper to calculate router gas fee in token
  *
+ * @param sendingAssetId The asset address on source chain
  * @param sendingChainId The source chain Id
  * @param receivingAssetId The asset address on destination chain
  * @param receivingChainId The destination chain Id
@@ -71,6 +72,47 @@ export const calculateGasFeeInReceivingToken = async (
 
   return totalCost;
 };
+
+/**
+ * Helper to calculate router gas fee in token for meta transaction
+ *
+ * @param receivingAssetId The asset address on destination chain
+ * @param receivingChainId The destination chain Id
+ * @param outputDecimals Decimal number of receiving asset
+ * @param requestContext Request context instance
+ */
+export const calculateGasFeeInReceivingTokenForFulfill = async (
+  receivingAssetId: string,
+  receivingChainId: number,
+  outputDecimals: number,
+  requestContext: RequestContext,
+): Promise<BigNumber> => {
+  const chaindIdsForGasFee = getChainIdForGasFee();
+
+  if (!chaindIdsForGasFee.includes(receivingChainId)) return constants.Zero;
+  let totalCost = constants.Zero;
+
+  if (chaindIdsForGasFee.includes(receivingChainId)) {
+    const gasLimitForFulfill = BigNumber.from(GAS_ESTIMATES.fulfill);
+    const ethPriceInReceivingChain = await getTokenPrice(receivingChainId, constants.AddressZero, requestContext);
+    const receivingTokenPrice = await getTokenPrice(receivingChainId, receivingAssetId, requestContext);
+    const gasPriceInReceivingChain = await getGasPrice(receivingChainId, requestContext);
+
+    const gasAmountInUsd = gasPriceInReceivingChain.mul(gasLimitForFulfill).mul(ethPriceInReceivingChain);
+    const tokenAmountForGasFee = receivingTokenPrice.isZero()
+      ? constants.Zero
+      : gasAmountInUsd.div(receivingTokenPrice).div(BigNumber.from(10).pow(18 - outputDecimals));
+
+    console.log("gasLimitForFulfill = ", gasLimitForFulfill.toString());
+    console.log("gasPriceInReceivingChain = ", gasPriceInReceivingChain.toString());
+    console.log("ethPriceInReceivingChain = ", ethPriceInReceivingChain.toString());
+    console.log("receivingTokenPrice = ", receivingTokenPrice.toString());
+    totalCost = totalCost.add(tokenAmountForGasFee);
+  }
+
+  return totalCost;
+};
+
 /**
  * Gets token price in usd from price oracle
  *

diff --git a/packages/router/src/lib/operations/fulfill.ts b/packages/router/src/lib/operations/fulfill.ts
@@ -11,6 +11,7 @@ import { getContext } from "../../router";
 import { FulfillInput, FulfillInputSchema } from "../entities";
 import { NoChainConfig, ParamsInvalid, NotEnoughRelayerFee } from "../errors";
 import { NotAllowedFulfillRelay } from "../errors/fulfill";
+import { calculateGasFeeInReceivingTokenForFulfill } from "../helpers/shared";
 
 export const fulfill = async (
   invariantData: InvariantTransactionData,
@@ -19,7 +20,7 @@ export const fulfill = async (
 ): Promise<providers.TransactionReceipt | undefined> => {
   const { requestContext, methodContext } = createLoggingContext(fulfill.name, _requestContext);
 
-  const { logger, contractWriter, config } = getContext();
+  const { logger, contractWriter, config, chainData, txService } = getContext();
   logger.info("Method start", requestContext, methodContext, { invariantData, input });
 
   // Validate InvariantData schema
@@ -73,9 +74,26 @@ export const fulfill = async (
       });
     }
 
-    const recvAmountLowerBound = BigNumber.from(amount)
-      .mul(100 - relayerFeeLowerBound)
-      .div(100);
+    let outputDecimals = chainData.get(invariantData.receivingChainId.toString())?.assetId[
+      invariantData.receivingAssetId
+    ]?.decimals;
+    if (!outputDecimals) {
+      outputDecimals = await txService.getDecimalsForAsset(
+        invariantData.receivingChainId,
+        invariantData.receivingAssetId,
+      );
+    }
+    logger.info("Got output decimals", requestContext, methodContext, { outputDecimals });
+    const expectedFulfillFee = await calculateGasFeeInReceivingTokenForFulfill(
+      invariantData.receivingAssetId,
+      invariantData.receivingChainId,
+      outputDecimals,
+      requestContext,
+    );
+    logger.info("Expected Fulfill fee in router side", requestContext, methodContext, {
+      expectedFulfillFee: expectedFulfillFee.toString(),
+    });
+    const recvAmountLowerBound = expectedFulfillFee.mul(100 - relayerFeeLowerBound).div(100);
 
     if (BigNumber.from(amount).sub(input.relayerFee).lt(recvAmountLowerBound)) {
       throw new NotEnoughRelayerFee(fulfillChain, {