cctp: gas drop-off fix

- use wormhole circle relayer instead of token bridge relayer to compute
max swap and gas drop-off amounts
- the connect interface specifies a percentage that is applied to the
the max swap amount to get the gas drop-off amount

Author: kev1n-peters

connect/src/protocols/cctp/cctpTransfer.ts

@@ -34,7 +34,13 @@ import type {
   TransferQuote,
   TransferReceipt as _TransferReceipt,
 } from "../../types.js";
-import { TransferState, isAttested, isSourceFinalized, isSourceInitiated } from "../../types.js";
+import {
+  TransferState,
+  isAttested,
+  isRedeemed,
+  isSourceFinalized,
+  isSourceInitiated,
+} from "../../types.js";
 import { Wormhole } from "../../wormhole.js";
 import type { WormholeTransfer } from "../wormholeTransfer.js";
 import { finality } from "@wormhole-foundation/sdk-base";
@@ -537,7 +543,7 @@ export namespace CircleTransfer {
     // Fall back to asking the destination chain if this VAA has been redeemed
     // assuming we have the full attestation
 
-    if (isAttested(receipt)) {
+    if (isAttested(receipt) || isRedeemed(receipt)) {
       const isComplete = await CircleTransfer.isTransferComplete(
         _toChain,
         receipt.attestation.attestation,
@@ -605,15 +611,15 @@ export namespace CircleTransfer {
 
     // The fee is also removed from the amount transferred
     // quoted on the source chain
-    const stb = await srcChain.getAutomaticCircleBridge();
-    const fee = await stb.getRelayerFee(dstChain.chain);
+    const scb = await srcChain.getAutomaticCircleBridge();
+    const fee = await scb.getRelayerFee(dstChain.chain);
     dstAmount -= fee;
 
     // The expected destination gas can be pulled from the destination token bridge
     let destinationNativeGas = 0n;
     if (transfer.nativeGas) {
-      const dtb = await dstChain.getAutomaticTokenBridge();
-      destinationNativeGas = await dtb.nativeTokenAmount(dstToken.address, _nativeGas);
+      const dcb = await dstChain.getAutomaticCircleBridge();
+      destinationNativeGas = await dcb.nativeTokenAmount(_nativeGas);
     }
 
     return {

connect/src/routes/cctp/automatic.ts

@@ -168,7 +168,7 @@ export class AutomaticCCTPRoute<N extends Network>
       );
     }
 
-    const transferableAmount = amount.units(amt) - fee;
+    const redeemableAmount = amount.units(amt) - fee;
 
     const options = params.options ?? this.getDefaultOptions();
 
@@ -179,9 +179,21 @@ export class AutomaticCCTPRoute<N extends Network>
     let nativeGasAmount = 0n;
 
     if (nativeGasPerc > 0.0) {
+      const dcb = await request.toChain.getAutomaticCircleBridge();
+      let maxSwapAmount = await dcb.maxSwapAmount();
+      if (redeemableAmount < maxSwapAmount) {
+        // can't swap more than the receivable amount
+        maxSwapAmount = redeemableAmount;
+      }
+
       const scale = 10000;
-      const scaledGas = BigInt(nativeGasPerc * scale);
-      nativeGasAmount = (transferableAmount * scaledGas) / BigInt(scale);
+      const scaledGas = BigInt(Math.floor(nativeGasPerc * scale));
+      // the native gas percentage is applied to the max swap amount
+      nativeGasAmount = (maxSwapAmount * scaledGas) / BigInt(scale);
+      if (nativeGasAmount === redeemableAmount && nativeGasAmount > 0n) {
+        // edge case: transfer will revert if the native gas amount is equal to the redeemable amount
+        nativeGasAmount -= 1n;
+      }
     }
 
     return {

core/definitions/src/protocols/circleBridge/circleBridge.ts

@@ -187,4 +187,8 @@ export interface AutomaticCircleBridge<N extends Network = Network, C extends Ch
     amount: bigint,
     nativeGas?: bigint,
   ): AsyncGenerator<UnsignedTransaction<N, C>>;
+  /** Amount of native tokens a user would receive by swapping x amount of sending tokens */
+  nativeTokenAmount(amount: bigint): Promise<bigint>;
+  /** Maximum amount of sending tokens that can be swapped for native tokens */
+  maxSwapAmount(): Promise<bigint>;
 }

platforms/evm/protocols/cctp/src/automaticCircleBridge.ts

@@ -163,4 +163,15 @@ export class EvmAutomaticCircleBridge<N extends Network, C extends EvmChains>
       parallelizable,
     );
   }
+
+  async nativeTokenAmount(amount: bigint): Promise<bigint> {
+    return await this.circleRelayer.calculateNativeSwapAmountOut(
+      this.tokenAddr,
+      amount,
+    );
+  }
+
+  async maxSwapAmount(): Promise<bigint> {
+    return await this.circleRelayer.calculateMaxSwapAmountIn(this.tokenAddr);
+  }
 }