feat: adding relayer fee commitment with signed message

packages/relayer/src/handlers/relayer/quote.ts

@@ -1,9 +1,12 @@
 import { NextFunction, Request, Response } from "express";
 import { getAddress } from "viem";
-import { getAssetConfig } from "../../config/index.js";
+import { getAssetConfig, getFeeReceiverAddress } from "../../config/index.js";
 import { QuoterError } from "../../exceptions/base.exception.js";
 import { quoteProvider, web3Provider } from "../../providers/index.js";
 import { QuoteMarshall } from "../../types.js";
+import { encodeWithdrawalData } from "../../utils.js";
+
+const TIME_20_SECS = 20 * 1000;
 
 export async function relayQuoteHandler(
   req: Request,
@@ -25,11 +28,28 @@ export async function relayQuoteHandler(
   const quote = await quoteProvider.quoteNativeTokenInERC20(chainId, tokenAddress, amountIn);
   const feeBPS = await quoteProvider.quoteFeeBPSNative(config.fee_bps, amountIn, quote, gasPrice, value);
 
+  const recipient = req.body.recipient ? getAddress(req.body.recipient.toString()) : undefined
+
+  const quoteResponse = new QuoteMarshall({
+    baseFeeBPS: config.fee_bps,
+    feeBPS,
+  });
+
+  if (recipient) {
+    const feeReceiverAddress = getFeeReceiverAddress(chainId);
+    const withdrawalData = encodeWithdrawalData({
+      feeRecipient: getAddress(feeReceiverAddress),
+      recipient,
+      relayFeeBPS: feeBPS
+    })
+    const expiration = Number(new Date()) + TIME_20_SECS
+    const relayerCommitment = { withdrawalData, expiration };
+    const signedRelayerCommitment = await web3Provider.signRelayerCommitment(chainId, relayerCommitment);
+    quoteResponse.addFeeCommitment({ expiration, withdrawalData, signedRelayerCommitment })
+  }
+
   res
     .status(200)
-    .json(res.locals.marshalResponse(new QuoteMarshall({
-      baseFeeBPS: config.fee_bps,
-      feeBPS,
-    })));
+    .json(res.locals.marshalResponse(quoteResponse));
 
 }

packages/relayer/src/interfaces/relayer/quote.ts

@@ -8,10 +8,15 @@ export interface QuotetBody {
   /** Asset address */
   asset: string;
   /** Asset address */
-  address?: string;
+  recipient?: string;
 }
 
 export interface QuoteResponse {
   baseFeeBPS: bigint,
   feeBPS: bigint,
+  feeCommitment?: {
+    expiration: number,
+    withdrawalData: string
+    signedRelayerCommitment: string
+  }
 }

packages/relayer/src/providers/web3.provider.ts

@@ -1,14 +1,29 @@
-import { Chain, createPublicClient, http, PublicClient } from "viem";
+import { Chain, createPublicClient, Hex, http, PublicClient } from "viem";
 import {
-  CONFIG
+  CONFIG,
+  getSignerPrivateKey
 } from "../config/index.js";
 import { createChainObject } from "../utils.js";
+import { privateKeyToAccount } from "viem/accounts";
 
 interface IWeb3Provider {
   client(chainId: number): PublicClient;
   getGasPrice(chainId: number): Promise<bigint>;
 }
 
+const domain = (chainId: number) => ({
+  name: "Privacy Pools Relayer",
+  version: "1",
+  chainId,
+} as const)
+
+const RelayerCommitmentTypes = {
+  RelayerCommitment: [
+    { name: "withdrawalData", type: "bytes" },
+    { name: "expiration", type: "uint256" },
+  ]
+} as const;
+
 /**
  * Class representing the provider for interacting with several chains
  */
@@ -42,4 +57,19 @@ export class Web3Provider implements IWeb3Provider {
     return await this.client(chainId).getGasPrice()
   }
 
+  async signRelayerCommitment(chainId: number, commitment: { withdrawalData: `0x${string}`, expiration: number }) {
+    const pk = getSignerPrivateKey(chainId) as Hex;
+    const signer = privateKeyToAccount(pk);
+    const {withdrawalData, expiration} = commitment;
+    return signer.signTypedData({
+      domain: domain(chainId),
+      types: RelayerCommitmentTypes,
+      primaryType: 'RelayerCommitment',
+      message: {
+        withdrawalData,
+        expiration: BigInt(expiration)
+      }
+    })
+  }
+
 }

packages/relayer/src/schemes/relayer/quote.scheme.ts

@@ -10,7 +10,7 @@ const quoteSchema: JSONSchemaType<QuotetBody> = {
     chainId: { type: ["string", "number"] },
     amount: { type: ["string"] },
     asset: { type: ["string"] },
-    address: { type: ["string"], nullable: true },
+    recipient: { type: ["string"], nullable: true },
   },
   required: ["chainId", "amount", "asset"],
 } as const;

packages/relayer/src/types.ts

@@ -41,10 +41,20 @@ export class QuoteMarshall extends RelayerMarshall {
   constructor(readonly response: QuoteResponse) {
     super();
   }
+
+  addFeeCommitment(feeCommitment: {
+    expiration: number
+    withdrawalData: string,
+    signedRelayerCommitment: string
+  }) {
+    this.response.feeCommitment = feeCommitment;
+  }
+
   override toJSON(): object {
     return {
       baseFeeBPS: this.response.baseFeeBPS.toString(),
       feeBPS: this.response.feeBPS.toString(),
+      feeCommitment: this.response.feeCommitment
     }
   }
 }