Batch Drafting w. Fixed Fee (#14)

This PR introduces the invoking of "draft" and "fine" in a single transaction as a Multisend. 
For simplification we still use the Fixed Fee Model. In a follow up, we will introduce dynamic fines calculated based on gas estimation.

.github/workflows/pull-request.yaml

@@ -31,3 +31,4 @@ jobs:
           RPC_URL: https://rpc2.sepolia.org
           BILLING_CONTRACT_ADDRESS: "0xF1436859a0F04A827b79F8c92736F6331ebB64A1"
           ROLE_KEY: "0x6d622d6472616674000000000000000000000000000000000000000000000000"
+          FINE_FEE: 3

package.json

@@ -14,6 +14,7 @@
   "license": "MIT",
   "dependencies": {
     "@duneanalytics/client-sdk": "^0.1.5",
+    "@ethersproject/bytes": "^5.7.0",
     "@types/node": "^20.11.30",
     "ethers": "^6.12.0",
     "loglevel": "^1.9.1",

src/abis.ts

@@ -7,3 +7,5 @@ export const BILLING_CONTRACT_ABI = [
 export const ROLE_MODIFIER_ABI = [
   "function execTransactionWithRole(address to, uint256 value, bytes data, uint8 operation, bytes32 roleKey, bool shouldRevert) returns (bool success)",
 ];
+
+export const MULTI_SEND_ABI = ["function multiSend(bytes memory transactions)"];

src/billingContract.ts

@@ -1,6 +1,7 @@
 import { ethers, formatEther } from "ethers";
 import { BillingData, LatestBillingStatus, PaymentStatus } from "./types";
 import { BILLING_CONTRACT_ABI, ROLE_MODIFIER_ABI } from "./abis";
+import { MetaTransaction, encodeMulti } from "./multisend";
 
 interface BillingInput {
   addresses: `0x${string}`[];
@@ -12,6 +13,7 @@ export class BillingContract {
   readonly contract: ethers.Contract;
   readonly roleContract: ethers.Contract;
   private roleKey?: string;
+  fineRecipient: ethers.AddressLike;
   fineAmount: bigint;
 
   constructor(
@@ -26,6 +28,7 @@ export class BillingContract {
       ROLE_MODIFIER_ABI,
       signer,
     );
+    this.fineRecipient = signer.address;
     this.roleKey = roleKey;
     if (!roleKey) {
       console.warn(
@@ -69,7 +72,7 @@ export class BillingContract {
 
   async processPaymentStatuses(
     paymentStatuses: LatestBillingStatus[],
-  ): Promise<string[]> {
+  ): Promise<string> {
     const unpaidRecords = paymentStatuses.filter((record) => {
       const { account, status, paidAmount, billedAmount } = record;
       if (status == PaymentStatus.UNPAID) {
@@ -85,34 +88,49 @@ export class BillingContract {
       }
       return false;
     });
-    // These drafts must be processed sequentially
-    // Otherwise the owner account nonce will not be incremented.
-    const resultHashes = [];
+    let txBatch: MetaTransaction[] = [];
     for (const rec of unpaidRecords) {
-      console.log(`Executing draft for ${rec.account}...`);
-      const draftHash = await this.draft(
-        rec.account,
-        rec.billedAmount - rec.paidAmount,
+      console.log(`Attaching Draft and Fine for ${rec.account}...`);
+      txBatch.push(
+        await this.buildDraft(rec.account, rec.billedAmount - rec.paidAmount),
       );
-      resultHashes.push(draftHash);
       if (this.fineAmount > 0) {
-        console.log(`Executing fine for ${rec.account}...`);
-        const fineHash = await this.fine(rec.account, this.fineAmount);
-        resultHashes.push(fineHash);
+        txBatch.push(
+          await this.buildFine(
+            rec.account,
+            this.fineAmount,
+            this.fineRecipient,
+          ),
+        );
       }
     }
-    return resultHashes;
+    console.log(txBatch);
+    const tx = await this.execWithRole(txBatch, this.roleKey!);
+    await tx.wait();
+    return tx.hash;
+  }
+
+  async buildDraft(
+    account: `0x${string}`,
+    amount: bigint,
+  ): Promise<MetaTransaction> {
+    return {
+      to: await this.contract.getAddress(),
+      data: this.contract.interface.encodeFunctionData("draft", [
+        account,
+        amount,
+      ]),
+      value: 0,
+      operation: 0,
+    };
   }
 
   async draft(account: `0x${string}`, amount: bigint): Promise<string> {
     try {
       let tx: ethers.ContractTransactionResponse;
       if (this.roleKey) {
         tx = await this.execWithRole(
-          this.contract.interface.encodeFunctionData("draft", [
-            account,
-            amount,
-          ]),
+          [await this.buildDraft(account, amount)],
           this.roleKey,
         );
       } else {
@@ -126,18 +144,33 @@ export class BillingContract {
     }
   }
 
-  async fine(account: `0x${string}`, amount: bigint): Promise<string> {
+  async buildFine(
+    account: ethers.AddressLike,
+    amount: bigint,
+    feeRecipient: ethers.AddressLike,
+  ): Promise<MetaTransaction> {
+    return {
+      to: await this.contract.getAddress(),
+      data: this.contract.interface.encodeFunctionData("fine", [
+        account,
+        amount,
+        feeRecipient,
+      ]),
+      value: 0,
+      operation: 0,
+    };
+  }
+
+  async fine(
+    account: `0x${string}`,
+    amount: bigint,
+    feeRecipient: `0x${string}`,
+  ): Promise<string> {
     try {
       let tx: ethers.ContractTransactionResponse;
-      // Fee Recipient is MEVBlockerFeeTill Contract.
-      const feeRecipient = await this.contract.getAddress();
       if (this.roleKey) {
         tx = await this.execWithRole(
-          this.contract.interface.encodeFunctionData("fine", [
-            account,
-            amount,
-            feeRecipient,
-          ]),
+          [await this.buildFine(account, amount, feeRecipient)],
           this.roleKey,
         );
       } else {
@@ -152,14 +185,22 @@ export class BillingContract {
   }
 
   async execWithRole(
-    data: string,
+    metaTransactions: MetaTransaction[],
     roleKey: string,
   ): Promise<ethers.ContractTransactionResponse> {
+    if (metaTransactions.length === 0)
+      throw new Error("No transactions to execute");
+
+    // Combine transactions into one.
+    const metaTx =
+      metaTransactions.length === 1
+        ? metaTransactions[0]
+        : encodeMulti(metaTransactions);
     return this.roleContract.execTransactionWithRole(
-      this.contract.getAddress(), // to
-      0, // value
-      data,
-      0, // operation
+      metaTx.to,
+      metaTx.value,
+      metaTx.data,
+      metaTx.operation,
       roleKey,
       true, // shouldRevert
     );

src/multisend.ts

@@ -0,0 +1,66 @@
+import { ethers } from "ethers";
+import { hexDataLength } from "@ethersproject/bytes";
+import { MULTI_SEND_ABI } from "./abis";
+
+export const MULTISEND_141 = "0x38869bf66a61cF6bDB996A6aE40D5853Fd43B526";
+const MULTISEND_CALLONLY_141 = "0x9641d764fc13c8B624c04430C7356C1C7C8102e2";
+
+export enum OperationType {
+  Call = 0,
+  DelegateCall = 1,
+}
+/**
+ *
+ */
+export interface MetaTransaction {
+  /// A `uint8` with `0` for a `call` or `1` for a `delegatecall` (=> 1 byte),
+  readonly operation?: OperationType;
+  /// `to` as an `address` (=> 20 bytes),
+  readonly to: string;
+  /// ETH value of the transaction (uint256)
+  readonly value: ethers.BigNumberish;
+  /// Transaction call data (bytes)
+  readonly data: string;
+}
+
+const remove0x = (hexString: string) => hexString.slice(2);
+
+/**
+ * Encodes the MetaTransaction as packed bytes
+ */
+export function encodeMetaTransaction(metaTx: MetaTransaction): string {
+  const types = ["uint8", "address", "uint256", "uint256", "bytes"];
+  const values = [
+    // Default to CALL if operation is undefined
+    metaTx.operation ?? OperationType.Call,
+    metaTx.to,
+    metaTx.value,
+    hexDataLength(metaTx.data),
+    metaTx.data,
+  ];
+  return ethers.solidityPacked(types, values);
+}
+
+export const encodeMulti = (
+  transactions: readonly MetaTransaction[],
+  multiSendContractAddress: string = transactions.some(
+    (t) => t.operation && t.operation === OperationType.DelegateCall,
+  )
+    ? MULTISEND_141
+    : MULTISEND_CALLONLY_141,
+): MetaTransaction => {
+  const transactionsEncoded =
+    "0x" + transactions.map(encodeMetaTransaction).map(remove0x).join("");
+
+  const multiSendContract = new ethers.Interface(MULTI_SEND_ABI);
+  const data = multiSendContract.encodeFunctionData("multiSend", [
+    transactionsEncoded,
+  ]);
+
+  return {
+    operation: OperationType.DelegateCall,
+    to: multiSendContractAddress,
+    value: "0x00",
+    data,
+  };
+};

tests/e2e/e2e.test.ts

@@ -40,18 +40,16 @@ describe("e2e - Sepolia", () => {
   it("Runs the drafting flow with mainnet data on Sepolia billing contract", async () => {
     const paymentStatus = await dataFetcher.getPaymentStatus();
     const billingContract = BillingContract.fromEnv();
-    const draftingHashes =
+    const draftHash =
       await billingContract.processPaymentStatuses(paymentStatus);
     // This is a non-deterministic test.
-    console.log("Drafting Hashes");
-    expect(draftingHashes.length).toEqual(2);
+    console.log("Drafting Hashes", draftHash);
 
     const provider = billingContract.contract.runner!.provider;
-    draftingHashes.map(async (hash) => {
-      const receipt = await provider!.getTransactionReceipt(hash);
-      const logs = receipt?.logs;
-      expect(logs!.length).toEqual(1);
-    });
+    const receipt = await provider!.getTransactionReceipt(draftHash);
+    // 2 drafts + 2 fines + 2 safe module transactions.
+    const expectedLogs = 1 + 2 + 2 + 1;
+    expect(receipt?.logs!.length).toEqual(expectedLogs);
   });
 
   it.skip("e2e: successfully calls bill on BillingContract (with mock billing data)", async () => {

yarn.lock

@@ -312,6 +312,18 @@
     deprecated "^0.0.2"
     loglevel "^1.8.0"
 
+"@ethersproject/bytes@^5.7.0":
+  version "5.7.0"
+  resolved "https://registry.yarnpkg.com/@ethersproject/bytes/-/bytes-5.7.0.tgz#a00f6ea8d7e7534d6d87f47188af1148d71f155d"
+  integrity sha512-nsbxwgFXWh9NyYWo+U8atvmMsSdKJprTcICAkvbBffT75qDocbuggBU0SJiVK2MuTrp0q+xvLkTnGMPK1+uA9A==
+  dependencies:
+    "@ethersproject/logger" "^5.7.0"
+
+"@ethersproject/logger@^5.7.0":
+  version "5.7.0"
+  resolved "https://registry.yarnpkg.com/@ethersproject/logger/-/logger-5.7.0.tgz#6ce9ae168e74fecf287be17062b590852c311892"
+  integrity sha512-0odtFdXu/XHtjQXJYA3u9G0G8btm0ND5Cu8M7i5vhEcE8/HmF4Lbdqanwyv4uQTr2tx6b7fQRmgLrsnpQlmnig==
+
 "@istanbuljs/load-nyc-config@^1.0.0":
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/@istanbuljs/load-nyc-config/-/load-nyc-config-1.1.0.tgz#fd3db1d59ecf7cf121e80650bb86712f9b55eced"