feat(relayer): add relayer service boilerplate

.github/workflows/relayer-build.yml

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+name: Relayer
+
+on:
+  push:
+    branches: [dev]
+  pull_request:
+
+env:
+  RPC_URL: "http://localhost:8545"
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-22.04
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 9
+
+      - name: Use Node.js 20
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: "pnpm"
+
+      - name: Install
+        run: |
+          pnpm install --frozen-lockfile --prefer-offline
+
+      - name: Build
+        run: |
+          pnpm run build
+
+      - name: Run hardhat
+        run: |
+          pnpm run hardhat &
+          sleep 5
+        working-directory: apps/relayer
+
+      - name: Test
+        run: pnpm run test:coverage
+        working-directory: apps/relayer
+
+      - name: Stop Hardhat
+        if: always()
+        run: kill $(lsof -t -i:8545)

apps/relayer/.env.example

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+# Rate limit configuation
+TTL=60000
+LIMIT=10
+
+# Coordinator RPC url
+RELAYER_RPC_URL=http://localhost:8545
+
+# Allowed origin host, use comma to separate each of them
+ALLOWED_ORIGINS=
+
+# Specify port for coordinator service (optional)
+PORT=
+
+# Mnemonic phrase
+MNEMONIC=""

apps/relayer/.eslintrc.cjs

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+const path = require("path");
+
+module.exports = {
+  root: true,
+  env: {
+    node: true,
+    jest: true,
+  },
+  extends: ["../../.eslintrc.js"],
+  parser: "@typescript-eslint/parser",
+  parserOptions: {
+    project: path.resolve(__dirname, "./tsconfig.json"),
+    sourceType: "module",
+    typescript: true,
+    ecmaVersion: 2022,
+    experimentalDecorators: true,
+    requireConfigFile: false,
+    ecmaFeatures: {
+      classes: true,
+      impliedStrict: true,
+    },
+    warnOnUnsupportedTypeScriptVersion: true,
+  },
+  overrides: [
+    {
+      files: ["./ts/**/*.module.ts"],
+      rules: {
+        "@typescript-eslint/no-extraneous-class": "off",
+      },
+    },
+  ],
+};

apps/relayer/.gitignore

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+build/
+coverage/
+.env

apps/relayer/README.md

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+# Relayer service
+
+## Instructions
+
+1. Add `.env` file (see `.env.example`).

apps/relayer/hardhat.config.cjs

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+/* eslint-disable @typescript-eslint/no-var-requires */
+require("@nomicfoundation/hardhat-toolbox");
+const dotenv = require("dotenv");
+
+const path = require("path");
+
+dotenv.config();
+
+const parentDir = __dirname.includes("build") ? ".." : "";
+const TEST_MNEMONIC = "test test test test test test test test test test test junk";
+
+module.exports = {
+  defaultNetwork: "hardhat",
+  networks: {
+    localhost: {
+      url: process.env.RELAYER_RPC_URL || "",
+      accounts: {
+        mnemonic: process.env.MNEMONIC || TEST_MNEMONIC,
+        path: "m/44'/60'/0'/0",
+        initialIndex: 0,
+        count: 20,
+      },
+      loggingEnabled: false,
+    },
+    hardhat: {
+      loggingEnabled: false,
+    },
+  },
+  paths: {
+    sources: path.resolve(__dirname, parentDir, "./node_modules/maci-contracts/contracts"),
+    artifacts: path.resolve(__dirname, parentDir, "./node_modules/maci-contracts/build/artifacts"),
+  },
+};

apps/relayer/nest-cli.json

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+{
+  "$schema": "https://json.schemastore.org/nest-cli",
+  "collection": "@nestjs/schematics",
+  "sourceRoot": "ts",
+  "compilerOptions": {
+    "deleteOutDir": true
+  }
+}

apps/relayer/package.json

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+{
+  "name": "maci-relayer",
+  "version": "0.1.0",
+  "private": true,
+  "description": "Relayer service for MACI",
+  "main": "build/ts/main.js",
+  "type": "module",
+  "exports": {
+    ".": "./build/ts/main.js"
+  },
+  "files": [
+    "build",
+    "CHANGELOG.md",
+    "README.md"
+  ],
+  "scripts": {
+    "hardhat": "hardhat node",
+    "build": "nest build",
+    "run:node": "node --import 'data:text/javascript,import { register } from \"node:module\"; import { pathToFileURL } from \"node:url\"; register(\"ts-node/esm\", pathToFileURL(\"./\"));'",
+    "start": "pnpm run run:node ./ts/main.ts",
+    "start:prod": "pnpm run run:node build/ts/main.js",
+    "test": "jest --forceExit",
+    "test:coverage": "jest --coverage --forceExit",
+    "types": "tsc -p tsconfig.json --noEmit"
+  },
+  "dependencies": {
+    "@nestjs/common": "^10.4.7",
+    "@nestjs/core": "^10.4.7",
+    "@nestjs/platform-express": "^10.4.7",
+    "@nestjs/platform-socket.io": "^10.3.10",
+    "@nestjs/swagger": "^8.0.3",
+    "@nestjs/throttler": "^6.3.0",
+    "@nestjs/websockets": "^10.4.7",
+    "@nomicfoundation/hardhat-ethers": "^3.0.8",
+    "@nomicfoundation/hardhat-toolbox": "^5.0.0",
+    "class-transformer": "^0.5.1",
+    "class-validator": "^0.14.1",
+    "date-fns": "^4.1.0",
+    "dotenv": "^16.4.5",
+    "ethers": "^6.13.4",
+    "hardhat": "^2.22.15",
+    "helmet": "^8.0.0",
+    "maci-contracts": "workspace:^2.5.0",
+    "mustache": "^4.2.0",
+    "reflect-metadata": "^0.2.0",
+    "rxjs": "^7.8.1",
+    "ts-node": "^10.9.1"
+  },
+  "devDependencies": {
+    "@nestjs/cli": "^10.4.2",
+    "@nestjs/schematics": "^10.1.2",
+    "@nestjs/testing": "^10.4.15",
+    "@types/express": "^5.0.0",
+    "@types/jest": "^29.5.2",
+    "@types/node": "^22.10.5",
+    "@types/supertest": "^6.0.2",
+    "fast-check": "^3.23.1",
+    "jest": "^29.5.0",
+    "supertest": "^7.0.0",
+    "ts-jest": "^29.2.5",
+    "typescript": "^5.7.2"
+  },
+  "jest": {
+    "testTimeout": 900000,
+    "moduleFileExtensions": [
+      "js",
+      "json",
+      "ts"
+    ],
+    "rootDir": ".",
+    "roots": [
+      "<rootDir>/ts",
+      "<rootDir>/tests"
+    ],
+    "testRegex": ".*\\.test\\.ts$",
+    "transform": {
+      "^.+\\.js$": [
+        "<rootDir>/ts/jest/transform.js",
+        {
+          "useESM": true
+        }
+      ],
+      "^.+\\.(t|j)s$": [
+        "ts-jest",
+        {
+          "useESM": true
+        }
+      ]
+    },
+    "collectCoverageFrom": [
+      "**/*.(t|j)s",
+      "!<rootDir>/ts/main.ts",
+      "!<rootDir>/ts/jest/*.js",
+      "!<rootDir>/hardhat.config.js"
+    ],
+    "coveragePathIgnorePatterns": [
+      "<rootDir>/ts/sessionKeys/__tests__/utils.ts"
+    ],
+    "coverageDirectory": "<rootDir>/coverage",
+    "testEnvironment": "node"
+  }
+}

apps/relayer/tests/app.test.ts

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+import { HttpStatus, ValidationPipe, type INestApplication } from "@nestjs/common";
+import { Test } from "@nestjs/testing";
+import request from "supertest";
+
+import type { App } from "supertest/types";
+
+import { AppModule } from "../ts/app.module";
+
+describe("e2e", () => {
+  let app: INestApplication;
+
+  beforeAll(async () => {
+    const moduleFixture = await Test.createTestingModule({
+      imports: [AppModule],
+    }).compile();
+
+    app = moduleFixture.createNestApplication();
+    app.useGlobalPipes(new ValidationPipe({ transform: true }));
+    await app.listen(3000);
+  });
+
+  afterAll(async () => {
+    await app.close();
+  });
+
+  test("should throw an error if api is not found", async () => {
+    const result = await request(app.getHttpServer() as App)
+      .get("/unknown")
+      .send()
+      .expect(404);
+
+    expect(result.body).toStrictEqual({
+      error: "Not Found",
+      statusCode: HttpStatus.NOT_FOUND,
+      message: "Cannot GET /unknown",
+    });
+  });
+});

apps/relayer/ts/app.module.ts

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+import { Module } from "@nestjs/common";
+import { ThrottlerModule } from "@nestjs/throttler";
+
+@Module({
+  imports: [
+    ThrottlerModule.forRoot([
+      {
+        ttl: Number(process.env.TTL),
+        limit: Number(process.env.LIMIT),
+      },
+    ]),
+  ],
+})
+export class AppModule {}

apps/relayer/ts/jest/setup.ts

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+import type { HardhatEthersHelpers } from "@nomicfoundation/hardhat-ethers/types";
+import type { ethers } from "ethers";
+
+declare module "hardhat/types/runtime" {
+  interface HardhatRuntimeEnvironment {
+    // We omit the ethers field because it is redundant.
+    ethers: typeof ethers & HardhatEthersHelpers;
+  }
+}

apps/relayer/ts/jest/transform.js

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+/* eslint-disable */
+
+export function process(sourceText) {
+  return {
+    code: sourceText.replace("#!/usr/bin/env node", ""),
+  };
+}
+
+export default {
+  process,
+};

apps/relayer/ts/main.ts

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+import { ValidationPipe } from "@nestjs/common";
+import { NestFactory } from "@nestjs/core";
+import { SwaggerModule, DocumentBuilder } from "@nestjs/swagger";
+import dotenv from "dotenv";
+import helmet from "helmet";
+
+import path from "path";
+import url from "url";
+
+/* eslint-disable no-underscore-dangle */
+/* eslint-disable @typescript-eslint/no-shadow */
+const __filename = url.fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+/* eslint-enable no-underscore-dangle */
+/* eslint-disable @typescript-eslint/no-shadow */
+
+dotenv.config({
+  path: [path.resolve(__dirname, "../.env"), path.resolve(__dirname, "../.env.example")],
+});
+
+async function bootstrap() {
+  const { AppModule } = await import("./app.module");
+  const app = await NestFactory.create(AppModule, {
+    logger: ["log", "fatal", "error", "warn"],
+  });
+
+  app.useGlobalPipes(new ValidationPipe({ transform: true }));
+  app.use(
+    helmet({
+      contentSecurityPolicy: {
+        directives: {
+          defaultSrc: [`'self'`],
+          styleSrc: [`'self'`, `'unsafe-inline'`],
+          imgSrc: [`'self'`, "data:", "validator.swagger.io"],
+          scriptSrc: [`'self'`, `https: 'unsafe-inline'`],
+        },
+      },
+    }),
+  );
+  app.enableCors({ origin: process.env.ALLOWED_ORIGINS?.split(",") });
+
+  const config = new DocumentBuilder()
+    .setTitle("Relayer service")
+    .setDescription("Relayer service API methods")
+    .setVersion("1.0")
+    .addTag("relayer")
+    .addBearerAuth()
+    .build();
+  const document = SwaggerModule.createDocument(app, config);
+  SwaggerModule.setup("api", app, document);
+
+  await app.listen(process.env.PORT || 3000);
+}
+
+bootstrap();