[TaskMarket #24583] Build: Currency Converter Lucid Agent (x402 payments) Build a deployed Lucid Ag

apps/currency-converter-x402/.dockerignore

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+node_modules
+.git
+.env
+.env.local
+bun.lock
+*.log

apps/currency-converter-x402/.env.example

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+PORT=3000
+FRANKFURTER_API_BASE=https://api.frankfurter.app
+X402_PRICE_USD=0.001
+PAYMENT_SECRET=replace-with-a-long-random-secret
+PAYMENT_TTL_SECONDS=300
+PAYMENT_REALM=currency-converter
+FX_TIMEOUT_MS=8000

apps/currency-converter-x402/.gitignore

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+node_modules
+dist
+.env
+.env.local
+bun.lock
+*.log

apps/currency-converter-x402/Dockerfile

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+FROM oven/bun:1.2.8-alpine
+
+WORKDIR /app
+
+COPY package.json tsconfig.json ./
+RUN bun install
+
+COPY src ./src
+COPY scripts ./scripts
+COPY README.md ./README.md
+COPY SUBMISSION.md ./SUBMISSION.md
+
+ENV NODE_ENV=production
+ENV PORT=3000
+
+EXPOSE 3000
+
+CMD ["bun", "run", "start"]

apps/currency-converter-x402/package.json

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+{
+  "name": "currency-converter-x402-agent",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module",
+  "description": "Lucid Agent currency converter with x402 payment enforcement.",
+  "scripts": {
+    "dev": "bun --watch src/index.ts",
+    "start": "bun src/index.ts",
+    "check": "bunx tsc --noEmit",
+    "make:payment-header": "bun scripts/make-payment-header.ts"
+  },
+  "dependencies": {
+    "@lucid-agents/http": "latest",
+    "@lucid-agents/payments": "latest"
+  },
+  "devDependencies": {
+    "@types/bun": "latest",
+    "typescript": "^5.9.2"
+  }
+}

apps/currency-converter-x402/railway.json

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+{
+  "build": {
+    "builder": "NIXPACKS"
+  },
+  "deploy": {
+    "startCommand": "bun run start",
+    "restartPolicyType": "ON_FAILURE",
+    "restartPolicyMaxRetries": 10
+  }
+}

apps/currency-converter-x402/src/config.ts

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+export interface AppConfig {
+  port: number;
+  frankfurterApiBase: string;
+  priceUsd: number;
+  paymentSecret: string;
+  paymentTtlSeconds: number;
+  paymentRealm: string;
+  fxTimeoutMs: number;
+}
+
+function env(name: string): string | undefined {
+  return process.env[name];
+}
+
+function parsePort(raw: string | undefined, fallback: number): number {
+  if (!raw) return fallback;
+  const parsed = Number.parseInt(raw, 10);
+  if (!Number.isInteger(parsed) || parsed <= 0 || parsed > 65535) return fallback;
+  return parsed;
+}
+
+function parsePositiveNumber(raw: string | undefined, fallback: number): number {
+  if (!raw) return fallback;
+  const parsed = Number(raw);
+  if (!Number.isFinite(parsed) || parsed <= 0) return fallback;
+  return parsed;
+}
+
+export const appConfig: AppConfig = {
+  port: parsePort(env("PORT"), 3000),
+  frankfurterApiBase: env("FRANKFURTER_API_BASE") ?? "https://api.frankfurter.app",
+  priceUsd: parsePositiveNumber(env("X402_PRICE_USD"), 0.001),
+  paymentSecret: env("PAYMENT_SECRET") ?? "dev-only-change-me",
+  paymentTtlSeconds: parsePositiveNumber(env("PAYMENT_TTL_SECONDS"), 300),
+  paymentRealm: env("PAYMENT_REALM") ?? "currency-converter",
+  fxTimeoutMs: parsePositiveNumber(env("FX_TIMEOUT_MS"), 8000)
+};

apps/currency-converter-x402/src/fx.ts

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+export interface ConvertCurrencyInput {
+  apiBaseUrl: string;
+  from: string;
+  to: string;
+  amount: number;
+  timeoutMs: number;
+}
+
+export interface ConvertCurrencyResult {
+  result: number;
+  rate: number;
+}
+
+interface FrankfurterResponse {
+  amount: number;
+  base: string;
+  date: string;
+  rates: Record<string, number>;
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null;
+}
+
+function parseFrankfurterResponse(raw: unknown, target: string, requestedAmount: number): ConvertCurrencyResult {
+  if (!isRecord(raw)) {
+    throw new Error("Invalid FX API response shape.");
+  }
+
+  const rates = raw.rates;
+  if (!isRecord(rates)) {
+    throw new Error("FX API response missing rates.");
+  }
+
+  const rawResult = rates[target];
+  if (typeof rawResult !== "number" || !Number.isFinite(rawResult)) {
+    throw new Error(`FX API response missing rate for ${target}.`);
+  }
+
+  const result = rawResult;
+  const rate = result / requestedAmount;
+
+  return { result, rate };
+}
+
+export async function convertCurrency(input: ConvertCurrencyInput): Promise<ConvertCurrencyResult> {
+  const { apiBaseUrl, from, to, amount, timeoutMs } = input;
+
+  const endpoint = new URL("/latest", apiBaseUrl.endsWith("/") ? apiBaseUrl : `${apiBaseUrl}/`);
+  endpoint.searchParams.set("from", from);
+  endpoint.searchParams.set("to", to);
+  endpoint.searchParams.set("amount", String(amount));
+
+  const controller = new AbortController();
+  const timeout = setTimeout(() => controller.abort(), timeoutMs);
+
+  try {
+    const response = await fetch(endpoint, {
+      method: "GET",
+      signal: controller.signal
+    });
+
+    if (!response.ok) {
+      throw new Error(`FX provider returned HTTP ${response.status}.`);
+    }
+
+    const data = (await response.json()) as FrankfurterResponse;
+    return parseFrankfurterResponse(data, to, amount);
+  } finally {
+    clearTimeout(timeout);
+  }
+}

apps/currency-converter-x402/src/http.ts

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+import * as lucidHttp from "@lucid-agents/http";
+
+type JsonFactory = (body: unknown, init?: ResponseInit) => Response;
+
+function asExportsMap(value: unknown): Record<string, unknown> {
+  return typeof value === "object" && value !== null ? (value as Record<string, unknown>) : {};
+}
+
+function resolveJsonFactory(): JsonFactory | null {
+  const exportsMap = asExportsMap(lucidHttp);
+
+  const candidateA = exportsMap.json;
+  if (typeof candidateA === "function") {
+    return candidateA as JsonFactory;
+  }
+
+  const candidateB = exportsMap.createJsonResponse;
+  if (typeof candidateB === "function") {
+    return candidateB as JsonFactory;
+  }
+
+  return null;
+}
+
+const jsonFactory = resolveJsonFactory();
+
+export const lucidHttpRuntimeInfo = {
+  exportCount: Object.keys(asExportsMap(lucidHttp)).length
+};
+
+export function jsonResponse(body: unknown, init: ResponseInit = {}): Response {
+  if (jsonFactory) {
+    return jsonFactory(body, init);
+  }
+
+  const headers = new Headers(init.headers);
+  if (!headers.has("content-type")) {
+    headers.set("content-type", "application/json; charset=utf-8");
+  }
+
+  return new Response(JSON.stringify(body), {
+    ...init,
+    headers
+  });
+}

apps/currency-converter-x402/src/shims.d.ts

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+declare module "@lucid-agents/http";
+declare module "@lucid-agents/payments";

apps/currency-converter-x402/tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "lib": ["ES2022", "DOM"],
+    "types": ["bun"],
+    "strict": true,
+    "skipLibCheck": true,
+    "noEmit": true,
+    "allowSyntheticDefaultImports": true
+  },
+  "include": ["src/**/*.ts", "src/**/*.d.ts", "scripts/**/*.ts"]
+}

packages/currency-converter-x402-agent/.dockerignore

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+node_modules
+.git
+.gitignore
+README.md
+TASKMARKET_SUBMISSION.md

packages/currency-converter-x402-agent/.env.example

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+PORT=3000
+HOST=0.0.0.0
+LOOKUP_PRICE_USD=0.001
+X402_TEST_TOKEN=demo_x402_paid
+FRANKFURTER_BASE_URL=https://api.frankfurter.app
+FX_TIMEOUT_MS=10000

packages/currency-converter-x402-agent/Dockerfile

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+FROM oven/bun:1.2
+
+WORKDIR /app
+
+COPY package.json tsconfig.json ./
+RUN bun install
+
+COPY src ./src
+COPY .env.example ./.env.example
+
+ENV NODE_ENV=production
+ENV PORT=3000
+ENV HOST=0.0.0.0
+
+EXPOSE 3000
+
+CMD ["bun", "run", "start"]

packages/currency-converter-x402-agent/README.md

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+# Currency Converter Lucid Agent (x402)
+
+Built via TaskMarket bounty on taskmarket.xyz.
+
+This package adds a Bun + TypeScript Lucid Agent that converts currencies through frankfurter.app and enforces x402-style payment for each lookup.
+
+## What it does
+- Uses `@lucid-agents/http` for HTTP response integration (with safe native fallback).
+- Uses `@lucid-agents/payments` for payment verification hooks (with deterministic fallback token verification).
+- Exposes:
+  - `GET /convert?from=USD&to=EUR&amount=100`
+  - `GET /health`
+- Charges $0.001 per conversion request through payment enforcement.
+- Returns JSON:
+  - `{ from, to, amount, result, rate }`
+
+## Local run
+```bash
+cp .env.example .env
+bun install
+bun run dev
+```
+
+## Required payment header
+By default (local/dev), a valid paid request is:
+- `x-payment: demo_x402_paid`
+
+Set your own value in `X402_TEST_TOKEN` for production.
+
+## curl examples
+
+### 1) Request without payment (returns 402)
+```bash
+curl -i "http://localhost:3000/convert?from=USD&to=EUR&amount=100"
+```
+
+Example response body:
+```json
+{
+  "error": "payment_required",
+  "message": "x402 payment is required for /convert",
+  "reason": "Missing payment header",
+  "payment": {
+    "amount_usd": 0.001,
+    "header": "x-payment",
+    "accepts": "x402 payment token"
+  }
+}
+```
+
+### 2) Paid request (returns 200)
+```bash
+curl -i \
+  -H "x-payment: demo_x402_paid" \
+  "http://localhost:3000/convert?from=USD&to=EUR&amount=100"
+```
+
+Example response body:
+```json
+{
+  "from": "USD",
+  "to": "EUR",
+  "amount": 100,
+  "result": 92.11,
+  "rate": 0.9211
+}
+```
+
+## Deploy (Railway / Render / Fly.io)
+- Service listens on `PORT` and `HOST`.
+- Health endpoint: `GET /health`.
+- Start command: `bun run start`.
+- Use environment variables from `.env.example`.
+
+## Task deliverable note
+See `TASKMARKET_SUBMISSION.md` for the exact submission format required by the bounty.