Project: Build a Token Swap Trader

A complete, runnable project implementing a full round-trip through the Uniswap V2 AMM on Celo — minting the input token, pricing the trade, approving the router, and executing — in both directions. See the AMM API for the endpoint reference.

Celo only

This is Celo's Uniswap V2 AMM specifically — no chain selector on this page, since Stellar's AMM (see Stellar AMM) is a separate native protocol-level mechanism with its own distinct API, not another chain for this same swap flow.

▸API ConfigurationNot configured

What you'll build

A trade.js script with one reusable swap() function that mints the input token, prices the trade, approves the router, and executes — run once for USDT → IMC and once for IMC → USDT.

Prerequisites

• Node.js 18+ (for global fetch)
• A running comet-engine with a tenant API key/secret — see Authentication
• A funded USDT/IMC pool already created — see Liquidity Pool Setup

Project setup

mkdir amm-trade && cd amm-trade && npm init -y && npm install dotenv

.env:

COMET_BASE_URL=http://localhost:8100
COMET_API_KEY=your-tenant-api-key
COMET_API_SECRET=your-tenant-api-secret

Create trade.js with this shared helper at the top — every step below adds to the same file:

import 'dotenv/config';

const base = process.env.COMET_BASE_URL;
const headers = {
  'Content-Type': 'application/json',
  'X-API-Key': process.env.COMET_API_KEY,
  'X-API-Secret': process.env.COMET_API_SECRET,
};

async function comet(method, path, body) {
  const res = await fetch(base + path, { method, headers, body: body ? JSON.stringify(body) : undefined });
  const data = await res.json();
  if (!res.ok) throw new Error(`${method} ${path} -> ${res.status}: ${JSON.stringify(data)}`);
  return data;
}

Step 1: Swap USDT → IMC

1. Mint USDT to user

curl -X POST "http://localhost:8100/api/v1/assets/usdt/mint" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "X-API-Secret: YOUR_API_SECRET" \
  -d '{
  "userId": 123,
  "amountBase": "10000000",
  "externalId": "swap-001"
}'

Response200

{
  "amount": 10,
  "chain": "celo",
  "symbol": "USDT",
  "txHash": "0x..."
}

2. Get quote

curl -X GET "http://localhost:8100/api/v1/swap/quote?from=USDT&to=IMC&amountIn=10000000" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "X-API-Secret: YOUR_API_SECRET"

Response200

{
  "from": "USDT",
  "to": "IMC",
  "amountIn": "10000000",
  "amounts": [
    "10000000",
    "9970000"
  ]
}

3. Approve router

curl -X POST "http://localhost:8100/api/v1/assets/usdt/approve" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "X-API-Secret: YOUR_API_SECRET" \
  -d '{
  "userId": 123,
  "amountBase": "10000000"
}'

Response200

{
  "txHash": "0x...",
  "chain": "celo",
  "symbol": "USDT"
}

4. Execute swap

curl -X POST "http://localhost:8100/api/v1/swap/tokens" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "X-API-Secret: YOUR_API_SECRET" \
  -d '{
  "userId": 123,
  "from": "USDT",
  "to": "IMC",
  "amountIn": "10000000"
}'

Response200

{
  "status": "success",
  "from": "USDT",
  "to": "IMC",
  "txHash": "0x...",
  "chainId": 11142220
}

Step 2: Swap IMC → USDT (the reverse direction)

1. Get quote

curl -X GET "http://localhost:8100/api/v1/swap/quote?from=IMC&to=USDT&amountIn=5000000" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "X-API-Secret: YOUR_API_SECRET"

Response200

{
  "from": "IMC",
  "to": "USDT",
  "amountIn": "5000000",
  "amounts": [
    "5000000",
    "4985000"
  ]
}

2. Approve router

curl -X POST "http://localhost:8100/api/v1/assets/imc/approve" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "X-API-Secret: YOUR_API_SECRET" \
  -d '{
  "userId": 123,
  "amountBase": "5000000"
}'

Response200

{
  "txHash": "0x...",
  "chain": "celo",
  "symbol": "IMC"
}

3. Execute swap

curl -X POST "http://localhost:8100/api/v1/swap/tokens" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "X-API-Secret: YOUR_API_SECRET" \
  -d '{
  "userId": 123,
  "from": "IMC",
  "to": "USDT",
  "amountIn": "5000000"
}'

Response200

{
  "status": "success",
  "from": "IMC",
  "to": "USDT",
  "txHash": "0x...",
  "chainId": 11142220
}

How it works

1. User's wallet must hold the input token
2. User approves the Uniswap V2 Router to spend input tokens
3. Engine calls swapExactTokensForTokens() on the Router
4. Router executes the swap on-chain
5. Output tokens arrive in the user's wallet
6. Gas is paid by the platform relayer

Supported pools:

Pool	Fee
USDT/USDC	0.3%
USDT/IMC	0.3%
USDC/IMC	0.3%

Step 3: Run both directions as one script

Add to trade.js:

async function swap(userId, from, to, amountIn) {
  // 1. Mint the input token to the user (skip this in production — the
  // user's balance comes from wherever they actually acquired it)
  await comet('POST', `/api/v1/assets/${from.toLowerCase()}/mint`, { userId, amountBase: amountIn, externalId: `swap-mint-${Date.now()}` });

  // 2. Price it
  const quote = await comet('GET', `/api/v1/swap/quote?from=${from}&to=${to}&amountIn=${amountIn}`);
  console.log(`quote: ${amountIn} ${from} -> ${quote.amounts[1]} ${to}`);

  // 3. Approve the router to spend the input token
  await comet('POST', `/api/v1/assets/${from.toLowerCase()}/approve`, { userId, amountBase: amountIn });

  // 4. Execute
  const result = await comet('POST', '/api/v1/swap/tokens', { userId, from, to, amountIn });
  console.log('swapped:', result.txHash);
  return result;
}

async function main() {
  const userId = 123;
  await swap(userId, 'USDT', 'IMC', '10000000');   // USDT -> IMC
  await swap(userId, 'IMC', 'USDT', '5000000');    // IMC -> USDT
}

main().catch((e) => { console.error(e); process.exit(1); });

node trade.js

What you built

• A reusable swap() function covering mint → quote → approve → execute for any pair on the pool.
• Both directions of a real USDT/IMC round-trip, gas paid by the platform relayer.

Next steps: replace the mint step with your own balance-acquisition flow, or see Liquidity Pool Setup if you need to create the pool this project trades against first.