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Making a Trade

This guide demonstrates how to execute a swap. In this example, we will be swapping 20 USDC for WETH.

1. Required imports for this guide​

import {
  ChainId,
  EventDecoder,
  IERC20,
  IRouter,
  LB_ROUTER_ADDRESS,
  PairV2,
  Percent,
  RouteV2,
  Token,
  TokenAmount,
  TradeV2,
  USDC as _USDC,
  WETH as _WETH,
  WMAS as _WMAS,
  parseUnits,
} from "@dusalabs/sdk";
import {
  BUILDNET_CHAIN_ID,
  ClientFactory,
  EOperationStatus,
  DefaultProviderUrls,
  ProviderType,
  WalletClient,
} from "@massalabs/massa-web3";

2. Declare required constants​

const BUILDNET_URL = DefaultProviderUrls.BUILDNET;
const CHAIN_ID = ChainId.BUILDNET;
const privateKey = "{WALLET_PRIVATE_KEY}";
const account = await WalletClient.getAccountFromSecretKey(privateKey);
if (!account.address) throw new Error("Missing address in account");
const client = await ClientFactory.createCustomClient(
  [
    { url: BUILDNET_URL, type: ProviderType.PUBLIC },
    { url: BUILDNET_URL, type: ProviderType.PRIVATE },
  ],
  BUILDNET_CHAIN_ID,
  true,
  account
);

Note that in your project, you most likely will not hardcode the private key at any time. You would be using libraries like wallet-provider to connect to a wallet, sign messages, interact with contracts, and get the above constants.

// initialize tokens
const WMAS = _WMAS[CHAIN_ID];
const USDC = _USDC[CHAIN_ID];
const WETH = _WETH[CHAIN_ID];

// declare bases used to generate trade routes
const BASES = [WMAS, USDC, WETH];

3. Declare user inputs and initialize TokenAmount​

// the input token in the trade
const inputToken = USDC;

// the output token in the trade
const outputToken = WMAS;

// specify whether user gave an exact inputToken or outputToken value for the trade
const isExactIn = true;

// user string input; in this case representing 20 USDC
const typedValueIn = "20";

// parse user input into inputToken's decimal precision, which is 6 for USDC
const typedValueInParsed = parseUnits(typedValueIn, inputToken.decimals).toString(); // returns 20000000

// wrap into TokenAmount
const amountIn = new TokenAmount(inputToken, typedValueInParsed);

4. Use PairV2 and RouteV2 functions to generate all possible routes​

// get all [Token, Token] combinations
const allTokenPairs = PairV2.createAllTokenPairs(inputToken, outputToken, BASES);

// init PairV2 instances for the [Token, Token] pairs
const allPairs = PairV2.initPairs(allTokenPairs);

// generates all possible routes to consider
const allRoutes = RouteV2.createAllRoutes(
  allPairs,
  inputToken,
  outputToken,
  2 // maxHops
);

5. Generate TradeV2 instances and get the best trade​

const isMasIn = false; // set to 'true' if swapping from MAS; otherwise, 'false'
const isMasOut = true; // set to 'true' if swapping to MAS; otherwise, 'false'

// generates all possible TradeV2 instances
const trades = await TradeV2.getTradesExactIn(allRoutes, amountIn, outputToken, isMasIn, isMasOut, client, CHAIN_ID);

// chooses the best trade
const bestTrade = TradeV2.chooseBestTrade(trades, isExactIn);

6. Check trade information​

// print useful information about the trade, such as the quote, executionPrice, fees, etc
console.log(bestTrade.toLog());

// get trade fee information
const { totalFeePct, feeAmountIn } = bestTrade.getTradeFee();
console.log("Total fees percentage", totalFeePct.toSignificant(6), "%");
console.log(`Fee: ${feeAmountIn.toSignificant(6)} ${feeAmountIn.token.symbol}`);

7. Declare slippage tolerance and swap method/parameters​

// set slippage tolerance
const userSlippageTolerance = new Percent(BigInt(50), BigInt(10000)); // 0.5%

// set deadline for the transaction
const currentTimeInMs = new Date().getTime();
const deadline = currentTimeInMs + 3_600_000; // 1 hour

// set swap options
const swapOptions = {
  recipient: account.address,
  allowedSlippage: userSlippageTolerance,
  deadline,
  feeOnTransfer: false, // or true
};

// generate swap method and parameters for contract call
const params = bestTrade.swapCallParameters(swapOptions);

8. Execute trade using massa-web3​

// init router contract
const router = new IRouter(LB_ROUTER_ADDRESS[CHAIN_ID], client);

// increase allowance for the router (not needed if inputToken is MAS)
const approveTxId = await new IERC20(inputToken.address, client).approve(router.address, amountIn);

// execute swap
const txId = await router.swap(params);
console.log("txId", txId);

// await transaction confirmation and log output events
const status = await client.smartContracts().awaitRequiredOperationStatus(txId, EOperationStatus.FINAL_SUCCESS);
if (status !== EOperationStatus.FINAL_SUCCESS) throw new Error("Something went wrong");
await client
  .smartContracts()
  .getFilteredScOutputEvents({
    emitter_address: null,
    start: null,
    end: null,
    original_caller_address: null,
    is_final: null,
    original_operation_id: txId,
  })
  .then((r) => 
    r.forEach(({data}) => {
      if (data.startsWith("SWAP:")) console.log(EventDecoder.decodeSwap(data));
      else console.log(data);
    });
  );