⚪Implement a Swap

This guide will walk you through the process of swapping tokens using the Xfai protocol. The swapTokens function allows you to execute token swaps with flexibility based on the specified trade type. The function signatures for swapping tokens are as follows:

export async function swapTokens<T = TradeType.EXACT_INPUT>(
  xfai: Xfai,
  tradeType: T,
  tokenIn: Token,
  tokenOut: Token,
  amountIn: BigNumber,
  minAmountOut: BigNumber,
  options: TransactionOptions,
): Promise<PopulatedTransaction>;

export async function swapTokens<T = TradeType.EXACT_OUTPUT>(
  xfai: Xfai,
  tradeType: T,
  tokenIn: Token,
  tokenOut: Token,
  maxAmountIn: BigNumber,
  minAmountOut: BigNumber,
  options: TransactionOptions,
): Promise<PopulatedTransaction>;

To use the swapTokens function effectively, follow the steps below:

Step 1: Choose the Trade Type

The swapTokens function supports two trade types:

1. TradeType.EXACT_INPUT: In this trade type, you specify the exact amount of the input token and the minimum amount of the output token you expect to receive.

2. TradeType.EXACT_OUTPUT: In this trade type, you specify the maximum amount of the input token you are willing to spend and the minimum amount of the output token you expect to receive.

Choose the appropriate trade type based on your requirements.

Step 2: Define the Tokens

The tokenIn and tokenOut parameters represent the input and output tokens, respectively. You need to provide the relevant token objects for these parameters. Ensure that you have the necessary token information and instances before proceeding.

Step 3: Specify the Amounts

The amountIn and minAmountOut parameters are used when TradeType.EXACT_INPUT is selected.

• amountIn represents the exact amount of the input token you want to swap.

• desiredAmountOut represents the desired amount of the output token you expect to receive from the swap, the minimum amount out will be calcuated based on slippage parameter

Alternatively, when TradeType.EXACT_OUTPUT is selected, you will use the maxAmountIn parameter instead.

• desiredAmountIn represents the desired amount of the input token you are willing to spend, the maximum amount in will be calcuated based on slippage parameter

• amountOut represents the amount of the output token you expect to receive.

Ensure that you have the required token amounts ready for the swap and you have given allowance to the periphery contract.

Step 4: Set Transaction Options

The options parameter allows you to specify additional transaction options such as deadline, slippage and more. Review the available options and set them according to your needs.

Step 5: Perform the Token Swap

Call the swapTokens function with the appropriate parameters to initiate the token swap. The function will return a PopulatedTransaction object, which represents the populated transaction that can be executed.

Example Usage

Here's an example usage of the swapTokens function:

import { Xfai, Token, TradeType, BasisPoint, sendPopulatedTx, swapTokens } from '@xfai-labs/sdk';
import { BigNumber } from 'ethers';
const xfai = new Xfai(...);

// Step 1: Choose the Trade Type
const tradeType = TradeType.EXACT_INPUT;

// Step 2: Define the Tokens
const tokenIn = Token('0x0....');

const tokenOut = xfai.underlyingToken;

// Step 3: Specify the Amounts
const amountIn = new BigNumber(100); 
const desiredAmountOut = new BigNumber(50);


// Construct the Transaction
const populatedTx =  swapTokens(
                      xfai,
                      tradeType,
                      tokenIn,
                      tokenOut,
                      amountIn,
                      desiredAmountOut,
                      {
                        deadline: addMinutes(new Date(), 20),
                        from: xfai.provider.getSigner(),
                        // .1%
                        slippage: BasisPoint.from(10),
                      },
                    );

// Send the tx
const tx  = await sendPopulatedTx(xfai,populatedTx),