rdonmez / uniswap-flashswap

FlashSwap On Uniswap Like Protocols

An example of quering token prices and swaping token on uniswap like protocols.

1. Install Dependencies

$ npm install

2. Compile Contract

$ npx hardhat compile

3. Test Contract

$ npx hardhat test

4. Using Contract

a. Flash Query

    Deploy contract to EVM based chain then find the uniswap like protocol factory address. 

    ```
        require('dotenv').config();

        const { BigNumber, Wallet, Contract, providers, utils } = require( "ethers" );

        const provider = new providers.StaticJsonRpcProvider(process.env.RPC_URL);

        const queryContract = new Contract(FLASHQUERY_CONTRACT_ADDRESS, FLASHQUERY_CONTRACT_ABI, provider); 

        // get reserves for each pairs to calculate token price
         
        const pairs  = (await queryContract.functions.getPairs("UNISWAP_FACTORY_ADDRESS", 0, 10))[0]; 
        const reserves  = (await queryContract.functions.getReservesByPairs(pairs))[0]; 
        
        const combined = pairs.map((i, j) => {  
                return { 
                    pairAddress: pairs[j],
                    reserve0: reserves[j][0], 
                    reserve1: reserves[j][1], 
                    lastBlockTs: reserves[j][2]
                } 

        const amountIn = 1; // token amount to sell 
        const buyPrice = getAmountOut(combined[0].reserve0, combined[0].reserve1, 1, 997);

    ```

a. Flash Swap

5. Calculation Token Price

You can calculate token buy/sell price by the following code.

function getAmountIn(reserveIn, reserveOut, amountOut, exchangeFee) {
    const numerator = reserveIn.mul(amountOut).mul(10000);
    const denominator = reserveOut.sub(amountOut).mul(exchangeFee);
    return numerator.div(denominator).add(1);
}

function getAmountOut(reserveIn, reserveOut, amountIn, exchangeFee) {
    const amountInWithFee = amountIn.mul(exchangeFee);
    const numerator = amountInWithFee.mul(reserveOut);
    const denominator = reserveIn.mul(10000).add(amountInWithFee);
    return numerator.div(denominator);
}