[UniswapV2] SwapRouter by @Dialectic

Source

https://github.com/dialecticch/router

Overview

Simple router to exchange tokens for best price for any UniswapV2 like AMM. This contract can only be used for exchanges that uses the code of Uniswapv2 .

SwapRouterMock

swap

Returns SwapRouter.swap function.

swap in SwapRouter library

Parameters

• swaps is the candidates of exchanges that we can choose.
• path is the array of token address which we will use for swap.
• amount is the amount of token we want to sell.
• slippage is the max slippage in basis points.

1. Find the best profitable exchange and the corresponding amountOut for given amount by using dataForBestExchange function.
   

   (UniswapV2 swap, uint256 amountOut) = dataForBestExchange(swaps, path, amount);
   

2. Approve swap (exchange we choose) to use path[0] (input token for swap) for amount .
   

   ERC20(path[0]).approve(address(swap), amount);
   

3. Swap the token using swapExactTokensForTokens function from the exchange address. out is the real amount of output token we receive.
   

   uint256[] memory amountsOut = swap.swapExactTokensForTokens(
       amount,
       (amountOut * (1000 - slippage)) / 1000,
       path,
       address(this),
       block.timestamp + 180
       );
   
   uint256 out = amountsOut[amountsOut.length - 1];
   

dataForBestExchange

Returns the best exchange and the corresponding output value.

For given swap, we calculate the biggest out value by using amountOutFor function.

for (uint256 i = 0; i < length; i++) {
            uint256 out = amountOutFor(swaps[i], path, amount);
            if (out > bestAmount) {
                bestExchange = swaps[i];
                bestAmount = out;
            }
        }

amountOutFor

Use getAmountsOut function to calculate the optimal output value from given amountIn and path.

try exchange.getAmountsOut(amountIn, path) returns (uint256[] memory amountsOut) {
    return amountsOut[amountsOut.length - 1];
} catch {
    return 0;
}