I am using sushiswap to transfer weth to dai. Everything goes fine when I use web3.js to call swapExactTokensForTokens directory. However, thing goes wrong when I try to include the swapExactTokensForTokens in IUniswapV2Router02.sol. My code runing on remix below:
pragma solidity ^0.6.6;
import "https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/interfaces/IUniswapV2Router02.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/docs-v3.x/contracts/token/ERC20/IERC20.sol";
contract Arbitrage {
IUniswapV2Router02 public sushiRouter = IUniswapV2Router02(0x1b02dA8Cb0d097eB8D57A175b88c7D8b47997506);
event test (uint timestamp, uint amountIn, uint amountOut, address[] path, uint allowance, address sender);
function swapper(address token1, address token2) public {
address[] memory path = new address[](2);
path[0] = token1;
path[1] = token2;
uint amountOut = 1 ether;
uint amountIn = sushiRouter.getAmountsIn(
amountOut,
path
)[0];
IERC20(token1).approve(address(sushiRouter), amountIn);
uint allowed = IERC20(token1).allowance(msg.sender, address(sushiRouter));
emit test(now+90, amountIn, amountOut, path, allowed, msg.sender);
sushiRouter.swapExactTokensForTokens(
amountIn,
amountOut,
path,
msg.sender,
now + 60
);
}
}
The error message shows on Remix is
Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?
The execution failed due to an exception. Reverted
I also use truffle + ganache-cli (folked from mainnet). The error shows on truffle console is
Uncaught:
Error: Returned error: VM Exception while processing transaction: revert TransferHelper: TRANSFER_FROM_FAILED -- Reason given: TransferHelper: TRANSFER_FROM_FAILED.
I believes things go wrong inside "sushiRouter.swapExactTokensForTokens()" because the code goes through with emitting the event successfully once I comment it out.
It will be very appreciate if anybody can let me know in which part I mess it up.
------ Some more information below -----
After removing the swapping section like below:
...
contract Arbitrage {
IUniswapV2Router02 public sushiRouter = IUniswapV2Router02(0x1b02dA8Cb0d097eB8D57A175b88c7D8b47997506);
event test (uint timestamp, uint amountIn, uint amountOut, address[] path, uint allowance, address sender);
function swapper(address token1, address token2) public {
address[] memory path = new address[](2);
path[0] = token1;
path[1] = token2;
uint amountOut = 1 ether;
uint amountIn = sushiRouter.getAmountsIn(
amountOut,
path
)[0];
IERC20(token1).approve(address(sushiRouter), amountIn);
IERC20(token2).approve(address(sushiRouter), amountOut);
uint allowed = IERC20(token1).allowance(msg.sender, address(sushiRouter));
emit test(now+90, amountIn, amountOut, path, allowed, msg.sender);
}
}
The transaction gone through with following tx detail:
---- 4/21 update ----
I might find some clues when I am trying error on my ganache forked mainnet.
Google says the cause of "TRANSFER_FROM_FAILED" is that sushiswap router contract does not have enough allowance to transfer the token. So I check again the allowance field in "test event". Surprisingly, it is actually "0" even though I have already done the approve.
WHY?? following line of code does not take effect?? Do I miss anything?
IERC20(token1).approve(address(sushiRouter), amountIn);
Apart from that, the swap still fails even I manually approve 100 weth by truffle console:
truffle(development)> weth.approve(srouter.address, web3.utils.toWei("1000"))
truffle(development)> allowed = await weth.allowance(accounts[0], srouter.address)
truffle(development)> allowed.toString()
'1000000000000000000000'
truffle(development)> tx = await sw.swapper(weth.address, dai.address)
Uncaught:
Error: Returned error: VM Exception while processing transaction: revert TransferHelper: TRANSFER_FROM_FAILED -- Reason given: TransferHelper: TRANSFER_FROM_FAILED.
I am quite sure that my environment setting should not be any problem because I do similar process manually with problem:
process below:
- fork the mainnet by ganache-cli
ganache-cli --fork https://mainnet.infura.io/v3/<projectID> --unlock 0x47ac0fb4f2d84898e4d9e7b4dab3c24507a6d503 -p 7545
truffle console and migrate
implement swaptoken on truffle console without any problem
truffle(development)> dai = await Dai.at("0x6b175474e89094c44da98b954eedeac495271d0f")
truffle(development)> weth = await Weth.at("0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2")
truffle(development)> sw = await SwapTokens.deployed()
truffle(development)> srouter =await Router.at("0xd9e1cE17f2641f24aE83637ab66a2cca9C378B9F")
truffle(development)> web3.eth.sendTransaction({from:accounts[0], to: "0x47ac0fb4f2d84898e4d9e7b4dab3c24507a6d503", value:web3.utils.toWei("20")})
truffle(development)> dai.transfer(accounts[0], web3.utils.toWei("5000"), {from: "0x47ac0fb4f2d84898e4d9e7b4dab3c24507a6d503"}
truffle(development)> weth.deposit({from:accounts[0], value:web3.utils.toWei("50")})
truffle(development)> amountIn = await srouter.getAmountsIn(web3.utils.toWei("1"), [weth.address, dai.address])
truffle(development)> amountIn = amountIn[0]
truffle(development)> weth.approve(srouter.address, amountIn)
truffle(development)> amountOut = web3.utils.toWei("1")
truffle(development)> time = Math.floor((Date.now()/1000)) + 60*300
srouter.swapExactTokensForTokens(amountIn, amountOut, [weth.address, dai.address], accounts[0], time)
Everything gone through without issue.
But It fail when I call it in smart contract?
Please help , I have stuck here for so long @@