How to fix PancakeLibrary: INSUFFICIENT_INPUT_AMOUNT?

Question

I'm trying to make a multiple swap function in my smart contract using solidity. For example we want to swap BNB->BUSD->USDT->ADA->BNB. The contract interacts with PancakeSwap. I deployed it on BSC testnet. Here's my code:

function multyswap(uint256 amountIn, address[] calldata path) external payable {
      if (path[0] == WETH) {
         require(amountIn == msg.value, "Germes: INVALID_INPUT");
      } else {
         IBEP20(path[0]).transferFrom(msg.sender, address(this), amountIn);
      }

      for (uint i = 0; i < path.length-1; ++i) {
         address receiver;
         address[] memory tempPath = new address[](2);

         tempPath[0] = path[i];
         tempPath[1] = path[i+1];

         if (i == path.length-2) {
            receiver = msg.sender;
         } else {
            receiver = address(this);
         }

         if (path[i] == WETH) {
            router.swapExactETHForTokens{value: msg.value}(
               0,
               tempPath,
               receiver,
               block.timestamp + 100
            );
            amountIn = address(this).balance;

         } else if (path[i+1] == WETH) {
            IBEP20(path[i]).approve(routerAddress, amountIn);
            router.swapExactTokensForETH(
               amountIn,
               0,
               tempPath,
               receiver,
               block.timestamp + 100
            );
            amountIn = IBEP20(tempPath[1]).balanceOf(receiver);

         } else {
            IBEP20(path[i]).approve(routerAddress, amountIn);
            router.swapExactTokensForTokens(
               amountIn,
               0,
               tempPath,
               receiver,
               block.timestamp + 100
            );
            amountIn = IBEP20(tempPath[1]).balanceOf(receiver);
         }
      }
   }

The problem is that i cant swap TOKEN for BNB , but I can swap BNB for TOKEN. Here is the error:

PancakeLibrary: INSUFFICIENT_INPUT_AMOUNT

I tried to use this contract on BSC mainnet, but it failed. I suppose the reason of this error is this function from PancakeLibrary.sol:

function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut) internal pure returns (uint amountOut) {
        require(amountIn > 0, 'PancakeLibrary: INSUFFICIENT_INPUT_AMOUNT');
        require(reserveIn > 0 && reserveOut > 0, 'PancakeLibrary: INSUFFICIENT_LIQUIDITY');
        uint amountInWithFee = amountIn.mul(998);
        uint numerator = amountInWithFee.mul(reserveOut);
        uint denominator = reserveIn.mul(1000).add(amountInWithFee);
        amountOut = numerator / denominator;
    }

It raises an error when amountIn = 0 , but i definetly input correct value. Could anybody help me? I would appreciate it very much

Answer 1

your problem is about the amount size. Remember most tokens in blockchain are based on 18 decimals systems.

If you want to call or to swap an amount of "10", because of the decimals, that amount is going to be counted as 0.00000000000000000000010

this number is just to small an the solidity contract will consider it like 0.

You need to convert your amounts before sending them on the blockchain

Answer 2

For pancakeswap,

uint amountInWithFee = amountIn.mul(998); uint denominator = reserveIn.mul(1000).add(amountInWithFee);

Replace to:

uint amountInWithFee = amountIn.mul(9975); uint denominator = reserveIn.mul(10000).add(amountInWithFee);