TestDydxSoloMargin.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.7.1;
pragma experimental ABIEncoderV2;

import "./interfaces/dydx/DydxFlashloanBase.sol";
import "./interfaces/dydx/ICallee.sol";

contract TestDydxSoloMargin is ICallee, DydxFlashloanBase {
  address internal _solo = 0x1E0447b19BB6EcFdAe1e4AE1694b0C3659614e4e;

  // JUST FOR TESTING - ITS OKAY TO REMOVE ALL OF THESE VARS
  address public lastTokenBorrow;
  uint256 public lastAmount;
  address public lastTokenPay;
  uint256 public lastamountToRepay;
  bytes public lastUserData;
  address public flashUser;

  constructor() payable {}

  struct MyCustomData {
    address token;
    uint256 repayAmount;
  }

  // This is the function that will be called postLoan
  // i.e. Encode the logic to handle your flashloaned funds here
  function callFunction(
    address sender,
    // Account.Info memory account,
    // no variable name to remove Solidity warning
    Account.Info memory,
    bytes memory data
  ) public override {
    MyCustomData memory mcd = abi.decode(data, (MyCustomData));
    uint256 balOfLoanedToken = IERC20(mcd.token).balanceOf(address(this));

    // Note that you can ignore the line below
    // if your dydx account (this contract in this case)
    // has deposited at least ~2 Wei of assets into the account
    // to balance out the collaterization ratio
    require(
      balOfLoanedToken >= mcd.repayAmount,
      "Not enough funds to repay dydx loan!"
    );

    // TODO: Encode your logic here
    // E.g. arbitrage, liquidate accounts, etc
    //revert("Hello, you haven't encoded your logic");

    /*
        
        ACTION HERE

        */

    flashUser = sender; // just for testing
    lastTokenBorrow = mcd.token; // just for testing
    lastAmount = mcd.repayAmount - 2; // just for testing
    lastTokenPay = mcd.token; // just for testing
    lastamountToRepay = mcd.repayAmount; // just for testing
  }

  function initiateFlashLoan(address _token, uint256 _amount) external {
    ISoloMargin solo = ISoloMargin(_solo);

    // Get marketId from token address
    uint256 marketId = _getMarketIdFromTokenAddress(_solo, _token);

    // Calculate repay amount (_amount + (2 wei))
    uint256 repayAmount = _getRepaymentAmountInternal(_amount);
    // Approve transfer from
    IERC20(_token).approve(_solo, repayAmount);

    // Create operations
    Actions.ActionArgs[] memory operations = new Actions.ActionArgs[](3);
    //Borrow x amount of tokens. (Withdraw)
    operations[0] = _getWithdrawAction(marketId, _amount);
    //Call a function (i.e. Logic to handle flashloaned funds). (Call)
    operations[1] = _getCallAction(
      // Encode MyCustomData for callFunction
      abi.encode(MyCustomData({ token: _token, repayAmount: repayAmount }))
    );
    //Deposit back x (+2 wei) amount of tokens. (Deposit)
    operations[2] = _getDepositAction(marketId, repayAmount);

    Account.Info[] memory accountInfos = new Account.Info[](1);
    accountInfos[0] = _getAccountInfo();
    // Call this to start flashloan.
    solo.operate(accountInfos, operations);
  }
}
// Solo margin contract mainnet - 0x1e0447b19bb6ecfdae1e4ae1694b0c3659614e4e
// payable proxy - 0xa8b39829cE2246f89B31C013b8Cde15506Fb9A76

// https://etherscan.io/tx/0xda79adea5cdd8cb069feb43952ea0fc510e4b6df4a270edc8130d8118d19e3f4