Contract Source Code:

// File: contracts/busd/IBUSD.sol

pragma solidity 0.5.17;

interface IBUSD {
    function balanceOf(address _addr) external returns (uint256);
    function transferFrom(address _from, address _to, uint256 _value) external returns (bool);
    function transfer(address _to, uint256 _value) external returns (bool);
    function increaseSupply(uint256 _value) external returns (bool success);
    function decreaseSupply(uint256 _value) external returns (bool success);
}

// File: @openzeppelin/contracts/math/SafeMath.sol

pragma solidity ^0.5.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: contracts/busd/BUSDEthManager.sol

pragma solidity 0.5.17;



contract BUSDEthManager {
    using SafeMath for uint256;

    IBUSD public busd_;

    mapping(bytes32 => bool) public usedEvents_;

    event Locked(
        address indexed token,
        address indexed sender,
        uint256 amount,
        address recipient
    );

    event Unlocked(
        address ethToken,
        uint256 amount,
        address recipient,
        bytes32 receiptId
    );

    address public wallet;
    modifier onlyWallet {
        require(msg.sender == wallet, "HmyManager/not-authorized");
        _;
    }

    /**
     * @dev constructor
     * @param busd token contract address, e.g., erc20 contract
     * @param _wallet is the multisig wallet
     */
    constructor(IBUSD busd, address _wallet) public {
        busd_ = busd;
        wallet = _wallet;
    }

    /**
     * @dev lock tokens to be minted on harmony chain
     * @param amount amount of tokens to lock
     * @param recipient recipient address on the harmony chain
     */
    function lockToken(uint256 amount, address recipient) public {
        require(
            recipient != address(0),
            "EthManager/recipient is a zero address"
        );
        require(amount > 0, "EthManager/zero token locked");
        uint256 _balanceBefore = busd_.balanceOf(msg.sender);
        require(
            busd_.transferFrom(msg.sender, address(this), amount),
            "EthManager/lock failed"
        );
        uint256 _balanceAfter = busd_.balanceOf(msg.sender);
        uint256 _actualAmount = _balanceBefore.sub(_balanceAfter);
        emit Locked(address(busd_), msg.sender, _actualAmount, recipient);
    }

    /**
     * @dev lock tokens for an user address to be minted on harmony chain
     * @param amount amount of tokens to lock
     * @param recipient recipient address on the harmony chain
     */
    function lockTokenFor(
        address userAddr,
        uint256 amount,
        address recipient
    ) public onlyWallet {
        require(
            recipient != address(0),
            "EthManager/recipient is a zero address"
        );
        require(amount > 0, "EthManager/zero token locked");
        uint256 _balanceBefore = busd_.balanceOf(userAddr);
        require(
            busd_.transferFrom(userAddr, address(this), amount),
            "EthManager/lock failed"
        );
        uint256 _balanceAfter = busd_.balanceOf(userAddr);
        uint256 _actualAmount = _balanceBefore.sub(_balanceAfter);
        emit Locked(address(busd_), userAddr, _actualAmount, recipient);
    }

    /**
     * @dev unlock tokens after burning them on harmony chain
     * @param amount amount of unlock tokens
     * @param recipient recipient of the unlock tokens
     * @param receiptId transaction hash of the burn event on harmony chain
     */
    function unlockToken(
        uint256 amount,
        address recipient,
        bytes32 receiptId
    ) public onlyWallet {
        require(
            !usedEvents_[receiptId],
            "EthManager/The burn event cannot be reused"
        );
        usedEvents_[receiptId] = true;
        require(busd_.transfer(recipient, amount), "EthManager/unlock failed");
        emit Unlocked(address(busd_), amount, recipient, receiptId);
    }
}