Contract Source Code:
// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.6.12;
import "SwapperSimpleBase.sol";
import "SwapPriceCalculatorInterface.sol";
contract Swapper
{
using SafeMath for uint256;
address private admin;
IERC20 private token;
ISwapPriceCalculator private priceCalculator;
uint256 private ethReserve;
uint256 private ethReserveTaken;
uint256 private ethFee;
uint256 private ethFeeTaken;
uint256 private tokensSold;
string private constant ERR_MSG_SENDER = "ERR_MSG_SENDER";
string private constant ERR_AMOUNT = "ERR_AMOUNT";
string private constant ERR_ZERO_ETH = "ERR_ZERO_ETH";
event Swap(uint256 receivedEth,
uint256 expectedTokens,
uint16 slippage,
uint256 ethFeeAdd,
uint256 actualTokens,
uint256 tokensSold);
// constructor:
//--------------------------------------------------------------------------------------------------------------------------
constructor(address _admin, address _token, address _priceCalculator) public
{
admin = _admin;
token = IERC20(_token);
priceCalculator = ISwapPriceCalculator(_priceCalculator);
}
function getAdmin() external view returns (address)
{
return admin;
}
function getToken() external view returns (address)
{
return address(token);
}
//--------------------------------------------------------------------------------------------------------------------------
// ETH balance methods:
//--------------------------------------------------------------------------------------------------------------------------
function getTotalEthBalance() external view returns (uint256)
{
return address(this).balance;
}
function sendEth(address payable _to) external returns (uint256 ethReserveTaken_, uint256 ethFeeTaken_)
{
require(msg.sender == admin, ERR_MSG_SENDER);
_to.transfer(address(this).balance);
ethReserveTaken_ = ethReserve - ethReserveTaken;
ethFeeTaken_ = ethFee - ethFeeTaken;
ethReserveTaken = ethReserve;
ethFeeTaken = ethFee;
}
//--------------------------------------------------------------------------------------------------------------------------
// Tokens balance methods:
//--------------------------------------------------------------------------------------------------------------------------
function getTotalTokensBalance() external view returns (uint256)
{
return token.balanceOf(address(this));
}
function sendTokens(address _to, uint256 _amount) external
{
require(msg.sender == admin, ERR_MSG_SENDER);
if(_amount == 0)
{
token.transfer(_to, token.balanceOf(address(this)));
}
else
{
token.transfer(_to, _amount);
}
}
//--------------------------------------------------------------------------------------------------------------------------
// Price calculator:
//--------------------------------------------------------------------------------------------------------------------------
function getPriceCalculator() external view returns (address)
{
return address(priceCalculator);
}
function setPriceCalculator(address _priceCalculator) external
{
require(msg.sender == admin, ERR_MSG_SENDER);
priceCalculator = ISwapPriceCalculator(_priceCalculator);
}
function calcPrice(uint256 _ethAmount, bool _excludeFee) external view returns (uint256, uint256, uint256)
{
require(_ethAmount > 0, ERR_ZERO_ETH);
return priceCalculator.calc(_ethAmount, 0, 0, ethReserve, tokensSold, _excludeFee);
}
//--------------------------------------------------------------------------------------------------------------------------
// Current state:
//--------------------------------------------------------------------------------------------------------------------------
function getState() external view returns (uint256 ethReserve_,
uint256 ethReserveTaken_,
uint256 ethFee_,
uint256 ethFeeTaken_,
uint256 tokensSold_)
{
ethReserve_ = ethReserve;
ethReserveTaken_ = ethReserveTaken;
ethFee_ = ethFee;
ethFeeTaken_ = ethFeeTaken;
tokensSold_ = tokensSold;
}
//--------------------------------------------------------------------------------------------------------------------------
// Swap logic methods:
//--------------------------------------------------------------------------------------------------------------------------
function swap(uint256 _expectedTokensAmount, uint16 _slippage, bool _excludeFee) external payable
{
require(msg.value > 0, ERR_ZERO_ETH);
require(_expectedTokensAmount > 0, "ERR_ZERO_EXP_AMOUNT");
require(_slippage <= 500, "ERR_SLIPPAGE_TOO_BIG");
(uint256 actualTokensAmount, uint256 ethFeeAdd, uint256 actualEthAmount)
= priceCalculator.calc(msg.value, _expectedTokensAmount, _slippage, ethReserve, tokensSold, _excludeFee);
require(actualTokensAmount > 0, "ERR_ZERO_ACTUAL_TOKENS");
require(msg.value == actualEthAmount, "ERR_WRONG_ETH_AMOUNT");
ethFee = ethFee.add(ethFeeAdd);
ethReserve = ethReserve.add(msg.value.sub(ethFeeAdd));
tokensSold = tokensSold.add(actualTokensAmount);
token.transfer(msg.sender, actualTokensAmount);
emit Swap(msg.value, _expectedTokensAmount, _slippage, ethFeeAdd, actualTokensAmount, tokensSold);
}
//--------------------------------------------------------------------------------------------------------------------------
}
// SPDX-License-Identifier: UNLICENSED
pragma solidity >=0.6.0 <0.8.0; // use 0.6.12 to compile this file
/**
* @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.
*/
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.
*/
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
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.
*/
function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b != 0, errorMessage);
return a % b;
}
}
/**
* @dev Interface of the ERC20 standard as defined in the EIP.
*/
interface IERC20 {
/**
* @dev Returns the amount of tokens in existence.
*/
function totalSupply() external view returns (uint256);
/**
* @dev Returns the amount of tokens owned by `account`.
*/
function balanceOf(address account) external view returns (uint256);
/**
* @dev Moves `amount` tokens from the caller's account to `recipient`.
*
* Returns a boolean value indicating whether the operation succeeded.
*
* Emits a {Transfer} event.
*/
function transfer(address recipient, uint256 amount) external returns (bool);
/**
* @dev Returns the remaining number of tokens that `spender` will be
* allowed to spend on behalf of `owner` through {transferFrom}. This is
* zero by default.
*
* This value changes when {approve} or {transferFrom} are called.
*/
function allowance(address owner, address spender) external view returns (uint256);
/**
* @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
*
* Returns a boolean value indicating whether the operation succeeded.
*
* IMPORTANT: Beware that changing an allowance with this method brings the risk
* that someone may use both the old and the new allowance by unfortunate
* transaction ordering. One possible solution to mitigate this race
* condition is to first reduce the spender's allowance to 0 and set the
* desired value afterwards:
* https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
*
* Emits an {Approval} event.
*/
function approve(address spender, uint256 amount) external returns (bool);
/**
* @dev Moves `amount` tokens from `sender` to `recipient` using the
* allowance mechanism. `amount` is then deducted from the caller's
* allowance.
*
* Returns a boolean value indicating whether the operation succeeded.
*
* Emits a {Transfer} event.
*/
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
/**
* @dev Emitted when `value` tokens are moved from one account (`from`) to
* another (`to`).
*
* Note that `value` may be zero.
*/
event Transfer(address indexed from, address indexed to, uint256 value);
/**
* @dev Emitted when the allowance of a `spender` for an `owner` is set by
* a call to {approve}. `value` is the new allowance.
*/
event Approval(address indexed owner, address indexed spender, uint256 value);
}
// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.6.12;
interface ISwapPriceCalculator
{
function calc(uint256 receivedEthAmount,
uint256 expectedTokensAmount,
uint16 slippage,
uint256 ethReserve,
uint256 tokensSold,
bool excludeFee) external view returns (uint256 actualTokensAmount,
uint256 ethFeeAdd,
uint256 actualEthAmount);
}