/**
 *Submitted for verification at Etherscan.io on 2022-02-22
*/

// SPDX-License-Identifier: MIT

pragma solidity >=0.7.0 <0.9.0;

interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    function mint(address to, uint256 amount) external;

    /**
     * @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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, 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 `from` to `to` 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 from,
        address to,
        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);
}

interface IUniswapV2Pair {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    function name() external pure returns (string memory);
    function symbol() external pure returns (string memory);
    function decimals() external pure returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint value) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);
    function PERMIT_TYPEHASH() external pure returns (bytes32);
    function nonces(address owner) external view returns (uint);

    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;

    event Mint(address indexed sender, uint amount0, uint amount1);
    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
    event Swap(
        address indexed sender,
        uint amount0In,
        uint amount1In,
        uint amount0Out,
        uint amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint);
    function factory() external view returns (address);
    function token0() external view returns (address);
    function token1() external view returns (address);
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function price0CumulativeLast() external view returns (uint);
    function price1CumulativeLast() external view returns (uint);
    function kLast() external view returns (uint);

    function mint(address to) external returns (uint liquidity);
    function burn(address to) external returns (uint amount0, uint amount1);
    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function skim(address to) external;
    function sync() external;

    function initialize(address, address) external;
}


/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}



/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

 

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}


 
library SafeMath {


 
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {



        unchecked {



            uint256 c = a + b;



            if (c < a) return (false, 0);



            return (true, c);



        }



    }


 

    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {



        unchecked {



            if (b > a) return (false, 0);



            return (true, a - b);



        }



    }




 

    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {



        unchecked {



            // 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 (true, 0);



            uint256 c = a * b;



            if (c / a != b) return (false, 0);



            return (true, c);



        }



    }


 

    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {



        unchecked {



            if (b == 0) return (false, 0);



            return (true, a / b);



        }



    }






 

    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {



        unchecked {



            if (b == 0) return (false, 0);



            return (true, a % b);



        }



    }




 

    function add(uint256 a, uint256 b) internal pure returns (uint256) {



        return a + b;



    }


 

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {



        return a - b;



    }



 


    function mul(uint256 a, uint256 b) internal pure returns (uint256) {



        return a * b;



    }






 



    function div(uint256 a, uint256 b) internal pure returns (uint256) {



        return a / b;



    }




 


    function mod(uint256 a, uint256 b) internal pure returns (uint256) {



        return a % b;



    }




 

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {



        unchecked {



            require(b <= a, errorMessage);



            return a - b;



        }



    }




 


    /**



     * @dev Returns the integer division of two unsigned integers, reverting with custom message on



     * division by zero. The result is rounded towards 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).



     *



     * 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) {



        unchecked {



            require(b > 0, errorMessage);



            return a / b;



        }



    }


 


    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {



        unchecked {



            require(b > 0, errorMessage);



            return a % b;



        }



    }



} 



contract Bonding is Ownable, ReentrancyGuard, Pausable{
   
    using SafeMath for uint256;
 
    /* ========== STATE VARIABLES ========== */

    IERC20 public rewardsToken;
    IERC20 public stakingToken;
    IUniswapV2Pair public brainWETHUniswapPair;
    uint256 public periodFinish;
    uint256 public discountRateNumerator;
    uint256 public discountRateDenominator;       
    uint256 public vestingPeriod;
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;
    bool public isPaused;

    struct Deposit{
        uint256 bondedAt;
        uint256 bondedQty;
        uint256 discountNumerator;
        uint256 discountDenominator;
        uint256 exchangeRate;
        uint256 vestingPeriod;
        bool isWithdrawn;
    }

    mapping(address => uint256) public userRewardPerTokenPaid;
    mapping(address => uint256) public rewards;
    uint256 private _totalSupply;
    mapping(address => Deposit[]) private _balances;

    /* ========== EVENTS ========== */

    event RewardAdded(uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);
    event VestingPeriodUpdated(uint256 newDuration);
    event DiscountRateUpdated(uint256 newNumerator, uint256 newDenominator);
 

    /* ========== CONSTRUCTOR ========== */

    constructor( 
        address _rewardsToken,
        address _stakingToken,
        address _brainWETHUniswapPair,
        uint256 _discountRateNumerator,
        uint256 _discountRateDenominator,
        uint256 _vestingPeriod
    )  {
        rewardsToken = IERC20(_rewardsToken);
        stakingToken = IERC20(_stakingToken);
        brainWETHUniswapPair = IUniswapV2Pair(_brainWETHUniswapPair); 
        discountRateNumerator = _discountRateNumerator;
        discountRateDenominator = _discountRateDenominator;
        vestingPeriod = _vestingPeriod; 
    }
    
    /* ========== VIEWS ========== */

    function getBonds(address bonder) public view returns (Deposit[] memory){
        Deposit[] memory d = _balances[bonder];
        return (d);
    }

    function getBrainPrice(uint256 amount) public view returns (uint256){
        (uint Res0, uint Res1,) = brainWETHUniswapPair.getReserves();

        return((amount*Res1)/Res0); // return amount of BRAIN that can be bought with amount wETH
    }
   
    /* ========== MUTATIVE FUNCTIONS ========== */
    function bond(uint256 amount) external nonReentrant whenNotPaused {
        require(amount > 0, "Cannot stake 0");
        address bonder = msg.sender;

        //get the current wETH/BRAIN price
        uint256 currentExchangeRate = getBrainPrice(10**18);

        _balances[bonder].push(
            Deposit(
                block.timestamp,
                amount,
                discountRateNumerator,
                discountRateDenominator,
                currentExchangeRate,
                vestingPeriod,
                false
            )
        );

        stakingToken.transferFrom(bonder, address(this), amount);
        emit Staked(msg.sender, amount);
    }

    function withdraw(uint256 id) public nonReentrant {
        require(
            _balances[msg.sender].length > id, 
            "Deposit does not exist"
        );
        require(
            block.timestamp > _balances[msg.sender][id].bondedAt.add(_balances[msg.sender][id].vestingPeriod),
            "vesting period has not passed yet"
        );
        require(
            _balances[msg.sender][id].bondedQty > 0,
            "There is nothing to withdraw"
        );
        require(
            _balances[msg.sender][id].isWithdrawn == false,
            "This bond has already been widthdrawn"
        );

        uint256 amount = _balances[msg.sender][id].bondedQty;
        uint256 oldExchangeRate = _balances[msg.sender][id].exchangeRate;
        uint256 oldNumerator = _balances[msg.sender][id].discountNumerator;
        uint256 oldDenominator = _balances[msg.sender][id].discountDenominator;

        //we are buying back brain, so divide by exhchange rate to get wETH / (wETH / Brain) to convert to the brain quantity 
        //then multiply by the discount denominator and divide by the numerator to convert the discount price to a quantity returned
        uint256 brainReceived = amount.mul(oldExchangeRate).mul(oldDenominator).div(oldNumerator).div(10**18);

        //_totalSupply = _totalSupply.sub(amount);
        _balances[msg.sender][id].isWithdrawn = true;

        //get the reward after the discount rate is applied
        //rewardsToken.transfer(msg.sender, brainReceived);
        mint(msg.sender, brainReceived);
        emit Withdrawn(msg.sender, brainReceived);
    }

    function mint(address to, uint256 amount) internal{
        rewardsToken.mint(to, amount);
    }

    /* ========== RESTRICTED FUNCTIONS ========== */
    function setVestingPeriod(uint256 _vestingPeriod) external onlyOwner{
        vestingPeriod = _vestingPeriod;
        emit VestingPeriodUpdated(vestingPeriod);
    }

    function setDiscountRate(uint256 _discountRateNumerator, uint256 _discountRateDenominator) external onlyOwner{
        discountRateNumerator = _discountRateNumerator;
        discountRateDenominator = _discountRateDenominator;

        emit DiscountRateUpdated(discountRateNumerator, discountRateDenominator);
    }

    function unpause() external onlyOwner {
        isPaused = false;
        _unpause(); 
    } 

    function pause() external onlyOwner{
        isPaused = true;
        _pause();
    }
 
}