/**
 *Submitted for verification at polygonscan.com on 2021-07-22
*/

// SPDX-License-Identifier: MIT

/*
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 *
 *       $$___$_$$$$$$_$$$$$$_$$__$$
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 *       $$_$_$___$$_____$$___$$$$$$
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 */

pragma solidity ^0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

/**
 * @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);
}

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract OwnableData {
    address public owner;
    address public pendingOwner;
}

abstract contract Ownable is OwnableData {
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor () {
        owner = 0x4e5b3043FEB9f939448e2F791a66C4EA65A315a8;
        emit OwnershipTransferred(address(0), owner);
    }

    function transferOwnership(address newOwner, bool direct, bool renounce) public onlyOwner {
        if (direct) {

            require(newOwner != address(0) || renounce, "Ownable: zero address");

            emit OwnershipTransferred(owner, newOwner);
            owner = newOwner;
        } else {
            pendingOwner = newOwner;
        }
    }

    function claimOwnership() public {
        address _pendingOwner = pendingOwner;

        require(msg.sender == _pendingOwner, "Ownable: caller != pending owner");

        emit OwnershipTransferred(owner, _pendingOwner);
        owner = _pendingOwner;
        pendingOwner = address(0);
    }

    modifier onlyOwner() {
        require(msg.sender == owner, "Ownable: caller is not the owner");
        _;
    }
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// Genetic & Genome intakes one token and allows the user to farm another token.

contract Ribose_iFARM is Ownable {
    using SafeERC20 for IERC20;
    // Info of each user.
    struct UserInfo {
        uint256 amount; // How many tokens the user has provided.
        uint256 rewardDebt; // Reward debt. See explanation below.
        uint256 remainingYelTokenReward;  // YEL Tokens that weren't distributed for user per pool.
        //
        // Any point in time, the amount of YEL entitled to a user but is pending to be distributed is:
        // pending reward = (user.amount * pool.accYELPerShare) - user.rewardDebt
        //
        // Whenever a user deposits or withdraws Staked tokens to a pool. Here's what happens:
        //   1. The pool's `accYELPerShare` (and `lastRewardTime`) gets updated.
        //   2. User receives the pending reward sent to his/her address.
        //   3. User's `amount` gets updated.
        //   4. User's `rewardDebt` gets updated.
    }
    // Info of each pool.
    struct PoolInfo {
        IERC20 stakingToken; // Contract address of staked token
        uint256 stakingTokenTotalAmount; //Total amount of deposited tokens
        uint256 accYelPerShare; // Accumulated YEL per share, times 1e12. See below.
        uint32 lastRewardTime; // Last timestamp number that YEL distribution occurs.
        uint16 allocPoint; // How many allocation points assigned to this pool. YEL to distribute per second.
    }
    
    IERC20 immutable public yel; // The YEL token
    
    uint256 public yelPerSecond; // YEL tokens vested per second.
    
    PoolInfo[] public poolInfo; // Info of each pool.
    
    mapping(uint256 => mapping(address => UserInfo)) public userInfo; // Info of each user that stakes tokens.
    
    uint256 public totalAllocPoint = 0; // Total allocation points. Must be the sum of all allocation points in all pools.
    
    uint32 immutable public startTime; // The timestamp when YEL farming starts.
    
    uint32 public endTime; // Time on which the reward calculation should end

    event Deposit(address indexed user, uint256 indexed pid, uint256 amount);
    event Withdraw(address indexed user, uint256 indexed pid, uint256 amount);
    event EmergencyWithdraw(address indexed user, uint256 indexed pid, uint256 amount);

    constructor(
        IERC20 _yel,
        uint256 _yelPerSecond,
        uint32 _startTime
    ) {
        yel = _yel;

        yelPerSecond = _yelPerSecond;
        startTime = _startTime;
        endTime = _startTime + 7 days;
    }
    
    function changeEndTime(uint32 addSeconds) external onlyOwner {
        endTime += addSeconds;
    }
    
    // Changes YEL token reward per second. Use this function to moderate the `lockup amount`.
    // Essentially this function changes the amount of the reward which is entitled to the user
    // for his token staking by the time the `endTime` is passed.
    // Good practice to update pools without messing up the contract
    function setYelPerSecond(uint256 _yelPerSecond,  bool _withUpdate) external onlyOwner {
        if (_withUpdate) {
            massUpdatePools();
        }
        yelPerSecond= _yelPerSecond;
    }

    // How many pools are in the contract
    function poolLength() external view returns (uint256) {
        return poolInfo.length;
    }

    // Add a new staking token to the pool. Can only be called by the owner.
    // VERY IMPORTANT NOTICE 
    // ----------- DO NOT add the same staking token more than once. Rewards will be messed up if you do. -------------
    // Good practice to update pools without messing up the contract
    function add(
        uint16 _allocPoint,
        IERC20 _stakingToken,
        bool _withUpdate
    ) external onlyOwner {
        if (_withUpdate) {
            massUpdatePools();
        }
        uint256 lastRewardTime =
            block.timestamp > startTime ? block.timestamp : startTime;
        totalAllocPoint +=_allocPoint;
        poolInfo.push(
            PoolInfo({
                stakingToken: _stakingToken,
                stakingTokenTotalAmount: 0,
                allocPoint: _allocPoint,
                lastRewardTime: uint32(lastRewardTime),
                accYelPerShare: 0
            })
        );
    }

    // Update the given pool's YEL allocation point. Can only be called by the owner.
    // Good practice to update pools without messing up the contract
    function set(
        uint256 _pid,
        uint16 _allocPoint,
        bool _withUpdate
    ) external onlyOwner {
        if (_withUpdate) {
            massUpdatePools();
        }
        totalAllocPoint = totalAllocPoint - poolInfo[_pid].allocPoint + _allocPoint;
        poolInfo[_pid].allocPoint = _allocPoint;
    }

    // Return reward multiplier over the given _from to _to time.
    function getMultiplier(uint256 _from, uint256 _to)
        public
        view
        returns (uint256)
    {
        _from = _from > startTime ? _from : startTime;
        if (_from > endTime || _to < startTime) {
            return 0;
        }
        if (_to > endTime) {
            return endTime - _from;
        }
        return _to - _from;
    }

    // View function to see pending YEL on frontend.
    function pendingYel(uint256 _pid, address _user)
        external
        view
        returns (uint256)
    {
        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][_user];
        uint256 accYelPerShare = pool.accYelPerShare;
       
        if (block.timestamp > pool.lastRewardTime && pool.stakingTokenTotalAmount != 0) {
            uint256 multiplier =
                getMultiplier(pool.lastRewardTime, block.timestamp);
            uint256 yelReward =
                multiplier * yelPerSecond * pool.allocPoint / totalAllocPoint;
            accYelPerShare += yelReward * 1e12 / pool.stakingTokenTotalAmount;
        }
        return user.amount * accYelPerShare / 1e12 - user.rewardDebt + user.remainingYelTokenReward;
    }

    // Update reward variables for all pools. Be careful of gas spending!
    function massUpdatePools() public {
        uint256 length = poolInfo.length;
        for (uint256 pid = 0; pid < length; ++pid) {
            updatePool(pid);
        }
    }

    // Update reward variables of the given pool to be up-to-date.
    function updatePool(uint256 _pid) public {
        PoolInfo storage pool = poolInfo[_pid];
        if (block.timestamp <= pool.lastRewardTime) {
            return;
        }

        if (pool.stakingTokenTotalAmount == 0) {
            pool.lastRewardTime = uint32(block.timestamp);
            return;
        }
        uint256 multiplier = getMultiplier(pool.lastRewardTime, block.timestamp);
        uint256 yelReward =
            multiplier * yelPerSecond * pool.allocPoint / totalAllocPoint;
        pool.accYelPerShare += yelReward * 1e12 / pool.stakingTokenTotalAmount;
        pool.lastRewardTime = uint32(block.timestamp);
    }

    // Deposit staking tokens to Genetic & Genome for YEL allocation.
    function deposit(uint256 _pid, uint256 _amount) public {
        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][msg.sender];
        updatePool(_pid);
        if (user.amount > 0) {
            uint256 pending =
                user.amount * pool.accYelPerShare / 1e12 - user.rewardDebt + user.remainingYelTokenReward;
            user.remainingYelTokenReward = safeRewardTransfer(msg.sender, pending);
        }
        pool.stakingToken.safeTransferFrom(
            address(msg.sender),
            address(this),
            _amount
        );
        user.amount += _amount;
        pool.stakingTokenTotalAmount += _amount;
        user.rewardDebt = user.amount * pool.accYelPerShare / 1e12;
        emit Deposit(msg.sender, _pid, _amount);
    }

    // Withdraw staked tokens from Genetic & Genome.
    function withdraw(uint256 _pid, uint256 _amount) public {
        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][msg.sender];
        require(user.amount >= _amount, "Genetic & Genome: you do not have enough tokens to complete this operation");
        updatePool(_pid);
        uint256 pending =
            user.amount * pool.accYelPerShare / 1e12 - user.rewardDebt + user.remainingYelTokenReward;
        user.remainingYelTokenReward = safeRewardTransfer(msg.sender, pending);
        user.amount -= _amount;
        pool.stakingTokenTotalAmount -= _amount;
        user.rewardDebt = user.amount * pool.accYelPerShare / 1e12;
        pool.stakingToken.safeTransfer(address(msg.sender), _amount);
        emit Withdraw(msg.sender, _pid, _amount);
    }
    
    // Withdraw without caring about rewards. EMERGENCY ONLY.
    function emergencyWithdraw(uint256 _pid) public {
        PoolInfo storage pool = poolInfo[_pid];
        UserInfo storage user = userInfo[_pid][msg.sender];
        uint256 userAmount = user.amount;
        pool.stakingTokenTotalAmount -= userAmount;
        user.amount = 0;
        user.rewardDebt = 0;
        user.remainingYelTokenReward = 0;
        pool.stakingToken.safeTransfer(address(msg.sender), userAmount);
        emit EmergencyWithdraw(msg.sender, _pid, userAmount);
    }

    // Safe YEL transfer function. Just in case if the pool does not have enough YEL token,
    // The function returns the amount which is owed to the user
    function safeRewardTransfer(address _to, uint256 _amount) internal returns(uint256) {
        uint256 yelTokenBalance = yel.balanceOf(address(this));
        if (_amount > yelTokenBalance) {
            yel.safeTransfer(_to, yelTokenBalance);
            return _amount - yelTokenBalance;
        }
        yel.safeTransfer(_to, _amount);
        return 0;
    }
}