// File: lib/communal/Address.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.11 <0.9.0;

/**
 * @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);
            }
        }
    }
}
// File: lib/communal/Context.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.11;

/*
 * @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 GSN 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 payable) {
        return payable(msg.sender);
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// File: lib/communal/IERC20.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.11;

import "./Context.sol";
import "./SafeMath.sol";

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
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);
}


// File: lib/communal/Math.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.11;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }

    // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
    function sqrt(uint y) internal pure returns (uint z) {
        if (y > 3) {
            z = y;
            uint x = y / 2 + 1;
            while (x < z) {
                z = x;
                x = (y / x + x) / 2;
            }
        } else if (y != 0) {
            z = 1;
        }
    }
}
// File: lib/communal/Owned.sol



// SPDX-License-Identifier: GPL-2.0-or-later
pragma solidity >=0.6.11;

// https://docs.synthetix.io/contracts/Owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor (address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        require(msg.sender == owner, "Only the contract owner may perform this action");
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}
// File: lib/communal/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.11;

/**
 * @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 () internal {
        _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 make 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;
    }
}
// File: lib/communal/SafeERC20.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.11;

import "./IERC20.sol";
import "./SafeMath.sol";
import "./Address.sol";

/**
 * @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 SafeMath for uint256;
    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).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _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");
        }
    }
}
// File: lib/communal/SafeMath.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.11;

/**
 * @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: lib/communal/TransferHelper.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.11;

// helper methods for interacting with ERC20 tokens and sending ETH that do not consistently return true/false
library TransferHelper {
    function safeApprove(address token, address to, uint value) internal {
        // bytes4(keccak256(bytes('approve(address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x095ea7b3, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: APPROVE_FAILED');
    }

    function safeTransfer(address token, address to, uint value) internal {
        // bytes4(keccak256(bytes('transfer(address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0xa9059cbb, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: TRANSFER_FAILED');
    }

    function safeTransferFrom(address token, address from, address to, uint value) internal {
        // bytes4(keccak256(bytes('transferFrom(address,address,uint256)')));
        (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x23b872dd, from, to, value));
        require(success && (data.length == 0 || abi.decode(data, (bool))), 'TransferHelper: TRANSFER_FROM_FAILED');
    }

    function safeTransferETH(address to, uint value) internal {
        (bool success,) = to.call{value:value}(new bytes(0));
        require(success, 'TransferHelper: ETH_TRANSFER_FAILED');
    }
}
// File: src/CommunalFarm.sol



// SPDX-License-Identifier: GPL-2.0-or-later
pragma solidity >=0.6.11;
pragma experimental ABIEncoderV2;

// ====================================================================
// |     ______                   _______                             |
// |    / _____________ __  __   / ____(_____  ____ _____  ________   |
// |   / /_  / ___/ __ `| |/_/  / /_  / / __ \/ __ `/ __ \/ ___/ _ \  |
// |  / __/ / /  / /_/ _>  <   / __/ / / / / / /_/ / / / / /__/  __/  |
// | /_/   /_/   \__,_/_/|_|  /_/   /_/_/ /_/\__,_/_/ /_/\___/\___/   |
// |                                                                  |
// ====================================================================
// =========================== CommunalFarm ===========================
// ====================================================================
// Multiple tokens with different reward rates can be emitted
// Multiple teams can set the reward rates for their token(s)
// Apes together strong

// Frax Finance: https://github.com/FraxFinance

// Primary Author(s)
// Travis Moore: https://github.com/FortisFortuna

// Reviewer(s) / Contributor(s)
// Jason Huan: https://github.com/jasonhuan 
// Sam Kazemian: https://github.com/samkazemian
// Saddle Team: https://github.com/saddle-finance
// Fei Team: https://github.com/fei-protocol
// Alchemix Team: https://github.com/alchemix-finance
// Liquity Team: https://github.com/liquity

// Originally inspired by Synthetix.io, but heavily modified by the Frax team
// https://raw.githubusercontent.com/Synthetixio/synthetix/develop/contracts/StakingRewards.sol

import "communal/Math.sol";
import "communal/SafeMath.sol";
import "communal/SafeERC20.sol";
import 'communal/TransferHelper.sol';
import "communal/ReentrancyGuard.sol";

// Inheritance
import "communal/Owned.sol";

contract USHFarm is Owned, ReentrancyGuard {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    /* ========== STATE VARIABLES ========== */

    // Instances
    IERC20 public stakingToken;
    
    // Constant for various precisions
    uint256 private constant MULTIPLIER_PRECISION = 1e18;

    // Time tracking
    uint256 public periodFinish;
    uint256 public lastUpdateTime;

    // Lock time and multiplier settings
    uint256 public lock_max_multiplier = uint256(3e18); // E18. 1x = e18
    uint256 public lock_time_for_max_multiplier = 1 * 60 * 86400; // 1 year
    uint256 public lock_time_min = 86400; // 1 * 86400  (1 day)

    // Reward addresses, rates, and managers
    mapping(address => address) public rewardManagers; // token addr -> manager addr
    address[] public rewardTokens;
    uint256[] public rewardRates;
    string[] public rewardSymbols;
    mapping(address => uint256) public rewardTokenAddrToIdx; // token addr -> token index
    
    // Reward period
    uint256 public rewardsDuration = 604800; // 7 * 86400  (7 days)

    // Reward tracking
    uint256[] private rewardsPerTokenStored;
    mapping(address => mapping(uint256 => uint256)) private userRewardsPerTokenPaid; // staker addr -> token id -> paid amount
    mapping(address => mapping(uint256 => uint256)) private rewards; // staker addr -> token id -> reward amount
    mapping(address => uint256) private lastRewardClaimTime; // staker addr -> timestamp

    // Balance tracking
    uint256 private _total_liquidity_locked;
    uint256 private _total_combined_weight;
    mapping(address => uint256) private _locked_liquidity;
    mapping(address => uint256) private _combined_weights;

    // Stake tracking
    mapping(address => LockedStake[]) private lockedStakes;

    // Greylisting of bad addresses
    mapping(address => bool) public greylist; //how long until this one is offensive too?

    // Administrative booleans
    bool public stakesUnlocked; // Release locked stakes in case of emergency
    bool public withdrawalsPaused; // For emergencies
    bool public rewardsCollectionPaused; // For emergencies
    bool public stakingPaused; // For emergencies

    /* ========== STRUCTS ========== */
    
    struct LockedStake {
        bytes32 kek_id;
        uint256 start_timestamp;
        uint256 liquidity;
        uint256 ending_timestamp;
        uint256 lock_multiplier; // 6 decimals of precision. 1x = 1000000
    }

    /* ========== MODIFIERS ========== */

    modifier onlyByOwner() {
        require(msg.sender == owner, "Not the owner");
        _;
    }

    modifier onlyTknMgrs(address reward_token_address) {
        require(msg.sender == owner || isTokenManagerFor(msg.sender, reward_token_address), "Not owner or tkn mgr");
        _;
    }

    modifier notStakingPaused() {
        require(stakingPaused == false, "Staking paused");
        _;
    }

    modifier updateRewardAndBalance(address account, bool sync_too) {
        _updateRewardAndBalance(account, sync_too);
        _;
    }
    
    /* ========== CONSTRUCTOR ========== */

    constructor (
        address _owner,
        address _stakingToken,
        string[] memory _rewardSymbols,
        address[] memory _rewardTokens,
        address[] memory _rewardManagers,
        uint256[] memory _rewardRates
    ) Owned(_owner){
        stakingToken = IERC20(_stakingToken);

        rewardTokens = _rewardTokens;
        rewardRates = _rewardRates;
        rewardSymbols = _rewardSymbols;

        for (uint256 i = 0; i < _rewardTokens.length; i++){ 
            // For fast token address -> token ID lookups later
            rewardTokenAddrToIdx[_rewardTokens[i]] = i;

            // Initialize the stored rewards
            rewardsPerTokenStored.push(0);

            // Initialize the reward managers
            rewardManagers[_rewardTokens[i]] = _rewardManagers[i];
        }

        // Other booleans
        stakesUnlocked = false;

        // Initialization
        lastUpdateTime = block.timestamp;
        periodFinish = block.timestamp.add(rewardsDuration);
    }

    /* ========== VIEWS ========== */

    // Total locked liquidity tokens
    function totalLiquidityLocked() external view returns (uint256) {
        return _total_liquidity_locked;
    }

    // Locked liquidity for a given account
    function lockedLiquidityOf(address account) external view returns (uint256) {
        return _locked_liquidity[account];
    }

    // Total 'balance' used for calculating the percent of the pool the account owns
    // Takes into account the locked stake time multiplier
    function totalCombinedWeight() external view returns (uint256) {
        return _total_combined_weight;
    }

    // Combined weight for a specific account
    function combinedWeightOf(address account) external view returns (uint256) {
        return _combined_weights[account];
    }

    // Calculated the combined weight for an account
    function calcCurCombinedWeight(address account) public view
        returns (
            uint256 old_combined_weight,
            uint256 new_combined_weight
        )
    {
        // Get the old combined weight
        old_combined_weight = _combined_weights[account];

        // Loop through the locked stakes, first by getting the liquidity * lock_multiplier portion
        new_combined_weight = 0;
        for (uint256 i = 0; i < lockedStakes[account].length; i++) {
            LockedStake memory thisStake = lockedStakes[account][i];
            uint256 lock_multiplier = thisStake.lock_multiplier;

            // If the lock is expired
            if (thisStake.ending_timestamp <= block.timestamp) {
                // If the lock expired in the time since the last claim, the weight needs to be proportionately averaged this time
                if (lastRewardClaimTime[account] < thisStake.ending_timestamp){
                    uint256 time_before_expiry = (thisStake.ending_timestamp).sub(lastRewardClaimTime[account]);
                    uint256 time_after_expiry = (block.timestamp).sub(thisStake.ending_timestamp);

                    // Get the weighted-average lock_multiplier
                    uint256 numerator = ((lock_multiplier).mul(time_before_expiry)).add(((MULTIPLIER_PRECISION).mul(time_after_expiry)));
                    lock_multiplier = numerator.div(time_before_expiry.add(time_after_expiry));
                }
                // Otherwise, it needs to just be 1x
                else {
                    lock_multiplier = MULTIPLIER_PRECISION;
                }
            }

            uint256 liquidity = thisStake.liquidity;
            uint256 combined_boosted_amount = liquidity.mul(lock_multiplier).div(MULTIPLIER_PRECISION);
            new_combined_weight = new_combined_weight.add(combined_boosted_amount);
        }
    }

    // All the locked stakes for a given account
    function lockedStakesOf(address account) external view returns (LockedStake[] memory) {
        return lockedStakes[account];
    }

    // All the locked stakes for a given account
    function getRewardSymbols() external view returns (string[] memory) {
        return rewardSymbols;
    }

    // All the reward tokens
    function getAllRewardTokens() external view returns (address[] memory) {
        return rewardTokens;
    }

    // All the reward rates
    function getAllRewardRates() external view returns (uint256[] memory) {
        return rewardRates;
    }
    
    // Multiplier amount, given the length of the lock
    function lockMultiplier(uint256 secs) public view returns (uint256) {
        uint256 lock_multiplier =
            uint256(MULTIPLIER_PRECISION).add(
                secs
                    .mul(lock_max_multiplier.sub(MULTIPLIER_PRECISION))
                    .div(lock_time_for_max_multiplier)
            );
        if (lock_multiplier > lock_max_multiplier) lock_multiplier = lock_max_multiplier;
        return lock_multiplier;
    }

    // Last time the reward was applicable
    function lastTimeRewardApplicable() internal view returns (uint256) {
        return Math.min(block.timestamp, periodFinish);
    }

    // Amount of reward tokens per LP token
    function rewardsPerToken() public view returns (uint256[] memory newRewardsPerTokenStored) {
        if (_total_liquidity_locked == 0 || _total_combined_weight == 0) {
            return rewardsPerTokenStored;
        }
        else {
            newRewardsPerTokenStored = new uint256[](rewardTokens.length);
            for (uint256 i = 0; i < rewardsPerTokenStored.length; i++){ 
                newRewardsPerTokenStored[i] = rewardsPerTokenStored[i].add(
                    lastTimeRewardApplicable().sub(lastUpdateTime).mul(rewardRates[i]).mul(1e18).div(_total_combined_weight)
                );
            }
            return newRewardsPerTokenStored;
        }
    }

    // Amount of reward tokens an account has earned / accrued
    // Note: In the edge-case of one of the account's stake expiring since the last claim, this will
    // return a slightly inflated number
    function earned(address account) public view returns (uint256[] memory new_earned) {
        uint256[] memory reward_arr = rewardsPerToken();
        new_earned = new uint256[](rewardTokens.length);

        if (_combined_weights[account] == 0){
            for (uint256 i = 0; i < rewardTokens.length; i++){ 
                new_earned[i] = 0;
            }
        }
        else {
            for (uint256 i = 0; i < rewardTokens.length; i++){ 
                new_earned[i] = (_combined_weights[account])
                    .mul(reward_arr[i].sub(userRewardsPerTokenPaid[account][i]))
                    .div(1e18)
                    .add(rewards[account][i]);
            }
        }
    }

    // Total reward tokens emitted in the given period
    function getRewardForDuration() external view returns (uint256[] memory rewards_per_duration_arr) {
        rewards_per_duration_arr = new uint256[](rewardRates.length);

        for (uint256 i = 0; i < rewardRates.length; i++){ 
            rewards_per_duration_arr[i] = rewardRates[i].mul(rewardsDuration);
        }
    }

    // See if the caller_addr is a manager for the reward token 
    function isTokenManagerFor(address caller_addr, address reward_token_addr) public view returns (bool){
        if (caller_addr == owner) return true; // Contract owner
        else if (rewardManagers[reward_token_addr] == caller_addr) return true; // Reward manager
        return false; 
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    function _updateRewardAndBalance(address account, bool sync_too) internal {
        // Need to retro-adjust some things if the period hasn't been renewed, then start a new one
        if (sync_too){
            sync();
        }
        
        if (account != address(0)) {
            // To keep the math correct, the user's combined weight must be recomputed
            (   
                uint256 old_combined_weight,
                uint256 new_combined_weight
            ) = calcCurCombinedWeight(account);

            // Calculate the earnings first
            _syncEarned(account);

            // Update the user's and the global combined weights
            if (new_combined_weight >= old_combined_weight) {
                uint256 weight_diff = new_combined_weight.sub(old_combined_weight);
                _total_combined_weight = _total_combined_weight.add(weight_diff);
                _combined_weights[account] = old_combined_weight.add(weight_diff);
            } else {
                uint256 weight_diff = old_combined_weight.sub(new_combined_weight);
                _total_combined_weight = _total_combined_weight.sub(weight_diff);
                _combined_weights[account] = old_combined_weight.sub(weight_diff);
            }

        }
    }

    function _syncEarned(address account) internal {
        if (account != address(0)) {
            // Calculate the earnings
            uint256[] memory earned_arr = earned(account);

            // Update the rewards array
            for (uint256 i = 0; i < earned_arr.length; i++){ 
                rewards[account][i] = earned_arr[i];
            }

            // Update the rewards paid array
            for (uint256 i = 0; i < earned_arr.length; i++){ 
                userRewardsPerTokenPaid[account][i] = rewardsPerTokenStored[i];
            }
        }
    }

    // Two different stake functions are needed because of delegateCall and msg.sender issues
    function stakeLocked(uint256 liquidity, uint256 secs) nonReentrant public {
        _stakeLocked(msg.sender, msg.sender, liquidity, secs, block.timestamp);
    }

    // If this were not internal, and source_address had an infinite approve, this could be exploitable
    // (pull funds from source_address and stake for an arbitrary staker_address)
    function _stakeLocked(
        address staker_address, 
        address source_address, 
        uint256 liquidity, 
        uint256 secs,
        uint256 start_timestamp
    ) internal updateRewardAndBalance(staker_address, true) {
        require(!stakingPaused, "Staking paused");
        require(liquidity > 0, "Must stake more than zero");
        require(greylist[staker_address] == false, "Address has been greylisted");
        require(secs >= lock_time_min, "Minimum stake time not met");
        require(secs <= lock_time_for_max_multiplier,"Trying to lock for too long");

        uint256 lock_multiplier = lockMultiplier(secs);
        bytes32 kek_id = keccak256(abi.encodePacked(staker_address, start_timestamp, liquidity, _locked_liquidity[staker_address]));
        lockedStakes[staker_address].push(LockedStake(
            kek_id,
            start_timestamp,
            liquidity,
            start_timestamp.add(secs),
            lock_multiplier
        ));

        // Pull the tokens from the source_address
        //TODO: do we even need this if we're dealing with Sushi LP not saddle?
        TransferHelper.safeTransferFrom(address(stakingToken), source_address, address(this), liquidity);

        // Update liquidities
        _total_liquidity_locked = _total_liquidity_locked.add(liquidity);
        _locked_liquidity[staker_address] = _locked_liquidity[staker_address].add(liquidity);

        // Need to call to update the combined weights
        _updateRewardAndBalance(staker_address, false);

        // Needed for edge case if the staker only claims once, and after the lock expired
        if (lastRewardClaimTime[staker_address] == 0) lastRewardClaimTime[staker_address] = block.timestamp;

        emit StakeLocked(staker_address, liquidity, secs, kek_id, source_address);
    }

    // Two different withdrawLocked functions are needed because of delegateCall and msg.sender issues
    function withdrawLocked(bytes32 kek_id) nonReentrant public {
        require(withdrawalsPaused == false, "Withdrawals paused");
        _withdrawLocked(msg.sender, msg.sender, kek_id);
    }

    // No withdrawer == msg.sender check needed since this is only internally callable and the checks are done in the wrapper
    // functions like withdraw()
    function _withdrawLocked(address staker_address, address destination_address, bytes32 kek_id) internal  {
        // Collect rewards first and then update the balances
        _getReward(staker_address, destination_address);

        LockedStake memory thisStake;
        thisStake.liquidity = 0;
        uint theArrayIndex;
        for (uint256 i = 0; i < lockedStakes[staker_address].length; i++){ 
            if (kek_id == lockedStakes[staker_address][i].kek_id){
                thisStake = lockedStakes[staker_address][i];
                theArrayIndex = i;
                break;
            }
        }
        require(thisStake.kek_id == kek_id, "Stake not found");
        require(block.timestamp >= thisStake.ending_timestamp || stakesUnlocked == true, "Stake is still locked!");

        uint256 liquidity = thisStake.liquidity;

        if (liquidity > 0) {
            // Update liquidities
            _total_liquidity_locked = _total_liquidity_locked.sub(liquidity);
            _locked_liquidity[staker_address] = _locked_liquidity[staker_address].sub(liquidity);

            // Remove the stake from the array
            delete lockedStakes[staker_address][theArrayIndex];

            // Need to call to update the combined weights
            _updateRewardAndBalance(staker_address, false);

            // Give the tokens to the destination_address
            // Should throw if insufficient balance
            stakingToken.transfer(destination_address, liquidity);

            emit WithdrawLocked(staker_address, liquidity, kek_id, destination_address);
        }

    }
    
    // Two different getReward functions are needed because of delegateCall and msg.sender issues
    function getReward() external nonReentrant returns (uint256[] memory) {
        require(rewardsCollectionPaused == false,"Rewards collection paused");
        return _getReward(msg.sender, msg.sender);
    }

    // No withdrawer == msg.sender check needed since this is only internally callable
    function _getReward(address rewardee, address destination_address) internal updateRewardAndBalance(rewardee, true) returns (uint256[] memory rewards_before) {
        // Update the rewards array and distribute rewards
        rewards_before = new uint256[](rewardTokens.length);

        for (uint256 i = 0; i < rewardTokens.length; i++){ 
            rewards_before[i] = rewards[rewardee][i];
            rewards[rewardee][i] = 0;
            //use SafeERC20.transfer
            IERC20(rewardTokens[i]).transfer(destination_address, rewards_before[i]);
            emit RewardPaid(rewardee, rewards_before[i], rewardTokens[i], destination_address);
        }

        lastRewardClaimTime[rewardee] = block.timestamp;
    }

    // If the period expired, renew it
    function retroCatchUp() internal {
        // Failsafe check
        require(block.timestamp > periodFinish, "Period has not expired yet!");

        // Ensure the provided reward amount is not more than the balance in the contract.
        // This keeps the reward rate in the right range, preventing overflows due to
        // very high values of rewardRate in the earned and rewardsPerToken functions;
        // Reward + leftover must be less than 2^256 / 10^18 to avoid overflow.
        uint256 num_periods_elapsed = uint256(block.timestamp.sub(periodFinish)) / rewardsDuration; // Floor division to the nearest period
        
        // Make sure there are enough tokens to renew the reward period
        for (uint256 i = 0; i < rewardTokens.length; i++){ 
            require(rewardRates[i].mul(rewardsDuration).mul(num_periods_elapsed + 1) <= IERC20(rewardTokens[i]).balanceOf(address(this)), string(abi.encodePacked("Not enough reward tokens available: ", rewardTokens[i])) );
        }
        
        // uint256 old_lastUpdateTime = lastUpdateTime;
        // uint256 new_lastUpdateTime = block.timestamp;

        // lastUpdateTime = periodFinish;
        periodFinish = periodFinish.add((num_periods_elapsed.add(1)).mul(rewardsDuration));

        _updateStoredRewardsAndTime();

        emit RewardsPeriodRenewed(address(stakingToken));
    }

    function _updateStoredRewardsAndTime() internal {
        // Get the rewards
        uint256[] memory rewards_per_token = rewardsPerToken();

        // Update the rewardsPerTokenStored
        for (uint256 i = 0; i < rewardsPerTokenStored.length; i++){ 
            rewardsPerTokenStored[i] = rewards_per_token[i];
        }

        // Update the last stored time
        lastUpdateTime = lastTimeRewardApplicable();
    }

    function sync() public {
        if (block.timestamp > periodFinish) {
            retroCatchUp();
        }
        else {
            _updateStoredRewardsAndTime();
        }
    }

    /* ========== RESTRICTED FUNCTIONS ========== */

    // Added to support recovering LP Rewards and other mistaken tokens from other systems to be distributed to holders
    function recoverERC20(address tokenAddress, uint256 tokenAmount) external onlyTknMgrs(tokenAddress) {
        // Cannot rug the staking / LP tokens
        require(tokenAddress != address(stakingToken), "Cannot rug staking / LP tokens");

        // Check if the desired token is a reward token
        bool isRewardToken = false;
        for (uint256 i = 0; i < rewardTokens.length; i++){ 
            if (rewardTokens[i] == tokenAddress) {
                isRewardToken = true;
                break;
            }
        }

        // Only the reward managers can take back their reward tokens
        if (isRewardToken && rewardManagers[tokenAddress] == msg.sender){
            IERC20(tokenAddress).transfer(msg.sender, tokenAmount);
            emit Recovered(msg.sender, tokenAddress, tokenAmount);
            return;
        }

        // Other tokens, like airdrops or accidental deposits, can be withdrawn by the owner
        else if (!isRewardToken && (msg.sender == owner)){
            IERC20(tokenAddress).transfer(msg.sender, tokenAmount);
            emit Recovered(msg.sender, tokenAddress, tokenAmount);
            return;
        }

        // If none of the above conditions are true
        else {
            revert("No valid tokens to recover");
        }
    }

    function setRewardsDuration(uint256 _rewardsDuration) external onlyByOwner {
        require(_rewardsDuration >= 86400, "Rewards duration too short");
        require(
            periodFinish == 0 || block.timestamp > periodFinish,
            "Reward period incomplete"
        );
        rewardsDuration = _rewardsDuration;
        emit RewardsDurationUpdated(rewardsDuration);
    }

    function setMultipliers(uint256 _lock_max_multiplier) external onlyByOwner {
        require(_lock_max_multiplier >= uint256(1e18), "Multiplier must be greater than or equal to 1e18");
        lock_max_multiplier = _lock_max_multiplier;
        emit LockedStakeMaxMultiplierUpdated(lock_max_multiplier);
    }

    function setLockedStakeTimeForMinAndMaxMultiplier(uint256 _lock_time_for_max_multiplier, uint256 _lock_time_min) external onlyByOwner {
        require(_lock_time_for_max_multiplier >= 1, "Mul max time must be >= 1");
        require(_lock_time_min >= 1, "Mul min time must be >= 1");

        lock_time_for_max_multiplier = _lock_time_for_max_multiplier;
        lock_time_min = _lock_time_min;

        emit LockedStakeTimeForMaxMultiplier(lock_time_for_max_multiplier);
        emit LockedStakeMinTime(_lock_time_min);
    }

    function greylistAddress(address _address) external onlyByOwner {
        greylist[_address] = !(greylist[_address]);
    }

    function unlockStakes() external onlyByOwner {
        stakesUnlocked = !stakesUnlocked;
    }

    function toggleStaking() external onlyByOwner {
        stakingPaused = !stakingPaused;
    }

    function toggleWithdrawals() external onlyByOwner {
        withdrawalsPaused = !withdrawalsPaused;
    }

    function toggleRewardsCollection() external onlyByOwner {
        rewardsCollectionPaused = !rewardsCollectionPaused;
    }

    // The owner or the reward token managers can set reward rates 
    function setRewardRate(address reward_token_address, uint256 new_rate, bool sync_too) external onlyTknMgrs(reward_token_address) {
        rewardRates[rewardTokenAddrToIdx[reward_token_address]] = new_rate;
        
        if (sync_too){
            sync();
        }
    }

    // The owner or the reward token managers can change managers
    function changeTokenManager(address reward_token_address, address new_manager_address) external onlyTknMgrs(reward_token_address) {
        rewardManagers[reward_token_address] = new_manager_address;
    }

    /* ========== EVENTS ========== */

    event StakeLocked(address indexed user, uint256 amount, uint256 secs, bytes32 kek_id, address source_address);
    event WithdrawLocked(address indexed user, uint256 amount, bytes32 kek_id, address destination_address);
    event RewardPaid(address indexed user, uint256 reward, address token_address, address destination_address);
    event RewardsDurationUpdated(uint256 newDuration);
    event Recovered(address destination_address, address token, uint256 amount);
    event RewardsPeriodRenewed(address token);
    event LockedStakeMaxMultiplierUpdated(uint256 multiplier);
    event LockedStakeTimeForMaxMultiplier(uint256 secs);
    event LockedStakeMinTime(uint256 secs);
}