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*/

// SPDX-License-Identifier: MIT
pragma solidity 0.6.10;


/**
 * @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 in 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");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        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 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 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;
    }
}

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;
    using Address for address;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name, string memory symbol) public {
        _name = name;
        _symbol = symbol;
        _decimals = 18;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5,05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is
     * called.
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view returns (uint8) {
        return _decimals;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20};
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal {
        _decimals = decimals_;
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }
}

/**
 * @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");
        }
    }
}

interface ITrueFiPool2 is IERC20 {
    function token() external view returns (IERC20);

    /**
     * @dev Join the pool by depositing tokens
     * @param amount amount of tokens to deposit
     */
    function join(uint256 amount) external;

    /**
     * @dev borrow from pool
     * 1. Transfer TUSD to sender
     * 2. Only lending pool should be allowed to call this
     */
    function borrow(uint256 amount) external;

    /**
     * @dev pay borrowed money back to pool
     * 1. Transfer TUSD from sender
     * 2. Only lending pool should be allowed to call this
     */
    function repay(uint256 currencyAmount) external;
}

interface ILoanFactory2 {
    function createLoanToken(
        ITrueFiPool2 _pool,
        uint256 _amount,
        uint256 _term,
        uint256 _apy
    ) external;

    function isLoanToken(address) external view returns (bool);
}

interface ILoanToken2 is IERC20 {
    enum Status {Awaiting, Funded, Withdrawn, Settled, Defaulted, Liquidated}

    function borrower() external view returns (address);

    function amount() external view returns (uint256);

    function term() external view returns (uint256);

    function apy() external view returns (uint256);

    function start() external view returns (uint256);

    function lender() external view returns (address);

    function debt() external view returns (uint256);

    function pool() external view returns (ITrueFiPool2);

    function profit() external view returns (uint256);

    function status() external view returns (Status);

    function getParameters()
        external
        view
        returns (
            uint256,
            uint256,
            uint256
        );

    function fund() external;

    function withdraw(address _beneficiary) external;

    function settle() external;

    function enterDefault() external;

    function liquidate() external;

    function redeem(uint256 _amount) external;

    function repay(address _sender, uint256 _amount) external;

    function repayInFull(address _sender) external;

    function reclaim() external;

    function allowTransfer(address account, bool _status) external;

    function repaid() external view returns (uint256);

    function isRepaid() external view returns (bool);

    function balance() external view returns (uint256);

    function value(uint256 _balance) external view returns (uint256);

    function token() external view returns (IERC20);

    function version() external pure returns (uint8);
}

/**
 * @title LoanToken V2
 * @dev A token which represents share of a debt obligation
 *
 * Each LoanToken has:
 * - borrower address
 * - borrow amount
 * - loan term
 * - loan APY
 *
 * Loan progresses through the following states:
 * Awaiting:    Waiting for funding to meet capital requirements
 * Funded:      Capital requirements met, borrower can withdraw
 * Withdrawn:   Borrower withdraws money, loan waiting to be repaid
 * Settled:     Loan has been paid back in full with interest
 * Defaulted:   Loan has not been paid back in full
 * Liquidated:  Loan has Defaulted and stakers have been Liquidated
 *
 * - LoanTokens are non-transferable except for whitelisted addresses
 * - This version of LoanToken only supports a single funder
 */
contract LoanToken2 is ILoanToken2, ERC20 {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    uint128 public constant LAST_MINUTE_PAYBACK_DURATION = 1 days;
    uint256 private constant APY_PRECISION = 10000;

    address public override borrower;
    address public liquidator;
    uint256 public override amount;
    uint256 public override term;

    // apy precision: 10000 = 100%
    uint256 public override apy;

    uint256 public override start;
    address public override lender;
    uint256 public override debt;

    uint256 public redeemed;

    // whitelist for transfers
    mapping(address => bool) public canTransfer;

    Status public override status;

    IERC20 public override token;

    ITrueFiPool2 public override pool;

    /**
     * @dev Emitted when the loan is funded
     * @param lender Address which funded the loan
     */
    event Funded(address lender);

    /**
     * @dev Emitted when transfer whitelist is updated
     * @param account Account to whitelist for transfers
     * @param status New whitelist status
     */
    event TransferAllowanceChanged(address account, bool status);

    /**
     * @dev Emitted when borrower withdraws funds
     * @param beneficiary Account which will receive funds
     */
    event Withdrawn(address beneficiary);

    /**
     * @dev Emitted when loan has been fully repaid
     * @param returnedAmount Amount that was returned
     */
    event Settled(uint256 returnedAmount);

    /**
     * @dev Emitted when term is over without full repayment
     * @param returnedAmount Amount that was returned before expiry
     */
    event Defaulted(uint256 returnedAmount);

    /**
     * @dev Emitted when a LoanToken is redeemed for underlying tokens
     * @param receiver Receiver of tokens
     * @param burnedAmount Amount of LoanTokens burned
     * @param redeemedAmount Amount of token received
     */
    event Redeemed(address receiver, uint256 burnedAmount, uint256 redeemedAmount);

    /**
     * @dev Emitted when a LoanToken is repaid by the borrower in underlying tokens
     * @param repayer Sender of tokens
     * @param repaidAmount Amount of token repaid
     */
    event Repaid(address repayer, uint256 repaidAmount);

    /**
     * @dev Emitted when borrower reclaims remaining tokens
     * @param borrower Receiver of remaining tokens
     * @param reclaimedAmount Amount of tokens repaid
     */
    event Reclaimed(address borrower, uint256 reclaimedAmount);

    /**
     * @dev Emitted when loan gets liquidated
     * @param status Final loan status
     */
    event Liquidated(Status status);

    /**
     * @dev Create a Loan
     * @param _pool Pool to lend from
     * @param _borrower Borrower address
     * @param _lender Lender address
     * @param _liquidator Liquidator address
     * @param _amount Borrow amount of loaned tokens
     * @param _term Loan length
     * @param _apy Loan APY
     */
    constructor(
        ITrueFiPool2 _pool,
        address _borrower,
        address _lender,
        address _liquidator,
        uint256 _amount,
        uint256 _term,
        uint256 _apy
    ) public ERC20("TrueFi Loan Token", "LOAN") {
        require(_lender != address(0), "LoanToken2: Lender is not set");

        pool = _pool;
        token = _pool.token();
        borrower = _borrower;
        liquidator = _liquidator;
        amount = _amount;
        term = _term;
        apy = _apy;
        lender = _lender;
        debt = interest(amount);
    }

    /**
     * @dev Only borrower can withdraw & repay loan
     */
    modifier onlyBorrower() {
        require(msg.sender == borrower, "LoanToken2: Caller is not the borrower");
        _;
    }

    /**
     * @dev Only liquidator can liquidate
     */
    modifier onlyLiquidator() {
        require(msg.sender == liquidator, "LoanToken2: Caller is not the liquidator");
        _;
    }

    /**
     * @dev Only after loan has been closed: Settled, Defaulted, or Liquidated
     */
    modifier onlyAfterClose() {
        require(status >= Status.Settled, "LoanToken2: Only after loan has been closed");
        _;
    }

    /**
     * @dev Only when loan is Funded
     */
    modifier onlyOngoing() {
        require(status == Status.Funded || status == Status.Withdrawn, "LoanToken2: Current status should be Funded or Withdrawn");
        _;
    }

    /**
     * @dev Only when loan is Funded
     */
    modifier onlyFunded() {
        require(status == Status.Funded, "LoanToken2: Current status should be Funded");
        _;
    }

    /**
     * @dev Only when loan is Withdrawn
     */
    modifier onlyAfterWithdraw() {
        require(status >= Status.Withdrawn, "LoanToken2: Only after loan has been withdrawn");
        _;
    }

    /**
     * @dev Only when loan is Awaiting
     */
    modifier onlyAwaiting() {
        require(status == Status.Awaiting, "LoanToken2: Current status should be Awaiting");
        _;
    }

    /**
     * @dev Only when loan is Defaulted
     */
    modifier onlyDefaulted() {
        require(status == Status.Defaulted, "LoanToken2: Current status should be Defaulted");
        _;
    }

    /**
     * @dev Only whitelisted accounts or lender
     */
    modifier onlyWhoCanTransfer(address sender) {
        require(
            sender == lender || canTransfer[sender],
            "LoanToken2: This can be performed only by lender or accounts allowed to transfer"
        );
        _;
    }

    /**
     * @dev Only lender can perform certain actions
     */
    modifier onlyLender() {
        require(msg.sender == lender, "LoanToken2: This can be performed only by lender");
        _;
    }

    /**
     * @dev Get loan parameters
     * @return amount, term, apy
     */
    function getParameters()
        external
        override
        view
        returns (
            uint256,
            uint256,
            uint256
        )
    {
        return (amount, apy, term);
    }

    /**
     * @dev Get coupon value of this loan token in token
     * This assumes the loan will be paid back on time, with interest
     * @param _balance number of LoanTokens to get value for
     * @return coupon value of _balance LoanTokens in tokens
     */
    function value(uint256 _balance) external override view returns (uint256) {
        if (_balance == 0) {
            return 0;
        }

        uint256 passed = block.timestamp.sub(start);
        if (passed > term || status == Status.Settled) {
            passed = term;
        }

        // assume year is 365 days
        uint256 interest = amount.mul(apy).mul(passed).div(365 days).div(APY_PRECISION);

        return amount.add(interest).mul(_balance).div(debt);
    }

    /**
     * @dev Fund a loan
     * Set status, start time, lender
     */
    function fund() external override onlyAwaiting onlyLender {
        status = Status.Funded;
        start = block.timestamp;
        _mint(msg.sender, debt);
        token.safeTransferFrom(msg.sender, address(this), amount);

        emit Funded(msg.sender);
    }

    /**
     * @dev Whitelist accounts to transfer
     * @param account address to allow transfers for
     * @param _status true allows transfers, false disables transfers
     */
    function allowTransfer(address account, bool _status) external override onlyLender {
        canTransfer[account] = _status;
        emit TransferAllowanceChanged(account, _status);
    }

    /**
     * @dev Borrower calls this function to withdraw funds
     * Sets the status of the loan to Withdrawn
     * @param _beneficiary address to send funds to
     */
    function withdraw(address _beneficiary) external override onlyBorrower onlyFunded {
        status = Status.Withdrawn;
        token.safeTransfer(_beneficiary, amount);

        emit Withdrawn(_beneficiary);
    }

    /**
     * @dev Settle the loan after checking it has been repaid
     */
    function settle() public override onlyOngoing {
        require(isRepaid(), "LoanToken2: loan must be repaid to settle");
        status = Status.Settled;
        emit Settled(_balance());
    }

    /**
     * @dev Default the loan if it has not been repaid by the end of term
     */
    function enterDefault() external override onlyOngoing {
        require(!isRepaid(), "LoanToken2: cannot default a repaid loan");
        require(start.add(term).add(LAST_MINUTE_PAYBACK_DURATION) <= block.timestamp, "LoanToken2: Loan cannot be defaulted yet");
        status = Status.Defaulted;
        emit Defaulted(_balance());
    }

    /**
     * @dev Liquidate the loan if it has defaulted
     */
    function liquidate() external override onlyDefaulted onlyLiquidator {
        status = Status.Liquidated;

        emit Liquidated(status);
    }

    /**
     * @dev Redeem LoanToken balances for underlying token
     * Can only call this function after the loan is Closed
     * @param _amount amount to redeem
     */
    function redeem(uint256 _amount) external override onlyAfterClose {
        uint256 amountToReturn = _amount.mul(_balance()).div(totalSupply());
        redeemed = redeemed.add(amountToReturn);
        _burn(msg.sender, _amount);
        token.safeTransfer(msg.sender, amountToReturn);

        emit Redeemed(msg.sender, _amount, amountToReturn);
    }

    /**
     * @dev Function for borrower to repay the loan
     * Borrower can repay at any time
     * @param _sender account sending token to repay
     * @param _amount amount of token to repay
     */
    function repay(address _sender, uint256 _amount) external override {
        _repay(_sender, _amount);
    }

    /**
     * @dev Function for borrower to repay all of the remaining loan balance
     * Borrower should use this to ensure full repayment
     * @param _sender account sending token to repay
     */
    function repayInFull(address _sender) external override {
        _repay(_sender, debt.sub(_balance()));
    }

    /**
     * @dev Internal function for loan repayment
     * If _amount is sufficient, then this also settles the loan
     * @param _sender account sending token to repay
     * @param _amount amount of token to repay
     */
    function _repay(address _sender, uint256 _amount) internal onlyAfterWithdraw {
        require(_amount <= debt.sub(_balance()), "LoanToken2: Cannot repay over the debt");
        emit Repaid(_sender, _amount);

        token.safeTransferFrom(_sender, address(this), _amount);
        if (isRepaid()) {
            settle();
        }
    }

    /**
     * @dev Function for borrower to reclaim stuck token
     * Can only call this function after the loan is Closed
     * and all of LoanToken holders have been burnt
     */
    function reclaim() external override onlyAfterClose onlyBorrower {
        require(totalSupply() == 0, "LoanToken2: Cannot reclaim when LoanTokens are in circulation");
        uint256 balanceRemaining = _balance();
        require(balanceRemaining > 0, "LoanToken2: Cannot reclaim when balance 0");

        token.safeTransfer(borrower, balanceRemaining);
        emit Reclaimed(borrower, balanceRemaining);
    }

    /**
     * @dev Check how much was already repaid
     * Funds stored on the contract's address plus funds already redeemed by lenders
     * @return Uint256 representing what value was already repaid
     */
    function repaid() external override view onlyAfterWithdraw returns (uint256) {
        return _balance().add(redeemed);
    }

    /**
     * @dev Check whether an ongoing loan has been repaid in full
     * @return true if and only if this loan has been repaid
     */
    function isRepaid() public override view onlyOngoing returns (bool) {
        return _balance() >= debt;
    }

    /**
     * @dev Public currency token balance function
     * @return token balance of this contract
     */
    function balance() external override view returns (uint256) {
        return _balance();
    }

    /**
     * @dev Get currency token balance for this contract
     * @return token balance of this contract
     */
    function _balance() internal view returns (uint256) {
        return token.balanceOf(address(this));
    }

    /**
     * @dev Calculate interest that will be paid by this loan for an amount (returned funds included)
     * amount + ((amount * apy * term) / 365 days / precision)
     * @param _amount amount
     * @return uint256 Amount of interest paid for _amount
     */
    function interest(uint256 _amount) internal view returns (uint256) {
        return _amount.add(_amount.mul(apy).mul(term).div(365 days).div(APY_PRECISION));
    }

    /**
     * @dev get profit for this loan
     * @return profit for this loan
     */
    function profit() external override view returns (uint256) {
        return debt.sub(amount);
    }

    /**
     * @dev Override ERC20 _transfer so only whitelisted addresses can transfer
     * @param sender sender of the transaction
     * @param recipient recipient of the transaction
     * @param _amount amount to send
     */
    function _transfer(
        address sender,
        address recipient,
        uint256 _amount
    ) internal override onlyWhoCanTransfer(sender) {
        return super._transfer(sender, recipient, _amount);
    }

    function version() external override pure returns (uint8) {
        return 4;
    }
}