Theta Smart Contracts | ThetaScan.io

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Published Contract:

// File @openzeppelin/contracts/utils/Context.sol@v3.4.2

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @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;
 }
}


// File @openzeppelin/contracts/access/Ownable.sol@v3.4.2



pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
 address private _owner;

 event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

 /**
 * @dev Initializes the contract setting the deployer as the initial owner.
 */
 constructor () internal {
 address msgSender = _msgSender();
 _owner = msgSender;
 emit OwnershipTransferred(address(0), msgSender);
 }

 /**
 * @dev Returns the address of the current owner.
 */
 function owner() public view virtual returns (address) {
 return _owner;
 }

 /**
 * @dev Throws if called by any account other than the owner.
 */
 modifier onlyOwner() {
 require(owner() == _msgSender(), "Ownable: caller is not the owner");
 _;
 }

 /**
 * @dev Leaves the contract without owner. It will not be possible to call
 * `onlyOwner` functions anymore. Can only be called by the current owner.
 *
 * NOTE: Renouncing ownership will leave the contract without an owner,
 * thereby removing any functionality that is only available to the owner.
 */
 function renounceOwnership() public virtual onlyOwner {
 emit OwnershipTransferred(_owner, address(0));
 _owner = address(0);
 }

 /**
 * @dev Transfers ownership of the contract to a new account (`newOwner`).
 * Can only be called by the current owner.
 */
 function transferOwnership(address newOwner) public virtual onlyOwner {
 require(newOwner != address(0), "Ownable: new owner is the zero address");
 emit OwnershipTransferred(_owner, newOwner);
 _owner = newOwner;
 }
}


// File @openzeppelin/contracts/GSN/Context.sol@v3.4.2



pragma solidity >=0.6.0 <0.8.0;


// File contracts/libs/IERC20.sol

pragma solidity >=0.6.4;

/**
 * @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);
}


// File @openzeppelin/contracts/math/SafeMath.sol@v3.4.2



pragma solidity >=0.6.0 <0.8.0;

/**
 * @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, with an overflow flag.
 *
 * _Available since v3.4._
 */
 function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
 uint256 c = a + b;
 if (c < a) return (false, 0);
 return (true, c);
 }

 /**
 * @dev Returns the substraction of two unsigned integers, with an overflow flag.
 *
 * _Available since v3.4._
 */
 function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
 if (b > a) return (false, 0);
 return (true, a - b);
 }

 /**
 * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
 *
 * _Available since v3.4._
 */
 function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
 uint256 c = a * b;
 if (c / a != b) return (false, 0);
 return (true, c);
 }

 /**
 * @dev Returns the division of two unsigned integers, with a division by zero flag.
 *
 * _Available since v3.4._
 */
 function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
 if (b == 0) return (false, 0);
 return (true, a / b);
 }

 /**
 * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
 *
 * _Available since v3.4._
 */
 function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
 if (b == 0) return (false, 0);
 return (true, a % b);
 }

 /**
 * @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) {
 require(b <= a, "SafeMath: subtraction overflow");
 return a - b;
 }

 /**
 * @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) {
 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, reverting 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) {
 require(b > 0, "SafeMath: division by zero");
 return a / b;
 }

 /**
 * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
 * reverting 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) {
 require(b > 0, "SafeMath: modulo by zero");
 return a % b;
 }

 /**
 * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
 * overflow (when the result is negative).
 *
 * CAUTION: This function is deprecated because it requires allocating memory for the error
 * message unnecessarily. For custom revert reasons use {trySub}.
 *
 * 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);
 return a - b;
 }

 /**
 * @dev Returns the integer division of two unsigned integers, reverting with custom message on
 * division by zero. The result is rounded towards zero.
 *
 * CAUTION: This function is deprecated because it requires allocating memory for the error
 * message unnecessarily. For custom revert reasons use {tryDiv}.
 *
 * 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);
 return a / b;
 }

 /**
 * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
 * reverting with custom message when dividing by zero.
 *
 * CAUTION: This function is deprecated because it requires allocating memory for the error
 * message unnecessarily. For custom revert reasons use {tryMod}.
 *
 * 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;
 }
}


// File @openzeppelin/contracts/utils/Address.sol@v3.4.2



pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
 /**
 * @dev Returns true if `account` is a contract.
 *
 * [IMPORTANT]
 * ====
 * It is unsafe to assume that an address for which this function returns
 * false is an externally-owned account (EOA) and not a contract.
 *
 * Among others, `isContract` will return false for the following
 * types of addresses:
 *
 * - an externally-owned account
 * - a contract in construction
 * - an address where a contract will be created
 * - an address where a contract lived, but was destroyed
 * ====
 */
 function isContract(address account) internal view returns (bool) {
 // This method relies on extcodesize, which returns 0 for contracts in
 // construction, since the code is only stored at the end of the
 // constructor execution.

 uint256 size;
 // solhint-disable-next-line no-inline-assembly
 assembly { size := extcodesize(account) }
 return size > 0;
 }

 /**
 * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
 * `recipient`, forwarding all available gas and reverting on errors.
 *
 * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
 * of certain opcodes, possibly making contracts go over the 2300 gas limit
 * imposed by `transfer`, making them unable to receive funds via
 * `transfer`. {sendValue} removes this limitation.
 *
 * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
 *
 * IMPORTANT: because control is transferred to `recipient`, care must be
 * taken to not create reentrancy vulnerabilities. Consider using
 * {ReentrancyGuard} or the
 * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
 */
 function sendValue(address payable recipient, uint256 amount) internal {
 require(address(this).balance >= amount, "Address: insufficient balance");

 // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
 (bool success, ) = recipient.call{ value: amount }("");
 require(success, "Address: unable to send value, recipient may have reverted");
 }

 /**
 * @dev Performs a Solidity function call using a low level `call`. A
 * plain`call` is an unsafe replacement for a function call: use this
 * function instead.
 *
 * If `target` reverts with a revert reason, it is bubbled up by this
 * function (like regular Solidity function calls).
 *
 * Returns the raw returned data. To convert to the expected return value,
 * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
 *
 * Requirements:
 *
 * - `target` must be a contract.
 * - calling `target` with `data` must not revert.
 *
 * _Available since v3.1._
 */
 function functionCall(address target, bytes memory data) internal returns (bytes memory) {
 return functionCall(target, data, "Address: low-level call failed");
 }

 /**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
 * `errorMessage` as a fallback revert reason when `target` reverts.
 *
 * _Available since v3.1._
 */
 function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
 return functionCallWithValue(target, data, 0, errorMessage);
 }

 /**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
 * but also transferring `value` wei to `target`.
 *
 * Requirements:
 *
 * - the calling contract must have an ETH balance of at least `value`.
 * - the called Solidity function must be `payable`.
 *
 * _Available since v3.1._
 */
 function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
 return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
 }

 /**
 * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
 * with `errorMessage` as a fallback revert reason when `target` reverts.
 *
 * _Available since v3.1._
 */
 function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
 require(address(this).balance >= value, "Address: insufficient balance for call");
 require(isContract(target), "Address: call to non-contract");

 // solhint-disable-next-line avoid-low-level-calls
 (bool success, bytes memory returndata) = target.call{ value: value }(data);
 return _verifyCallResult(success, returndata, errorMessage);
 }

 /**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
 * but performing a static call.
 *
 * _Available since v3.3._
 */
 function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
 return functionStaticCall(target, data, "Address: low-level static call failed");
 }

 /**
 * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
 * but performing a static call.
 *
 * _Available since v3.3._
 */
 function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
 require(isContract(target), "Address: static call to non-contract");

 // solhint-disable-next-line avoid-low-level-calls
 (bool success, bytes memory returndata) = target.staticcall(data);
 return _verifyCallResult(success, returndata, errorMessage);
 }

 /**
 * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
 * but performing a delegate call.
 *
 * _Available since v3.4._
 */
 function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
 return functionDelegateCall(target, data, "Address: low-level delegate call failed");
 }

 /**
 * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
 * but performing a delegate call.
 *
 * _Available since v3.4._
 */
 function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
 require(isContract(target), "Address: delegate call to non-contract");

 // solhint-disable-next-line avoid-low-level-calls
 (bool success, bytes memory returndata) = target.delegatecall(data);
 return _verifyCallResult(success, returndata, errorMessage);
 }

 function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
 if (success) {
 return returndata;
 } else {
 // Look for revert reason and bubble it up if present
 if (returndata.length > 0) {
 // The easiest way to bubble the revert reason is using memory via assembly

 // solhint-disable-next-line no-inline-assembly
 assembly {
 let returndata_size := mload(returndata)
 revert(add(32, returndata), returndata_size)
 }
 } else {
 revert(errorMessage);
 }
 }
 }
}


// File contracts/libs/ERC20.sol



pragma solidity >=0.4.0;





/**
 * @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, Ownable {
 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 { }
}


// File contracts/ThetaverseToken.sol

pragma solidity 0.6.12;

// ThetaverseToken with Governance.
contract ThetaverseToken is ERC20('Thetaverse Token)', 'TVT') {
 uint256 private _cap = 1000000000e18;
 uint256 private _initial_supply = 1000000e18;

 /**
 * @dev Returns the cap on the token's total supply.
 */
 function cap() public view returns (uint256) {
 return _cap;
 }

 /**
 * @dev See {ERC20-_beforeTokenTransfer}.
 *
 * Requirements:
 *
 * - minted tokens must not cause the total supply to go over the cap.
 */
 function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual override {
 super._beforeTokenTransfer(from, to, amount);

 if (from == address(0)) { // When minting tokens
 require(totalSupply().add(amount) <= _cap, "ERC20Capped: cap exceeded");
 }
 }

 /**
 * @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 override {
 super._transfer(sender, recipient, amount);
 _moveDelegates(_delegates[sender], _delegates[recipient], amount);
 }

 /// @notice Creates `_amount` token to `_to`. Must only be called by the owner (MasterChef).
 function mint(address _to, uint256 _amount) public onlyOwner {
 _mint(_to, _amount);
 _moveDelegates(address(0), _delegates[_to], _amount);
 }

 // Copied and modified from YAM code:
 // https://github.com/yam-finance/yam-protocol/blob/master/contracts/token/YAMGovernanceStorage.sol
 // https://github.com/yam-finance/yam-protocol/blob/master/contracts/token/YAMGovernance.sol
 // Which is copied and modified from COMPOUND:
 // https://github.com/compound-finance/compound-protocol/blob/master/contracts/Governance/Comp.sol

 /// @notice A record of each accounts delegate
 mapping (address => address) internal _delegates;

 /// @notice A checkpoint for marking number of votes from a given block
 struct Checkpoint {
 uint32 fromBlock;
 uint256 votes;
 }

 /// @notice A record of votes checkpoints for each account, by index
 mapping (address => mapping (uint32 => Checkpoint)) public checkpoints;

 /// @notice The number of checkpoints for each account
 mapping (address => uint32) public numCheckpoints;

 /// @notice The EIP-712 typehash for the contract's domain
 bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)");

 /// @notice The EIP-712 typehash for the delegation struct used by the contract
 bytes32 public constant DELEGATION_TYPEHASH = keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");

 /// @notice A record of states for signing / validating signatures
 mapping (address => uint) public nonces;

 /// @notice An event thats emitted when an account changes its delegate
 event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);

 /// @notice An event thats emitted when a delegate account's vote balance changes
 event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);

 /**
 * @notice Delegate votes from `msg.sender` to `delegatee`
 * @param delegator The address to get delegatee for
 */
 function delegates(address delegator)
 external
 view
 returns (address)
 {
 return _delegates[delegator];
 }

 /**
 * @notice Delegate votes from `msg.sender` to `delegatee`
 * @param delegatee The address to delegate votes to
 */
 function delegate(address delegatee) external {
 return _delegate(msg.sender, delegatee);
 }

 /**
 * @notice Delegates votes from signatory to `delegatee`
 * @param delegatee The address to delegate votes to
 * @param nonce The contract state required to match the signature
 * @param expiry The time at which to expire the signature
 * @param v The recovery byte of the signature
 * @param r Half of the ECDSA signature pair
 * @param s Half of the ECDSA signature pair
 */
 function delegateBySig(
 address delegatee,
 uint nonce,
 uint expiry,
 uint8 v,
 bytes32 r,
 bytes32 s
 )
 external
 {
 bytes32 domainSeparator = keccak256(
 abi.encode(
 DOMAIN_TYPEHASH,
 keccak256(bytes(name())),
 getChainId(),
 address(this)
 )
 );

 bytes32 structHash = keccak256(
 abi.encode(
 DELEGATION_TYPEHASH,
 delegatee,
 nonce,
 expiry
 )
 );

 bytes32 digest = keccak256(
 abi.encodePacked(
 "\x19\x01",
 domainSeparator,
 structHash
 )
 );

 address signatory = ecrecover(digest, v, r, s);
 require(signatory != address(0), "TVT::delegateBySig: invalid signature");
 require(nonce == nonces[signatory]++, "TVT::delegateBySig: invalid nonce");
 require(now <= expiry, "TVT::delegateBySig: signature expired");
 return _delegate(signatory, delegatee);
 }

 /**
 * @notice Gets the current votes balance for `account`
 * @param account The address to get votes balance
 * @return The number of current votes for `account`
 */
 function getCurrentVotes(address account)
 external
 view
 returns (uint256)
 {
 uint32 nCheckpoints = numCheckpoints[account];
 return nCheckpoints > 0 ? checkpoints[account][nCheckpoints - 1].votes : 0;
 }

 /**
 * @notice Determine the prior number of votes for an account as of a block number
 * @dev Block number must be a finalized block or else this function will revert to prevent misinformation.
 * @param account The address of the account to check
 * @param blockNumber The block number to get the vote balance at
 * @return The number of votes the account had as of the given block
 */
 function getPriorVotes(address account, uint blockNumber)
 external
 view
 returns (uint256)
 {
 require(blockNumber < block.number, "TVT::getPriorVotes: not yet determined");

 uint32 nCheckpoints = numCheckpoints[account];
 if (nCheckpoints == 0) {
 return 0;
 }

 // First check most recent balance
 if (checkpoints[account][nCheckpoints - 1].fromBlock <= blockNumber) {
 return checkpoints[account][nCheckpoints - 1].votes;
 }

 // Next check implicit zero balance
 if (checkpoints[account][0].fromBlock > blockNumber) {
 return 0;
 }

 uint32 lower = 0;
 uint32 upper = nCheckpoints - 1;
 while (upper > lower) {
 uint32 center = upper - (upper - lower) / 2; // ceil, avoiding overflow
 Checkpoint memory cp = checkpoints[account][center];
 if (cp.fromBlock == blockNumber) {
 return cp.votes;
 } else if (cp.fromBlock < blockNumber) {
 lower = center;
 } else {
 upper = center - 1;
 }
 }
 return checkpoints[account][lower].votes;
 }

 function _delegate(address delegator, address delegatee)
 internal
 {
 address currentDelegate = _delegates[delegator];
 uint256 delegatorBalance = balanceOf(delegator); // balance of underlying TVTs (not scaled);
 _delegates[delegator] = delegatee;

 emit DelegateChanged(delegator, currentDelegate, delegatee);

 _moveDelegates(currentDelegate, delegatee, delegatorBalance);
 }

 function _moveDelegates(address srcRep, address dstRep, uint256 amount) internal {
 if (srcRep != dstRep && amount > 0) {
 if (srcRep != address(0)) {
 // decrease old representative
 uint32 srcRepNum = numCheckpoints[srcRep];
 uint256 srcRepOld = srcRepNum > 0 ? checkpoints[srcRep][srcRepNum - 1].votes : 0;
 uint256 srcRepNew = srcRepOld.sub(amount);
 _writeCheckpoint(srcRep, srcRepNum, srcRepOld, srcRepNew);
 }

 if (dstRep != address(0)) {
 // increase new representative
 uint32 dstRepNum = numCheckpoints[dstRep];
 uint256 dstRepOld = dstRepNum > 0 ? checkpoints[dstRep][dstRepNum - 1].votes : 0;
 uint256 dstRepNew = dstRepOld.add(amount);
 _writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew);
 }
 }
 }

 function _writeCheckpoint(
 address delegatee,
 uint32 nCheckpoints,
 uint256 oldVotes,
 uint256 newVotes
 )
 internal
 {
 uint32 blockNumber = safe32(block.number, "TVT::_writeCheckpoint: block number exceeds 32 bits");

 if (nCheckpoints > 0 && checkpoints[delegatee][nCheckpoints - 1].fromBlock == blockNumber) {
 checkpoints[delegatee][nCheckpoints - 1].votes = newVotes;
 } else {
 checkpoints[delegatee][nCheckpoints] = Checkpoint(blockNumber, newVotes);
 numCheckpoints[delegatee] = nCheckpoints + 1;
 }

 emit DelegateVotesChanged(delegatee, oldVotes, newVotes);
 }

 function safe32(uint n, string memory errorMessage) internal pure returns (uint32) {
 require(n < 2**32, errorMessage);
 return uint32(n);
 }

 function getChainId() internal pure returns (uint) {
 uint256 chainId;
 assembly { chainId := chainid() }
 return chainId;
 }

 constructor() public {
 _mint(msg.sender, _initial_supply);
 _moveDelegates(address(0), msg.sender, _initial_supply);
 }
}

Contract ABI:

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":"address"},{"internalType":"uint256","name":"_amount","type":"uint256"}],"name":"mint","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"nonces","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"numCheckpoints","outputs":[{"internalType":"uint32","name":"","type":"uint32"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"owner","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"renounceOwnership","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"recipient","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transfer","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"sender","type":"address"},{"internalType":"address","name":"recipient","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transferFrom","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"stateMutability":"nonpayable","type":"function"}]