// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @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() {
        _transferOwnership(_msgSender());
    }

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

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

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

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

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/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 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'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 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");

        (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");

        (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");

        (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");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal 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

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^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 meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: @openzeppelin/contracts/utils/math/SafeMath.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/math/SafeMath.sol)

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
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) {
        unchecked {
            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) {
        unchecked {
            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) {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @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) {
        unchecked {
            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) {
        unchecked {
            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) {
        return a + b;
    }

    /**
     * @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 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) {
        return a * b;
    }

    /**
     * @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.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        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) {
        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) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @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) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// File: contracts/lib/utils/TransferHelper.sol



// SPDX-License-Identifier: GPL-3.0-or-later

pragma solidity >=0.6.0;

// 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,
        uint256 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,
        uint256 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,
        uint256 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, uint256 value) internal {
        (bool success, ) = to.call{value: value}(new bytes(0));
        require(success, 'TransferHelper: ETH_TRANSFER_FAILED');
    }
}

// File: contracts/periphery/interfaces/IWETH.sol



pragma solidity >=0.5.0;

interface IWETH {
    function deposit() external payable;

    function transfer(address to, uint256 value) external returns (bool);

    function withdraw(uint256) external;
}

// File: contracts/topic/ITopic.sol



pragma solidity >=0.8.0;

interface ITopic {

    event SetTopic(
        uint256 indexed id,
        string name,
        uint256 startTime,
        uint256 totalSupply
    );

    event SetOpinion(
        uint256 indexed id,
        string name,
        uint256 startTime,
        uint256 totalSupply,
        uint256 parentId
    );

    event BuyPower(
        address indexed sender,
        uint256 id,
        uint256 price,
        uint256 costIn,
        uint256 amount,
        uint256 burned,
        uint256 fee
    );

    event SellPower(
        address indexed sender,
        uint256 id,
        uint256 price,
        uint256 gainOut,
        uint256 amount,
        uint256 burned,
        uint256 fee
    );

    event BuyVote(
        address indexed sender,
        uint256 id,
        uint256 ethPrice,
        uint256 price,
        uint256 powerIn,
        uint256 amount,
        uint256 burned,
        uint256 fee
    );

    event SellVote(
        address indexed sender,
        uint256 id,
        uint256 ethPrice,
        uint256 price,
        uint256 powerOut,
        uint256 amount,
        uint256 burned,
        uint256 fee
    );

    event Transfer(
        uint256 indexed id,
        address indexed from,
        address indexed to,
        uint256 amount);

    event Burn(
        uint256 indexed id,
        address indexed from,
        uint256 amount);

    function decimals() external view returns (uint8);

    function transfer(
        uint256 id,
        address to,
        uint256 amount
    ) external;

    function burn(
        uint256 id,
        uint256 amount
    ) external;

    function getLiquidity(uint256 id) external view returns (uint256 liquidityPower, uint256 liquidity);

    function topicPrice(uint256 id) external view returns (uint256);

    function opinionPrice(uint256 id) external view returns (uint256);

    function buyTopicPower(uint256 id, uint256 cost) external view returns (uint256);

    function sellTopicGain(uint256 id, uint256 amount) external view returns (uint256);

    function buyPower(uint256 id, uint256 amountOutMin) external payable;

    function sellPower(uint256 id, uint256 amount, uint256 amountOutMin) external;

    function buyOpinionVote(uint256 id, uint256 cost) external view returns (uint256);

    function sellOpinionGain(uint256 id, uint256 amount) external view returns (uint256);

    function buyVote(uint256 id, uint256 amountOutMin, uint256 cost) external;

    function sellVote(uint256 id, uint256 amount, uint256 amountOutMin) external;

    function buyVoteInETH(uint256 id, uint256 amountOutMin) external payable;

    function sellVote2ETH(uint256 id, uint256 amount, uint256 amountOutMin) external;
}

// File: contracts/topic/Topic.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "../periphery/interfaces/IWETH.sol";
import '../lib/utils/TransferHelper.sol';
import "./ITopic.sol";

contract Topic is ITopic, Ownable {
    using SafeERC20 for IERC20;
    using SafeMath for uint256;

    mapping(uint256 => uint) private locked;
    mapping(uint256 => uint) public status;

    address constant private DEAD = 0x000000000000000000000000000000000000dEaD;
    address public immutable WETH;
    uint256 public fees;
    address public operatorAddress;

    mapping(uint256 => uint256) public parentIds;
    mapping(uint256 => uint256) public childCount;
    mapping(uint256 => string) public name;
    mapping(uint256 => uint256) public start;
    mapping(uint256 => uint256) public totalSupply;
    mapping(uint256 => uint256) private _liquidityPower;
    mapping(uint256 => uint256) private _liquidity;
    mapping(uint256 => mapping(address => uint256)) public balanceOf;
    mapping(uint256 => uint256) public holders;

    uint256 constant private BASE_PRICE = 1E15;
    uint256 constant private X = 1E6;

    constructor(address _WETH){
        WETH = _WETH;
        operatorAddress = msg.sender;
    }

    function decimals() override virtual public view returns (uint8) {
        return 18;
    }

    receive() external payable {
        assert(msg.sender == WETH); // only accept ETH via fallback from the WETH contract
    }

    modifier lock(uint256 id) {
        require(locked[id] == 0, 'LOCKED');
        locked[id] = 1;
        _;
        locked[id] = 0;
    }

    modifier created(uint256 id){
        require(status[id] > 0, 'Not created');
        _;
    }


    modifier started(uint256 id){
        if (parentIds[id] > 0) {
            require(block.timestamp >= start[id] && block.timestamp >= start[parentIds[id]], 'Not started');
        } else {
            require(block.timestamp >= start[id], 'Not started');
        }
        _;
    }

    modifier onlyOperator(){
        require(msg.sender == operatorAddress, 'caller is not the operator');
        _;
    }

    function setOperatorAddress(address newAddress) onlyOwner public {
        require(newAddress != DEAD, 'Error newAddress');
        operatorAddress = newAddress;
    }

    function withdrawFee(uint256 amount) onlyOwner public {
        require(amount <= fees, 'Insufficient');
        fees -= amount;
        IWETH(WETH).withdraw(amount);
        TransferHelper.safeTransferETH(msg.sender, amount);
    }

    function withdraw() onlyOwner public {
        uint256 amount = IERC20(WETH).balanceOf(address(this));
        IWETH(WETH).withdraw(amount);
        TransferHelper.safeTransferETH(msg.sender, amount);
    }

    function getBaseData(uint256 id) public view returns (uint _status,
        uint256 _activeSupply,
        uint256 _holders,
        uint256 _price,
        uint256 liquidityPower,
        uint256 liquidity,
        uint256 burned,
        uint256 hold){
        if (status[id] == 0) {
            _status = 0; // Not created
            _holders = 0;
            _price = 0;
        } else {
            _holders = holders[id];
            if (block.timestamp < start[id]) {
                _status = 1; // Not start
                if (parentIds[id] == 0) _price = 1E15;
                else _price = 1E18;
            } else {
                if (parentIds[id] == 0) _price = topicPrice(id);
                else _price = opinionPrice(id);
                _status = 2; // Trading
            }
        }
        (liquidityPower, liquidity) = getLiquidity(id);
        if (parentIds[id] == 0) _activeSupply = totalSupply[id] - liquidityPower - balanceOf[id][DEAD];
        else _activeSupply = totalSupply[id] - liquidity - balanceOf[id][DEAD];
        burned = balanceOf[id][DEAD];
        hold = balanceOf[id][address(this)];
    }

    function createTopic(uint256 _id,
        uint256 _start,
        string memory _name,
        uint256 _totalSupply) public onlyOperator {
        require(status[_id] == 0, 'Created');
        require(_id > 0, '_id zero');
        require(_totalSupply >= 20, '_totalSupply low');
        _liquidityPower[_id] = totalSupply[_id] = _totalSupply;
        _liquidity[_id] = _totalSupply * BASE_PRICE / 1E18;
        balanceOf[_id][address(this)] = totalSupply[_id];
        emit Transfer(_id, DEAD, address(this), totalSupply[_id]);
        holders[_id] += 1;
        childCount[0] += 1;
        parentIds[_id] = 0;
        status[_id] = 1;
        start[_id] = _start;
        name[_id] = _name;
        emit SetTopic(_id, _name, _start, totalSupply[_id]);
    }

    function createOpinion(uint256 _id,
        uint256 _start,
        string memory _name,
        uint256 _topic) public onlyOperator {
        require(status[_id] == 0, 'Created');
        require(_id > 0, '_id zero');
        require(_id != _topic, '_id == _topic');
        require(status[_topic] > 0, '_topic Not created');
        require(parentIds[_topic] == 0, '_topic error');
        require(start[_topic] <= _start, '_start < topic start');
        _liquidityPower[_id] = _liquidity[_id] = totalSupply[_id] = totalSupply[_topic] * 5E4 / X;
        balanceOf[_id][address(this)] = totalSupply[_id];
        emit Transfer(_id, DEAD, address(this), totalSupply[_id]);
        holders[_id] += 1;
        childCount[_topic] += 1;
        parentIds[_id] = _topic;
        status[_id] = 1;
        start[_id] = _start;
        name[_id] = _name;
        emit SetOpinion(_id, _name, _start, totalSupply[_id], _topic);
    }

    function setStartTime(uint256 _id, uint256 _start) created(_id) public onlyOperator {
        require(block.timestamp < start[_id], 'Trading');
        start[_id] = _start;
        if (parentIds[_id] == 0) emit SetTopic(_id, name[_id], _start, totalSupply[_id]);
        else emit SetOpinion(_id, name[_id], _start, totalSupply[_id], parentIds[_id]);
    }

    function setName(uint256 _id, string memory _name) created(_id) public onlyOperator {
        name[_id] = _name;
        if (parentIds[_id] == 0) emit SetTopic(_id, _name, start[_id], totalSupply[_id]);
        else emit SetOpinion(_id, _name, start[_id], totalSupply[_id], parentIds[_id]);
    }

    function getLiquidity(uint256 id) override virtual public view returns (uint256 liquidityPower, uint256 liquidity){
        liquidityPower = _liquidityPower[id];
        liquidity = _liquidity[id];
    }

    function topicPrice(uint256 id) override virtual public view returns (uint256){
        require(parentIds[id] == 0, 'Opinion');
        return _liquidity[id].mul(1E18).div(_liquidityPower[id]);
    }

    function opinionPrice(uint256 id) override virtual public view returns (uint256){
        require(parentIds[id] > 0, 'Topic');
        return _liquidityPower[id].mul(1E18).div(_liquidity[id]);
    }

    function buyTopicPower(uint256 id, uint256 cost) override virtual public view returns (uint256){
        (uint256 amount,uint256 price,uint256 fee,uint256 burned,uint256 k) = _buyTopicPower(id, cost);
        return amount;
    }

    function _buyTopicPower(uint256 id, uint256 cost) created(id) started(id) internal virtual view returns (uint256 amount, uint256 price, uint256 fee, uint256 burned, uint256 k){
        require(parentIds[id] == 0, 'Opinion');
        require(_liquidityPower[id] > 0, 'Insufficient liquidity');
        require(cost >= 1E12 && cost < 1E26, 'Overflow');
        k = _liquidityPower[id] * _liquidity[id];
        uint256 a1 = 2E4;
        uint256 a2 = 63E4;
        uint256 time = block.timestamp - start[id];
        time = time / 30;
        if (time < 60) a2 -= (time * 1E4);
        else a2 = 3E4;
        fee = cost * a1 / X;
        amount = _liquidityPower[id] - k / (_liquidity[id] + (cost - fee));
        price = (cost - fee) * 1E18 / amount;
        burned = amount * a2 / X;
        amount = amount * (X - a2) / X;
        require(amount > 0 && amount < _liquidityPower[id], 'Insufficient liquidity');
    }

    function sellTopicGain(uint256 id, uint256 amount) override virtual public view returns (uint256){
        (uint256 gain,uint256 price,uint256 fee,uint256 burned,uint256 k) = _sellTopicGain(id, amount);
        return gain;
    }

    function _sellTopicGain(uint256 id, uint256 amount) created(id) started(id) internal virtual view returns (uint256 gain, uint256 price, uint256 fee, uint256 burned, uint256 k){
        require(block.timestamp >= start[id], 'Not started');
        require(parentIds[id] == 0, 'Opinion');
        require(amount > 0 && _liquidity[id] > 0, 'Insufficient liquidity');
        uint256 b1 = 2E4;
        uint256 b2 = 3E4;
        k = _liquidityPower[id] * _liquidity[id];
        burned = amount * b2 / X;
        gain = _liquidity[id] - k / (_liquidityPower[id] + (amount - burned));
        fee = gain * b1 / X;
        gain = gain * (X - b1) / X;
        price = gain * 1E18 / amount;
        require(gain < _liquidity[id], 'Insufficient liquidity');
    }

    function buyPower(uint256 id, uint256 amountOutMin) override virtual external payable {
        IWETH(WETH).deposit{value: msg.value}();
        _buyPower(id, msg.sender, amountOutMin, msg.value);
    }

    function _buyPower(uint256 id, address to, uint256 amountOutMin, uint256 cost) lock(id) internal virtual returns (uint256) {
        (uint256 amount,uint256 price,uint256 fee,uint256 burned,uint256 k) = _buyTopicPower(id, cost);
        require(amount >= amountOutMin, 'LT amountOutMin');
        _transfer(id, address(this), to, amount);
        _liquidityPower[id] -= (amount + burned);
        if (burned > 0) _burn(id, address(this), burned, k);
        _liquidity[id] += (cost - fee);
        fees += fee;
        emit BuyPower(to, id, price, cost, amount, burned, fee);
        return amount;
    }

    function sellPower(uint256 id, uint256 amount, uint256 amountOutMin) override virtual external {
        _sellPower(id, msg.sender, amount, amountOutMin, false);
    }

    function _sellPower(uint256 id, address to, uint256 amount, uint256 amountOutMin, bool isSellFee) lock(id) internal virtual returns (uint256){
        (uint256 gain,uint256 price,uint256 fee,uint256 burned,uint256 k) = _sellTopicGain(id, amount);
        require(gain >= amountOutMin, 'Insufficient output amount');
        _transfer(id, to, address(this), amount);
        if (burned > 0) _burn(id, address(this), burned, k);
        _liquidityPower[id] += (amount - burned);
        _liquidity[id] -= (gain + fee);
        fees += fee;
        if (isSellFee) fees += gain;
        else {
            require(gain <= IERC20(WETH).balanceOf(address(this)), 'Insufficient ETH');
            IWETH(WETH).withdraw(gain);
            TransferHelper.safeTransferETH(to, gain);
        }
        emit SellPower(to, id, price, gain, amount, burned, fee);
        return gain;
    }

    function buyOpinionVote(uint256 id, uint256 cost) override virtual public view returns (uint256){
        (uint256 amount,uint256 price,uint256 fee,uint256 burned,uint256 k) = _buyOpinionVote(id, cost);
        return amount;
    }

    function _buyOpinionVote(uint256 id, uint256 cost) created(id) started(id) internal view returns (uint256 amount, uint256 price, uint256 fee, uint256 burned, uint256 k){
        require(parentIds[id] > 0, 'Topic');
        require(cost >= 1E12, 'The minimum cost is 0.000001');
        require(_liquidity[id] > 0, 'Insufficient liquidity');
        uint256 a1 = 2E4;
        uint256 a2 = 63E4;
        k = _liquidity[id] * _liquidityPower[id];
        fee = cost * a1 / X;
        amount = _liquidity[id] - k / (_liquidityPower[id] + (cost - fee));
        price = (cost - fee) * 1E18 / amount;
        uint256 time = block.timestamp - start[id];
        time = time / 30;
        if (time < 60) a2 -= (time * 1E4);
        else a2 = 3E4;
        burned = amount * a2 / X;
        amount = amount * (X - a2) / X;
        require(amount > 0 && amount < _liquidity[id], 'Insufficient liquidity');
    }

    function sellOpinionGain(uint256 id, uint256 amount) override virtual public view returns (uint256){
        (uint256 gain,uint256 price,uint256 fee,uint256 burned,uint256 k) = _sellOpinionGain(id, amount);
        return gain;
    }

    function _sellOpinionGain(uint256 id, uint256 amount) created(id) started(id) internal view returns (uint256 gain, uint256 price, uint256 fee, uint256 burned, uint256 k){
        require(parentIds[id] > 0, 'Topic');
        require(amount >= 1E12, 'The minimum amount is 0.000001');
        require(_liquidityPower[id] > 0, 'Insufficient liquidity');
        uint256 b1 = 2E4;
        uint256 b2 = 3E4;
        k = _liquidityPower[id] * _liquidity[id];
        burned = amount * b2 / X;
        gain = _liquidityPower[id] - k / (_liquidity[id] + (amount - burned));
        fee = gain * b1 / X;
        gain = gain * (X - b1) / X;
        price = gain * 1E18 / amount;
        require(gain < _liquidityPower[id], 'Insufficient liquidity');
    }

    function buyVote(uint256 id, uint256 amountOutMin, uint256 cost) override virtual external {
        _buyVote(id, msg.sender, amountOutMin, cost);
    }

    function _buyVote(uint256 id, address to, uint256 amountOutMin, uint256 cost) lock(id) internal virtual {
        (uint256 amount,uint256 price,uint256 fee,uint256 burned,uint256 k) = _buyOpinionVote(id, cost);
        require(amount >= amountOutMin, 'Insufficient amount');
        uint256 parentId = parentIds[id];
        _transfer(parentId, to, address(this), cost - fee);
        _transfer(parentId, to, owner(), fee);
        _liquidity[id] -= (amount + burned);
        if (burned > 0) _burn(id, address(this), burned, k);
        _transfer(id, address(this), to, amount);
        _liquidityPower[id] += (cost - fee);
        _sellPower(parentId, owner(), fee, 0, true);
        uint256 ethPrice = (price * topicPrice(parentId)) / 1E18;
        emit BuyVote(to, id, ethPrice, price, cost, amount, burned, fee);
    }

    function sellVote(uint256 id, uint256 amount, uint256 amountOutMin) override virtual external {
        _sellVote(id, msg.sender, amount, amountOutMin);
    }

    function _sellVote(uint256 id, address to, uint256 amount, uint256 amountOutMin) lock(id) internal virtual returns (uint256) {
        (uint256 gain,uint256 price,uint256 fee,uint256 burned,uint256 k) = _sellOpinionGain(id, amount);
        require(gain >= amountOutMin, 'Insufficient output amount');
        _transfer(id, to, address(this), amount);
        if (burned > 0) _burn(id, address(this), burned, k);
        _liquidityPower[id] -= (gain + fee);
        _liquidity[id] += (amount - burned);
        uint256 parentId = parentIds[id];
        _transfer(parentId, address(this), owner(), fee);
        _sellPower(parentId, owner(), fee, 0, true);
        _transfer(parentId, address(this), to, gain);
        emit SellVote(to, id, (price * topicPrice(parentId)) / 1E18, price, gain, amount, burned, fee);
        return gain;
    }


    function buyVoteInETH(uint256 id, uint256 amountOutMin) override virtual external payable {
        IWETH(WETH).deposit{value: msg.value}();
        uint256 power = _buyPower(parentIds[id], msg.sender, 0, msg.value);
        _buyVote(id, msg.sender, amountOutMin, power);
    }

    function sellVote2ETH(uint256 id, uint256 amount, uint256 amountOutMin) override virtual external {
        uint256 power = _sellVote(id, msg.sender, amount, 0);
        _sellPower(parentIds[id], msg.sender, power, amountOutMin, false);
    }

    function _transfer(
        uint256 id,
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        if (to == DEAD) {
            uint256 k = _liquidityPower[id] * _liquidity[id];
            _burn(id, from, amount, k);
        } else {
            require(balanceOf[id][from] >= amount, 'Insufficient');
            balanceOf[id][from] -= amount;
            if (balanceOf[id][from] == 0 && holders[id] >= 1) holders[id] -= 1;
            if (balanceOf[id][to] == 0) holders[id] += 1;
            balanceOf[id][to] += amount;
            emit Transfer(id, from, to, amount);
        }
    }

    function transfer(
        uint256 id,
        address to,
        uint256 amount
    ) created(id) public override {
        _transfer(id, msg.sender, to, amount);
    }

    function burn(
        uint256 id,
        uint256 amount
    ) created(id) public override {
        uint256 k = _liquidityPower[id] * _liquidity[id];
        _burn(id, msg.sender, amount, k);
    }

    function _burn(uint256 id, address from, uint256 amount, uint256 k) internal virtual {
        require(balanceOf[id][from] >= amount, 'Insufficient');
        balanceOf[id][from] -= amount;
        if (balanceOf[id][from] == 0 && holders[id] >= 1) holders[id] -= 1;
        if (balanceOf[id][DEAD] == 0) holders[id] += 1;
        balanceOf[id][DEAD] += amount;
        uint256 getEth = 0;
        if (parentIds[id] == 0) {
            getEth = k / (totalSupply[id] - balanceOf[id][DEAD]) - k / (totalSupply[id] - balanceOf[id][DEAD] + amount);
        } else {
            uint256 getPower = k / (totalSupply[id] - balanceOf[id][DEAD]) - k / (totalSupply[id] - balanceOf[id][DEAD] + amount);
            uint256 parentId = parentIds[id];
            k = _liquidityPower[parentId] * _liquidity[parentId];
            _burn(parentId, address(this), getPower, k);
        }
        fees += getEth;
        emit Transfer(id, from, DEAD, amount);
        emit Burn(id, from, amount);
    }
}