// File: contracts/CarbonCoinProxy.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.16;

import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

interface CarbonCoinI {
    function isAddressInBlackList (address) external view returns (bool);
    function balanceOf (address) external view returns (uint);
    function transfer (address, uint) external returns (bool);
    function redeemDebit (address, uint) external returns (bool);
}

interface CarbonCoinProxyI {
    function listCert (uint) external view returns (uint256, address, uint, uint, uint256);
    function getCertIndex() external view returns (uint);
}

interface USDTERC20 {
    function transferFrom(address, address, uint) external;
    function transfer(address, uint) external;
    function Transfer(address, address, uint) external;
    function balanceOf (address) external view returns (uint);
}

contract CarbonCoinProxy {
    address private _owner;
    address private _admin;
    address private _gcxTokenAddress;
    address private exchangeCollector;
    address private exchangeFeeCollector;
    address private redeemCollector;
    address private redeemFeeCollector;
    uint public exchangeFee;
    uint private redeemFee;
    USDTERC20 public exchangeableToken;
    uint public certIndex;
    uint private exchangeRate;
    bool private allowExchange;
    uint public _totalSupply;
    CarbonCoinI private gcxToken;
    //CarbonCoinProxyI private previousCarbonCoinProxy;

    struct Cert{
        uint256 fullName;
        address recipient;
        uint datetime;
        uint quantity; 
        uint256 email;
    }

    Cert[] public cert;
    
    constructor(address gcxTokenAddress, address gcxRateUpdateAddress) {
        //exchangeableToken = USDTERC20(0xdAC17F958D2ee523a2206206994597C13D831ec7);
        exchangeableToken = USDTERC20(0xE912639B6Ea8C2EFaAC9c47A4CF4d510e508368B);
        allowExchange = true;
        exchangeRate = 48010500;
        certIndex = 0;
        _owner = msg.sender;
        _admin = gcxRateUpdateAddress;
        _gcxTokenAddress = gcxTokenAddress;
        gcxToken = CarbonCoinI(gcxTokenAddress);
        exchangeFee = 100;
        redeemFee = 1000000000000000;
        exchangeCollector = 0xE3D8f9063A4527ae2c4d33157fc145bAD63cdE53;
        exchangeFeeCollector = 0xE3D8f9063A4527ae2c4d33157fc145bAD63cdE53;
        redeemCollector = 0xE3D8f9063A4527ae2c4d33157fc145bAD63cdE53;
        redeemFeeCollector = 0xE3D8f9063A4527ae2c4d33157fc145bAD63cdE53;
        //previousCarbonCoinProxy = CarbonCoinProxyI(0x1E0FACc2e7AeE4e79B4cCe2e32Ca18021678be29);
    }    

    function name() public view virtual returns (string memory) {
        return "Green Carbon Proxy";
    }

    function symbol() public view virtual returns (string memory) {
        return "GCXProxy";
    }

    function exchangeToken (uint amountInGCX) external returns (bool) {
        require(1 <= amountInGCX, 'Invalid amount');
        require(allowExchange, 'Service unavailable');
        require(!gcxToken.isAddressInBlackList(msg.sender), 'Address is in Black List');
        uint amountInUSDT = amountInGCX * exchangeRate;
        amountInUSDT = amountInUSDT / 1000000;
        uint fee = 0;
        if (exchangeFee > 0) {
            fee = amountInUSDT / exchangeFee;
        }
        require(amountInUSDT + fee <= exchangeableToken.balanceOf(msg.sender), 'Insufficient token');
        require(gcxToken.balanceOf(address(this)) >= amountInGCX, 'Insufficient balance');
        exchangeableToken.transferFrom(msg.sender, exchangeCollector, amountInUSDT);
        if (fee > 0) {
            exchangeableToken.transferFrom(msg.sender, exchangeFeeCollector, fee);
        }
        gcxToken.transfer(msg.sender, amountInGCX);
        return true;
    }

    function redeem (uint256 fullName, uint quantity, uint256 email) external payable returns (uint) {
        require(gcxToken.balanceOf(msg.sender) >= quantity, 'Insufficient balance');
        require(msg.value == redeemFee, 'Insufficient to cover fees');
        payable(redeemFeeCollector).transfer(redeemFee);
        Cert memory userCert = Cert(fullName, msg.sender, block.timestamp, quantity, email);
        cert.push(userCert);
        certIndex += 1;
        gcxToken.redeemDebit(msg.sender, quantity);
        gcxToken.transfer(redeemCollector, quantity);
        return quantity;
    }

    function updateExchangeRate (uint rate) external {
        require(msg.sender == _admin || msg.sender == _owner);
        require(rate > 0);
        exchangeRate = rate;
    }

    function transferToken (address token, uint amount) external {
        require(msg.sender == _owner);
        require(amount > 0);
        USDTERC20 tokenContract = USDTERC20(token);
        tokenContract.transfer(_owner, amount);        
    }
    
    function updateOwner (address newOwner) external {
        require(msg.sender == _owner);
        _owner = newOwner;
    }
    
    function updateAdmin (address newAdmin) external {
        require(msg.sender == _owner);
        _admin = newAdmin;
    }

    function updateExchangeTokenAllow (bool allow) external {
        require(msg.sender == _owner);
        allowExchange = allow;
    }

    function updateExchangeTokenAddress (address newAddress) external {
        require(msg.sender == _owner);
        exchangeableToken = USDTERC20(newAddress);
    }
    
    function updateExchangeFee(uint fee) external {
        require(msg.sender == _owner);
        exchangeFee = fee;
    }
    
    function updateRedeemFee(uint fee) external {
        require(msg.sender == _owner);
        redeemFee = fee;
    }
    
    function updateExchangeCollector(address collector) external {
        require(msg.sender == _owner);
        exchangeCollector = collector;
    }
    
    function updateExchangeFeeCollector(address collector) external {
        require(msg.sender == _owner);
        exchangeFeeCollector = collector;
    }
    
    function updateRedeemFeeCollector(address collector) external {
        require(msg.sender == _owner);
        redeemFeeCollector = collector;
    }

    function updateRedeemCollector(address collector) external {
        require(msg.sender == _owner);
        redeemCollector = collector;
    }

    function getExchangeRate() public view returns (uint) {
        return exchangeRate;
    }

    function listCert (uint index) public view returns(uint256, address, uint, uint, uint256) {
        //uint previousIndex = previousCarbonCoinProxy.getCertIndex();
        //require(index < previousIndex + certIndex);
        //if (index < previousIndex) {
        //    return previousCarbonCoinProxy.listCert(index);
        //} else {
        //    uint currentIndex = index - previousIndex;
        //    return (cert[currentIndex].fullName, cert[currentIndex].recipient, cert[currentIndex].datetime ,cert[currentIndex].quantity, cert[currentIndex].email);
        //}
        return (cert[index].fullName, cert[index].recipient, cert[index].datetime ,cert[index].quantity, cert[index].email);
    }

    function getCertIndex() public view returns (uint) {
        //uint previousIndex = previousCarbonCoinProxy.getCertIndex();
        //return previousIndex + certIndex;
        return certIndex;
    }

    function getOwner() public view returns (address) {
        return _owner;
    }
    
    function getAdmin() public view returns (address) {
        return _admin;
    }
    
    function getExchangeTokenAllow() public view returns (bool) {
        return allowExchange;
    }
    
    function getExchangeTokenAddress() public view returns (address) {
        return address(exchangeableToken);
    }
    
    function getExchangeFee() public view returns (uint) {
        return exchangeFee;
    }
    
    function getRedeemFee() public view returns (uint) {
        return redeemFee;
    }
    
    function getExchangeCollector() public view returns (address) {
        return exchangeCollector;
    }
    
    function getExchangeFeeCollector() public view returns (address) {
        return exchangeFeeCollector;
    }
    
    function getRedeemCollector() public view returns (address) {
        return redeemCollector;
    }

    function getRedeemFeeCollector() public view returns (address) {
        return redeemFeeCollector;
    }
}
// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/draft-IERC20Permit.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));
        }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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 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);
}

// File: @openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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
                /// @solidity memory-safe-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}