Contract Source Code:

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (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 Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

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

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling 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);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == _ENTERED;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

import "../../utils/introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Note that the caller is responsible to confirm that the recipient is capable of receiving ERC721
     * or else they may be permanently lost. Usage of {safeTransferFrom} prevents loss, though the caller must
     * understand this adds an external call which potentially creates a reentrancy vulnerability.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool approved) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);
}

// 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;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (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 subtraction 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;
        }
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";

interface IPrivixNFTPass {
    function getTier(uint256 tokenId) external view returns (string memory);
    function ownerOf(uint256 tokenId) external view returns (address);
    function balanceOf(address owner) external view returns (uint256);
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256);
}

contract DiamondStakingMigrated is Ownable, ReentrancyGuard {
    using SafeMath for uint256;

    /* ─────────────────── Constants ─────────────────── */
    uint256 public constant STAKING_AMOUNT = 5000 * 10**9;  // 5000 PRIVIX (9 decimals)
    uint256 public constant LOCKUP_PERIOD = 30 days;        // 30 days lockup
    uint256 public constant REWARD_PERIOD = 30 days;        // 30 days reward period
    uint256 public constant DIAMOND_START = 501;            // Diamond NFT range start
    uint256 public constant DIAMOND_END = 1000;             // Diamond NFT range end

    /* ─────────────────── Contract References ─────────────────── */
    IERC20 public immutable privixToken;
    IERC20 public immutable usdtToken;
    IPrivixNFTPass public immutable nftContract;

    /* ─────────────────── Staking Data ─────────────────── */
    struct StakeInfo {
        uint256 amount;              // Amount of PRIVIX staked
        uint256 stakeTime;           // Timestamp when staked
        uint256 lastClaimTime;       // Last time rewards were claimed
        uint256 diamondTokenId;      // Diamond NFT token ID used for staking
        bool isActive;               // Whether stake is active
        uint256 totalClaimed;        // Total USDT claimed by this user
        bool isMigrated;             // Whether this stake was migrated from old contract
        uint256 originalStakeTime;   // Original stake time from old contract (for migrated stakes)
    }

    mapping(address => StakeInfo) public stakes;
    mapping(uint256 => bool) public nftUsedForStaking;  // Track which NFTs are being used for staking

    /* ─────────────────── Staker Tracking ─────────────────── */
    address[] public activeStakers;  // Array of all active staker addresses
    mapping(address => uint256) public stakerIndex;  // Maps staker address to their index in activeStakers array

    /* ─────────────────── Pool Stats ─────────────────── */
    uint256 public totalStaked;
    uint256 public totalStakers;
    uint256 public totalRewardsPaid;
    uint256 public totalMigratedStakers;  // Track migrated stakers
    uint256 public totalMigratedAmount;   // Track migrated amounts

    /* ─────────────────── Migration Support ─────────────────── */
    bool public migrationMode = true;     // Allow migration initially
    address public migrationOperator;     // Address authorized to perform migrations
    uint256 public migrationDeadline;     // After this, migration is locked forever
    
    /* ─────────────────── Events ─────────────────── */
    event Staked(address indexed user, uint256 amount, uint256 diamondTokenId, uint256 timestamp);
    event Unstaked(address indexed user, uint256 amount, uint256 timestamp);
    event RewardsClaimed(address indexed user, uint256 amount, uint256 timestamp);
    event StakeMigrated(address indexed user, uint256 amount, uint256 diamondTokenId, uint256 originalStakeTime);
    event MigrationCompleted(uint256 totalMigrated, uint256 totalAmount);
    event MigrationModeDisabled();

    /* ─────────────────── Constructor ─────────────────── */
    constructor(
        address _privixToken,
        address _usdtToken,
        address _nftContract,
        address _migrationOperator
    ) {
        require(_privixToken != address(0), "Invalid PRIVIX token address");
        require(_usdtToken != address(0), "Invalid USDT token address");
        require(_nftContract != address(0), "Invalid NFT contract address");
        require(_migrationOperator != address(0), "Invalid migration operator address");

        privixToken = IERC20(_privixToken);
        usdtToken = IERC20(_usdtToken);
        nftContract = IPrivixNFTPass(_nftContract);
        migrationOperator = _migrationOperator;
        
        // Set migration deadline to 30 days from deployment
        migrationDeadline = block.timestamp + 30 days;
    }

    /* ─────────────────── Migration Functions ─────────────────── */
    
    /// Migrate a staker from the old contract
    function migrateStaker(
        address staker,
        uint256 amount,
        uint256 originalStakeTime,
        uint256 lastClaimTime,
        uint256 diamondTokenId,
        uint256 totalClaimed
    ) external {
        require(migrationMode, "Migration mode disabled");
        require(msg.sender == migrationOperator || msg.sender == owner(), "Not authorized for migration");
        require(block.timestamp <= migrationDeadline, "Migration deadline passed");
        require(!stakes[staker].isActive, "Staker already active");
        require(amount == STAKING_AMOUNT, "Invalid stake amount");
        require(diamondTokenId >= DIAMOND_START && diamondTokenId <= DIAMOND_END, "Invalid diamond token ID");

        // Verify NFT ownership (current owner should still own the NFT)
        require(nftContract.ownerOf(diamondTokenId) == staker, "Staker no longer owns NFT");
        
        // Verify NFT tier
        string memory tier = nftContract.getTier(diamondTokenId);
        require(keccak256(bytes(tier)) == keccak256(bytes("Diamond")), "NFT is not Diamond tier");
        
        require(!nftUsedForStaking[diamondTokenId], "NFT already used for staking");

        // Create migrated stake record
        stakes[staker] = StakeInfo({
            amount: amount,
            stakeTime: block.timestamp,           // Current time for lockup calculations
            lastClaimTime: lastClaimTime,         // Preserve last claim time
            diamondTokenId: diamondTokenId,
            isActive: true,
            totalClaimed: totalClaimed,           // Preserve total claimed
            isMigrated: true,                     // Mark as migrated
            originalStakeTime: originalStakeTime  // Preserve original stake time
        });

        // Mark NFT as used for staking
        nftUsedForStaking[diamondTokenId] = true;

        // Add to active stakers tracking
        _addStaker(staker);

        // Update pool stats
        totalStaked = totalStaked.add(amount);
        totalStakers = totalStakers.add(1);
        totalMigratedStakers = totalMigratedStakers.add(1);
        totalMigratedAmount = totalMigratedAmount.add(amount);

        emit StakeMigrated(staker, amount, diamondTokenId, originalStakeTime);
    }

    /// Migrate multiple stakers in batch
    function batchMigrateStakers(
        address[] calldata stakers,
        uint256[] calldata amounts,
        uint256[] calldata originalStakeTimes,
        uint256[] calldata lastClaimTimes,
        uint256[] calldata diamondTokenIds,
        uint256[] calldata totalClaimeds
    ) external {
        require(migrationMode, "Migration mode disabled");
        require(msg.sender == migrationOperator || msg.sender == owner(), "Not authorized for migration");
        require(block.timestamp <= migrationDeadline, "Migration deadline passed");
        
        uint256 length = stakers.length;
        require(length == amounts.length, "Arrays length mismatch");
        require(length == originalStakeTimes.length, "Arrays length mismatch");
        require(length == lastClaimTimes.length, "Arrays length mismatch");
        require(length == diamondTokenIds.length, "Arrays length mismatch");
        require(length == totalClaimeds.length, "Arrays length mismatch");

        for (uint256 i = 0; i < length; i++) {
            // Call individual migration function for each staker
            this.migrateStaker(
                stakers[i],
                amounts[i],
                originalStakeTimes[i],
                lastClaimTimes[i],
                diamondTokenIds[i],
                totalClaimeds[i]
            );
        }
    }

    /// Complete migration and disable migration mode
    function completeMigration() external onlyOwner {
        require(migrationMode, "Migration already completed");
        
        migrationMode = false;
        
        emit MigrationCompleted(totalMigratedStakers, totalMigratedAmount);
        emit MigrationModeDisabled();
    }

    /* ─────────────────── Staking Functions ─────────────────── */

    /// Stake PRIVIX tokens with diamond NFT verification (for new stakers post-migration)
    function stake(uint256 diamondTokenId) external nonReentrant {
        require(!migrationMode, "Contract in migration mode - new staking disabled");
        require(!stakes[msg.sender].isActive, "Already staking");
        require(diamondTokenId >= DIAMOND_START && diamondTokenId <= DIAMOND_END, "Invalid diamond token ID");
        require(nftContract.ownerOf(diamondTokenId) == msg.sender, "Not owner of this NFT");
        require(!nftUsedForStaking[diamondTokenId], "NFT already used for staking");

        // Verify NFT tier
        string memory tier = nftContract.getTier(diamondTokenId);
        require(keccak256(bytes(tier)) == keccak256(bytes("Diamond")), "NFT is not Diamond tier");

        // Transfer PRIVIX tokens
        require(
            privixToken.transferFrom(msg.sender, address(this), STAKING_AMOUNT),
            "PRIVIX transfer failed"
        );

        // Record stake
        stakes[msg.sender] = StakeInfo({
            amount: STAKING_AMOUNT,
            stakeTime: block.timestamp,
            lastClaimTime: block.timestamp,
            diamondTokenId: diamondTokenId,
            isActive: true,
            totalClaimed: 0,
            isMigrated: false,
            originalStakeTime: block.timestamp
        });

        // Mark NFT as used for staking
        nftUsedForStaking[diamondTokenId] = true;

        // Add to active stakers tracking
        _addStaker(msg.sender);

        // Update pool stats
        totalStaked = totalStaked.add(STAKING_AMOUNT);
        totalStakers = totalStakers.add(1);

        emit Staked(msg.sender, STAKING_AMOUNT, diamondTokenId, block.timestamp);
    }

    /// Claim rewards
    function claimRewards() external nonReentrant {
        require(!migrationMode, "Contract in migration mode");
        require(stakes[msg.sender].isActive, "No active stake");
        
        uint256 pendingRewards = getPendingRewards(msg.sender);
        require(pendingRewards > 0, "No rewards to claim");
        
        // Check if enough time has passed since last claim
        require(
            block.timestamp >= stakes[msg.sender].lastClaimTime.add(REWARD_PERIOD),
            "Reward period not elapsed"
        );

        // Update last claim time
        stakes[msg.sender].lastClaimTime = block.timestamp;
        stakes[msg.sender].totalClaimed = stakes[msg.sender].totalClaimed.add(pendingRewards);

        // Update total rewards paid
        totalRewardsPaid = totalRewardsPaid.add(pendingRewards);

        // Transfer USDT rewards
        require(usdtToken.transfer(msg.sender, pendingRewards), "USDT transfer failed");

        emit RewardsClaimed(msg.sender, pendingRewards, block.timestamp);
    }

    /// Unstake PRIVIX tokens
    function unstake() external nonReentrant {
        require(!migrationMode, "Contract in migration mode");
        require(stakes[msg.sender].isActive, "No active stake");
        require(canUnstake(msg.sender), "Cannot unstake yet");

        StakeInfo memory stakeInfo = stakes[msg.sender];
        
        // Clear stake data
        stakes[msg.sender].isActive = false;
        nftUsedForStaking[stakeInfo.diamondTokenId] = false;

        // Remove from active stakers
        _removeStaker(msg.sender);

        // Update pool stats
        totalStaked = totalStaked.sub(stakeInfo.amount);
        totalStakers = totalStakers.sub(1);

        // Transfer PRIVIX tokens back
        require(privixToken.transfer(msg.sender, stakeInfo.amount), "PRIVIX transfer failed");

        emit Unstaked(msg.sender, stakeInfo.amount, block.timestamp);
    }

    /* ─────────────────── View Functions ─────────────────── */

    /// Get pending rewards for a staker
    function getPendingRewards(address staker) public view returns (uint256) {
        if (!stakes[staker].isActive) return 0;
        
        uint256 contractUsdtBalance = usdtToken.balanceOf(address(this));
        if (contractUsdtBalance == 0 || totalStakers == 0) return 0;

        // Simple equal distribution among all stakers
        return contractUsdtBalance.div(totalStakers);
    }

    /// Check if a staker can unstake (30 days lockup from stake time)
    function canUnstake(address staker) public view returns (bool) {
        if (!stakes[staker].isActive) return false;
        return block.timestamp >= stakes[staker].stakeTime.add(LOCKUP_PERIOD);
    }

    /// Check if staker still owns their NFT
    function stakerStillOwnsNFT(address staker) public view returns (bool) {
        if (!stakes[staker].isActive) return false;
        try nftContract.ownerOf(stakes[staker].diamondTokenId) returns (address owner) {
            return owner == staker;
        } catch {
            return false;
        }
    }

    /// Get comprehensive staker info
    function getStakeInfo(address staker) external view returns (
        uint256 amount,
        uint256 stakeTime,
        uint256 lastClaimTime,
        uint256 diamondTokenId,
        bool isActive,
        bool canUnstakeNow,
        bool isMigrated,
        uint256 originalStakeTime
    ) {
        StakeInfo memory stakeInfo = stakes[staker];
        return (
            stakeInfo.amount,
            stakeInfo.stakeTime,
            stakeInfo.lastClaimTime,
            stakeInfo.diamondTokenId,
            stakeInfo.isActive,
            canUnstake(staker),
            stakeInfo.isMigrated,
            stakeInfo.originalStakeTime
        );
    }

    /// Get pool statistics
    function getPoolStats() external view returns (
        uint256 _totalStaked,
        uint256 _totalStakers,
        uint256 _totalRewardsPaid,
        uint256 _contractUsdtBalance,
        uint256 _contractPrivixBalance,
        uint256 _totalMigratedStakers,
        uint256 _totalMigratedAmount
    ) {
        return (
            totalStaked,
            totalStakers,
            totalRewardsPaid,
            usdtToken.balanceOf(address(this)),
            privixToken.balanceOf(address(this)),
            totalMigratedStakers,
            totalMigratedAmount
        );
    }

    /// Get all active stakers
    function getAllStakers() external view returns (address[] memory) {
        return activeStakers;
    }

    /// Get all stakers with details (for compatibility with existing scripts)
    function getAllStakersWithDetails() external view returns (
        address[] memory stakers,
        uint256[] memory amounts,
        uint256[] memory stakeTimes,
        uint256[] memory diamondTokenIds,
        bool[] memory canUnstakeFlags
    ) {
        uint256 count = activeStakers.length;
        stakers = new address[](count);
        amounts = new uint256[](count);
        stakeTimes = new uint256[](count);
        diamondTokenIds = new uint256[](count);
        canUnstakeFlags = new bool[](count);

        for (uint256 i = 0; i < count; i++) {
            address staker = activeStakers[i];
            StakeInfo memory stakeInfo = stakes[staker];
            
            stakers[i] = staker;
            amounts[i] = stakeInfo.amount;
            stakeTimes[i] = stakeInfo.originalStakeTime; // Use original stake time for migrated stakers
            diamondTokenIds[i] = stakeInfo.diamondTokenId;
            canUnstakeFlags[i] = canUnstake(staker);
        }

        return (stakers, amounts, stakeTimes, diamondTokenIds, canUnstakeFlags);
    }

    /* ─────────────────── Helper Functions ─────────────────── */

    /// Add staker to active stakers array
    function _addStaker(address staker) internal {
        activeStakers.push(staker);
        stakerIndex[staker] = activeStakers.length - 1;
    }

    /// Remove staker from active stakers array
    function _removeStaker(address staker) internal {
        uint256 index = stakerIndex[staker];
        uint256 lastIndex = activeStakers.length - 1;

        if (index != lastIndex) {
            address lastStaker = activeStakers[lastIndex];
            activeStakers[index] = lastStaker;
            stakerIndex[lastStaker] = index;
        }

        activeStakers.pop();
        delete stakerIndex[staker];
    }

    /* ─────────────────── Owner Functions ─────────────────── */

    /// Emergency withdraw USDT (owner only)
    function emergencyWithdrawUSDT(uint256 amount) external onlyOwner {
        require(amount <= usdtToken.balanceOf(address(this)), "Insufficient USDT balance");
        require(usdtToken.transfer(owner(), amount), "USDT transfer failed");
    }

    /// Emergency withdraw PRIVIX (owner only)
    function emergencyWithdrawPrivix(uint256 amount) external onlyOwner {
        require(amount <= privixToken.balanceOf(address(this)), "Insufficient PRIVIX balance");
        require(privixToken.transfer(owner(), amount), "PRIVIX transfer failed");
    }

    /// Set migration operator
    function setMigrationOperator(address newOperator) external onlyOwner {
        require(newOperator != address(0), "Invalid operator address");
        migrationOperator = newOperator;
    }

    /// Extend migration deadline (can only extend, not reduce)
    function extendMigrationDeadline(uint256 newDeadline) external onlyOwner {
        require(migrationMode, "Migration already completed");
        require(newDeadline > migrationDeadline, "Can only extend deadline");
        migrationDeadline = newDeadline;
    }
}