// File: KCGStakingV2.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;

import "@openzeppelin/contracts/token/ERC721/extensions/IERC721Enumerable.sol";
import "@openzeppelin/contracts/token/ERC721/utils/ERC721Holder.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

contract KCGStakingV2 is ERC721Holder, Ownable, ReentrancyGuard {
    IERC721Enumerable public immutable nftToken;

    // Determine if staking is paused
    bool public isPaused = false;
    // Minimal staking period, in days
    uint256 public minStakingPeriod = 90 days;
    // Staking growth parameter
    uint256 public growthParameter = 3;
    // Mapping of user to number of tokens staked
    mapping(address => uint256) public numOfTokenStaked;
    // Mapping from NFT token ID to staking record
    mapping(uint256 => StakingRecord) public stakingRecords;
    // Staking record struct
    struct StakingRecord {
        address tokenOwner;
        uint256 stakedAt;
        uint256 claimedAt;
        uint256 lockPeriod;
        uint256 endingTimestamp;
    }

    ////////////
    // Events //
    ////////////

    // Event emitted when NFTs are staked
    event Staked(
        address user,
        uint256[] tokenIds,
        uint256 stakedAt,
        uint256 lockPeriod,
        uint256 endingTimestamp
    );
    // Event emitted when NFTs are restaked
    event Restaked(
        address user,
        uint256[] tokenIds,
        uint256 stakedAt,
        uint256 lockPeriod,
        uint256 endingTimestamp
    );
    // Event emitted when NFTs are unstaked
    event Unstaked(address user, uint256[] tokenIds, uint256 amount);
    // Event emitted when rewards are claimed
    event Claimed(address user, uint256 amount);

    /////////////////
    // Constructor //
    /////////////////

    constructor(address _nftTokenAddress) {
        nftToken = IERC721Enumerable(_nftTokenAddress);
    }

    ////////////
    // Public //
    ////////////

    function stake(uint256[] memory tokenIds, uint256 lockPeriod)
        public
        nonReentrant
    {
        require(isPaused == false, "Staking paused");
        uint256 totalDays = lockPeriod * 1 days;
        require(totalDays >= minStakingPeriod, "Not within min staking period");
        require(totalDays <= (1095 * 1 days), "Above max staking period");
        uint256 endingTimestamp = block.timestamp + totalDays;

        for (uint256 i = 0; i < tokenIds.length; i++) {
            uint256 tokenId = tokenIds[i];
            require(
                nftToken.ownerOf(tokenId) == msg.sender,
                "NFT not owned by user"
            );
            require(
                stakingRecords[tokenId].lockPeriod == 0,
                "NFT already staked"
            );
            stakingRecords[tokenId] = StakingRecord(
                msg.sender,
                block.timestamp,
                block.timestamp,
                lockPeriod,
                endingTimestamp
            );
            nftToken.safeTransferFrom(msg.sender, address(this), tokenId);
        }
        numOfTokenStaked[msg.sender] += tokenIds.length;

        emit Staked(
            msg.sender,
            tokenIds,
            block.timestamp,
            lockPeriod,
            endingTimestamp
        );
    }

    function restake(uint256[] memory tokenIds, uint256 lockPeriod)
        public
        nonReentrant
    {
        require(isPaused == false, "Staking paused");
        uint256 totalDays = lockPeriod * 1 days;
        require(totalDays >= minStakingPeriod, "Not within min staking period");
        require(totalDays <= (1095 * 1 days), "Above max staking period");
        uint256 endingTimestamp = block.timestamp + totalDays;

        for (uint256 i = 0; i < tokenIds.length; i++) {
            uint256 tokenId = tokenIds[i];
            require(
                stakingRecords[tokenId].tokenOwner == msg.sender,
                "NFT not staked or not owned by user"
            );
            require(
                block.timestamp >= stakingRecords[tokenId].endingTimestamp,
                "NFT is still locked"
            );
            stakingRecords[tokenId].stakedAt = block.timestamp;
            stakingRecords[tokenId].claimedAt = block.timestamp;
            stakingRecords[tokenId].lockPeriod = lockPeriod;
            stakingRecords[tokenId].endingTimestamp = endingTimestamp;
        }

        emit Restaked(
            msg.sender,
            tokenIds,
            block.timestamp,
            lockPeriod,
            endingTimestamp
        );
    }

    function unstake(uint256[] memory tokenIds) public nonReentrant {
        uint256 totalRewards = 0;

        for (uint256 i = 0; i < tokenIds.length; i++) {
            uint256 tokenId = tokenIds[i];
            require(
                stakingRecords[tokenId].tokenOwner == msg.sender,
                "NFT not owned by user"
            );
            require(
                block.timestamp >= stakingRecords[tokenId].endingTimestamp,
                "NFT is still locked"
            );
            totalRewards += getPendingRewards(tokenId);
            nftToken.safeTransferFrom(address(this), msg.sender, tokenId);
            delete stakingRecords[tokenId];
        }
        numOfTokenStaked[msg.sender] -= tokenIds.length;

        emit Unstaked(msg.sender, tokenIds, totalRewards);
    }

    function claim(uint256[] memory tokenIds) external {
        uint256 totalRewards = 0;

        for (uint256 i = 0; i < tokenIds.length; i++) {
            uint256 tokenId = tokenIds[i];
            require(
                stakingRecords[tokenId].tokenOwner == msg.sender,
                "NFT not owned by user"
            );
            totalRewards += getPendingRewards(tokenId);
            stakingRecords[tokenId].claimedAt = block.timestamp;
        }

        emit Claimed(msg.sender, totalRewards);
    }

    //////////
    // View //
    //////////

    function getPendingRewards(uint256 tokenId) public view returns (uint256) {
        require(stakingRecords[tokenId].stakedAt > 0, "NFT not staked");
        uint256 rewardPerSecond = getRewardPerSecond(
            stakingRecords[tokenId].lockPeriod
        );

        uint256 stakingPeriodInSeconds = block.timestamp -
            stakingRecords[tokenId].claimedAt;
        if (stakingRecords[tokenId].endingTimestamp < block.timestamp) {
            // end reached
            if (
                stakingRecords[tokenId].endingTimestamp <=
                stakingRecords[tokenId].claimedAt
            ) {
                // already claimed
                return 0;
            }
            // end reached, but not claimed
            stakingPeriodInSeconds =
                stakingRecords[tokenId].endingTimestamp -
                stakingRecords[tokenId].claimedAt;
        }
        return rewardPerSecond * stakingPeriodInSeconds;
    }

    function getPendingRewardsForUser(address user)
        public
        view
        returns (uint256)
    {
        uint256 totalRewards = 0;
        for (uint256 i = 0; i < nftToken.totalSupply(); i++) {
            if (stakingRecords[i].tokenOwner == user) {
                totalRewards += getPendingRewards(i);
            }
        }
        return totalRewards;
    }

    function getStakingRecords(address user)
        public
        view
        returns (
            uint256[] memory,
            uint256[] memory,
            uint256[] memory,
            uint256[] memory,
            uint256[] memory
        )
    {
        uint256[] memory tokenIds = new uint256[](numOfTokenStaked[user]);
        uint256[] memory stakedAt = new uint256[](numOfTokenStaked[user]);
        uint256[] memory lockPeriod = new uint256[](numOfTokenStaked[user]);
        uint256[] memory endingTimestamp = new uint256[](
            numOfTokenStaked[user]
        );
        uint256[] memory rewards = new uint256[](numOfTokenStaked[user]);
        uint256 counter = 0;
        for (uint256 i = 0; i < nftToken.totalSupply(); i++) {
            if (stakingRecords[i].tokenOwner == user) {
                tokenIds[counter] = i;
                stakedAt[counter] = stakingRecords[i].stakedAt;
                lockPeriod[counter] = stakingRecords[i].lockPeriod;
                endingTimestamp[counter] = stakingRecords[i].endingTimestamp;
                rewards[counter] = getPendingRewards(tokenIds[counter]);
                counter++;
            }
        }
        return (tokenIds, stakedAt, lockPeriod, endingTimestamp, rewards);
    }

    //////////////
    // Internal //
    //////////////

    function getRewardPerSecond(uint256 lockPeriodInDays)
        internal
        view
        returns (uint256)
    {
        uint256 decimal = 18;
        uint256 growth = growthParameter * (10**(decimal - 2));

        if (lockPeriodInDays > 1095) {
            return (growth * 1095) / 86400;
        } else if (lockPeriodInDays >= (minStakingPeriod / 1 days)) {
            return (growth * lockPeriodInDays) / 86400;
        } else {
            return 0;
        }
    }

    ///////////
    // Owner //
    ///////////

    // Owner can pause and unpause staking
    function setPaused(bool _paused) external onlyOwner {
        isPaused = _paused;
    }

    // Owner can adjust the growth parameter
    function setGrowthParameter(uint256 _growthParameter) external onlyOwner {
        growthParameter = _growthParameter;
    }

    // Owner can adjust the growth parameter
    function setMinStakingPeriod(uint256 _minStakingPeriod) external onlyOwner {
        minStakingPeriod = _minStakingPeriod * 1 days;
    }

    // Owner can unlock an NFT, user can unstake now
    function emergencyUnlock(uint256[] memory tokenIds) external onlyOwner {
        for (uint256 i = 0; i < tokenIds.length; i++) {
            uint256 tokenId = tokenIds[i];
            stakingRecords[tokenId].endingTimestamp = block.timestamp;
            stakingRecords[tokenId].claimedAt = block.timestamp;
        }
    }
}

// File: @openzeppelin/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

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

        _;

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

// 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/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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`, 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 be 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: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * 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 Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @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 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);

    /**
     * @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;
}

// File: @openzeppelin/contracts/token/ERC721/utils/ERC721Holder.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/utils/ERC721Holder.sol)

pragma solidity ^0.8.0;

import "../IERC721Receiver.sol";

/**
 * @dev Implementation of the {IERC721Receiver} interface.
 *
 * Accepts all token transfers.
 * Make sure the contract is able to use its token with {IERC721-safeTransferFrom}, {IERC721-approve} or {IERC721-setApprovalForAll}.
 */
contract ERC721Holder is IERC721Receiver {
    /**
     * @dev See {IERC721Receiver-onERC721Received}.
     *
     * Always returns `IERC721Receiver.onERC721Received.selector`.
     */
    function onERC721Received(
        address,
        address,
        uint256,
        bytes memory
    ) public virtual override returns (bytes4) {
        return this.onERC721Received.selector;
    }
}

// File: @openzeppelin/contracts/token/ERC721/extensions/IERC721Enumerable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Enumerable.sol)

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721Receiver.sol)

pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// File: @openzeppelin/contracts/utils/introspection/IERC165.sol



// 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);
}

// 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;
    }
}