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n-lend smart contract
// Sources flattened with hardhat v2.6.3 https://hardhat.org
// File @openzeppelin/contracts/security/ReentrancyGuard.sol@v4.3.1
// SPDX-License-Identifier: MIT
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 make 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/utils/Context.sol@v4.3.1
// SPDX-License-Identifier: MIT
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/access/Ownable.sol@v4.3.1
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
/**
* @dev Contract module which provides a basic access control mechanism, where
* there is an account (an owner) that can be granted exclusive access to
* specific functions.
*
* By default, the owner account will be the one that deploys the contract. This
* can later be changed with {transferOwnership}.
*
* This module is used through inheritance. It will make available the modifier
* `onlyOwner`, which can be applied to your functions to restrict their use to
* the owner.
*/
abstract contract Ownable is Context {
address private _owner;
event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
/**
* @dev Initializes the contract setting the deployer as the initial owner.
*/
constructor() {
_setOwner(_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 {
_setOwner(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");
_setOwner(newOwner);
}
function _setOwner(address newOwner) private {
address oldOwner = _owner;
_owner = newOwner;
emit OwnershipTransferred(oldOwner, newOwner);
}
}
// File @openzeppelin/contracts/utils/introspection/IERC165.sol@v4.3.1
// SPDX-License-Identifier: MIT
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/token/ERC721/IERC721.sol@v4.3.1
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
/**
* @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/extensions/IERC721Enumerable.sol@v4.3.1
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
/**
* @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/extensions/IERC721Metadata.sol@v4.3.1
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
/**
* @title ERC-721 Non-Fungible Token Standard, optional metadata extension
* @dev See https://eips.ethereum.org/EIPS/eip-721
*/
interface IERC721Metadata is IERC721 {
/**
* @dev Returns the token collection name.
*/
function name() external view returns (string memory);
/**
* @dev Returns the token collection symbol.
*/
function symbol() external view returns (string memory);
/**
* @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
*/
function tokenURI(uint256 tokenId) external view returns (string memory);
}
// File contracts/interfaces/IN.sol
// SPDX-License-Identifier: MIT
pragma solidity 0.8.6;
interface IN is IERC721Enumerable, IERC721Metadata {
function getFirst(uint256 tokenId) external view returns (uint256);
function getSecond(uint256 tokenId) external view returns (uint256);
function getThird(uint256 tokenId) external view returns (uint256);
function getFourth(uint256 tokenId) external view returns (uint256);
function getFifth(uint256 tokenId) external view returns (uint256);
function getSixth(uint256 tokenId) external view returns (uint256);
function getSeventh(uint256 tokenId) external view returns (uint256);
function getEight(uint256 tokenId) external view returns (uint256);
}
// File contracts/core/NLend.sol
// SPDX-License-Identifier: MIT
pragma solidity >=0.8.4;
interface IReceiver {
function receiveN(uint256 id, address owner, bytes calldata data) external payable;
}
interface TokenOrNFT {
function transferFrom(address from, address to, uint256 amountOrId) external;
}
contract nLend is ReentrancyGuard, Ownable {
//State variables
IN public immutable n;
uint256 public adminFee;
mapping(uint256 => address) public nOwner;
mapping(uint256 => uint256) public borrowPrice;
//Do I need arrays with the current NFTs?
//With it, we easily find which NFTs are available for loaning
//Events
event Deposit(address indexed _from, uint256 indexed _id, uint256 _value);
event Withdraw(address indexed _from, uint256 indexed _id);
event FlashBorrow(address indexed borrower,address indexed recipient, uint256 indexed _id, uint256 _value);
event borrowFeeUpdated(uint256 indexed id, uint256 price);
event adminFeeUpdated(uint256 indexed newAdminFee);
constructor(
IN _n,
uint256 _adminFee
)
{
n = _n;
adminFee = _adminFee;
}
/*
* unprotected write functions
* All functions should be protected with a reentrancy guard
* None should have access control
*/
/**
* @notice Allow a n token holder to bulk mint tokens with id of their n tokens' id
* @param id The n with ID id to deposit
* @param price The price the owner wants to set to borrow their n, in wei
* @notice Is checks-effects followed here? Yes
*/
function deposit(uint256 id, uint256 price) external nonReentrant {
//check if the msg.sender is the owner of id N
require(n.ownerOf(id) == msg.sender, "nLend:INVALID_OWNER");
//credit the owner with the ID in the nOwners mapping
nOwner[id] = msg.sender;
//assign the NFT the owner's price
borrowPrice[id] = price;
//transfer the NFT from the owner to this contract
//NFT transfer does not return a bool so no need to require
//we don't want safeTransferFrom since we don't want a callback
n.transferFrom(msg.sender, address(this), id);
//emit a deposit event
emit Deposit(msg.sender, id, price);
}
/**
* @notice Allow user's to withdraw their deposited n NFT with ID id
* @param id The n with ID id to withdraw
* @notice Is checks-effects followed here? Yes
*/
function withdraw(uint256 id) external nonReentrant {
//check if the msg.sender is the owner of id N
require(nOwner[id] == msg.sender, "nLend:INVALID_OWNER");
//clear the ownership
nOwner[id] = address(0);
//clear the price
borrowPrice[id] = 0 ether;
//transfer the NFT from this contract to the owner
//NFT transfer does not return a bool so no need to require
//we don't want safeTransferFrom since we don't want a callback
n.transferFrom(address(this), msg.sender, id);
//emit a deposit event
emit Withdraw(msg.sender,id);
}
/**
* @notice Flash borrow an n NFT with ID id
* @param id The n NFT with ID id you want to borrow
* @notice The receive contract needs to approve this contract in it's logic
* @notice You can grief an unprotected receiver that has enough ETH in it + working logic to execute
*/
function flashBorrow(uint256 id, address receiver, bytes calldata data) external payable nonReentrant {
//check that we have the NFT - this is to say that there is some owner in our mapping
require(nOwner[id] != address(0));
//check that the msg.value is enough incl fees
uint amountReceived = msg.value;
require(amountReceived >= borrowPrice[id] + (borrowPrice[id]*adminFee)/10000);
//duduct admin fees and borrow fee from the amountReceived
amountReceived -= borrowPrice[id] + (borrowPrice[id]*adminFee)/10000;
//transfer the NFT
//NFT transfer does not return a bool so no need to require
//we don't want safeTransferFrom since we don't want a callback
n.transferFrom(address(this), receiver, id);
//send the rest of the msg.value to the receiver
//Do the things
IReceiver(receiver).receiveN{value: amountReceived}(id, nOwner[id], data);
//transfer the NFT back
//NFT transfer does not return a bool so no need to require
//we don't want safeTransferFrom since we don't want a callback
n.transferFrom(receiver, address(this), id);
//send the borrower fees to the id owner
payable(nOwner[id]).transfer(borrowPrice[id]);
//emit an event - should we use the tracked msg.value?
emit FlashBorrow(msg.sender, receiver, id, msg.value);
}
/**
* @notice Allows the owner to withdraw all admin fees
*/
function withdrawAll() external onlyOwner {
payable(owner()).transfer(address(this).balance);
}
/**
* @notice Allows the owner to withdraw all admin fees
*/
function updateAdminFee(uint256 newAdminFee) external onlyOwner {
require(newAdminFee <= 10000);
adminFee = newAdminFee;
emit adminFeeUpdated(newAdminFee);
}
/**
* @notice Allows an owner to update their borrow fee
*/
function updateBorrowFee(uint256 id, uint256 price) external nonReentrant {
require(msg.sender == nOwner[id]);
borrowPrice[id] = price;
emit borrowFeeUpdated(id, price);
}
/**
* @notice Allows an owner to recover any token or NFT other than n
*/
function recovertokenOrNFT(address tokenOrNFT, uint256 amountOrAmount) external nonReentrant onlyOwner {
require(tokenOrNFT != n.address);
TokenOrNFT(token).transferFrom(address(this), owner(), amountOrAmount);
}
}
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