// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "./nf-token.sol";
import "./erc721-enumerable.sol";
/**
* @dev Optional enumeration implementation for ERC-721 non-fungible token standard.
*/
contract NFTokenEnumerable is
NFToken,
ERC721Enumerable
{
/**
* @dev List of revert message codes. Implementing dApp should handle showing the correct message.
* Based on 0xcert framework error codes.
*/
string constant INVALID_INDEX = "005007";
/**
* @dev Array of all NFT IDs.
*/
uint256[] internal tokens;
/**
* @dev Mapping from token ID to its index in global tokens array.
*/
mapping(uint256 => uint256) internal idToIndex;
/**
* @dev Mapping from owner to list of owned NFT IDs.
*/
mapping(address => uint256[]) internal ownerToIds;
/**
* @dev Mapping from NFT ID to its index in the owner tokens list.
*/
mapping(uint256 => uint256) internal idToOwnerIndex;
/**
* @dev Contract constructor.
*/
constructor()
{
supportedInterfaces[0x780e9d63] = true; // ERC721Enumerable
}
/**
* @dev Returns the count of all existing NFTokens.
* @return Total supply of NFTs.
*/
function totalSupply()
external
override
view
returns (uint256)
{
return tokens.length;
}
/**
* @dev Returns NFT ID by its index.
* @param _index A counter less than `totalSupply()`.
* @return Token id.
*/
function tokenByIndex(
uint256 _index
)
external
override
view
returns (uint256)
{
require(_index < tokens.length, INVALID_INDEX);
return tokens[_index];
}
/**
* @dev returns the n-th NFT ID from a list of owner's tokens.
* @param _owner Token owner's address.
* @param _index Index number representing n-th token in owner's list of tokens.
* @return Token id.
*/
function tokenOfOwnerByIndex(
address _owner,
uint256 _index
)
external
override
view
returns (uint256)
{
require(_index < ownerToIds[_owner].length, INVALID_INDEX);
return ownerToIds[_owner][_index];
}
/**
* @notice This is an internal function which should be called from user-implemented external
* mint function. Its purpose is to show and properly initialize data structures when using this
* implementation.
* @dev Mints a new NFT.
* @param _to The address that will own the minted NFT.
* @param _tokenId of the NFT to be minted by the msg.sender.
*/
function _mint(
address _to,
uint256 _tokenId
)
internal
override
virtual
{
super._mint(_to, _tokenId);
tokens.push(_tokenId);
idToIndex[_tokenId] = tokens.length - 1;
}
/**
* @notice This is an internal function which should be called from user-implemented external
* burn function. Its purpose is to show and properly initialize data structures when using this
* implementation. Also, note that this burn implementation allows the minter to re-mint a burned
* NFT.
* @dev Burns a NFT.
* @param _tokenId ID of the NFT to be burned.
*/
function _burn(
uint256 _tokenId
)
internal
override
virtual
{
super._burn(_tokenId);
uint256 tokenIndex = idToIndex[_tokenId];
uint256 lastTokenIndex = tokens.length - 1;
uint256 lastToken = tokens[lastTokenIndex];
tokens[tokenIndex] = lastToken;
tokens.pop();
// This wastes gas if you are burning the last token but saves a little gas if you are not.
idToIndex[lastToken] = tokenIndex;
idToIndex[_tokenId] = 0;
}
/**
* @notice Use and override this function with caution. Wrong usage can have serious consequences.
* @dev Removes a NFT from an address.
* @param _from Address from wich we want to remove the NFT.
* @param _tokenId Which NFT we want to remove.
*/
function _removeNFToken(
address _from,
uint256 _tokenId
)
internal
override
virtual
{
Erequire(idToOwner[_tokenId] == _from, NOT_OWNER);
delete idToOwner[_tokenId];
uint256 tokenToRemoveIndex = idToOwnerIndex[_tokenId];
uint256 lastTokenIndex = ownerToIds[_from].length - 1;
if (lastTokenIndex != tokenToRemoveIndex)
{
uint256 lastToken = ownerToIds[_from][lastTokenIndex];
ownerToIds[_from][tokenToRemoveIndex] = lastToken;
idToOwnerIndex[lastToken] = tokenToRemoveIndex;
}
ownerToIds[_from].pop();
}
/**
* @notice Use and override this function with caution. Wrong usage can have serious consequences.
* @dev Assigns a new NFT to an address.
* @param _to Address to wich we want to add the NFT.
* @param _tokenId Which NFT we want to add.
*/
function _addNFToken(
address _to,
uint256 _tokenId
)
internal
override
virtual
{
Erequire(idToOwner[_tokenId] == address(0), NFT_ALREADY_EXISTS);
idToOwner[_tokenId] = _to;
ownerToIds[_to].push(_tokenId);
idToOwnerIndex[_tokenId] = ownerToIds[_to].length - 1;
}
/**
* @dev Helper function that gets NFT count of owner. This is needed for overriding in enumerable
* extension to remove double storage(gas optimization) of owner NFT count.
* @param _owner Address for whom to query the count.
* @return Number of _owner NFTs.
*/
function _getOwnerNFTCount(
address _owner
)
internal
override
virtual
view
returns (uint256)
{
return ownerToIds[_owner].length;
}
}
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