// SPDX-License-Identifier: MIT

pragma solidity ^0.8.4;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";

import "@openzeppelin/contracts/utils/Counters.sol";

// TO DO: Explain the reason/advantadge to use ERC721URIStorage instead of ERC721 itself

contract NFT is ERC721URIStorage {

using Counters for Counters.Counter;

Counters.Counter private _tokenIds;

address private marketplaceAddress;

mapping(uint256 => address) private _creators;

event TokenMinted(uint256 indexed tokenId, string tokenURI, address marketplaceAddress);

constructor(address _marketplaceAddress) ERC721("MarkKop", "MARK") {

marketplaceAddress = _marketplaceAddress;

}

function mintToken(string memory tokenURI) public returns (uint256) {

_tokenIds.increment();

uint256 newItemId = _tokenIds.current();

_mint(msg.sender, newItemId);

_creators[newItemId] = msg.sender;

_setTokenURI(newItemId, tokenURI);

// Give the marketplace approval to transact NFTs between users

setApprovalForAll(marketplaceAddress, true);

emit TokenMinted(newItemId, tokenURI, marketplaceAddress);

return newItemId;

}

function getTokensOwnedByMe() public view returns (uint256[] memory) {

uint256 numberOfExistingTokens = _tokenIds.current();

uint256 numberOfTokensOwned = balanceOf(msg.sender);

uint256[] memory ownedTokenIds = new uint256[](numberOfTokensOwned);

uint256 currentIndex = 0;

for (uint256 i = 0; i < numberOfExistingTokens; i++) {

uint256 tokenId = i + 1;

if (ownerOf(tokenId) != msg.sender) continue;

ownedTokenIds[currentIndex] = tokenId;

currentIndex += 1;

}

return ownedTokenIds;

}

function getTokenCreatorById(uint256 tokenId) public view returns (address) {

return _creators[tokenId];

}

function getTokensCreatedByMe() public view returns (uint256[] memory) {

uint256 numberOfExistingTokens = _tokenIds.current();

uint256 numberOfTokensCreated = 0;

for (uint256 i = 0; i < numberOfExistingTokens; i++) {

uint256 tokenId = i + 1;

if (_creators[tokenId] != msg.sender) continue;

numberOfTokensCreated += 1;

}

uint256[] memory createdTokenIds = new uint256[](numberOfTokensCreated);

uint256 currentIndex = 0;

for (uint256 i = 0; i < numberOfExistingTokens; i++) {

uint256 tokenId = i + 1;

if (_creators[tokenId] != msg.sender) continue;

createdTokenIds[currentIndex] = tokenId;

currentIndex += 1;

}

return createdTokenIds;

}

}