feat(task3): add MyERC20Token and MyNFT contracts with NFTMarket inte…

…rface

Add ERC20 and ERC721 smart contracts named `MyERC20Token` and `MyNFT`, respectively.
Introduce the `NFTMarket` contract that facilitates buying and selling of NFTs,
leveraging OpenZeppelin libraries for security and efficiency. README updated with
deployed contract addresses for list and buy functionalities.

members/veithly/task3/MyERC20Token.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+
+contract MyERC20Token is ERC20 {
+    constructor(uint256 initialSupply) ERC20("MyToken", "MTK") {
+        _mint(msg.sender, initialSupply);
+    }
+}

members/veithly/task3/MyNFT.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
+import "@openzeppelin/contracts/utils/Counters.sol";
+
+contract MyNFT is ERC721URIStorage {
+    using Counters for Counters.Counter;
+    Counters.Counter private _tokenIds;
+
+    constructor() ERC721("MyNFT", "MNFT") {}
+
+    function mintNFT(address recipient, string memory tokenURI) public returns (uint256) {
+        _tokenIds.increment();
+        uint256 newItemId = _tokenIds.current();
+        _mint(recipient, newItemId);
+        _setTokenURI(newItemId, tokenURI);
+        return newItemId;
+    }
+}

members/veithly/task3/NFTMarket.sol

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+pragma solidity ^0.8.0;
+
+import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import "@openzeppelin/contracts/access/Ownable.sol";
+
+contract NFTMarket is Ownable {
+    struct Listing {
+        address seller;
+        address nftContract;
+        uint256 tokenId;
+        uint256 price;
+    }
+
+    IERC20 public currencyToken;
+    uint256 public listingCount;
+    mapping(uint256 => Listing) public listings;
+
+    event NFTListed(uint256 listingId, address seller, address nftContract, uint256 tokenId, uint256 price);
+    event NFTBought(uint256 listingId, address buyer);
+
+    constructor(address _currencyToken) {
+        currencyToken = IERC20(_currencyToken);
+    }
+
+    function listNFT(address _nftContract, uint256 _tokenId, uint256 _price) external {
+        IERC721 nftContract = IERC721(_nftContract);
+        require(nftContract.ownerOf(_tokenId) == msg.sender, "You do not own this NFT");
+        require(nftContract.isApprovedForAll(msg.sender, address(this)), "Market contract is not approved");
+
+        listingCount++;
+        listings[listingCount] = Listing(msg.sender, _nftContract, _tokenId, _price);
+
+        emit NFTListed(listingCount, msg.sender, _nftContract, _tokenId, _price);
+    }
+
+    function buyNFT(uint256 _listingId) external {
+        Listing memory listing = listings[_listingId];
+        require(listing.price > 0, "NFT is not listed");
+
+        currencyToken.transferFrom(msg.sender, listing.seller, listing.price);
+        IERC721(listing.nftContract).transferFrom(listing.seller, msg.sender, listing.tokenId);
+
+        delete listings[_listingId];
+
+        emit NFTBought(_listingId, msg.sender);
+    }
+}

members/veithly/task3/README.md

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+List NFT: 0x9a659e39b29263ef2817c26a359e299580c1027982a27658dc486546adfa1097
+Buy NFT: 0x0b2f69f185a4936410509a1c16b8f5f5e5c0734ead93b871486cd00a7254d8a2