completed the basic structure of NFT contract

.gitignore

@@ -1,3 +1,5 @@
+# secrets
+
 # Logs
 logs
 *.log
@@ -102,3 +104,13 @@ dist
 
 # TernJS port file
 .tern-port
+
+node_modules
+.env
+coverage
+coverage.json
+typechain
+
+#Hardhat files
+cache
+artifacts

README.md

@@ -1,2 +1,15 @@
-# project_nft
-An NFT project
+# Basic Sample Hardhat Project
+
+This project demonstrates a basic Hardhat use case. It comes with a sample contract, a test for that contract, a sample script that deploys that contract, and an example of a task implementation, which simply lists the available accounts.
+
+Try running some of the following tasks:
+
+```shell
+npx hardhat accounts
+npx hardhat compile
+npx hardhat clean
+npx hardhat test
+npx hardhat node
+node scripts/sample-script.js
+npx hardhat help
+```

contracts/ERC721.sol

@@ -0,0 +1,96 @@
+pragma solidity ^0.8.2;
+
+contract ERC721 {
+    event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
+    event Approval(address indexed _owner, address indexed _approved, uint256 tokenId); // 允许动用单个NFT
+    event ApprovalForAll(address indexed _owner, address indexed _opeator, bool _approved); // 允许动用这个人下的所有NFT
+
+    mapping(address => uint256) internal _balances; // nft 余额数量
+    mapping(uint256 => address) internal _owners;
+    mapping(address => mapping(address => bool)) private _operatorApprovals;
+    mapping(uint256 => address) private _tokenApprovals;
+
+
+
+    // Returns the num of NFTs assigned to an owner
+    function balanceOf(address owner) public view returns(uint256){
+        require(owner != address(0), 'Address is zero');
+        return _balances[owner];
+    }
+
+    // Finds the owner of an NFT
+    function ownerOf(uint256 tokenId) public view returns(address){
+        address owner = _owners[tokenId];
+        require(owner != address(0), 'TokenID does not exist');
+        return owner;
+    }
+
+    // Enable / disable an operator to manage all of msg.senders' asset
+    function setApprovalForAll(address operator, bool approved) public {
+        _operatorApprovals[msg.sender][operator] = approved;
+        emit ApprovalForAll(msg.sender, operator, approved);
+    }
+
+    // Check if an addr is an operator for an other address
+    function isApprovedForAll(address owner, address operator) public view returns(bool) {
+        return _operatorApprovals[owner][operator];
+    }
+
+    // Update an approved address for an NFT 允许这个人搞这个nft 只允许一个人
+    function approve(address to, uint256 tokenId) public {
+        address owner = ownerOf(tokenId);
+        require(msg.sender == owner || isApprovedForAll(owner, msg.sender), 'Msg.sender is not the owner or the approved operator.');
+        _tokenApprovals[tokenId] = to;
+        emit Approval(owner, to, tokenId);
+    }
+
+    // Get the approved address for the single NFT.
+    function getApproved(uint256 tokenId) public view returns(address) {
+        require(_owners[tokenId] != address(0), 'TokenID not exist');
+        return _tokenApprovals[tokenId];
+    }
+
+    // Transfer ownership of an NFT  需要 owner 或者授权代理人操作
+    function transferFrom(address from, address to, uint tokenId) public {
+        address owner = ownerOf(tokenId);
+        require(
+            msg.sender == owner ||
+            getApproved(tokenId) == msg.sender ||
+            isApprovedForAll(owner, msg.sender),
+            'Msg.sender is not the owner or approved for the transfer'
+        );
+
+        require(owner == from, 'From address is not the owner');
+        require(to != address(0), 'Address is zero');
+        require(_owners[tokenId] != address(0), 'TokenID does not exist');
+        approve(address(0), tokenId);
+        _balances[from] -= 1;
+        _balances[to] += 1;
+        _owners[tokenId] = to;
+
+        emit Transfer(from, to, tokenId);
+    }
+
+    // Standard transferFrom
+    // Check if onERC721Received is implemented WHEN sending to smart contracts
+    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public {
+        transferFrom(from, to, tokenId);
+        require(_checkOnERC721Received(), 'Receiver not implemented');
+    }
+
+    function safeTransferFrom(address from, address to, uint256 tokenId) public {
+        safeTransferFrom(from, to, tokenId, "");
+    }
+
+    // Oversimplified
+    function _checkOnERC721Received() private pure returns(bool) {
+        return true;
+    }
+
+    // EIP165: Query if the contract implements another interface 确定另一个contract有一个implement.
+    function supportsInterface(bytes4 interfaceId) public pure virtual returns(bool) {
+        return interfaceId == 0x80ac58cd;
+    }
+
+
+}

hardhat.config.js

@@ -0,0 +1,21 @@
+require("@nomiclabs/hardhat-waffle");
+
+// This is a sample Hardhat task. To learn how to create your own go to
+// https://hardhat.org/guides/create-task.html
+task("accounts", "Prints the list of accounts", async (taskArgs, hre) => {
+  const accounts = await hre.ethers.getSigners();
+
+  for (const account of accounts) {
+    console.log(account.address);
+  }
+});
+
+// You need to export an object to set up your config
+// Go to https://hardhat.org/config/ to learn more
+
+/**
+ * @type import('hardhat/config').HardhatUserConfig
+ */
+module.exports = {
+  solidity: "0.8.4",
+};