SoulboundNFT

1// SPDX-License-Identifier: MIT
2pragma solidity ^0.8.20;
3 
4contract SoulboundNFT {
5    string public name;
6    string public symbol;
7    address public owner;
8    uint256 public nextTokenId;
9 
10    mapping(uint256 => address) public ownerOf;
11    mapping(address => uint256) public balanceOf;
12 
13    event Mint(address indexed to, uint256 indexed tokenId);
14 
15    constructor(string memory name_, string memory symbol_) {
16        name = name_;
17        symbol = symbol_;
18        owner = msg.sender;
19    }
20 
21    function mint(address to) external returns (uint256) {
22        require(msg.sender == owner, "NOT_OWNER");
23        require(to != address(0), "ZERO_ADDR");
24        uint256 id = nextTokenId++;
25        ownerOf[id] = to;
26        balanceOf[to] += 1;
27        emit Mint(to, id);
28        return id;
29    }
30 
31    // Soulbound: tokens can never be transferred or approved once minted.
32    function transferFrom(address, address, uint256) external pure {
33        revert("SOULBOUND");
34    }
35 
36    function approve(address, uint256) external pure {
37        revert("SOULBOUND");
38    }
39}