simple solidity BBS

BBS.sol

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;


contract BBS  {

    struct Post {
        string message;
        string name;
        address sender;
        uint blockNumber;
        uint blockTimestamp;
    }
    //last three are possibly redandant

    string public title;
    Post[] public posts;
    uint public post_limit = 100;

    mapping(address => string) public names;

    constructor() {
        title = "bbs1";
    }

    function post(string memory _message, string memory _name) public {
        require(posts.length <= post_limit, "exceed post limit"); 
        posts.push(Post(_message, _name, msg.sender, block.number, block.timestamp));
        if ( !_compareString(getName(),_name) ){
            names[msg.sender] = _name;
        }
    }

    function getPosts() view public returns(Post[] memory) {
        return posts;
    }

    function getName() view public returns(string memory){
        return names[msg.sender];
    }

    function _compareString(string memory s1, string memory s2) private pure returns(bool) {
        //https://qiita.com/bc_yuuuuuki/items/bbc4938da0ae09a0c57c
        return keccak256(abi.encodePacked(s1)) == keccak256(abi.encodePacked(s2));
    }

}