SimpleERC20

1// SPDX-License-Identifier: MIT
2pragma solidity ^0.8.20;
3 
4contract SimpleERC20 {
5    string public name;
6    string public symbol;
7    uint8 public constant decimals = 18;
8    uint256 public totalSupply;
9    address public owner;
10 
11    mapping(address => uint256) public balanceOf;
12    mapping(address => mapping(address => uint256)) public allowance;
13 
14    event Transfer(address indexed from, address indexed to, uint256 value);
15    event Approval(address indexed owner, address indexed spender, uint256 value);
16 
17    modifier onlyOwner() {
18        require(msg.sender == owner, "NOT_OWNER");
19        _;
20    }
21 
22    constructor(string memory name_, string memory symbol_, uint256 initialSupply_) {
23        name = name_;
24        symbol = symbol_;
25        owner = msg.sender;
26        uint256 supply = initialSupply_ * 10 ** decimals;
27        totalSupply = supply;
28        balanceOf[msg.sender] = supply;
29        emit Transfer(address(0), msg.sender, supply);
30    }
31 
32    function transfer(address to, uint256 value) external returns (bool) {
33        _transfer(msg.sender, to, value);
34        return true;
35    }
36 
37    function approve(address spender, uint256 value) external returns (bool) {
38        allowance[msg.sender][spender] = value;
39        emit Approval(msg.sender, spender, value);
40        return true;
41    }
42 
43    function transferFrom(address from, address to, uint256 value) external returns (bool) {
44        uint256 allowed = allowance[from][msg.sender];
45        require(allowed >= value, "ALLOWANCE");
46        if (allowed != type(uint256).max) allowance[from][msg.sender] = allowed - value;
47        _transfer(from, to, value);
48        return true;
49    }
50 
51    function mint(address to, uint256 amount) external onlyOwner {
52        totalSupply += amount;
53        balanceOf[to] += amount;
54        emit Transfer(address(0), to, amount);
55    }
56 
57    function burn(uint256 amount) external {
58        require(balanceOf[msg.sender] >= amount, "BALANCE");
59        balanceOf[msg.sender] -= amount;
60        totalSupply -= amount;
61        emit Transfer(msg.sender, address(0), amount);
62    }
63 
64    function _transfer(address from, address to, uint256 value) internal {
65        require(to != address(0), "ZERO_ADDR");
66        require(balanceOf[from] >= value, "BALANCE");
67        balanceOf[from] -= value;
68        balanceOf[to] += value;
69        emit Transfer(from, to, value);
70    }
71}