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_, address initialOwner_) {
23        require(initialOwner_ != address(0), "ZERO_OWNER");
24        name = name_;
25        symbol = symbol_;
26        owner = initialOwner_;
27        uint256 supply = initialSupply_ * 10 ** decimals;
28        totalSupply = supply;
29        balanceOf[initialOwner_] = supply;
30        emit Transfer(address(0), initialOwner_, supply);
31    }
32 
33    function transfer(address to, uint256 value) external returns (bool) {
34        _transfer(msg.sender, to, value);
35        return true;
36    }
37 
38    function approve(address spender, uint256 value) external returns (bool) {
39        allowance[msg.sender][spender] = value;
40        emit Approval(msg.sender, spender, value);
41        return true;
42    }
43 
44    function transferFrom(address from, address to, uint256 value) external returns (bool) {
45        uint256 allowed = allowance[from][msg.sender];
46        require(allowed >= value, "ALLOWANCE");
47        if (allowed != type(uint256).max) allowance[from][msg.sender] = allowed - value;
48        _transfer(from, to, value);
49        return true;
50    }
51 
52    function mint(address to, uint256 amount) external onlyOwner {
53        totalSupply += amount;
54        balanceOf[to] += amount;
55        emit Transfer(address(0), to, amount);
56    }
57 
58    function burn(uint256 amount) external {
59        require(balanceOf[msg.sender] >= amount, "BALANCE");
60        balanceOf[msg.sender] -= amount;
61        totalSupply -= amount;
62        emit Transfer(msg.sender, address(0), amount);
63    }
64 
65    function _transfer(address from, address to, uint256 value) internal {
66        require(to != address(0), "ZERO_ADDR");
67        require(balanceOf[from] >= value, "BALANCE");
68        balanceOf[from] -= value;
69        balanceOf[to] += value;
70        emit Transfer(from, to, value);
71    }
72}