// SPDX-License-Identifier: MIT
pragma solidity 0.8.30;

contract ERC20{
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    string constant public name = "MyTokenName";
    string constant public symbol = "MTN";
    uint8 constant public decimals = 18;

    uint256 public totalSupply;

    mapping( address => uint256) public balanceOf;

    mapping(address => mapping(address => uint256)) public allowance;
    
    function transfer(address to, uint256 value) external returns (bool){
        return _transfer(msg.sender, to, value);
    }

    function transferFrom(address from, address to, uint256 value) external  returns (bool){
        require(allowance[from][msg.sender] >= value,"ERC20: Insufficient allowance");
        allowance[from][msg.sender] -= value;
        return _transfer(from, to, value);
    }

    function _transfer(address from, address to , uint256 value) private returns (bool){
        require(balanceOf[msg.sender] >= value,"ERC20: Insufficient Token Balance");
        emit Transfer(from, to, value);
        balanceOf[from] -= value;
        balanceOf[to] += value;
        return true;
    }

    function approve(address spender, uint256 value) external returns (bool){
        allowance[msg.sender][spender] += value;
        emit Approval(msg.sender, spender, allowance[msg.sender][spender]);
        return true;
    }

    
}