R-COIN (RCN)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

contract RCoin {
    string private _name;
    string private _symbol;
    uint8 private constant _decimals = 6;
    uint256 private _totalSupply;
    
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;
    
    address private _owner;
    
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    
    error ERC20InsufficientBalance(address sender, uint256 balance, uint256 needed);
    error ERC20InvalidSender(address sender);
    error ERC20InvalidReceiver(address receiver);
    error ERC20InsufficientAllowance(address spender, uint256 allowance, uint256 needed);
    error ERC20InvalidApprover(address approver);
    error ERC20InvalidSpender(address spender);
    error OwnableUnauthorizedAccount(address account);
    error OwnableInvalidOwner(address owner);
    
    modifier onlyOwner() {
        _checkOwner();
        _;
    }
    
    constructor() {
        _name = "R-COIN";
        _symbol = "RCN";
        _owner = msg.sender;
        
        uint256 initialSupply = 100000000 * (10 ** uint256(_decimals));
        _mint(msg.sender, initialSupply);
        emit OwnershipTransferred(address(0), msg.sender);
    }
    
    function name() public view returns (string memory) {
        return _name;
    }
    
    function symbol() public view returns (string memory) {
        return _symbol;
    }
    
    function decimals() public pure returns (uint8) {
        return _decimals;
    }
    
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }
    
    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }
    
    function transfer(address to, uint256 value) public returns (bool) {
        address owner = msg.sender;
        _transfer(owner, to, value);
        return true;
    }
    
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowances[owner][spender];
    }
    
    function approve(address spender, uint256 value) public returns (bool) {
        address owner = msg.sender;
        _approve(owner, spender, value);
        return true;
    }
    
    function transferFrom(address from, address to, uint256 value) public returns (bool) {
        address spender = msg.sender;
        _spendAllowance(from, spender, value);
        _transfer(from, to, value);
        return true;
    }
    
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        address owner = msg.sender;
        _approve(owner, spender, allowance(owner, spender) + addedValue);
        return true;
    }
    
    function decreaseAllowance(address spender, uint256 requestedDecrease) public returns (bool) {
        address owner = msg.sender;
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance < requestedDecrease) {
            revert ERC20InsufficientAllowance(spender, currentAllowance, requestedDecrease);
        }
        unchecked {
            _approve(owner, spender, currentAllowance - requestedDecrease);
        }
        return true;
    }
    
    function owner() public view returns (address) {
        return _owner;
    }
    
    function renounceOwnership() public onlyOwner {
        _transferOwnership(address(0));
    }
    
    function transferOwnership(address newOwner) public onlyOwner {
        if (newOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(newOwner);
    }
    
    function _transfer(address from, address to, uint256 value) internal {
        if (from == address(0)) {
            revert ERC20InvalidSender(address(0));
        }
        if (to == address(0)) {
            revert ERC20InvalidReceiver(address(0));
        }
        _update(from, to, value);
    }
    
    function _update(address from, address to, uint256 value) internal virtual {
        if (from == address(0)) {
            // Minting new tokens
            _totalSupply = _totalSupply + value;
        } else {
            uint256 fromBalance = _balances[from];
            if (fromBalance < value) {
                revert ERC20InsufficientBalance(from, fromBalance, value);
            }
            unchecked {
                _balances[from] = fromBalance - value;
            }
        }

        if (to == address(0)) {
            // Burning tokens
            unchecked {
                _totalSupply = _totalSupply - value;
            }
        } else {
            unchecked {
                _balances[to] = _balances[to] + value;
            }
        }

        emit Transfer(from, to, value);
    }
    
    function _mint(address account, uint256 value) internal {
        if (account == address(0)) {
            revert ERC20InvalidReceiver(address(0));
        }
        _update(address(0), account, value);
    }
    
    function _burn(address account, uint256 value) internal {
        if (account == address(0)) {
            revert ERC20InvalidSender(address(0));
        }
        _update(account, address(0), value);
    }
    
    function _approve(address owner, address spender, uint256 value) internal {
        _approve(owner, spender, value, true);
    }
    
    function _approve(address owner, address spender, uint256 value, bool emitEvent) internal virtual {
        if (owner == address(0)) {
            revert ERC20InvalidApprover(address(0));
        }
        if (spender == address(0)) {
            revert ERC20InvalidSpender(address(0));
        }
        _allowances[owner][spender] = value;
        if (emitEvent) {
            emit Approval(owner, spender, value);
        }
    }
    
    function _spendAllowance(address owner, address spender, uint256 value) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            if (currentAllowance < value) {
                revert ERC20InsufficientAllowance(spender, currentAllowance, value);
            }
            unchecked {
                _approve(owner, spender, currentAllowance - value, false);
            }
        }
    }
    
    function _checkOwner() internal view {
        if (owner() != msg.sender) {
            revert OwnableUnauthorizedAccount(msg.sender);
        }
    }
    
    function _transferOwnership(address newOwner) internal {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
    
    // 额外功能：铸币权限（仅所有者）
    function mint(address to, uint256 amount) public onlyOwner {
        _mint(to, amount);
    }
    
    // 额外功能：销毁代币
    function burn(uint256 amount) public {
        _burn(msg.sender, amount);
    }
    
    function burnFrom(address account, uint256 amount) public {
        _spendAllowance(account, msg.sender, amount);
        _burn(account, amount);
    }
}