KETH (KCASH)

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

/**
 * @title KETH
 * @dev A decentralized, immutable ERC-20 token with fixed supply (100 billion tokens).
 *      - All tokens minted to deployer at construction.
 *      - NO owner, NO mint, NO pause, NO upgrade — fully immutable after deploy.
 *      - Users can voluntarily burn tokens to reduce total supply.
 *      - Long-term stability and trust through simplicity.
 */
contract KETH {
    // ———————— Metadata ————————
    string public constant name = "KETH";
    string public constant symbol = "KCASH";
    uint8 public constant decimals = 18;

    // ———————— State ————————
    uint256 public totalSupply;
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    // ———————— Events ————————
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Burn(address indexed from, uint256 value);

    // ———————— Constructor ————————
    constructor() {
        totalSupply = 100_000_000_000 * 10 ** decimals; // 100 billion tokens
        balanceOf[msg.sender] = totalSupply;
        emit Transfer(address(0), msg.sender, totalSupply);
    }

    // ———————— ERC-20: Transfers ————————
    function transfer(address to, uint256 value) external returns (bool) {
        require(to != address(0), "KETH: transfer to zero address");
        require(balanceOf[msg.sender] >= value, "KETH: insufficient balance");

        balanceOf[msg.sender] -= value;
        balanceOf[to] += value;
        emit Transfer(msg.sender, to, value);
        return true;
    }

    // ———————— ERC-20: Approvals ————————
    function approve(address spender, uint256 value) external returns (bool) {
        require(spender != address(0), "KETH: approve to zero address");
        allowance[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    function transferFrom(address from, address to, uint256 value) external returns (bool) {
        require(from != address(0), "KETH: transfer from zero address");
        require(to != address(0), "KETH: transfer to zero address");
        require(balanceOf[from] >= value, "KETH: insufficient balance");
        require(allowance[from][msg.sender] >= value, "KETH: insufficient allowance");

        balanceOf[from] -= value;
        balanceOf[to] += value;
        allowance[from][msg.sender] -= value;
        emit Transfer(from, to, value);
        return true;
    }

    // ———————— Safe Approve Helpers ————————
    function increaseAllowance(address spender, uint256 addedValue) external returns (bool) {
        require(spender != address(0), "KETH: increaseAllowance to zero address");
        allowance[msg.sender][spender] += addedValue;
        emit Approval(msg.sender, spender, allowance[msg.sender][spender]);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) external returns (bool) {
        require(spender != address(0), "KETH: decreaseAllowance to zero address");
        uint256 currentAllowance = allowance[msg.sender][spender];
        if (subtractedValue > currentAllowance) {
            allowance[msg.sender][spender] = 0;
        } else {
            allowance[msg.sender][spender] = currentAllowance - subtractedValue;
        }
        emit Approval(msg.sender, spender, allowance[msg.sender][spender]);
        return true;
    }

    // ———————— Burn Functions ————————
    function burn(uint256 value) external {
        require(balanceOf[msg.sender] >= value, "KETH: burn amount exceeds balance");
        balanceOf[msg.sender] -= value;
        totalSupply -= value;
        emit Burn(msg.sender, value);
        emit Transfer(msg.sender, address(0), value);
    }

    function burnFrom(address from, uint256 value) external returns (bool) {
        require(balanceOf[from] >= value, "KETH: burn amount exceeds balance");
        require(allowance[from][msg.sender] >= value, "KETH: insufficient allowance");

        allowance[from][msg.sender] -= value;
        balanceOf[from] -= value;
        totalSupply -= value;
        emit Burn(from, value);
        emit Transfer(from, address(0), value);
        return true;
    }
}