pragma solidity ^0.4.24;

// ----------------------------------------------------------------------------
// ERC20 Token Contract Terms and Specifics:
//
// Symbol        : KILB
// Name          : Killbit
// Total supply  : 100000000000000000000000000
// Decimals      : 18
// Owner Account : 0xAafDd2871e8FF26c1b2C46420453906B8069eC8c
//
//
//
// (c) by Sidharth Gautam 2021. MIT Licence.
// ----------------------------------------------------------------------------


// ----------------------------------------------------------------------------
// Lib: Safe Math
// ----------------------------------------------------------------------------
contract SafeMath {

    function safeAdd(uint a, uint b) public pure returns (uint c) {
        c = a + b;
        require(c >= a);
    }

    function safeSub(uint a, uint b) public pure returns (uint c) {
        require(b <= a);
        c = a - b;
    }

    function safeMul(uint a, uint b) public pure returns (uint c) {
        c = a * b;
        require(a == 0 || c / a == b);
    }

    function safeDiv(uint a, uint b) public pure returns (uint c) {
        require(b > 0);
        c = a / b;
    }
}


/**
ERC Token Standard #20 Interface
https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
*/
contract ERC20Interface {
    function totalSupply() public constant returns (uint);
    function balanceOf(address tokenOwner) public constant returns (uint balance);
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}


/**
The function in the contract to receive approval and execute function in a single call

Developed through MiniMeToken resources
*/
contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}

/**
ERC20 Token Property Classifications, with acclimation of properties such as symbol, name and decimals and token transfers
*/
contract KILBToken is ERC20Interface, SafeMath {
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint public _totalSupply;

    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;


    // ------------------------------------------------------------------------
    // A Constructor
    // ------------------------------------------------------------------------
    constructor() public {
        symbol = "KILB";
        name = "Killbit";
        decimals = 18;
        _totalSupply = 100000000000000000000000000;
        balances[0xAafDd2871e8FF26c1b2C46420453906B8069eC8c] = _totalSupply;
        emit Transfer(address(0), 0xAafDd2871e8FF26c1b2C46420453906B8069eC8c, _totalSupply);
    }


    // ------------------------------------------------------------------------
    // Total supply Function
    // ------------------------------------------------------------------------
    function totalSupply() public constant returns (uint) {
        return _totalSupply  - balances[address(0)];
    }


    // ------------------------------------------------------------------------
    // Function tasked with getting the token balance for account tokenOwner
    // ------------------------------------------------------------------------
    function balanceOf(address tokenOwner) public constant returns (uint balance) {
        return balances[tokenOwner];
    }


    // ------------------------------------------------------------------------
    // balance transfer from token owner's account to another account
    // - Owner's account must have enough or acceptable balance to transfer desired amount
    // - 0 value transfers are permitted but at cost to sender as gas fees cannot be waived
    // ------------------------------------------------------------------------
    function transfer(address to, uint tokens) public returns (bool success) {
        balances[msg.sender] = safeSub(balances[msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        emit Transfer(msg.sender, to, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // function implementing Token owner to approve for spender to transfer tokens using function transferFrom(...) tokens
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
    // no checks for the approval double-spend attack, source above
    // as this should be implemented in user interfaces 
    // ------------------------------------------------------------------------
    function approve(address spender, uint tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // Transfer tokens from the from account to another account
    // 
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from the from account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed as mentioned above
    // ------------------------------------------------------------------------
    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        balances[from] = safeSub(balances[from], tokens);
        allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        emit Transfer(from, to, tokens);
        return true;
    }


    // ------------------------------------------------------------------------
    // This function outputs the amount of tokens approved by the owner that can be
    // transferred to the spender's account, no function implemented to change allowance, set at null
    // ------------------------------------------------------------------------
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }


    // ------------------------------------------------------------------------
    // Function validates Token owner to approve spender to transferFrom(...) tokens
    // from the token owner's account. The spender contract function
    // receiveApproval(...) is then executed after this function
    // ------------------------------------------------------------------------
    function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
        return true;
    }


    // ------------------------------------------------------------------------
    // Don't accept ETH, although this has been resolved in Solidity 0.4.xx and above, this is a backup fallback function
    // ------------------------------------------------------------------------
    function () public payable {
        revert();
    }
}