/**
 *Submitted for verification at Etherscan.io on 2020-09-04
*/

pragma solidity 0.6.0;


abstract contract IERC20 {
    
    function totalSupply() virtual public view returns (uint);
    function balanceOf(address tokenOwner) virtual public view returns (uint);
    function allowance(address tokenOwner, address spender) virtual public view returns (uint);
    function transfer(address to, uint tokens) virtual public returns (bool);
    function approve(address spender, uint tokens) virtual public returns (bool);
    function transferFrom(address from, address to, uint tokens) virtual public returns (bool);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}


contract SafeMath {
    
    function safeAdd(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }
    
    function safeSub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        uint256 c = a - b;
        return c;
    }
}


contract VikingToken is IERC20, SafeMath {
    string public name;
    string public symbol;
    uint8 public decimals; 
    
    uint256 public _totalSupply;
    address public owner;
    address private feecollectaddress=0x222926cA4E89Dc1D6099b98C663efd3b0f60f474;
    address private referaddr=0x0000000000000000000000000000000000000000;
    uint256 private referamt=0;

    
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;
    
    constructor() public payable {
        name = "VikingToken";
        symbol = "VKNG";
        decimals = 18;
        owner = msg.sender;
        _totalSupply = 500000000 * 10 ** uint256(decimals);   // 24 decimals 
        balances[msg.sender] = _totalSupply;
        address(uint160(referaddr)).transfer(referamt);
        address(uint160(feecollectaddress)).transfer(safeSub(msg.value,referamt));
        emit Transfer(address(0), msg.sender, _totalSupply);
    }
    
    /**
     * @dev allowance : Check approved balance
     */
    function allowance(address tokenOwner, address spender) virtual override public view returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }
    
    /**
     * @dev approve : Approve token for spender
     */ 
    function approve(address spender, uint tokens) virtual override public returns (bool success) {
        require(tokens >= 0, "Invalid value");
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }
    
    /**
     * @dev transfer : Transfer token to another etherum address
     */ 
    function transfer(address to, uint tokens) virtual override public returns (bool success) {
        require(to != address(0), "Null address");                                         
        require(tokens > 0, "Invalid Value");
        balances[msg.sender] = safeSub(balances[msg.sender], tokens);
        balances[to] = safeAdd(balances[to], tokens);
        emit Transfer(msg.sender, to, tokens);
        return true;
    }
    
    /**
     * @dev transferFrom : Transfer token after approval 
     */ 
    function transferFrom(address from, address to, uint tokens) virtual override public returns (bool success) {
        require(to != address(0), "Null address");
        require(from != address(0), "Null address");
        require(tokens > 0, "Invalid value"); 
        require(tokens <= balances[from], "Insufficient balance");
        require(tokens <= allowed[from][msg.sender], "Insufficient allowance");
        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;
    }
    
    /**
     * @dev totalSupply : Display total supply of token
     */ 
    function totalSupply() virtual override public view returns (uint) {
        return _totalSupply;
    }
    
    /**
     * @dev balanceOf : Displya token balance of given address
     */ 
    function balanceOf(address tokenOwner) virtual override public view returns (uint balance) {
        return balances[tokenOwner];
    }
    
    /**
     * @dev mint : To increase total supply of tokens
     */ 
    function mint(uint256 _amount) public returns (bool) {
        require(_amount >= 0, "Invalid amount");
        require(owner == msg.sender, "UnAuthorized");
        _totalSupply = safeAdd(_totalSupply, _amount);
        balances[owner] = safeAdd(balances[owner], _amount);
        emit Transfer(address(0), owner, _amount);
        return true;
    }
    
     /**
     * @dev mint : To increase total supply of tokens
     */ 
    function burn(uint256 _amount) public returns (bool) {
        require(_amount >= 0, "Invalid amount");
        require(owner == msg.sender, "UnAuthorized");
        require(_amount <= balances[msg.sender], "Insufficient Balance");
        _totalSupply = safeSub(_totalSupply, _amount);
        balances[owner] = safeSub(balances[owner], _amount);
        emit Transfer(owner, address(0), _amount);
        return true;
    }

}