pragma solidity ^0.4.23;

interface IERC20 {
  function totalSupply() external view returns (uint256);
  function balanceOf(address who) external view returns (uint256);
  function allowance(address owner, address spender) external view returns (uint256);
  function transfer(address to, uint256 value) external returns (bool);
  function approve(address spender, uint256 value) external returns (bool);
  function transferFrom(address from, address to, uint256 value) external returns (bool);

  event Transfer(address indexed from, address indexed to, uint256 value);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

library SafeMath {
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0) {
      return 0;
    }
    uint256 c = a * b;
    assert(c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a / b;
    return c;
  }

  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }

  function ceil(uint256 a, uint256 m) internal pure returns (uint256) {
    uint256 c = add(a,m);
    uint256 d = sub(c,1);
    return mul(div(d,m),m);
  }
}

contract ApproveAndCallFallBack {
    function receiveApproval(address from, uint256 tokens, address token, bytes memory data) public;
}

contract VoidToken is IERC20 {
  using SafeMath for uint256;

  string constant tokenName = "Void Token";
  string constant tokenSymbol = "VOID";
  uint8  constant tokenDecimals = 18;               // 18 decimal places
  uint256 public totalSupply = 10000000e18;       // 10m VOID supply

  mapping (address => uint256) private balances;
  mapping (address => mapping (address => uint256)) private allowed;

  constructor() public {
    _mint(msg.sender, totalSupply);
  }

  function name() public pure returns(string memory) {
    return tokenName;
  }

  function symbol() public pure returns(string memory) {
    return tokenSymbol;
  }

  function decimals() public pure returns(uint8) {
    return tokenDecimals;
  }

  function totalSupply() public view returns (uint256) {
    return totalSupply;
  }

  function balanceOf(address owner) public view returns (uint256) {
    return balances[owner];
  }

  function allowance(address owner, address spender) public view returns (uint256) {
    return allowed[owner][spender];
  }

  function transfer(address to, uint256 value) public returns (bool) {
    require(value <= balances[msg.sender]);
    require(to != address(0));

    uint256 tokensToBurn = value.div(20);
    uint256 tokensToTransfer = value.sub(tokensToBurn);

    balances[msg.sender] = balances[msg.sender].sub(value);
    balances[to] = balances[to].add(tokensToTransfer);

    totalSupply = totalSupply.sub(tokensToBurn);

    emit Transfer(msg.sender, to, tokensToTransfer);
    emit Transfer(msg.sender, address(0), tokensToBurn);

    return true;
  }

  function multiTransfer(address[] memory receivers, uint256[] memory amounts) public {
    for (uint256 i = 0; i < receivers.length; i++) {
      transfer(receivers[i], amounts[i]);
    }
  }

  function approveAndCall(address spender, uint value, bytes memory data) public returns (bool success) {
    require(spender != address(0));
    allowed[msg.sender][spender] = value;
    emit Approval(msg.sender, spender, value);
    if (isContract(spender)) {
      ApproveAndCallFallBack(spender).receiveApproval(msg.sender, value, address(this), data);
    }

    return true;
  }

  function approve(address spender, uint256 value) public returns (bool) {
    require(spender != address(0));
    allowed[msg.sender][spender] = value;
    emit Approval(msg.sender, spender, value);

    return true;
  }

  function transferFrom(address from, address to, uint256 value) public returns (bool) {
    require(value <= balances[from]);
    require(value <= allowed[from][msg.sender]);
    require(to != address(0));

    balances[from] = balances[from].sub(value);

    uint256 tokensToBurn = value.div(20);
    uint256 tokensToTransfer = value.sub(tokensToBurn);

    balances[to] = balances[to].add(tokensToTransfer);
    totalSupply = totalSupply.sub(tokensToBurn);

    allowed[from][msg.sender] = allowed[from][msg.sender].sub(value);

    emit Transfer(from, to, tokensToTransfer);
    emit Transfer(from, address(0), tokensToBurn);

    return true;
  }

  function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
    require(spender != address(0));
    allowed[msg.sender][spender] = (allowed[msg.sender][spender].add(addedValue));
    emit Approval(msg.sender, spender, allowed[msg.sender][spender]);

    return true;
  }

  function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
    require(spender != address(0));
    allowed[msg.sender][spender] = (allowed[msg.sender][spender].sub(subtractedValue));
    emit Approval(msg.sender, spender, allowed[msg.sender][spender]);

    return true;
  }

  function _mint(address account, uint256 amount) internal {
    require(amount != 0);
    balances[account] = balances[account].add(amount);
    emit Transfer(address(0), account, amount);
  }

  function burn(uint256 amount) external {
    _burn(msg.sender, amount);
  }

  function burnFrom(address account, uint256 amount) external {
    require(amount <= allowed[account][msg.sender]);
    allowed[account][msg.sender] = allowed[account][msg.sender].sub(amount);
    _burn(account, amount);
  }

  function _burn(address account, uint256 amount) internal {
    require(amount != 0);
    require(amount <= balances[account]);
    totalSupply = totalSupply.sub(amount);
    balances[account] = balances[account].sub(amount);
    emit Transfer(account, address(0), amount);
  }

  function isContract(address _addr) private view returns (bool hasCode) {
    uint length;
    assembly { length := extcodesize(_addr) }
    return length > 0;
  }
}