pragma solidity ^0.5.13;

// ----------------------------------------------------------------------------
// 'GFT' 'GasFarm' token contract
//
// Symbol      : GFT
// Deployed to : // TODO: 0x32ec729bc57ae046bd4590a892a4306d0ebf3bee
// Name        : GasFarm Token
// Total supply: 100,000,000.000000000000000000
// Decimals    : 18
//
//
//
// Updated by Guang Nguyen - GasFarm Ltd (c) 2021. The MIT Licence.
// ----------------------------------------------------------------------------


// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------
library SafeMath {
  function add(uint a, uint b) internal pure returns (uint c) {
    c = a + b;
    require(c >= a);
  }
  function sub(uint a, uint b) internal pure returns (uint c) {
    require(b <= a);
    c = a - b;
  }
  function mul(uint a, uint b) internal pure returns (uint c) {
    c = a * b;
    require(a == 0 || c / a == b);
  }
  function div(uint a, uint b) internal 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.md
// ----------------------------------------------------------------------------
contract ERC20Interface {
  function totalSupply() public view returns (uint);
  function balanceOf(address tokenOwner) public view returns (uint balance);
  function allowance(address tokenOwner, address spender) public view 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);
}


// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
//
//
// ----------------------------------------------------------------------------
contract ApproveAndCallFallBack {
  function receiveApproval(address from, uint256 tokens, address token, bytes memory data) public;
}


// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------
contract Owned {

  address payable public owner;
  address payable public newOwner;

  event OwnershipTransferred(address indexed _from, address indexed _to);

  constructor() public {
    owner = msg.sender;
  }

  modifier onlyOwner {
    require(msg.sender == owner);
    _;
  }

  function transferOwnership(address payable _newOwner) public onlyOwner {
    newOwner = _newOwner;
  }
  function acceptOwnership() public {
    require(msg.sender == newOwner);
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
    newOwner = address(0);
  }
}


// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and a
// GFT supply
// ----------------------------------------------------------------------------
contract GasFarmToken is ERC20Interface, Owned {

  using SafeMath for uint;

  string public symbol;
  string public  name;
  uint8 public decimals;
  uint _totalSupply;

  // pre-sale bonus
  uint public startDate;
  uint public bonusEnds;
  uint public endDate;

  mapping(address => uint) balances;
  mapping(address => mapping(address => uint)) allowed;


  // ------------------------------------------------------------------------
  // Constructor
  // ------------------------------------------------------------------------
  constructor() public {
    symbol = "GFT";
    name = "GasFarm Token";
    decimals = 18;
    _totalSupply = 70000000 * 10**uint(decimals);
    balances[owner] = _totalSupply;
    bonusEnds = now + 32 days;
    startDate = now + 15 days;
    endDate = now + 32 days;
    emit Transfer(address(0), owner, _totalSupply);
  }


  // ------------------------------------------------------------------------
  // Total supply
  // ------------------------------------------------------------------------
  function totalSupply() public view returns (uint) {
    return _totalSupply.sub(balances[address(0)]);
  }


  // ------------------------------------------------------------------------
  // Get the token balance for account `tokenOwner`
  // ------------------------------------------------------------------------
  function balanceOf(address tokenOwner) public view returns (uint balance) {
    return balances[tokenOwner];
  }


  // ------------------------------------------------------------------------
  // Transfer the balance from token owner's account to `to` account
  // - Owner's account must have sufficient balance to transfer
  // - 0 value transfers are allowed
  // ------------------------------------------------------------------------
  function transfer(address to, uint tokens) public returns (bool success) {
    balances[msg.sender] = balances[msg.sender].sub(tokens);
    balances[to] = balances[to].add(tokens);
    emit Transfer(msg.sender, to, tokens);
    return true;
  }


  // ------------------------------------------------------------------------
  // Token owner can approve for `spender` to transferFrom(...) `tokens`
  // from the token owner's account
  //
  // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
  // recommends that there are no checks for the approval double-spend attack
  // 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 the `to` 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
  // ------------------------------------------------------------------------
  function transferFrom(address from, address to, uint tokens) public returns (bool success) {
    balances[from] = balances[from].sub(tokens);
    allowed[from][msg.sender] = allowed[from][msg.sender].sub(tokens);
    balances[to] = balances[to].add(tokens);
    emit Transfer(from, to, tokens);
    return true;
  }


  // ------------------------------------------------------------------------
  // Returns the amount of tokens approved by the owner that can be
  // transferred to the spender's account
  // ------------------------------------------------------------------------
  function allowance(address tokenOwner, address spender) public view returns (uint remaining) {
    return allowed[tokenOwner][spender];
  }


  // ------------------------------------------------------------------------
  // Token owner can approve for `spender` to transferFrom(...) `tokens`
  // from the token owner's account. The `spender` contract function
  // `receiveApproval(...)` is then executed
  // ------------------------------------------------------------------------
  function approveAndCall(address spender, uint tokens, bytes memory data) public returns (bool success) {
    allowed[msg.sender][spender] = tokens;
    emit Approval(msg.sender, spender, tokens);
    ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, address(this), data);
    return true;
  }

  // ------------------------------------------------------------------------
  // TODO: 26,000 GFT Tokens per 1 ETH 
  // ------------------------------------------------------------------------
  function () external payable {
    require(now >= startDate && now <= endDate);
    uint tokens;
    if (now <= bonusEnds) {
      tokens = msg.value * 26000; // TODO: define how many people will get within the BONUS.
    } else {
      tokens = msg.value * 26000; // TODO: define how many people will get without the BONUS.
    }
    balances[msg.sender] = SafeMath.add(balances[msg.sender], tokens);
    _totalSupply = SafeMath.add(_totalSupply, tokens);
    // sent to investor
    emit Transfer(address(0), msg.sender, tokens);
    // sent ETH to owner
    owner.transfer(msg.value);
  }


  // ------------------------------------------------------------------------
  // Owner can transfer out any accidentally sent ERC20 tokens
  // ------------------------------------------------------------------------
  function transferAnyERC20Token(address tokenAddress, uint tokens) public onlyOwner returns (bool success) {
    return ERC20Interface(tokenAddress).transfer(owner, tokens);
  }
}