pragma solidity ^0.5.0;

// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
//
// ----------------------------------------------------------------------------
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);
}

// ----------------------------------------------------------------------------
// Safe Math Library
// ----------------------------------------------------------------------------
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;
    }
}

// ----------------------------------------------------------------------------
// Ownable contract
// ----------------------------------------------------------------------------
contract Ownable {
  address public owner;
  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

  constructor() public {
    owner = msg.sender;
  }

  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

  function transferOwnership(address newOwner) onlyOwner public {
    require(newOwner != address(0));
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }
}


contract NostroCoin is ERC20Interface, SafeMath, Ownable {
    string public name;
    string public symbol;
    uint8 public decimals; // 18 decimals is the strongly suggested default, avoid changing it
   
    uint256 public _totalSupply;
   
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowed;
   
    /**
     * Constrctor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    constructor() public {
        name = "Nostro Coin";
        symbol = "NSTR";
        decimals = 2;
        _totalSupply = 10000000000;
       
        balances[msg.sender] = _totalSupply;
        emit Transfer(address(0), msg.sender, _totalSupply);
    }
   
    function totalSupply() public view returns (uint) {
        return _totalSupply  - balances[address(0)];
    }
   
    function balanceOf(address tokenOwner) public view returns (uint balance) {
        return balances[tokenOwner];
    }
   
    function allowance(address tokenOwner, address spender) public view returns (uint remaining) {
        return allowed[tokenOwner][spender];
    }
   
    function approve(address spender, uint tokens) public returns (bool success) {
        allowed[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }
   
    function transfer(address to, uint tokens) public returns (bool success) {
        if(balances[msg.sender] >= tokens) {
            balances[msg.sender] = safeSub(balances[msg.sender], tokens);
            balances[to] = safeAdd(balances[to], tokens);
            emit Transfer(msg.sender, to, tokens);
            return true;
        }
        else
        {
            return false;
        }
    }
   
    function transferFrom(address from, address to, uint tokens) public returns (bool success) {
        if(balances[from] >= tokens)
        {
            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;
        }
        else
        {
            return false;
        }
    }

    function mint(address account, uint256 amount) public onlyOwner {
        require(account != address(0), "ERC20: mint to the zero address");
        _totalSupply = safeAdd(_totalSupply, amount);
        balances[account] = safeAdd(balances[account], amount);
        emit Transfer(address(0), account, amount);
    }
}