pragma solidity ^0.4.18;


/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  function totalSupply() public view returns (uint256);
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}






/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender) public view returns (uint256);
  function transferFrom(address from, address to, uint256 value) public returns (bool);
  function approve(address spender, uint256 value) public returns (bool);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}


library SafeMath {
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a * b;
    assert(a == 0 || c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    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;
  }
}

contract Hive is ERC20 {

    using SafeMath for uint;
    string public constant name = "UHIVE";
    string public constant symbol = "HVE";    
    uint256 public constant decimals = 18;
    uint256 _totalSupply = 80000000000 * (10**decimals);

    mapping (address => bool) public frozenAccount;
    event FrozenFunds(address target, bool frozen);

    // Balances for each account
    mapping(address => uint256) balances;

    // Owner of account approves the transfer of an amount to another account
    mapping(address => mapping (address => uint256)) allowed;

    // Owner of this contract
    address public owner;

    // Functions with this modifier can only be executed by the owner
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    function changeOwner(address _newOwner) onlyOwner public {
        require(_newOwner != address(0));
        owner = _newOwner;
    }

    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        FrozenFunds(target, freeze);
    }

    function isFrozenAccount(address _addr) public constant returns (bool) {
        return frozenAccount[_addr];
    }

    function destroyCoins(address addressToDestroy, uint256 amount) onlyOwner public {
        require(addressToDestroy != address(0));
        require(amount > 0);
        require(amount <= balances[addressToDestroy]);
        balances[addressToDestroy] -= amount;    
        _totalSupply -= amount;
    }

    // Constructor
    function Hive() public {
        owner = msg.sender;
        balances[owner] = _totalSupply;
    }

    function totalSupply() public constant returns (uint256 supply) {
        supply = _totalSupply;
    }

    // What is the balance of a particular account?
    function balanceOf(address _owner) public constant returns (uint256 balance) {
        return balances[_owner];
    }
    
    // Transfer the balance from owner's account to another account
    function transfer(address _to, uint256 _value) public returns (bool success) {        
        if (_to != address(0) && isFrozenAccount(msg.sender) == false && balances[msg.sender] >= _value && _value > 0 && balances[_to].add(_value) > balances[_to]) {
            balances[msg.sender] = balances[msg.sender].sub(_value);
            balances[_to] = balances[_to].add(_value);
            Transfer(msg.sender, _to, _value);
            return true;
        } else {
            return false;
        }
    }

    // Send _value amount of tokens from address _from to address _to
    // The transferFrom method is used for a withdraw workflow, allowing contracts to send
    // tokens on your behalf, for example to "deposit" to a contract address and/or to charge
    // fees in sub-currencies; the command should fail unless the _from account has
    // deliberately authorized the sender of the message via some mechanism; we propose
    // these standardized APIs for approval:
    function transferFrom(address _from,address _to, uint256 _value) public returns (bool success) {
        if (_to != address(0) && isFrozenAccount(_from) == false && balances[_from] >= _value && allowed[_from][msg.sender] >= _value && _value > 0 && balances[_to].add(_value) > balances[_to]) {
            balances[_from] = balances[_from].sub(_value);
            allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
            balances[_to] = balances[_to].add(_value);
            Transfer(_from, _to, _value);
            return true;
        } else {
            return false;
        }
    }

    // Allow _spender to withdraw from your account, multiple times, up to the _value amount.
    // If this function is called again it overwrites the current allowance with _value.
    function approve(address _spender, uint256 _value) public returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }
    
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }
    
}