pragma solidity ^0.4.18;
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;
  }
}
contract ERC20Basic {
  uint256 public totalSupply;
  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);
}
contract BasicToken is ERC20Basic {
  using SafeMath for uint256;
  mapping(address => uint256) balances;
  function transfer(address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[msg.sender]);
    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    Transfer(msg.sender, _to, _value);
    return true;
  }
  function balanceOf(address _owner) public view returns (uint256 balance) {
    return balances[_owner];
  }
}
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);
}
contract StandardToken is ERC20, BasicToken {
  mapping (address => mapping (address => uint256)) internal allowed;
  function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[_from]);
    require(_value <= allowed[_from][msg.sender]);
    balances[_from] = balances[_from].sub(_value);
    balances[_to] = balances[_to].add(_value);
    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
    Transfer(_from, _to, _value);
    return true;
  }
  function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    Approval(msg.sender, _spender, _value);
    return true;
  }
  function allowance(address _owner, address _spender) public view returns (uint256) {
    return allowed[_owner][_spender];
  }
  function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
    allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
    Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }
  function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
    uint oldValue = allowed[msg.sender][_spender];
    if (_subtractedValue > oldValue) {
      allowed[msg.sender][_spender] = 0;
    } else {
      allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
    }
    Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }
}
contract MigrationAgent {
  function migrateFrom(address _from, uint _value) public;
}
contract SPXToken is StandardToken {
  string public constant name = "SP8DE Token";
  string public constant symbol = "SPX";
  uint8 public constant decimals = 18;
  address public ico;
  bool public isFrozen = true;  
  uint public constant TOKEN_LIMIT = 8888888888 * (1e18);
  address public migrationMaster;
  address public migrationAgent;
  uint public totalMigrated;
  event Migrate(address indexed _from, address indexed _to, uint _value);
  function SPXToken(address _ico, address _migrationMaster) public {
    require(_ico != 0);
    ico = _ico;
    migrationMaster = _migrationMaster;
  }
  function mint(address holder, uint value) public {
    require(msg.sender == ico);
    require(value > 0);
    require(totalSupply + value <= TOKEN_LIMIT);
    balances[holder] += value;
    totalSupply += value;
    Transfer(0x0, holder, value);
  }
  function unfreeze() public {
      require(msg.sender == ico);
      isFrozen = false;
  }
  function transfer(address _to, uint _value) public returns (bool) {
    require(_to != address(0));
    require(!isFrozen);
    return super.transfer(_to, _value);
  }
  function transferFrom(address _from, address _to, uint _value) public returns (bool) {
    require(!isFrozen);
    return super.transferFrom(_from, _to, _value);
  }
  function approve(address _spender, uint _value) public returns (bool) {
    require(!isFrozen);
    return super.approve(_spender, _value);
  }
  function migrate(uint value) external {
    require(migrationAgent != 0);
    require(value > 0);
    require(value <= balances[msg.sender]);
    balances[msg.sender] -= value;
    totalSupply -= value;
    totalMigrated += value;
    MigrationAgent(migrationAgent).migrateFrom(msg.sender, value);
    Migrate(msg.sender, migrationAgent, value);
  }
  function setMigrationAgent(address _agent) external {
    require(migrationAgent == 0);
    require(msg.sender == migrationMaster);
    migrationAgent = _agent;
  }
  function setMigrationMaster(address _master) external {
    require(msg.sender == migrationMaster);
    require(_master != 0);
    migrationMaster = _master;
  }
}