pragma solidity ^0.4.18;


/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
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) {
    // 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;
  }
}




/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
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);
}


/**
 * @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);
}



/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances.
 */
contract BasicToken is ERC20Basic {
  using SafeMath for uint256;

  mapping(address => uint256) balances;

  /**
  * @dev transfer token for a specified address
  * @param _to The address to transfer to.
  * @param _value The amount to be transferred.
  */
  function transfer(address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[msg.sender]);

    // SafeMath.sub will throw if there is not enough balance.
    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    Transfer(msg.sender, _to, _value);
    return true;
  }

  /**
  * @dev Gets the balance of the specified address.
  * @param _owner The address to query the the balance of.
  * @return An uint256 representing the amount owned by the passed address.
  */
  function balanceOf(address _owner) public view returns (uint256 balance) {
    return balances[_owner];
  }

}



/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is ERC20, BasicToken {

  mapping (address => mapping (address => uint256)) internal allowed;


  /**
   * @dev Transfer tokens from one address to another
   * @param _from address The address which you want to send tokens from
   * @param _to address The address which you want to transfer to
   * @param _value uint256 the amount of tokens to be transferred
   */
  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;
  }

  /**
   * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
   *
   * Beware that changing an allowance with this method brings the risk that someone may use both the old
   * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
   * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
   * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   * @param _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   */
  function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    Approval(msg.sender, _spender, _value);
    return true;
  }

  /**
   * @dev Function to check the amount of tokens that an owner allowed to a spender.
   * @param _owner address The address which owns the funds.
   * @param _spender address The address which will spend the funds.
   * @return A uint256 specifying the amount of tokens still available for the spender.
   */
  function allowance(address _owner, address _spender) public view returns (uint256) {
    return allowed[_owner][_spender];
  }

  /**
   * @dev Increase the amount of tokens that an owner allowed to a spender.
   *
   * approve should be called when allowed[_spender] == 0. To increment
   * allowed value is better to use this function to avoid 2 calls (and wait until
   * the first transaction is mined)
   * From MonolithDAO Token.sol
   * @param _spender The address which will spend the funds.
   * @param _addedValue The amount of tokens to increase the allowance by.
   */
  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;
  }

  /**
   * @dev Decrease the amount of tokens that an owner allowed to a spender.
   *
   * approve should be called when allowed[_spender] == 0. To decrement
   * allowed value is better to use this function to avoid 2 calls (and wait until
   * the first transaction is mined)
   * From MonolithDAO Token.sol
   * @param _spender The address which will spend the funds.
   * @param _subtractedValue The amount of tokens to decrease the allowance by.
   */
  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;
  }

}



/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
  address public owner;


  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  function Ownable() public {
    owner = msg.sender;
  }


  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }


  /**
   * @dev Allows the current owner to transfer control of the contract to a newOwner.
   * @param newOwner The address to transfer ownership to.
   */
  function transferOwnership(address newOwner) public onlyOwner {
    require(newOwner != address(0));
    OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}


/**
 * @title GSCToken
 * @dev Global Social Chain.
 */
contract GSCToken is StandardToken, Ownable {

  string public constant name = "Global Social Chain";
  string public constant symbol = "GSC";
  uint8 public constant decimals = 18;

  uint256 private constant TOKEN_UNIT = 10 ** uint256(decimals);
  uint256 private constant INITIAL_SUPPLY = (10 ** 9) * TOKEN_UNIT;

  uint256 private constant PRIVATE_SUPPLY              = INITIAL_SUPPLY * 30 / 100;  // 30% for private sale
  uint256 private constant RESERVED_FOR_TEAM            = INITIAL_SUPPLY * 10 / 100;  // 10% for team
  uint256 private constant COMMERCIAL_PLAN             = INITIAL_SUPPLY * 20 / 100; // 20% for commercial plan
  uint256 private constant RESERVED_FOR_FOUNDATION     = INITIAL_SUPPLY * 15 / 100; // 15% for foundation
  uint256 private constant COMMUNITY_REWARDS	     	= INITIAL_SUPPLY * 25 / 100; // 25% for community rewards

  uint256 private constant PRIVATE_SUPPLY_VESTING       = PRIVATE_SUPPLY * 50 / 100;  // 50% of private sale


  struct VestingGrant {
        address beneficiary;
        uint256 start;
        uint256 duration; //duration for each release
        uint256 amount; //total grant amount
        uint256 transfered; // transfered amount
        uint8 releaseCount; // schedule release count
  }


  address public constant PRIVATE_SUPPLY_ADDRESS = 0xd509bE99995A24e089C9789ed69B08031F830615; //private sale vesting beneficiary address
  VestingGrant privsteSupplyVestingGrant;

  address public constant TEAM_ADDRESS = 0x9C99b03224122b419a84a6bD7A609f7288d65Eb9; //team vesting  beneficiary address
  VestingGrant teamVestingGrant;

  /**
   * @dev Constructor that gives msg.sender all of existing tokens.
   */
  function GSCToken() public {
    uint256 senderBalance = COMMERCIAL_PLAN.add(RESERVED_FOR_FOUNDATION).add(COMMUNITY_REWARDS);
    uint256 privateSupplyBalance = PRIVATE_SUPPLY.sub(PRIVATE_SUPPLY_VESTING);
    totalSupply = senderBalance + privateSupplyBalance;
    balances[msg.sender] = senderBalance;
	  balances[PRIVATE_SUPPLY_ADDRESS] = privateSupplyBalance;

    privsteSupplyVestingGrant = makeGrant(PRIVATE_SUPPLY_ADDRESS, now, (30 days), PRIVATE_SUPPLY_VESTING, 10);
    teamVestingGrant = makeGrant(TEAM_ADDRESS, now, (182 days), RESERVED_FOR_TEAM, 4);
  }

  function makeGrant(address _beneficiary, uint256 _start, uint256 _duration, uint256 _amount, uint8 _releaseCount)
    internal pure returns  (VestingGrant) {
      return VestingGrant({ beneficiary : _beneficiary, start: _start, duration:_duration, amount:_amount, transfered:0, releaseCount:_releaseCount});
  }



  function releasePrivateSupplyVested() public onlyOwner {
      relaseVestingGrant(privsteSupplyVestingGrant);
  }

  function releaseTeamVested() public onlyOwner {
      relaseVestingGrant(teamVestingGrant);
  }

  function releasableAmount(uint256 time, VestingGrant grant) internal pure returns (uint256) {
      if (grant.amount == grant.transfered) {
          return 0;
      }
      uint256 amountPerRelease = grant.amount.div(grant.releaseCount);
      uint256 amount = amountPerRelease.mul((time.sub(grant.start)).div(grant.duration));
      if (amount > grant.amount) {
        amount = grant.amount;
      }
      amount = amount.sub(grant.transfered);
      return amount;
  }

  function relaseVestingGrant(VestingGrant storage grant) internal {
      uint256 amount = releasableAmount(now, grant);
      require(amount > 0);

      grant.transfered = grant.transfered.add(amount);
      totalSupply = totalSupply.add(amount);
      balances[grant.beneficiary] = balances[grant.beneficiary].add(amount);
      Transfer(address(0), grant.beneficiary, amount);
    }
}