pragma solidity ^0.4.18;


/**
 * @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 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 Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract Pausable is Ownable {
  event Pause();
  event Unpause();

  bool public paused = false;


  /**
   * @dev Modifier to make a function callable only when the contract is not paused.
   */
  modifier whenNotPaused() {
    require(!paused);
    _;
  }

  /**
   * @dev Modifier to make a function callable only when the contract is paused.
   */
  modifier whenPaused() {
    require(paused);
    _;
  }

  /**
   * @dev called by the owner to pause, triggers stopped state
   */
  function pause() onlyOwner whenNotPaused public {
    paused = true;
    Pause();
  }

  /**
   * @dev called by the owner to unpause, returns to normal state
   */
  function unpause() onlyOwner whenPaused public {
    paused = false;
    Unpause();
  }
}




/**
 * @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 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 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 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 Burnable Token
 * @dev Token that can be irreversibly burned (destroyed).
 */
contract BurnableToken is BasicToken {

    event Burn(address indexed burner, uint256 value);

    /**
     * @dev Burns a specific amount of tokens.
     * @param _value The amount of token to be burned.
     */
    function burn(uint256 _value) public {
        require(_value <= balances[msg.sender]);
        // no need to require value <= totalSupply, since that would imply the
        // sender's balance is greater than the totalSupply, which *should* be an assertion failure

        address burner = msg.sender;
        balances[burner] = balances[burner].sub(_value);
        totalSupply = totalSupply.sub(_value);
        Burn(burner, _value);
    }
}




/**
 * The Ether Based Source Chain token (EBSC - EBSCToken) has a fixed supply
 *
 * The owner can associate the token with a token sale contract. In that
 * case, the token balance is moved to the token sale contract, which
 * in turn can transfer its tokens to contributors to the sale.
 */
contract EBSCToken is StandardToken, BurnableToken, Ownable {

    // Constants
    string  public constant name = "Ether Based Source Chain";
    string  public constant symbol = "EBSC";
    uint8   public constant decimals = 18;
    string  public constant website = "www.ebsc.io"; 
    uint256 public constant INITIAL_SUPPLY      =  1000000000 * (10 ** uint256(decimals));
    uint256 public constant CROWDSALE_ALLOWANCE =   800000000 * (10 ** uint256(decimals));
    uint256 public constant ADMIN_ALLOWANCE     =   200000000 * (10 ** uint256(decimals));

    // Properties
    uint256 public crowdSaleAllowance;      // the number of tokens available for crowdsales
    uint256 public adminAllowance;          // the number of tokens available for the administrator
    address public crowdSaleAddr;           // the address of a crowdsale currently selling this token
    address public adminAddr;               // the address of a crowdsale currently selling this token
    //bool    public transferEnabled = false; // indicates if transferring tokens is enabled or not
    bool    public transferEnabled = true;  // Enables everyone to transfer tokens 

    // Modifiers

    /**
     * The listed addresses are not valid recipients of tokens.
     *
     * 0x0           - the zero address is not valid
     * this          - the contract itself should not receive tokens
     * owner         - the owner has all the initial tokens, but cannot receive any back
     * adminAddr     - the admin has an allowance of tokens to transfer, but does not receive any
     * crowdSaleAddr - the crowdsale has an allowance of tokens to transfer, but does not receive any
     */
    modifier validDestination(address _to) {
        require(_to != address(0x0));
        require(_to != address(this));
        require(_to != owner);
        require(_to != address(adminAddr));
        require(_to != address(crowdSaleAddr));
        _;
    }

    /**
     * Constructor - instantiates token supply and allocates balanace of
     * to the owner (msg.sender).
     */
    function EBSCToken(address _admin) public {
        // the owner is a custodian of tokens that can
        // give an allowance of tokens for crowdsales
        // or to the admin, but cannot itself transfer
        // tokens; hence, this requirement
        require(msg.sender != _admin);

        totalSupply = INITIAL_SUPPLY;
        crowdSaleAllowance = CROWDSALE_ALLOWANCE;
        adminAllowance = ADMIN_ALLOWANCE;

        // mint all tokens
        balances[msg.sender] = totalSupply.sub(adminAllowance);
        Transfer(address(0x0), msg.sender, totalSupply.sub(adminAllowance));

        balances[_admin] = adminAllowance;
        Transfer(address(0x0), _admin, adminAllowance);

        adminAddr = _admin;
        approve(adminAddr, adminAllowance);
    }

    /**
     * Associates this token with a current crowdsale, giving the crowdsale
     * an allowance of tokens from the crowdsale supply. This gives the
     * crowdsale the ability to call transferFrom to transfer tokens to
     * whomever has purchased them.
     *
     * Note that if _amountForSale is 0, then it is assumed that the full
     * remaining crowdsale supply is made available to the crowdsale.
     *
     * @param _crowdSaleAddr The address of a crowdsale contract that will sell this token
     * @param _amountForSale The supply of tokens provided to the crowdsale
     */
    function setCrowdsale(address _crowdSaleAddr, uint256 _amountForSale) external onlyOwner {
        require(_amountForSale <= crowdSaleAllowance);

        // if 0, then full available crowdsale supply is assumed
        uint amount = (_amountForSale == 0) ? crowdSaleAllowance : _amountForSale;

        // Clear allowance of old, and set allowance of new
        approve(crowdSaleAddr, 0);
        approve(_crowdSaleAddr, amount);

        crowdSaleAddr = _crowdSaleAddr;
    }

    /**
     * Overrides ERC20 transfer function with modifier that prevents the
     * ability to transfer tokens until after transfers have been enabled.
     */
    function transfer(address _to, uint256 _value) public validDestination(_to) returns (bool) {
        return super.transfer(_to, _value);
    }

    /**
     * Overrides ERC20 transferFrom function with modifier that prevents the
     * ability to transfer tokens until after transfers have been enabled.
     */
    function transferFrom(address _from, address _to, uint256 _value) public validDestination(_to) returns (bool) {
        bool result = super.transferFrom(_from, _to, _value);
        if (result) {
            if (msg.sender == crowdSaleAddr)
                crowdSaleAllowance = crowdSaleAllowance.sub(_value);
            if (msg.sender == adminAddr)
                adminAllowance = adminAllowance.sub(_value);
        }
        return result;
    }

    /**
     * Overrides the burn function so that it cannot be called until after
     * transfers have been enabled.
     *
     * @param _value    The amount of tokens to burn in wei-EBSC
     */
    function burn(uint256 _value) public {
        require(transferEnabled || msg.sender == owner);
        super.burn(_value);
        Transfer(msg.sender, address(0x0), _value);
    }
}


/**
 * The EBSCSale smart contract is used for selling EBSC tokens (EBSC).
 * It does so by converting ETH received into a quantity of
 * tokens that are transferred to the contributor via the ERC20-compatible
 * transferFrom() function.
 */
contract EBSCSale is Pausable {

    using SafeMath for uint256;

    // The beneficiary is the future recipient of the funds
    address public beneficiary;

    // The crowdsale has a funding goal, cap, deadline, and minimum contribution
    uint public fundingGoal;
    uint public fundingCap;
    uint public minContribution;
    bool public fundingGoalReached = false;
    bool public fundingCapReached = false;
    bool public saleClosed = false;

    // Time period of sale (UNIX timestamps)
    uint public startTime;
    uint public endTime;

    // Keeps track of the amount of wei raised
    uint public amountRaised;

    // Refund amount, should it be required
    uint public refundAmount;

    // The ratio of EBSC to Ether
    uint public rate = 6000;
    uint public constant LOW_RANGE_RATE = 500;
    uint public constant HIGH_RANGE_RATE = 20000;

    // prevent certain functions from being recursively called
    bool private rentrancy_lock = false;

    // The token being sold
    EBSCToken public tokenReward;

    // A map that tracks the amount of wei contributed by address
    mapping(address => uint256) public balanceOf;

    // Events
    event GoalReached(address _beneficiary, uint _amountRaised);
    event CapReached(address _beneficiary, uint _amountRaised);
    event FundTransfer(address _backer, uint _amount, bool _isContribution);

    // Modifiers
    modifier beforeDeadline()   { require (currentTime() < endTime); _; }
    modifier afterDeadline()    { require (currentTime() >= endTime); _; }
    modifier afterStartTime()    { require (currentTime() >= startTime); _; }

    modifier saleNotClosed()    { require (!saleClosed); _; }

    modifier nonReentrant() {
        require(!rentrancy_lock);
        rentrancy_lock = true;
        _;
        rentrancy_lock = false;
    }

    /**
     * Constructor for a crowdsale of QuantstampToken tokens.
     *
     * @param ifSuccessfulSendTo            the beneficiary of the fund
     * @param fundingGoalInEthers           the minimum goal to be reached
     * @param fundingCapInEthers            the cap (maximum) size of the fund
     * @param minimumContributionInWei      minimum contribution (in wei)
     * @param start                         the start time (UNIX timestamp)
     * @param end                           the end time (UNIX timestamp)
     * @param rateEBSCToEther                the conversion rate from EBSC to Ether
     * @param addressOfTokenUsedAsReward    address of the token being sold
     */
    function EBSCSale(
        address ifSuccessfulSendTo,
        uint fundingGoalInEthers,
        uint fundingCapInEthers,
        uint minimumContributionInWei,
        uint start,
        uint end,
        uint rateEBSCToEther,
        address addressOfTokenUsedAsReward
    ) public {
        require(ifSuccessfulSendTo != address(0) && ifSuccessfulSendTo != address(this));
        require(addressOfTokenUsedAsReward != address(0) && addressOfTokenUsedAsReward != address(this));
        require(fundingGoalInEthers <= fundingCapInEthers);
        require(end > 0);
        beneficiary = ifSuccessfulSendTo;
        fundingGoal = fundingGoalInEthers * 1 ether;
        fundingCap = fundingCapInEthers * 1 ether;
        minContribution = minimumContributionInWei;
        startTime = start;
        endTime = end; // TODO double check
        setRate(rateEBSCToEther);
        tokenReward = EBSCToken(addressOfTokenUsedAsReward);
    }

    /**
     * This fallback function is called whenever Ether is sent to the
     * smart contract. It can only be executed when the crowdsale is
     * not paused, not closed, and before the deadline has been reached.
     *
     * This function will update state variables for whether or not the
     * funding goal or cap have been reached. It also ensures that the
     * tokens are transferred to the sender, and that the correct
     * number of tokens are sent according to the current rate.
     */
    function () public payable whenNotPaused beforeDeadline afterStartTime saleNotClosed nonReentrant {
        require(msg.value >= minContribution);

        // Update the sender's balance of wei contributed and the amount raised
        uint amount = msg.value;
        uint currentBalance = balanceOf[msg.sender];
        balanceOf[msg.sender] = currentBalance.add(amount);
        amountRaised = amountRaised.add(amount);

        // Compute the number of tokens to be rewarded to the sender
        // Note: it's important for this calculation that both wei
        // and EBSC have the same number of decimal places (18)
        uint numTokens = amount.mul(rate);

        // Transfer the tokens from the crowdsale supply to the sender
        if (tokenReward.transferFrom(tokenReward.owner(), msg.sender, numTokens)) {
            FundTransfer(msg.sender, amount, true);
            // Check if the funding goal or cap have been reached
            // TODO check impact on gas cost
            checkFundingGoal();
            checkFundingCap();
        }
        else {
            revert();
        }
    }

    /**
     * The owner can terminate the crowdsale at any time.
     */
    function terminate() external onlyOwner {
        saleClosed = true;
    }

    /**
     * The owner can update the rate (EBSC to ETH).
     *
     * @param _rate  the new rate for converting EBSC to ETH
     */
    function setRate(uint _rate) public onlyOwner {
        require(_rate >= LOW_RANGE_RATE && _rate <= HIGH_RANGE_RATE);
        rate = _rate;
    }

    /**
     * The owner can allocate the specified amount of tokens from the
     * crowdsale allowance to the recipient (_to).
     *
     * NOTE: be extremely careful to get the amounts correct, which
     * are in units of wei and mini-EBSC. Every digit counts.
     *
     * @param _to            the recipient of the tokens
     * @param amountWei     the amount contributed in wei
     * @param amountMiniEbsc the amount of tokens transferred in mini-EBSC (18 decimals)
     */
    function ownerAllocateTokens(address _to, uint amountWei, uint amountMiniEbsc) external
            onlyOwner nonReentrant
    {
        if (!tokenReward.transferFrom(tokenReward.owner(), _to, amountMiniEbsc)) {
            revert();
        }
        balanceOf[_to] = balanceOf[_to].add(amountWei);
        amountRaised = amountRaised.add(amountWei);
        FundTransfer(_to, amountWei, true);
        checkFundingGoal();
        checkFundingCap();
    }

    /**
     * The owner can call this function to withdraw the funds that
     * have been sent to this contract for the crowdsale subject to
     * the funding goal having been reached. The funds will be sent
     * to the beneficiary specified when the crowdsale was created.
     */
    function ownerSafeWithdrawal() external onlyOwner nonReentrant {
        require(fundingGoalReached);
        uint balanceToSend = this.balance;
        beneficiary.transfer(balanceToSend);
        FundTransfer(beneficiary, balanceToSend, false);
    }

    /**
     * The owner can unlock the fund with this function. The use-
     * case for this is when the owner decides after the deadline
     * to allow contributors to be refunded their contributions.
     * Note that the fund would be automatically unlocked if the
     * minimum funding goal were not reached.
     */
    function ownerUnlockFund() external afterDeadline onlyOwner {
        fundingGoalReached = false;
    }

    /**
     * This function permits anybody to withdraw the funds they have
     * contributed if and only if the deadline has passed and the
     * funding goal was not reached.
     */
    function safeWithdrawal() external afterDeadline nonReentrant {
        if (!fundingGoalReached) {
            uint amount = balanceOf[msg.sender];
            balanceOf[msg.sender] = 0;
            if (amount > 0) {
                msg.sender.transfer(amount);
                FundTransfer(msg.sender, amount, false);
                refundAmount = refundAmount.add(amount);
            }
        }
    }

    /**
     * Checks if the funding goal has been reached. If it has, then
     * the GoalReached event is triggered.
     */
    function checkFundingGoal() internal {
        if (!fundingGoalReached) {
            if (amountRaised >= fundingGoal) {
                fundingGoalReached = true;
                GoalReached(beneficiary, amountRaised);
            }
        }
    }

    /**
     * Checks if the funding cap has been reached. If it has, then
     * the CapReached event is triggered.
     */
    function checkFundingCap() internal {
        if (!fundingCapReached) {
            if (amountRaised >= fundingCap) {
                fundingCapReached = true;
                saleClosed = true;
                CapReached(beneficiary, amountRaised);
            }
        }
    }

    /**
     * Returns the current time.
     * Useful to abstract calls to "now" for tests.
    */
    function currentTime() public constant returns (uint _currentTime) {
        return now;
    }


    /**
     * Given an amount in EBSC, this method returns the equivalent amount
     * in mini-EBSC.
     *
     * @param amount    an amount expressed in units of EBSC
     */
    function convertToMiniEbsc(uint amount) internal constant returns (uint) {
        return amount * (10 ** uint(tokenReward.decimals()));
    }

    /**
     * These helper functions are exposed for changing the start and end time dynamically   
     */
    function changeStartTime(uint256 _startTime) external onlyOwner {startTime = _startTime;}
    function changeEndTime(uint256 _endTime) external onlyOwner {endTime = _endTime;}
}