pragma solidity ^0.4.19;

contract SafeMath {
    function safeMul(uint256 a, uint256 b) internal returns (uint256) {
        uint c = a * b;
        assert(a == 0 || c / a == b);
        return c;
    }

    function safeSub(uint256 a, uint256 b) internal returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    function safeAdd(uint256 a, uint256 b) internal returns (uint256) {
        uint c = a + b;
        assert(c >= a && c >= b);
        return c;
    }

}

contract ERC20Interface {
    // Get the total token supply
    function totalSupply() public constant returns (uint256 totalSupply);

    // Get the account balance of another account with address _owner
    function balanceOf(address _owner) public constant returns (uint256 balance);

    // Send _value amount of tokens to address _to
    function transfer(address _to, uint256 _value) public returns (bool success);

    // Send _value amount of tokens from address _from to address _to
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);

    // 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.
    // this function is required for some DEX functionality
    function approve(address _spender, uint256 _value) public returns (bool success);

    // Returns the amount which _spender is still allowed to withdraw from _owner
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining);

    // Triggered when tokens are transferred.
    event Transfer(address indexed _from, address indexed _to, uint256 _value);

    // Triggered whenever approve(address _spender, uint256 _value) is called.
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}


contract GBT is ERC20Interface {
    uint256 public expirationBlock;
    function isActive(address _owner) public returns (bool activated);
}


contract GBIT is SafeMath {
    address public admin = 0xb772725c0e453aF4c93fcD00A4cF005C73889126; //the admin address
    address public feeAccount = 0xe04F320bCc0e8796e2e6092B3796C722a1220Bf5; //the account that will receive fees
    address public gbtAddress = 0xe04F320bCc0e8796e2e6092B3796C722a1220Bf5;

    uint256 public makeFee = 0; //percentage times (1 ether)
    uint256 public takeFee = 1; //percentage times (1 ether)
    uint256 public lastFreeBlock = 500000000;

    mapping (bytes32 => uint256) public sellOrderBalances; //a hash of available order balances holds a number of tokens
    mapping (bytes32 => uint256) public buyOrderBalances; //a hash of available order balances. holds a number of eth

    event MakeBuyOrder(bytes32 orderHash, address indexed token, uint256 tokenAmount, uint256 weiAmount, address indexed buyer);

    event MakeSellOrder(bytes32 orderHash, address indexed token, uint256 tokenAmount, uint256 weiAmount, address indexed seller);

    event CancelBuyOrder(bytes32 orderHash, address indexed token, uint256 tokenAmount, uint256 weiAmount, address indexed buyer);

    event CancelSellOrder(bytes32 orderHash, address indexed token, uint256 tokenAmount, uint256 weiAmount, address indexed seller);

    event TakeBuyOrder(bytes32 orderHash, address indexed token, uint256 tokenAmount, uint256 weiAmount, uint256 totalTransactionTokens, address indexed buyer, address indexed seller);

    event TakeSellOrder(bytes32 orderHash, address indexed token, uint256 tokenAmount, uint256 weiAmount, uint256 totalTransactionWei, address indexed buyer, address indexed seller);

    function() public {
        revert();
    }

    function changeAdmin(address admin_) public {
        require(msg.sender == admin);
        admin = admin_;
    }

    function changeGBTAddress(address gbtAddress_) public {
        require(msg.sender == admin);
        require(block.number > GBT(gbtAddress).expirationBlock());
        gbtAddress = gbtAddress_;
    }

    function changeLastFreeBlock(uint256 _lastFreeBlock) public {
        require(msg.sender == admin);
        require(_lastFreeBlock > block.number + 100); //announce at least 100 blocks ahead
        lastFreeBlock = _lastFreeBlock;
    }

    function changeFeeAccount(address feeAccount_) public {
        require(msg.sender == admin);
        feeAccount = feeAccount_;
    }

    function changeMakeFee(uint256 makeFee_) public {
        require(msg.sender == admin);
        require(makeFee_ < makeFee);
        makeFee = makeFee_;
    }

    function changeTakeFee(uint256 takeFee_) public {
        require(msg.sender == admin);
        require(takeFee_ < takeFee);
        takeFee = takeFee_;
    }

    function feeFromTotalCostForAccount(uint256 totalCost, uint256 feeAmount, address account) public constant returns (uint256) {
        return feeFromTotalCost(totalCost, feeAmount);
    }

    function feeFromTotalCost(uint256 totalCost, uint256 feeAmount) public constant returns (uint256) {

        uint256 cost = safeMul(totalCost, (1 ether)) / safeAdd((1 ether), feeAmount);

        // Calculate ceil(cost).
        uint256 remainder = safeMul(totalCost, (1 ether)) % safeAdd((1 ether), feeAmount);
        if (remainder != 0) {
            cost = safeAdd(cost, 1);
        }

        uint256 fee = safeSub(totalCost, cost);
        return fee;
    }

    function calculateFeeForAccount(uint256 cost, uint256 feeAmount, address account) public constant returns (uint256) {
        return calculateFee(cost, feeAmount);
    }

    function calculateFee(uint256 cost, uint256 feeAmount) public constant returns (uint256) {
        uint256 fee = safeMul(cost, feeAmount) / (1 ether);
        return fee;
    }

    // Makes an offer to trade tokenAmount of ERC20 token, token, for weiAmount of wei.
    function makeSellOrder(address token, uint256 tokenAmount, uint256 weiAmount) public {
        require(tokenAmount != 0);
        require(weiAmount != 0);

        bytes32 h = sha256(token, tokenAmount, weiAmount, msg.sender);


        // Update balance.
        sellOrderBalances[h] = safeAdd(sellOrderBalances[h], tokenAmount);

        // Check allowance.  -- Done after updating balance bc it makes a call to an untrusted contract.
        require(tokenAmount <= ERC20Interface(token).allowance(msg.sender, this));

        // Grab the token.
        if (!ERC20Interface(token).transferFrom(msg.sender, this, tokenAmount)) {
            revert();
        }


        MakeSellOrder(h, token, tokenAmount, weiAmount, msg.sender);
    }

    // Makes an offer to trade msg.value wei for tokenAmount of token (an ERC20 token).
    function makeBuyOrder(address token, uint256 tokenAmount) public payable {
        require(tokenAmount != 0);
        require(msg.value != 0);

        uint256 fee = feeFromTotalCost(msg.value, makeFee);
        uint256 valueNoFee = safeSub(msg.value, fee);
        bytes32 h = sha256(token, tokenAmount, valueNoFee, msg.sender);

        //put ether in the buyOrderBalances map
        buyOrderBalances[h] = safeAdd(buyOrderBalances[h], msg.value);

        // Notify all clients.
        MakeBuyOrder(h, token, tokenAmount, valueNoFee, msg.sender);
    }


    // Cancels all previous offers by msg.sender to trade tokenAmount of tokens for weiAmount of wei.
    function cancelAllSellOrders(address token, uint256 tokenAmount, uint256 weiAmount) public {
        bytes32 h = sha256(token, tokenAmount, weiAmount, msg.sender);
        uint256 remain = sellOrderBalances[h];
        delete sellOrderBalances[h];

        ERC20Interface(token).transfer(msg.sender, remain);

        CancelSellOrder(h, token, tokenAmount, weiAmount, msg.sender);
    }

    // Cancels any previous offers to trade weiAmount of wei for tokenAmount of tokens. Refunds the wei to sender.
    function cancelAllBuyOrders(address token, uint256 tokenAmount, uint256 weiAmount) public {
        bytes32 h = sha256(token, tokenAmount, weiAmount, msg.sender);
        uint256 remain = buyOrderBalances[h];
        delete buyOrderBalances[h];

        if (!msg.sender.send(remain)) {
            revert();
        }

        CancelBuyOrder(h, token, tokenAmount, weiAmount, msg.sender);
    }

    // Take some (or all) of the ether (minus fees) in the buyOrderBalances hash in exchange for totalTokens tokens.
    function takeBuyOrder(address token, uint256 tokenAmount, uint256 weiAmount, uint256 totalTokens, address buyer) public {
        require(tokenAmount != 0);
        require(weiAmount != 0);
        require(totalTokens != 0);

        bytes32 h = sha256(token, tokenAmount, weiAmount, buyer);

        // How many wei for the amount of tokens being sold?
        uint256 transactionWeiAmountNoFee = safeMul(totalTokens, weiAmount) / tokenAmount;

        // Does the buyer (maker) have enough money in the contract?
        uint256 unvestedMakeFee = calculateFee(transactionWeiAmountNoFee, makeFee);
        uint256 totalTransactionWeiAmount = safeAdd(transactionWeiAmountNoFee, unvestedMakeFee);
        require(buyOrderBalances[h] >= totalTransactionWeiAmount);


        // Calculate the actual vested fees.
        uint256 currentTakeFee = calculateFeeForAccount(transactionWeiAmountNoFee, takeFee, msg.sender);
        uint256 currentMakeFee = calculateFeeForAccount(transactionWeiAmountNoFee, makeFee, buyer);

        // Proceed with transferring balances.

        // Update our internal accounting.
        buyOrderBalances[h] = safeSub(buyOrderBalances[h], totalTransactionWeiAmount);


        // Did the seller send enough tokens?  -- This check is here bc it calls to an untrusted contract.
        require(ERC20Interface(token).allowance(msg.sender, this) >= totalTokens);

        // Send buyer their tokens and any fee refund.
        if (currentMakeFee < unvestedMakeFee) {// the buyer got a fee discount. Send the refund.
            uint256 refundAmount = safeSub(unvestedMakeFee, currentMakeFee);
            if (!buyer.send(refundAmount)) {
                revert();
            }
        }
        if (!ERC20Interface(token).transferFrom(msg.sender, buyer, totalTokens)) {
            revert();
        }

        // Grab our fee.
        if (safeAdd(currentTakeFee, currentMakeFee) > 0) {
            if (!feeAccount.send(safeAdd(currentTakeFee, currentMakeFee))) {
                revert();
            }
        }

        // Send seller the proceeds.
        if (!msg.sender.send(safeSub(transactionWeiAmountNoFee, currentTakeFee))) {
            revert();
        }

        TakeBuyOrder(h, token, tokenAmount, weiAmount, totalTokens, buyer, msg.sender);
    }


    function takeSellOrder(address token, uint256 tokenAmount, uint256 weiAmount, address seller) public payable {

        require(tokenAmount != 0);
        require(weiAmount != 0);

        bytes32 h = sha256(token, tokenAmount, weiAmount, seller);

        // Check that the contract has enough token to satisfy this order.
        uint256 currentTakeFee = feeFromTotalCostForAccount(msg.value, takeFee, msg.sender);
        uint256 transactionWeiAmountNoFee = safeSub(msg.value, currentTakeFee);
        uint256 totalTokens = safeMul(transactionWeiAmountNoFee, tokenAmount) / weiAmount;
        require(sellOrderBalances[h] >= totalTokens);

        // Calculate total vested fee.
        uint256 currentMakeFee = calculateFeeForAccount(transactionWeiAmountNoFee, makeFee, seller);
        uint256 totalFee = safeAdd(currentMakeFee, currentTakeFee);

        uint256 makerProceedsAfterFee = safeSub(transactionWeiAmountNoFee, currentMakeFee);

        // Transfer.

        // Update internal accounting.
        sellOrderBalances[h] = safeSub(sellOrderBalances[h], totalTokens);

        // Send buyer the tokens.
        if (!ERC20Interface(token).transfer(msg.sender, totalTokens)) {
            revert();
        }

        // Take our fee.
        if (totalFee > 0) {
            if (!feeAccount.send(totalFee)) {
                revert();
            }
        }

        // Send seller the proceeds.
        if (!seller.send(makerProceedsAfterFee)) {
            revert();
        }

        TakeSellOrder(h, token, tokenAmount, weiAmount, transactionWeiAmountNoFee, msg.sender, seller);
    }
}