TokenTrader

// Submitted by EthereumHistory (ethereumhistory.com)
pragma solidity ^0.4.0;

//https://github.com/nexusdev/erc20/blob/master/contracts/erc20.sol

contract ERC20Constant {
    function totalSupply() constant returns (uint supply);
    function balanceOf( address who ) constant returns (uint value);
    function allowance(address owner, address spender) constant returns (uint _allowance);
}
contract ERC20Stateful {
    function transfer( address to, uint value) returns (bool ok);
    function transferFrom( address from, address to, uint value) returns (bool ok);
    function approve(address spender, uint value) returns (bool ok);
}
contract ERC20Events {
    event Transfer(address indexed from, address indexed to, uint value);
    event Approval( address indexed owner, address indexed spender, uint value);
}
contract ERC20 is ERC20Constant, ERC20Stateful, ERC20Events {}

contract owned {
    address public owner;

    function owned() {
        owner = msg.sender;
    }

    modifier onlyOwner {
        if (msg.sender != owner) throw;
        _;
    }

    function transferOwnership(address newOwner) onlyOwner {
        owner = newOwner;
    }
}

// contract can buy or sell tokens for ETH
// prices are in amount of wei per batch of token units

contract TokenTrader is owned {

    address public asset;       // address of token
    uint256 public buyPrice;   // contact buys lots of token at this price
    uint256 public sellPrice;  // contract sells lots at this price
    uint256 public units;       // lot size (token-wei)

    bool public sellsTokens;    // is contract selling
    bool public buysTokens;     // is contract buying

    event ActivatedEvent(bool sells, bool buys);
    event UpdateEvent();

    function TokenTrader (
        address _asset, 
        uint256 _buyPrice, 
        uint256 _sellPrice, 
        uint256 _units,
        bool    _sellsTokens,
        bool    _buysTokens
        )
    {
          asset         = _asset; 
          buyPrice     = _buyPrice; 
          sellPrice    = _sellPrice;
          units         = _units; 
          sellsTokens   = _sellsTokens;
          buysTokens    = _buysTokens;

          ActivatedEvent(sellsTokens,buysTokens);
    }

    // modify trading behavior
    function activate (
        bool    _sellsTokens,
        bool    _buysTokens
        )
    {
          sellsTokens   = _sellsTokens;
          buysTokens    = _buysTokens;

          ActivatedEvent(sellsTokens,buysTokens);
    }

    // allows owner to deposit ETH
    // deposit tokens by sending them directly to contract
    // buyers must not send tokens to the contract, use: sell(...)
    function deposit() payable onlyOwner {
    }

    // allow owner to remove trade token
    function withdrawAsset(uint256 _value) onlyOwner returns (bool ok)
    {
        return ERC20(asset).transfer(owner,_value);
    }

    // allow owner to remove arbitrary tokens
    // included just in case contract receives wrong token
    function withdrawToken(address _token, uint256 _value) onlyOwner returns (bool ok)
    {
        return ERC20(_token).transfer(owner,_value);
    }

    // allow owner to remove ETH
    function withdraw(uint256 _value) onlyOwner returns (bool ok)
    {
        if(this.balance >= _value) {
            return owner.send(_value);
        }
    }

    //user buys token with ETH
    function buy() payable {
        if(sellsTokens || msg.sender == owner) 
        {
            uint order   = msg.value / sellPrice; 
            uint can_sell = ERC20(asset).balanceOf(address(this)) / units;

            if(order > can_sell)
            {
                uint256 change = msg.value - (can_sell * sellPrice);
                order = can_sell;
                if(!msg.sender.send(change)) throw;
            }

            if(order > 0) {
                if(!ERC20(asset).transfer(msg.sender,order * units)) throw;
            }
            UpdateEvent();
        }
        else throw;  // return user funds if the contract is not selling
    }

    // user sells token for ETH
    // user must set allowance for this contract before calling
    function sell(uint256 amount) {
        if (buysTokens || msg.sender == owner) {
            uint256 can_buy = this.balance / buyPrice;  // token lots contract can buy
            uint256 order = amount / units;             // token lots available

            if(order > can_buy) order = can_buy;        // adjust order for funds

            if (order > 0)
            { 
                // extract user tokens
                if(!ERC20(asset).transferFrom(msg.sender, address(this), amount)) throw;

                // pay user
                if(!msg.sender.send(order * buyPrice)) throw;
            }
            UpdateEvent();
        }
    }

    // sending ETH to contract sells ETH to user
    function () payable {
        buy();
    }
}

// This contract deploys TokenTrader contracts and logs the event
// trade pairs are identified with sha3(asset,units)

contract TokenTraderFactory {

    event TradeListing(bytes32 bookid, address owner, address addr);
    event NewBook(bytes32 bookid, address asset, uint256 units);

    mapping( address => bool ) public verify;
    mapping( bytes32 => bool ) pairExits;

    function createTradeContract(       
        address _asset, 
        uint256 _buyPrice, 
        uint256 _sellPrice, 
        uint256 _units,
        bool    _sellsTokens,
        bool    _buysTokens
        ) returns (address) 
    {
        if(_buyPrice > _sellPrice) throw; // must make profit on spread
        if(_units == 0) throw;              // can't sell zero units

        address trader = new TokenTrader (
                     _asset, 
                     _buyPrice, 
                     _sellPrice, 
                     _units,
                     _sellsTokens,
                     _buysTokens);

        var bookid = sha3(_asset,_units);

        verify[trader] = true; // record that this factory created the trader

        TokenTrader(trader).transferOwnership(msg.sender); // set the owner to whoever called the function

        if(pairExits[bookid] == false) {
            pairExits[bookid] = true;
            NewBook(bookid, _asset, _units);
        }

        TradeListing(bookid,msg.sender,trader);
    }

    function () {
        throw;     // Prevents accidental sending of ether to the factory
    }
}