TokenTrader

// Submitted by EthereumHistory (ethereumhistory.com)
pragma solidity ^0.4.4;

// ------------------------------------------------------------------------
// TokenTraderFactory
//
// Decentralised trustless ERC20-compliant token to ETH exchange contract
// on the Ethereum blockchain.
//
// Note that this TokenTrader cannot be used with the Golem Network Token
// directly as the token does not implement the ERC20
// transferFrom(...), approve(...) and allowance(...) methods
//
// Enjoy. (c) JonnyLatte & BokkyPooBah 2016. The MIT licence.
// ------------------------------------------------------------------------

// https://github.com/ethereum/EIPs/issues/20
contract ERC20 {
    function totalSupply() constant returns (uint totalSupply);
    function balanceOf(address _owner) constant returns (uint balance);
    function transfer(address _to, uint _value) returns (bool success);
    function transferFrom(address _from, address _to, uint _value) returns (bool success);
    function approve(address _spender, uint _value) returns (bool success);
    function allowance(address _owner, address _spender) constant returns (uint remaining);
    event Transfer(address indexed _from, address indexed _to, uint _value);
    event Approval(address indexed _owner, address indexed _spender, uint _value);
}

contract Owned {
    address public owner;
    event OwnershipTransferred(address indexed _from, address indexed _to);

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

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

    function transferOwnership(address newOwner) onlyOwner {
        OwnershipTransferred(owner, newOwner);
        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;    // contract 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 buysTokens;     // is contract buying
    bool public sellsTokens;    // is contract selling

    event ActivatedEvent(bool buys, bool sells);
    event MakerDepositedEther(uint256 amount);
    event MakerWithdrewAsset(uint256 tokens);
    event MakerWithdrewERC20Token(address tokenAddress, uint256 tokens);
    event MakerWithdrewEther(uint256 ethers);
    event TakerBoughtAsset(address indexed buyer, uint256 ethersSent,
        uint256 ethersReturned, uint256 tokensBought);
    event TakerSoldAsset(address indexed seller, uint256 tokensToSell,
        uint256 tokensSold, uint256 ethers);

    // Constructor - only to be called by the TokenTraderFactory contract
    function TokenTrader (
        address _asset,
        uint256 _buyPrice,
        uint256 _sellPrice,
        uint256 _units,
        bool    _buysTokens,
        bool    _sellsTokens
    ) internal {
        asset       = _asset;
        buyPrice    = _buyPrice;
        sellPrice   = _sellPrice;
        units       = _units;
        buysTokens  = _buysTokens;
        sellsTokens = _sellsTokens;
        ActivatedEvent(buysTokens, sellsTokens);
    }

    // Maker can activate or deactivate this contract's buying and
    // selling status
    //
    // The ActivatedEvent() event is logged with the following
    // parameter:
    //   buysTokens   this contract can buy asset tokens
    //   sellsTokens  this contract can sell asset tokens
    //
    function activate (
        bool _buysTokens,
        bool _sellsTokens
    ) onlyOwner {
        buysTokens  = _buysTokens;
        sellsTokens = _sellsTokens;
        ActivatedEvent(buysTokens, sellsTokens);
    }

    // Maker can deposit ethers to this contract so this contract
    // can buy asset tokens.
    //
    // Maker deposits asset tokens to this contract by calling the
    // asset's transfer() method with the following parameters
    //   _to     is the address of THIS contract
    //   _value  is the number of asset tokens to be transferred
    //
    // Taker MUST NOT send tokens directly to this contract. Takers
    // MUST use the takerSellAsset() method to sell asset tokens
    // to this contract
    //
    // The MakerDepositedEther() event is logged with the following
    // parameter:
    //   ethers  is the number of ethers deposited by the maker
    //
    // This method was called deposit() in the old version
    //
    function makerDepositEther() payable onlyOwner {
        MakerDepositedEther(msg.value);
    }

    // Maker can withdraw asset tokens from this contract, with the
    // following parameter:
    //   tokens  is the number of asset tokens to be withdrawn
    //
    // The MakerWithdrewAsset() event is logged with the following
    // parameter:
    //   tokens  is the number of tokens withdrawn by the maker
    //
    // This method was called withdrawAsset() in the old version
    //
    function makerWithdrawAsset(uint256 tokens) onlyOwner returns (bool ok) {
        MakerWithdrewAsset(tokens);
        return ERC20(asset).transfer(owner, tokens);
    }

    // Maker can withdraw any ERC20 asset tokens from this contract
    //
    // This method is included in the case where this contract receives
    // the wrong tokens
    //
    // The MakerWithdrewERC20Token() event is logged with the following
    // parameter:
    //   tokenAddress  is the address of the tokens withdrawn by the maker
    //   tokens        is the number of tokens withdrawn by the maker
    //
    // This method was called withdrawToken() in the old version
    //
    function makerWithdrawERC20Token(
        address tokenAddress,
        uint256 tokens
    ) onlyOwner returns (bool ok) {
        MakerWithdrewERC20Token(tokenAddress, tokens);
        return ERC20(tokenAddress).transfer(owner, tokens);
    }

    // Maker can withdraw ethers from this contract
    //
    // The MakerWithdrewEther() event is logged with the following parameter
    //   ethers  is the number of ethers withdrawn by the maker
    //
    // This method was called withdraw() in the old version
    //
    function makerWithdrawEther(uint256 ethers) onlyOwner returns (bool ok) {
        if (this.balance >= ethers) {
            MakerWithdrewEther(ethers);
            return owner.send(ethers);
        }
    }

    // Taker buys asset tokens by sending ethers
    //
    // The TakerBoughtAsset() event is logged with the following parameters
    //   buyer           is the buyer's address
    //   ethersSent      is the number of ethers sent by the buyer
    //   ethersReturned  is the number of ethers sent back to the buyer as
    //                   change
    //   tokensBought    is the number of asset tokens sent to the buyer
    //
    // This method was called buy() in the old version
    //
    function takerBuyAsset() payable {
        if (sellsTokens || msg.sender == owner) {
            uint order    = msg.value / sellPrice;
            uint can_sell = ERC20(asset).balanceOf(address(this)) / units;
            uint256 change = 0;
            if (order > can_sell) {
                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;
            }
            TakerBoughtAsset(msg.sender, msg.value, change, order * units);
        }
        // Return user funds if the contract is not selling
        else if (!msg.sender.send(msg.value)) throw;
    }

    // Taker sells asset tokens for ethers by:
    // 1. Calling the asset's approve() method with the following parameters
    //    _spender  is the address of this contract
    //    _value    is the number of tokens to be sold
    // 2. Calling this takerSellAsset() method with the following parameter
    //    tokens    is the number of asset tokens to be sold
    //
    // The TakerSoldAsset() event is logged with the following parameters
    //   seller        is the seller's address
    //   tokensToSell  is the number of asset tokens offered by the seller
    //   tokensSold    is the number of asset tokens sold
    //   ethers        is the number of ethers sent to the seller
    //
    // This method was called sell() in the old version
    //
    function takerSellAsset(uint256 tokens) {
        if (buysTokens || msg.sender == owner) {
            // Maximum number of token the contract can buy
            uint256 can_buy = this.balance / buyPrice;
            // Token lots available
            uint256 order = tokens / units;
            // Adjust order for funds available
            if (order > can_buy) order = can_buy;
            if (order > 0) {
                // Extract user tokens
                if(!ERC20(asset).transferFrom(msg.sender, address(this), order * units)) throw;
                // Pay user
                if(!msg.sender.send(order * buyPrice)) throw;
            }
            TakerSoldAsset(msg.sender, tokens, order * units, order * buyPrice);
        }
    }

    // Taker buys tokens by sending ethers
    function () payable {
        takerBuyAsset();
    }
}

// This contract deploys TokenTrader contracts and logs the event
contract TokenTraderFactory is Owned {

    event TradeListing(address ownerAddress, address tokenTraderAddress, address asset,
        uint256 buyPrice, uint256 sellPrice, uint256 units,
        bool buysTokens, bool sellsTokens);
    event OwnerWithdrewERC20Token(address tokenAddress, uint256 tokens);

    mapping(address => bool) _verify;

    // Anyone can call this method to verify the settings of a
    // TokenTrader contract. The parameters are:
    //   tradeContract  is the address of a TokenTrader contract
    //
    // Return values:
    //   valid        did this TokenTraderFactory create the TokenTrader contract?
    //   owner        is the owner of the TokenTrader contract
    //   asset        is the ERC20 asset address
    //   buyPrice     is the buy price in ethers per `units` of asset tokens
    //   sellPrice    is the sell price in ethers per `units` of asset tokens
    //   units        is the number of units of asset tokens
    //   buysTokens   is the TokenTrader contract buying tokens?
    //   sellsTokens  is the TokenTrader contract selling tokens?
    //
    function verify(address tradeContract) constant returns (
        bool    valid,
        address owner,
        address asset,
        uint256 buyPrice,
        uint256 sellPrice,
        uint256 units,
        bool    buysTokens,
        bool    sellsTokens
    ) {
        valid = _verify[tradeContract];
        if (valid) {
            TokenTrader t = TokenTrader(tradeContract);
            owner         = t.owner();
            asset         = t.asset();
            buyPrice      = t.buyPrice();
            sellPrice     = t.sellPrice();
            units         = t.units();
            buysTokens    = t.buysTokens();
            sellsTokens   = t.sellsTokens();
        }
    }

    // Maker can call this method to create a new TokenTrader contract
    // with the maker being the owner of this new contract
    //
    // Parameters:
    //   asset        is the ERC20 asset address
    //   buyPrice     is the buy price in ethers per `units` of asset tokens
    //   sellPrice    is the sell price in ethers per `units` of asset tokens
    //   units        is the number of units of asset tokens
    //   buysTokens   is the TokenTrader contract buying tokens?
    //   sellsTokens  is the TokenTrader contract selling tokens?
    //
    // For example, listing a TokenTrader contract on the REP Augur token where
    // the contract will buy REP tokens at a rate of 39000/100000 = 0.39 ETH
    // per REP token and sell REP tokens at a rate of 41000/100000 = 0.41 ETH
    // per REP token:
    //   asset        0x48c80f1f4d53d5951e5d5438b54cba84f29f32a5
    //   buyPrice     39000
    //   sellPrice    41000
    //   units        100000
    //   buysTokens   true
    //   sellsTokens  true
    //
    // The TradeListing() event is logged with the following parameters
    //   ownerAddress        is the Maker's address
    //   tokenTraderAddress  is the address of the newly created TokenTrader contract
    //   asset               is the ERC20 asset address
    //   buyPrice            is the buy price in ethers per `units` of asset tokens
    //   sellPrice           is the sell price in ethers per `units` of asset tokens
    //   unit                is the number of units of asset tokens
    //   buysTokens          is the TokenTrader contract buying tokens?
    //   sellsTokens         is the TokenTrader contract selling tokens?
    //
    function createTradeContract(
        address asset,
        uint256 buyPrice,
        uint256 sellPrice,
        uint256 units,
        bool    buysTokens,
        bool    sellsTokens
    ) returns (address trader) {
        // Cannot set negative price
        if (buyPrice < 0 || sellPrice < 0) throw;
        // Must make profit on spread
        if (buyPrice > sellPrice) throw;
        // Cannot buy or sell zero or negative units
        if (units <= 0) throw;
        trader = new TokenTrader(
            asset,
            buyPrice,
            sellPrice,
            units,
            buysTokens,
            sellsTokens);
        // Record that this factory created the trader
        _verify[trader] = true;
        // Set the owner to whoever called the function
        TokenTrader(trader).transferOwnership(msg.sender);
        TradeListing(msg.sender, trader, asset, buyPrice, sellPrice, units, buysTokens, sellsTokens);
    }

    // Factory owner can withdraw any ERC20 asset tokens from this contract
    //
    // This method is included in the case where this contract receives
    // the wrong tokens
    //
    // The OwnerWithdrewERC20Token() event is logged with the following
    // parameter:
    //   tokenAddress  is the address of the tokens withdrawn by the maker
    //   tokens        is the number of tokens withdrawn by the maker
    //
    function ownerWithdrawERC20Token(address tokenAddress, uint256 tokens) onlyOwner returns (bool ok) {
        OwnerWithdrewERC20Token(tokenAddress, tokens);
        return ERC20(tokenAddress).transfer(owner, tokens);
    }

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