Merge pull request #35 from gnosis/std_market_w_price_2

Std market w price 2

contracts/Markets/StandardMarketWithPriceLogger.sol

@@ -7,14 +7,16 @@ contract StandardMarketWithPriceLogger is StandardMarket {
     /*
      *  Constants
      */
+    uint constant ONE = 0x10000000000000000;
     uint8 public constant LONG = 1;
 
     /*
      *  Storage
      */
     uint public startDate;
     uint public endDate;
-    uint public lastTrade;
+    uint public lastTradeDate;
+    uint public lastTradePrice;
     uint public priceIntegral;
 
     /*
@@ -30,13 +32,19 @@ contract StandardMarketWithPriceLogger is StandardMarket {
         public
         StandardMarket(_creator, _eventContract, _marketMaker, _fee)
     {
+        require(eventContract.getOutcomeCount() == 2);
+
         if (_startDate == 0)
             startDate = now;
         else {
             // The earliest start date is the market creation date
             require(_startDate >= now);
             startDate = _startDate;
         }
+
+        lastTradeDate = startDate;
+        // initialize lastTradePrice to assuming uniform probabilities of outcomes
+        lastTradePrice = ONE / 2;
     }
 
     /// @dev Allows market creator to close the markets by transferring all remaining outcome tokens to the creator
@@ -56,8 +64,9 @@ contract StandardMarketWithPriceLogger is StandardMarket {
         public
         returns (uint cost)
     {
-        logPrice();
+        logPriceBefore();
         cost = super.buy(outcomeTokenIndex, outcomeTokenCount, maxCost);
+        logPriceAfter();
     }
 
     /// @dev Allows to sell outcome tokens to market maker
@@ -69,8 +78,9 @@ contract StandardMarketWithPriceLogger is StandardMarket {
         public
         returns (uint profit)
     {
-        logPrice();
+        logPriceBefore();
         profit = super.sell(outcomeTokenIndex, outcomeTokenCount, minProfit);
+        logPriceAfter();
     }
 
     /// @dev Buys all outcomes, then sells all shares of selected outcome which were bought, keeping
@@ -83,35 +93,42 @@ contract StandardMarketWithPriceLogger is StandardMarket {
         public
         returns (uint cost)
     {
-        logPrice();
+        logPriceBefore();
         cost = super.shortSell(outcomeTokenIndex, outcomeTokenCount, minProfit);
+        logPriceAfter();
     }
 
     /// @dev Calculates average price for long tokens based on price integral
-    /// @return Average price for long tokens
+    /// @return Average price for long tokens over time
     function getAvgPrice()
         public
         returns (uint)
     {
-        return priceIntegral / (now - startDate);
+        if(endDate > 0)
+            return (priceIntegral + lastTradePrice * (endDate - lastTradeDate)) / (endDate - startDate);
+        return (priceIntegral + lastTradePrice * (now - lastTradeDate)) / (now - startDate);
     }
 
     /*
      *  Private functions
      */
-    /// @dev Adds price integral since the last trade to the total price integral and updates last
-    ///      trade timestamp
-    function logPrice()
+    /// @dev Adds price integral since the last trade to the total price integral
+    function logPriceBefore()
         private
     {
         if (now >= startDate) {
-            // Calculate price of long tokens
-            uint price = marketMaker.calcMarginalPrice(this, LONG);
-            if (lastTrade > 0)
-                priceIntegral += price * (now - lastTrade);
-            else
-                priceIntegral += price * (now - startDate);
-            lastTrade = now;
+            // Accumulate price integral only if logging has begun
+            priceIntegral += lastTradePrice * (now - lastTradeDate);
         }
     }
+
+    /// @dev Updates last trade timestamp and price
+    function logPriceAfter()
+        private
+    {
+        // Refresh lastTradePrice after every transactions as we don't know if
+        // this will be the last transaction before logging period starts
+        lastTradePrice = marketMaker.calcMarginalPrice(this, LONG);
+        lastTradeDate = now;
+    }
 }

contracts/Oracles/FutarchyOracle.sol

@@ -27,7 +27,7 @@ contract FutarchyOracle is Oracle {
     address creator;
     StandardMarketWithPriceLogger[] public markets;
     CategoricalEvent public categoricalEvent;
-    uint public deadline;
+    uint public tradingPeriod;
     uint public winningMarketIndex;
     bool public isSet;
 
@@ -54,7 +54,7 @@ contract FutarchyOracle is Oracle {
     /// @param marketFactory Market factory contract
     /// @param marketMaker Market maker contract
     /// @param fee Market fee
-    /// @param _deadline Decision deadline
+    /// @param _tradingPeriod Trading period before decision can be determined
     /// @param startDate Start date for price logging
     function FutarchyOracle(
         address _creator,
@@ -67,14 +67,14 @@ contract FutarchyOracle is Oracle {
         StandardMarketWithPriceLoggerFactory marketFactory,
         MarketMaker marketMaker,
         uint24 fee,
-        uint _deadline,
+        uint _tradingPeriod,
         uint startDate
 
     )
         public
     {
-        // Deadline is in the future
-        require(_deadline > 0);
+        // trading period is at least a second
+        require(_tradingPeriod > 0);
         // Create decision event
         categoricalEvent = eventFactory.createCategoricalEvent(collateralToken, this, outcomeCount);
         // Create outcome events
@@ -88,7 +88,7 @@ contract FutarchyOracle is Oracle {
             markets.push(marketFactory.createMarket(scalarEvent, marketMaker, fee, startDate));
         }
         creator = _creator;
-        deadline = _deadline;
+        tradingPeriod = _tradingPeriod;
     }
 
     /// @dev Funds all markets with equal amount of funding
@@ -133,8 +133,8 @@ contract FutarchyOracle is Oracle {
     function setOutcome()
         public
     {
-        // Outcome is not set yet and deadline has passed
-        require(!isSet && markets[0].startDate() + deadline < now);
+        // Outcome is not set yet and trading period is over
+        require(!isSet && markets[0].startDate() + tradingPeriod < now);
         // Find market with highest marginal price for long outcome tokens
         uint highestAvgPrice = markets[0].getAvgPrice();
         uint highestIndex = 0;

contracts/Oracles/FutarchyOracleFactory.sol

@@ -19,7 +19,7 @@ contract FutarchyOracleFactory {
         int upperBound,
         MarketMaker marketMaker,
         uint24 fee,
-        uint deadline,
+        uint tradingPeriod,
         uint startDate
     );
 
@@ -51,7 +51,7 @@ contract FutarchyOracleFactory {
     /// @param upperBound Lower bound for event outcome
     /// @param marketMaker Market maker contract
     /// @param fee Market fee
-    /// @param deadline Decision deadline
+    /// @param tradingPeriod Trading period before decision can be determined
     /// @param startDate Start date for price logging
     /// @return Oracle contract
     function createFutarchyOracle(
@@ -62,7 +62,7 @@ contract FutarchyOracleFactory {
         int upperBound,
         MarketMaker marketMaker,
         uint24 fee,
-        uint deadline,
+        uint tradingPeriod,
         uint startDate
     )
         public
@@ -79,7 +79,7 @@ contract FutarchyOracleFactory {
             marketFactory,
             marketMaker,
             fee,
-            deadline,
+            tradingPeriod,
             startDate
         );
         FutarchyOracleCreation(
@@ -92,7 +92,7 @@ contract FutarchyOracleFactory {
             upperBound,
             marketMaker,
             fee,
-            deadline,
+            tradingPeriod,
             startDate
         );
     }