Ref bitshares#1604: Add matching logic

Add logic to match an updated limit order if the price is changed to be
higher than the previous top-of-book price.

I believe this completes bitshares#1604

libraries/chain/include/graphene/chain/market_evaluator.hpp

@@ -72,6 +72,7 @@ namespace graphene { namespace chain {
        void_result do_apply(const limit_order_update_operation& o);
 
        const limit_order_object* _order = nullptr;
+       bool should_match_orders = false;
    };
 
    class limit_order_cancel_evaluator : public evaluator<limit_order_cancel_evaluator>

libraries/chain/market_evaluator.cpp

@@ -134,11 +134,21 @@ void_result limit_order_update_evaluator::do_evaluate(const limit_order_update_o
    // Check this is my order
    FC_ASSERT(o.seller == _order->seller, "Cannot update someone else's order");
 
-   // Check new price is compatible
-   if (o.new_price)
-      FC_ASSERT(o.new_price->base.asset_id == _order->sell_price.base.asset_id &&
-                o.new_price->quote.asset_id == _order->sell_price.quote.asset_id,
+   // Check new price is compatible, and determine whether it becomes the best offer on the market
+   if (o.new_price) {
+      auto base_id = o.new_price->base.asset_id;
+      auto quote_id = o.new_price->quote.asset_id;
+      FC_ASSERT(base_id == _order->sell_price.base.asset_id && quote_id == _order->sell_price.quote.asset_id,
                 "Cannot update limit order with incompatible price");
+      const auto& order_index = d.get_index_type<limit_order_index>().indices().get<by_price>();
+      auto top_of_book = order_index.upper_bound(boost::make_tuple(price::max(base_id, quote_id)));
+      FC_ASSERT(top_of_book->sell_price.base.asset_id == base_id && top_of_book->sell_price.quote.asset_id == quote_id,
+                "Paradox: attempting to update an order in a market that has no orders? There's a logic error somewhere.");
+
+      // If the new price of our order is greater than the price of the order at the top of the book, we should match orders at the end.
+      // Otherwise, we can skip matching because there's no way this change could trigger orders to fill.
+      should_match_orders = (*o.new_price > top_of_book->sell_price);
+   }
 
    // Check delta asset is compatible
    if (o.delta_amount_to_sell) {
@@ -158,7 +168,7 @@ void_result limit_order_update_evaluator::do_evaluate(const limit_order_update_o
       FC_ASSERT(*o.new_expiration >= d.head_block_time(),
                 "Cannot update limit order with past expiration");
 
-   return void_result();
+   return {};
 } FC_CAPTURE_AND_RETHROW((o)) }
 
 void_result limit_order_update_evaluator::do_apply(const limit_order_update_operation& o)
@@ -184,9 +194,11 @@ void_result limit_order_update_evaluator::do_apply(const limit_order_update_oper
          loo.expiration = *o.new_expiration;
    });
 
-   // TODO: check if order is at front of book and price moved in favor of buyer; if so, trigger matching
+   // Perform order matching if necessary
+   if (should_match_orders)
+       d.apply_order(*_order);
 
-   return void_result();
+   return {};
 } FC_CAPTURE_AND_RETHROW((o)) }
 
 void_result limit_order_cancel_evaluator::do_evaluate(const limit_order_cancel_operation& o)

libraries/chain/protocol/market.cpp

@@ -65,6 +65,4 @@ void bid_collateral_operation::validate()const
    FC_ASSERT( debt_covered.amount == 0 || (debt_covered.amount > 0 && additional_collateral.amount > 0) );
 } FC_CAPTURE_AND_RETHROW((*this)) }
 
-}
-
-} // graphene::chain
+} } // graphene::chain

tests/tests/operation_tests.cpp

@@ -172,6 +172,50 @@ BOOST_AUTO_TEST_CASE(limit_order_update_test)
    }
 }
 
+BOOST_AUTO_TEST_CASE(limit_order_update_match_test)
+{
+   try {
+      ACTORS((nathan));
+      const auto& munee = create_user_issued_asset("MUNEE");
+
+      transfer(committee_account, nathan_id, asset(10000));
+      issue_uia(nathan, munee.amount(1000));
+
+      auto expiration = db.head_block_time() + 1000;
+      limit_order_id_type order_id_1 = create_sell_order(nathan, asset(999), munee.amount(100), expiration)->id;
+      limit_order_id_type order_id_2 = create_sell_order(nathan, munee.amount(100), asset(1001), expiration)->id;
+
+      update_limit_order(order_id_1, price(asset(1001), munee.amount(100)), asset(1));
+      BOOST_REQUIRE_EQUAL(db.find(order_id_1), nullptr);
+      BOOST_REQUIRE_EQUAL(db.find(order_id_2)->amount_for_sale().amount.value, 1);
+   } catch (fc::exception& e) {
+      edump((e.to_detail_string()));
+      throw;
+   }
+}
+
+BOOST_AUTO_TEST_CASE(limit_order_update_match_test_2)
+{
+   try {
+      ACTORS((nathan));
+      const auto& munee = create_user_issued_asset("MUNEE");
+
+      transfer(committee_account, nathan_id, asset(10000));
+      issue_uia(nathan, munee.amount(1000));
+
+      auto expiration = db.head_block_time() + 1000;
+      limit_order_id_type order_id_1 = create_sell_order(nathan, asset(999), munee.amount(100), expiration)->id;
+      limit_order_id_type order_id_2 = create_sell_order(nathan, munee.amount(100), asset(1001), expiration)->id;
+
+      update_limit_order(order_id_2, price(munee.amount(100), asset(999)));
+      BOOST_REQUIRE_EQUAL(db.find(order_id_1), nullptr);
+      BOOST_REQUIRE_EQUAL(db.find(order_id_2), nullptr);
+   } catch (fc::exception& e) {
+      edump((e.to_detail_string()));
+      throw;
+   }
+}
+
 BOOST_AUTO_TEST_CASE( call_order_update_test )
 {
    try {