Resolve #104: Set minimum feeds on bitassets

libraries/chain/asset_evaluator.cpp

@@ -299,8 +299,16 @@ void_result asset_update_bitasset_evaluator::do_evaluate(const asset_update_bita
 
 void_result asset_update_bitasset_evaluator::do_apply(const asset_update_bitasset_operation& o)
 { try {
-   db().modify(*bitasset_to_update, [&o](asset_bitasset_data_object& b) {
+   bool should_update_feeds = false;
+   // If the minimum number of feeds to calculate a median has changed, we need to recalculate the median
+   if( o.new_options.minimum_feeds != bitasset_to_update->options.minimum_feeds )
+      should_update_feeds = true;
+
+   db().modify(*bitasset_to_update, [&](asset_bitasset_data_object& b) {
       b.options = o.new_options;
+
+      if( should_update_feeds )
+         b.update_median_feeds(db().head_block_time());
    });
 
    return void_result();

libraries/chain/asset_object.cpp

@@ -52,8 +52,10 @@ void graphene::chain::asset_bitasset_data_object::update_median_feeds(time_point
       }
    }
 
-   if( current_feeds.empty() )
+   // If there are no valid feeds, or the number available is less than the minimum to calculate a median...
+   if( current_feeds.size() < options.minimum_feeds )
    {
+      //... don't calculate a median, and set a null feed
       current_feed_publication_time = current_time;
       current_feed = price_feed();
       return;
@@ -111,6 +113,7 @@ void asset_object::asset_options::validate()const
 
 void asset_object::bitasset_options::validate() const
 {
+   FC_ASSERT(minimum_feeds > 0);
    FC_ASSERT(force_settlement_offset_percent <= GRAPHENE_100_PERCENT);
    FC_ASSERT(maximum_force_settlement_volume <= GRAPHENE_100_PERCENT);
 }

libraries/chain/include/graphene/chain/asset_object.hpp

@@ -174,6 +174,8 @@ namespace graphene { namespace chain {
          struct bitasset_options {
             /// Time before a price feed expires
             uint32_t feed_lifetime_sec = GRAPHENE_DEFAULT_PRICE_FEED_LIFETIME;
+            /// Minimum number of unexpired feeds required to extract a median feed from
+            uint8_t minimum_feeds = 1;
             /// This is the delay between the time a long requests settlement and the chain evaluates the settlement
             uint32_t force_settlement_delay_sec = GRAPHENE_DEFAULT_FORCE_SETTLEMENT_DELAY;
             /// This is the percent to adjust the feed price in the short's favor in the event of a forced settlement
@@ -332,6 +334,7 @@ FC_REFLECT( graphene::chain::asset_object::asset_options,
           )
 FC_REFLECT( graphene::chain::asset_object::bitasset_options,
             (feed_lifetime_sec)
+            (minimum_feeds)
             (force_settlement_delay_sec)
             (force_settlement_offset_percent)
             (maximum_force_settlement_volume)

tests/tests/operation_tests2.cpp

@@ -373,6 +373,37 @@ BOOST_AUTO_TEST_CASE( mia_feeds )
    }
 } FC_LOG_AND_RETHROW() }
 
+BOOST_AUTO_TEST_CASE( feed_limit_test )
+{ try {
+   INVOKE( mia_feeds );
+   const asset_object& bit_usd = get_asset("BITUSD");
+   const asset_bitasset_data_object& bitasset = bit_usd.bitasset_data(db);
+   GET_ACTOR(nathan);
+
+   BOOST_CHECK(!bitasset.current_feed.settlement_price.is_null());
+
+   BOOST_TEST_MESSAGE("Setting minimum feeds to 4");
+   asset_update_bitasset_operation op;
+   op.new_options.minimum_feeds = 4;
+   op.asset_to_update = bit_usd.get_id();
+   op.issuer = bit_usd.issuer;
+   trx.operations = {op};
+   trx.sign(nathan_key_id, nathan_private_key);
+   db.push_transaction(trx);
+
+   BOOST_TEST_MESSAGE("Checking current_feed is null");
+   BOOST_CHECK(bitasset.current_feed.settlement_price.is_null());
+
+   BOOST_TEST_MESSAGE("Setting minimum feeds to 3");
+   op.new_options.minimum_feeds = 3;
+   trx.operations = {op};
+   trx.sign(nathan_key_id, nathan_private_key);
+   db.push_transaction(trx);
+
+   BOOST_TEST_MESSAGE("Checking current_feed is not null");
+   BOOST_CHECK(!bitasset.current_feed.settlement_price.is_null());
+} FC_LOG_AND_RETHROW() }
+
 BOOST_AUTO_TEST_CASE( witness_create )
 { try {
    ACTOR(nathan);