feat: Add WithinMedianDeviation keeper method (#1613)

* Add WithinMedianDeviation keeper method

* Fix comment

* Update x/oracle/keeper/historic_price.go

Co-authored-by: Robert Zaremba <robert@zaremba.ch>

* Cleanup WithinMedianDeviation method

Co-authored-by: Robert Zaremba <robert@zaremba.ch>

x/oracle/keeper/historic_price.go

@@ -106,6 +106,26 @@ func (k Keeper) GetMedianDeviation(
 	return decProto.Dec, nil
 }
 
+// WithinMedianDeviation returns whether or not a given price of a given
+// denom is within the Standard Deviation around the Median.
+func (k Keeper) WithinMedianDeviation(
+	ctx sdk.Context,
+	denom string,
+	price sdk.Dec,
+) (bool, error) {
+	median, err := k.GetMedian(ctx, denom)
+	if err != nil {
+		return false, err
+	}
+
+	medianDeviation, err := k.GetMedianDeviation(ctx, denom)
+	if err != nil {
+		return false, err
+	}
+
+	return price.Sub(median).Abs().LTE(medianDeviation), nil
+}
+
 // setMedianDeviation sets a given denom's standard deviation around
 // its median price in the last prune period since the current block.
 func (k Keeper) calcAndSetMedianDeviation(

x/oracle/keeper/historic_price_test.go

@@ -10,12 +10,6 @@ import (
 func (s *IntegrationTestSuite) TestSetHistoraclePricing() {
 	app, ctx := s.app, s.ctx
 
-	// set exchange rate in store before adding a historic price
-	app.OracleKeeper.SetExchangeRate(ctx, displayDenom, sdk.OneDec())
-	rate, err := app.OracleKeeper.GetExchangeRate(ctx, displayDenom)
-	s.Require().NoError(err)
-	s.Require().Equal(rate, sdk.OneDec())
-
 	// add multiple historic prices to store
 	exchangeRates := []string{"1.0", "1.2", "1.1", "1.4"}
 	for _, exchangeRate := range exchangeRates {
@@ -35,6 +29,16 @@ func (s *IntegrationTestSuite) TestSetHistoraclePricing() {
 	s.Require().NoError(err)
 	s.Require().Equal(medianDeviation, sdk.MustNewDecFromStr("0.0225"))
 
+	// check prices are within the median deviation
+	price1 := sdk.MustNewDecFromStr("1.13")
+	price2 := sdk.MustNewDecFromStr("1.12")
+	result, err := app.OracleKeeper.WithinMedianDeviation(ctx, displayDenom, price1)
+	s.Require().Equal(result, true)
+	s.Require().NoError(err)
+	result, err = app.OracleKeeper.WithinMedianDeviation(ctx, displayDenom, price2)
+	s.Require().Equal(result, false)
+	s.Require().NoError(err)
+
 	// delete first historic price, median, and median standard deviation
 	app.OracleKeeper.DeleteHistoricPrice(ctx, displayDenom, uint64(ctx.BlockHeight()-3))
 	app.OracleKeeper.DeleteMedian(ctx, displayDenom)
@@ -47,4 +51,8 @@ func (s *IntegrationTestSuite) TestSetHistoraclePricing() {
 	medianDeviation, err = app.OracleKeeper.GetMedianDeviation(ctx, displayDenom)
 	s.Require().Error(err, sdkerrors.Wrap(types.ErrUnknownDenom, displayDenom))
 	s.Require().Equal(median, sdk.ZeroDec())
+
+	result, err = app.OracleKeeper.WithinMedianDeviation(ctx, displayDenom, price1)
+	s.Require().Error(err, sdkerrors.Wrap(types.ErrUnknownDenom, displayDenom))
+	s.Require().Equal(result, false)
 }