feat: add differential fields to PositionChangedEvent: size and open …

…notional

proto/nibiru/perp/v2/event.proto

@@ -69,6 +69,24 @@ message PositionChangedEvent {
   // - CHANGE_REASON_CLOSE_POSITION: An existing position was closed.
   string change_reason = 9
       [ (gogoproto.customtype) = "ChangeReason", (gogoproto.nullable) = false ];
+
+  // exchanged_size represent the change in size for an existing position
+  // after the change. A positive value indicates that the position size
+  // increased, while a negative value indicates that the position size
+  // decreased.
+  string exchanged_size = 10 [
+    (gogoproto.customtype) = "github.com/cosmos/cosmos-sdk/types.Dec",
+    (gogoproto.nullable) = false
+  ];
+
+  // exchanged_notional represent the change in notional for an existing
+  // position after the change. A positive value indicates that the position
+  // notional increased, while a negative value indicates that the position
+  // notional decreased.
+  string exchanged_notional = 11 [
+    (gogoproto.customtype) = "github.com/cosmos/cosmos-sdk/types.Dec",
+    (gogoproto.nullable) = false
+  ];
 }
 
 // Emitted when a position is liquidated. Wraps a PositionChanged event since a

x/perp/v2/keeper/clearing_house.go

@@ -108,7 +108,7 @@ func (k Keeper) MarketOrder(
 	}
 
 	if err = k.afterPositionUpdate(
-		ctx, market, *updatedAMM, traderAddr, *positionResp, types.ChangeReason_MarketOrder,
+		ctx, market, *updatedAMM, traderAddr, *positionResp, types.ChangeReason_MarketOrder, position,
 	); err != nil {
 		return nil, err
 	}
@@ -537,6 +537,7 @@ func (k Keeper) afterPositionUpdate(
 	traderAddr sdk.AccAddress,
 	positionResp types.PositionResp,
 	changeType types.ChangeReason,
+	existingPosition types.Position,
 ) (err error) {
 	// transfer trader <=> vault
 	marginToVault := positionResp.MarginToVault.RoundInt()
@@ -576,15 +577,17 @@ func (k Keeper) afterPositionUpdate(
 
 	_ = ctx.EventManager().EmitTypedEvents(
 		&types.PositionChangedEvent{
-			FinalPosition:    positionResp.Position,
-			PositionNotional: positionNotional,
-			TransactionFee:   sdk.NewCoin(market.Pair.QuoteDenom(), transferredFee),
-			RealizedPnl:      positionResp.RealizedPnl,
-			BadDebt:          sdk.NewCoin(market.Pair.QuoteDenom(), positionResp.BadDebt.RoundInt()),
-			FundingPayment:   positionResp.FundingPayment,
-			BlockHeight:      ctx.BlockHeight(),
-			MarginToUser:     marginToVault.Neg().Sub(transferredFee),
-			ChangeReason:     changeType,
+			FinalPosition:     positionResp.Position,
+			PositionNotional:  positionNotional,
+			TransactionFee:    sdk.NewCoin(market.Pair.QuoteDenom(), transferredFee),
+			RealizedPnl:       positionResp.RealizedPnl,
+			BadDebt:           sdk.NewCoin(market.Pair.QuoteDenom(), positionResp.BadDebt.RoundInt()),
+			FundingPayment:    positionResp.FundingPayment,
+			BlockHeight:       ctx.BlockHeight(),
+			MarginToUser:      marginToVault.Neg().Sub(transferredFee),
+			ChangeReason:      changeType,
+			ExchangedSize:     positionResp.Position.Size_.Sub(existingPosition.Size_),
+			ExchangedNotional: positionResp.PositionNotional.Sub(existingPosition.OpenNotional),
 		},
 	)
 
@@ -726,6 +729,7 @@ func (k Keeper) ClosePosition(ctx sdk.Context, pair asset.Pair, traderAddr sdk.A
 		traderAddr,
 		*positionResp,
 		types.ChangeReason_ClosePosition,
+		position,
 	); err != nil {
 		return nil, err
 	}
@@ -887,6 +891,7 @@ func (k Keeper) PartialClose(
 		traderAddr,
 		*positionResp,
 		types.ChangeReason_PartialClose,
+		position,
 	)
 	if err != nil {
 		return nil, err