use interface for decay constructor

backend/src/graphql/model/Decay.ts

@@ -1,20 +1,22 @@
 import { ObjectType, Field, Int } from 'type-graphql'
 import Decimal from 'decimal.js-light'
 
+interface DecayInterface {
+  balance: Decimal
+  decay: Decimal
+  start: Date | null
+  end: Date | null
+  duration: number | null
+}
+
 @ObjectType()
 export class Decay {
-  constructor(
-    balance: Decimal,
-    decay: Decimal,
-    start: Date | null,
-    end: Date | null,
-    duration: number | null,
-  ) {
-    this.balance = balance
-    this.decay = decay
-    this.start = start
-    this.end = end
-    this.duration = duration
+  constructor(data: DecayInterface) {
+    this.balance = data.balance
+    this.decay = data.decay
+    this.start = data.start
+    this.end = data.end
+    this.duration = data.duration
   }
 
   @Field(() => Decimal)

backend/src/graphql/model/Transaction.ts

@@ -17,21 +17,23 @@ export class Transaction {
     this.balanceDate = transaction.balanceDate
     if (!transaction.decayStart) {
       // TODO: hot fix, we should separate decay calculation from decay graphql model
-      this.decay = new Decay(
-        transaction.balance.toDecimalPlaces(2, Decimal.ROUND_DOWN),
-        new Decimal(0),
-        null,
-        null,
-        null,
-      )
+      this.decay = new Decay({
+        balance: transaction.balance.toDecimalPlaces(2, Decimal.ROUND_DOWN),
+        decay: new Decimal(0),
+        start: null,
+        end: null,
+        duration: null,
+      })
     } else {
-      this.decay = new Decay(
-        transaction.balance.toDecimalPlaces(2, Decimal.ROUND_DOWN),
-        transaction.decay.toDecimalPlaces(2, Decimal.ROUND_FLOOR),
-        transaction.decayStart,
-        transaction.balanceDate,
-        Math.round((transaction.balanceDate.getTime() - transaction.decayStart.getTime()) / 1000),
-      )
+      this.decay = new Decay({
+        balance: transaction.balance.toDecimalPlaces(2, Decimal.ROUND_DOWN),
+        decay: transaction.decay.toDecimalPlaces(2, Decimal.ROUND_FLOOR),
+        start: transaction.decayStart,
+        end: transaction.balanceDate,
+        duration: Math.round(
+          (transaction.balanceDate.getTime() - transaction.decayStart.getTime()) / 1000,
+        ),
+      })
     }
     this.memo = transaction.memo
     this.creationDate = transaction.creationDate