Merge pull request #1699 from gradido/fix_decay

Fix: Correct calculation of decay

backend/src/graphql/resolver/BalanceResolver.ts

@@ -54,19 +54,23 @@ export class BalanceResolver {
             },
           })
 
+    // The decay is always calculated on the last booked transaction
+    const calculatedDecay = calculateDecay(
+      lastTransaction.balance,
+      lastTransaction.balanceDate,
+      now,
+    )
+
+    // The final balance is reduced by the link amount withheld
     const transactionLinkRepository = getCustomRepository(TransactionLinkRepository)
     const { sumHoldAvailableAmount } = context.sumHoldAvailableAmount
       ? { sumHoldAvailableAmount: context.sumHoldAvailableAmount }
       : await transactionLinkRepository.summary(user.id, now)
 
-    const calculatedDecay = calculateDecay(
-      lastTransaction.balance.minus(sumHoldAvailableAmount.toString()),
-      lastTransaction.balanceDate,
-      now,
-    )
-
     return new Balance({
-      balance: calculatedDecay.balance.toDecimalPlaces(2, Decimal.ROUND_DOWN), // round towards zero
+      balance: calculatedDecay.balance
+        .minus(sumHoldAvailableAmount.toString())
+        .toDecimalPlaces(2, Decimal.ROUND_DOWN), // round towards zero
       decay: calculatedDecay.decay.toDecimalPlaces(2, Decimal.ROUND_FLOOR), // round towards - infinity
       lastBookedBalance: lastTransaction.balance.toDecimalPlaces(2, Decimal.ROUND_DOWN),
       balanceGDT,

backend/src/graphql/resolver/TransactionResolver.ts

@@ -203,12 +203,15 @@ export class TransactionResolver {
 
     // decay & link transactions
     if (currentPage === 1 && order === Order.DESC) {
+      // The virtual decay is always on the booked amount, not including the generated, not yet booked links,
+      // since the decay is substantially different when the amount is less
       transactions.push(
         virtualDecayTransaction(
-          lastTransaction.balance.minus(sumHoldAvailableAmount.toString()),
+          lastTransaction.balance,
           lastTransaction.balanceDate,
           now,
           self,
+          sumHoldAvailableAmount,
         ),
       )
       // virtual transaction for pending transaction-links sum

backend/src/util/virtualTransactions.ts

@@ -59,6 +59,7 @@ const virtualDecayTransaction = (
   balanceDate: Date,
   time: Date = new Date(),
   user: User,
+  holdAvailabeAmount: Decimal,
 ): Transaction => {
   const decay = calculateDecay(balance, balanceDate, time)
   // const balance = decay.balance.minus(lastTransaction.balance)
@@ -67,10 +68,12 @@ const virtualDecayTransaction = (
     userId: -1,
     previous: -1,
     typeId: TransactionTypeId.DECAY,
-    amount: decay.decay ? decay.decay : new Decimal(0), // new Decimal(0), // this kinda is wrong, but helps with the frontend query
-    balance: decay.balance,
+    amount: decay.decay ? decay.decay.toDecimalPlaces(2, Decimal.ROUND_FLOOR) : new Decimal(0), // new Decimal(0), // this kinda is wrong, but helps with the frontend query
+    balance: decay.balance
+      .minus(holdAvailabeAmount.toString())
+      .toDecimalPlaces(2, Decimal.ROUND_DOWN),
     balanceDate: time,
-    decay: decay.decay ? decay.decay : new Decimal(0),
+    decay: decay.decay ? decay.decay.toDecimalPlaces(2, Decimal.ROUND_FLOOR) : new Decimal(0),
     decayStart: decay.start,
     memo: '',
     creationDate: null,