Rework real estate model: purchase price + mortgage + amortization only, no appreciation; amortization counts against savings quota; sale price/tax entered at transition time with correct mortgage payoff; carry over income/expenses to new phases

src/lib/calculations.ts

@@ -14,14 +14,10 @@ export interface SecurityComputed {
 export interface RealEstateComputed {
   id: string;
   name: string;
+  purchasePrice: number; // fix ueber die Haltedauer, keine Wertsteigerung im vereinfachten Modell
   startNet: number;
-  endNetIfKept: number;
-  sold: boolean;
-  saleNetProceeds: number | null;
-  taxAmount: number;
-  endContribution: number; // was tatsaechlich in die Endvermoegens-Summe der Phase einfliesst
-  marketValues: number[];
-  mortgages: number[];
+  endNet: number;
+  mortgages: number[]; // Index 0 = Start, Index durationYears = Ende
 }
 
 export interface RetirementComputed {
@@ -88,20 +84,18 @@ export function computeSecurityYearlyValues(
   return values;
 }
 
-export function computeRealEstateYearly(
-  marketValue: number,
+// Vereinfachtes Modell (keine Wertsteigerung): der Kaufpreis bleibt ueber die ganze
+// Haltedauer fix, nur die Hypothek sinkt jaehrlich um die Amortisationsrate.
+export function computeMortgageYearly(
   mortgage: number,
-  valueGrowth: number,
   amortization: number,
   durationYears: number
-): { marketValues: number[]; mortgages: number[] } {
-  const marketValues = [floorToThousand(marketValue)];
+): number[] {
   const mortgages = [floorToThousand(mortgage)];
   for (let year = 1; year <= durationYears; year++) {
-    marketValues.push(floorToThousand(marketValues[year - 1] * (1 + valueGrowth / 100)));
     mortgages.push(floorToThousand(Math.max(0, mortgages[year - 1] - amortization)));
   }
-  return { marketValues, mortgages };
+  return mortgages;
 }
 
 function computeRetirement(
@@ -149,7 +143,11 @@ function computePhase(
   const retirement = computeRetirement(household, phase);
   const effectiveIncome = incomeFromEntries + (retirement?.totalPensionIncome ?? 0);
   const savingsQuota = effectiveIncome - expenseTotal;
-  const allocatedSavings = phase.securities.reduce((sum, s) => sum + s.annualContribution, 0);
+  // Amortisationsraten aller Immobilien zaehlen gleichwertig mit den Sparbeitraegen der
+  // Wertschriften gegen dieselbe verfuegbare Sparquote (ein gemeinsamer Topf).
+  const allocatedSavings =
+    phase.securities.reduce((sum, s) => sum + s.annualContribution, 0) +
+    phase.realEstates.reduce((sum, re) => sum + re.amortization, 0);
   const savingsWarning = allocatedSavings > savingsQuota;
 
   const securities: SecurityComputed[] = phase.securities.map((s) => {
@@ -170,34 +168,14 @@ function computePhase(
   });
 
   const realEstates: RealEstateComputed[] = phase.realEstates.map((re) => {
-    const { marketValues, mortgages } = computeRealEstateYearly(
-      re.marketValue,
-      re.mortgage,
-      re.valueGrowth,
-      re.amortization,
-      phase.durationYears
-    );
-    const startNet = marketValues[0] - mortgages[0];
-    const endNetIfKept = marketValues[phase.durationYears] - mortgages[phase.durationYears];
-    const sold = re.salePrice != null;
-    let saleNetProceeds: number | null = null;
-    let taxAmount = 0;
-    if (sold) {
-      // Vereinfachung gemaess TDD 3.3: Gewinn = Verkaufspreis - urspruenglich erfasster Startwert
-      const gain = Math.max(0, re.salePrice! - re.marketValue);
-      taxAmount = gain * (re.saleTaxRate / 100);
-      saleNetProceeds = floorToThousand(re.salePrice! - taxAmount);
-    }
+    const mortgages = computeMortgageYearly(re.mortgage, re.amortization, phase.durationYears);
+    const purchasePrice = floorToThousand(re.purchasePrice);
     return {
       id: re.id,
       name: re.name,
-      startNet,
-      endNetIfKept,
-      sold,
-      saleNetProceeds,
-      taxAmount,
-      endContribution: sold ? saleNetProceeds! : endNetIfKept,
-      marketValues,
+      purchasePrice,
+      startNet: purchasePrice - mortgages[0],
+      endNet: purchasePrice - mortgages[phase.durationYears],
       mortgages,
     };
   });
@@ -213,7 +191,7 @@ function computePhase(
 
   const endWealthNominal =
     securities.reduce((sum, s) => sum + s.endValue, 0) +
-    realEstates.reduce((sum, re) => sum + re.endContribution, 0) +
+    realEstates.reduce((sum, re) => sum + re.endNet, 0) +
     oneTimeNet +
     (retirement?.lumpSumNetTotal ?? 0);
 
@@ -226,16 +204,13 @@ function computePhase(
   for (let year = 1; year <= phase.durationYears; year++) {
     let value =
       securities.reduce((sum, s) => sum + s.yearly[year], 0) +
-      realEstates.reduce((sum, re) => sum + (re.marketValues[year] - re.mortgages[year]), 0);
+      realEstates.reduce((sum, re) => sum + (re.purchasePrice - re.mortgages[year]), 0);
     if (year === phase.durationYears) {
-      // Einmalige Ereignisse, Verkaufserloese und Kapitalbezuege schlagen erst am Ende
-      // der Phase zu Buche (siehe Phasenuebergang, TDD Kapitel 10).
+      // Einmalige Ereignisse und Kapitalbezuege schlagen erst am Ende der Phase zu
+      // Buche (siehe Phasenuebergang, TDD Kapitel 10). Immobilien-/Wertschriften-
+      // Verkaeufe wirken sich nur auf die naechste Phase aus (incomingCapital), nicht
+      // mehr auf das Endvermoegen dieser Phase selbst.
       value += oneTimeNet + (retirement?.lumpSumNetTotal ?? 0);
-      const soldReplacement = realEstates.reduce(
-        (sum, re) => sum + (re.sold ? re.saleNetProceeds! - (re.marketValues[year] - re.mortgages[year]) : 0),
-        0
-      );
-      value += soldReplacement;
     }
     yearlyNominal.push(value);
   }