feat: Szenario-Einträge je Stichtag mit Zeitraum und Art Neuer Betrag (A14-T2)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

finance/app/engine/breakdown.py

@@ -3,7 +3,8 @@
 Rein (kein DB-Zugriff). Fixposten werden auf den Monat normalisiert
 (quartalsweise /3, jährlich /12), Einmalposten und Kreditraten zählen voll
 im Monat ihrer Fälligkeit; die Kredit-Auszahlung zählt nie. Modifikatoren
-wirken exakt wie in build_cashflows (gleiche Helfer).
+wirken wie in build_cashflows (gleiche Helfer); Stichtag je Fixposten ist sein
+Fälligkeitstag im Monat, je Einmalposten das Fälligkeitsdatum.
 """
 import calendar
 from collections import defaultdict
@@ -12,7 +13,7 @@ from datetime import date
 from decimal import ROUND_HALF_UP, Decimal
 
 from app.engine.loans import Installment
-from app.engine.recurrence import STEP
+from app.engine.recurrence import STEP, due_in_month
 from app.engine.scenario import (CENT, PlainModifier, PlainPlanned,
                                  PlainRecurring, effective_end, modified_amount)
 
@@ -77,7 +78,8 @@ def breakdown_rows(month: date, recurring: list[PlainRecurring],
             end = effective_end(r, modifiers)
             if end is not None and end < first:
                 continue
-            amount = modified_amount(r.amount, r.category_id, r.id, modifiers)
+            amount = modified_amount(r.amount, r.category_id, r.id, modifiers,
+                                     on=due_in_month(first, r.due_day))
             if amount is None:
                 continue
             monthly = (amount / STEP[r.rhythm]).quantize(CENT, ROUND_HALF_UP)
@@ -87,7 +89,7 @@ def breakdown_rows(month: date, recurring: list[PlainRecurring],
         for p in planned:
             if not first <= p.due <= last:
                 continue
-            amount = modified_amount(p.amount, p.category_id, None, modifiers)
+            amount = modified_amount(p.amount, p.category_id, None, modifiers, on=p.due)
             if amount is None:
                 continue
             out.append(BreakdownRow(p.name, cat(p.category_id), "planned", None,

finance/app/engine/recurrence.py

@@ -8,6 +8,12 @@ def _clamp(y: int, m: int, day: int) -> date:
     return date(y, m, min(day, calendar.monthrange(y, m)[1]))
 
 
+def due_in_month(month: date, due_day: int) -> date:
+    """Fälligkeitstag `due_day` im Monat von `month`, auf die Monatslänge
+    geklemmt (gleiche Regel wie occurrences)."""
+    return _clamp(month.year, month.month, due_day)
+
+
 def occurrences(rhythm: str, due_day: int, window_start: date, window_end: date,
                 item_start: date | None = None, item_end: date | None = None) -> list[date]:
     step = STEP[rhythm]

finance/app/engine/scenario.py

@@ -10,7 +10,7 @@ CENT = Decimal("0.01")
 
 @dataclass(frozen=True)
 class PlainRecurring:
-    id: int
+    id: int | None            # None = szenario-eigene Zahlung (Posten-Einträge treffen sie nie)
     name: str
     amount: Decimal
     rhythm: str
@@ -34,19 +34,36 @@ class PlainModifier:
     target_id: int
     kind: str
     value: Decimal
-    end_date: date | None = None
+    end_date: date | None = None     # ende: Enddatum; sonst „Gültig bis" (inklusiv)
+    start_date: date | None = None   # „Gültig ab" (inklusiv); bei ende immer None
+
+
+def _trifft(m: PlainModifier, category_id: int | None, recurring_id: int | None) -> bool:
+    return ((m.target_type == "category" and category_id is not None
+             and category_id == m.target_id)
+            or (m.target_type == "recurring" and recurring_id is not None
+                and recurring_id == m.target_id))
+
+
+def gilt_am(m: PlainModifier, on: date) -> bool:
+    """Liegt der Stichtag im Zeitraum des Eintrags (Grenzen inklusiv)?"""
+    return ((m.start_date is None or on >= m.start_date)
+            and (m.end_date is None or on <= m.end_date))
 
 
 def modified_amount(amount: Decimal, category_id: int | None, recurring_id: int | None,
-                    modifiers: list[PlainModifier]) -> Decimal | None:
+                    modifiers: list[PlainModifier], *, on: date) -> Decimal | None:
+    """Betrag einer Fälligkeit am Stichtag `on` nach allen treffenden, dort
+    gültigen Einträgen in Anlage-Reihenfolge. None = entfällt. Art "ende"
+    wirkt nur über effective_end."""
     for m in modifiers:
-        hit = ((m.target_type == "category" and category_id == m.target_id)
-               or (m.target_type == "recurring" and recurring_id == m.target_id))
-        if not hit:
+        if m.kind == "ende" or not _trifft(m, category_id, recurring_id) or not gilt_am(m, on):
             continue
         if m.kind == "remove":
             return None
-        if m.kind == "percent":
+        if m.kind == "set":
+            amount = m.value
+        elif m.kind == "percent":
             amount = (amount * (Decimal(100) - m.value) / Decimal(100)).quantize(CENT, ROUND_HALF_UP)
         elif m.kind == "absolute":
             if amount < 0:
@@ -57,15 +74,12 @@ def modified_amount(amount: Decimal, category_id: int | None, recurring_id: int
 
 
 def effective_end(r: PlainRecurring, modifiers: list[PlainModifier]) -> date | None:
-    """Fruehestes Ende aus eigenem end_date und allen treffenden ende-Modifikatoren."""
+    """Frühestes Ende aus eigenem end_date und allen treffenden ende-Modifikatoren."""
     end = r.end_date
     for m in modifiers:
-        if m.kind != "ende" or m.end_date is None:
+        if m.kind != "ende" or m.end_date is None or not _trifft(m, r.category_id, r.id):
             continue
-        hit = ((m.target_type == "category" and r.category_id == m.target_id)
-               or (m.target_type == "recurring" and r.id == m.target_id))
-        if hit:
-            end = m.end_date if end is None else min(end, m.end_date)
+        end = m.end_date if end is None else min(end, m.end_date)
     return end
 
 
@@ -76,15 +90,16 @@ def build_cashflows(recurring: list[PlainRecurring], planned: list[PlainPlanned]
                     window_start: date, window_end: date) -> list[tuple[date, Decimal]]:
     flows: list[tuple[date, Decimal]] = []
     for r in recurring:
-        amount = modified_amount(r.amount, r.category_id, r.id, modifiers)
-        if amount is None:
-            continue
         for d in occurrences(r.rhythm, r.due_day, window_start, window_end,
                              r.start_date, effective_end(r, modifiers)):
-            flows.append((d, amount))
+            amount = modified_amount(r.amount, r.category_id, r.id, modifiers, on=d)
+            if amount is not None:
+                flows.append((d, amount))
     for p in planned:
-        amount = modified_amount(p.amount, p.category_id, None, modifiers)
-        if amount is not None and window_start <= p.due <= window_end:
+        if not window_start <= p.due <= window_end:
+            continue
+        amount = modified_amount(p.amount, p.category_id, None, modifiers, on=p.due)
+        if amount is not None:
             flows.append((p.due, amount))
     for d, payout in loan_payouts:
         if window_start <= d <= window_end: