refactor: Tilgungsplan-Helfer schedule_for, Kredit-Laufzeit 1–1200 Monate (A14-T5)

- Neuer schedule_for() in app/engine/loans.py: vereinheitlicht Tilgungsplan-Erstellung
- Laufzeit-Validierung in LoanIn und LoanPatch: 1–1200 Monate
- Aufrufstellen aktualisiert (routers/planning.py, services/breakdown.py,
  services/projection_service.py, services/planning_chart.py)
- Keine direkten loan_schedule(Decimal(...)) Aufrufe außerhalb engine/loans.py mehr
- Tests für schedule_for und Laufzeit-Grenzen (1, 1200, sowie 0/-5/1201 Ablehnung)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

finance/app/engine/loans.py

@@ -54,3 +54,11 @@ def loan_schedule(principal: Decimal, annual_rate_pct: Decimal, term_months: int
                                 -(interest + principal_part), interest,
                                 principal_part, remaining.quantize(CENT)))
     return plan
+
+
+def schedule_for(loan) -> list[Installment]:
+    """Tilgungsplan eines Kredit-Objekts (ORM-Loan oder gleichartig mit
+    principal, annual_rate_pct, term_months, payout_date, repayment_type).
+    Ersetzt die wiederholte Feld-für-Feld-Übergabe an loan_schedule (A14)."""
+    return loan_schedule(Decimal(loan.principal), Decimal(loan.annual_rate_pct),
+                         loan.term_months, loan.payout_date, loan.repayment_type)

finance/app/routers/planning.py

@@ -9,7 +9,7 @@ from sqlalchemy.orm import Session
 
 from app.auth import require_auth
 from app.db import get_session
-from app.engine.loans import loan_schedule
+from app.engine.loans import schedule_for
 from app.models.tables import (Category, Loan, PlannedItem, RecurringItem,
                                ScenarioLoan)
 from app.services.double_count import (CODE as DOPPELZAEHLUNG_CODE, Konflikt,
@@ -227,7 +227,7 @@ class LoanIn(BaseModel):
     name: str
     principal: Decimal
     annual_rate_pct: Decimal
-    term_months: int
+    term_months: int = Field(ge=1, le=1200)
     payout_date: date
     repayment_type: Literal["annuity", "bullet"] = "annuity"
 
@@ -245,7 +245,7 @@ class LoanPatch(BaseModel):
     name: str | None = None
     principal: Decimal | None = None
     annual_rate_pct: Decimal | None = None
-    term_months: int | None = None
+    term_months: int | None = Field(default=None, ge=1, le=1200)
     payout_date: date | None = None
     repayment_type: Literal["annuity", "bullet"] | None = None
     doppelzaehlung_bestaetigt: bool = False
@@ -318,8 +318,7 @@ def get_loan_schedule(loan_id: int, session: Session = Depends(get_session)):
     loan = session.get(Loan, loan_id)
     if loan is None:
         raise HTTPException(404, "Kredit nicht gefunden")
-    plan = loan_schedule(Decimal(loan.principal), Decimal(loan.annual_rate_pct),
-                         loan.term_months, loan.payout_date, loan.repayment_type)
+    plan = schedule_for(loan)
     return [InstallmentOut(due=i.due, payment=i.payment, interest=i.interest,
                            principal=i.principal, remaining=i.remaining)
            for i in plan]

finance/app/services/breakdown.py

@@ -5,14 +5,13 @@ Modifikatoren) - dieselbe Datenbasis wie load_scenario_inputs(None).
 """
 from dataclasses import dataclass
 from datetime import date
-from decimal import Decimal
 
 from sqlalchemy import select
 from sqlalchemy.orm import Session
 
 from app.engine.breakdown import (BreakdownRow, Filters, PlainLoan, Summary,
                                   breakdown_rows, summarize)
-from app.engine.loans import loan_schedule
+from app.engine.loans import schedule_for
 from app.models.tables import Category, Scenario
 from app.reserved import SYSTEM_PREFIX
 from app.services.double_count import Konflikt, all_conflicts
@@ -34,10 +33,7 @@ def compute_breakdown(session: Session, month: date, scenario: Scenario | None,
                       filters: Filters) -> Breakdown:
     inputs = load_scenario_inputs(session, scenario)
     names = {c.id: c.name for c in session.execute(select(Category)).scalars()}
-    loans = [PlainLoan(l.id, l.name,
-                       loan_schedule(Decimal(l.principal), Decimal(l.annual_rate_pct),
-                                     l.term_months, l.payout_date, l.repayment_type))
-             for l in inputs.loans]
+    loans = [PlainLoan(l.id, l.name, schedule_for(l)) for l in inputs.loans]
     rows = breakdown_rows(month, inputs.recurring, inputs.planned, loans,
                           inputs.modifiers, filters, category_names=names,
                           loan_category=KREDITRATEN, uncategorized=UNKATEGORISIERT)

finance/app/services/planning_chart.py

@@ -15,7 +15,7 @@ from sqlalchemy.orm import Session
 
 from app.config import get_settings
 from app.db import advisory_xact_lock
-from app.engine.loans import loan_schedule
+from app.engine.loans import schedule_for
 from app.engine.recurrence import occurrences
 from app.models.tables import (Category, Loan, PlannedItem, PlanningMonthly,
                                RecurringItem)
@@ -46,9 +46,7 @@ def planning_monthly_totals(session: Session, today: date,
         if window_start <= p.due <= window_end:
             totals[(p.due.replace(day=1), category(p.category_id))] += Decimal(p.amount)
     for loan in session.execute(select(Loan)).scalars():
-        for inst in loan_schedule(Decimal(loan.principal), Decimal(loan.annual_rate_pct),
-                                  loan.term_months, loan.payout_date,
-                                  loan.repayment_type):
+        for inst in schedule_for(loan):
             if window_start <= inst.due <= window_end:
                 # payment ist bereits negativ (Abfluss), wie in build_cashflows.
                 totals[(inst.due.replace(day=1), KREDITRATEN)] += inst.payment

finance/app/services/projection_service.py

@@ -8,7 +8,7 @@ from sqlalchemy.orm import Session
 
 from app.config import get_settings
 from app.db import advisory_xact_lock
-from app.engine.loans import loan_schedule
+from app.engine.loans import schedule_for
 from app.engine.projection import project
 from app.engine.scenario import (PlainModifier, PlainPlanned, PlainRecurring,
                                  build_cashflows)
@@ -76,9 +76,7 @@ def run_projection(session: Session, scenario: Scenario, horizon_days: int,
                    start_date: date) -> ProjectionResult:
     end = start_date + timedelta(days=horizon_days)
     inputs = load_scenario_inputs(session, scenario)
-    schedules = [loan_schedule(Decimal(l.principal), Decimal(l.annual_rate_pct),
-                               l.term_months, l.payout_date, l.repayment_type)
-                 for l in inputs.loans]
+    schedules = [schedule_for(l) for l in inputs.loans]
     payouts = [(l.payout_date, Decimal(l.principal)) for l in inputs.loans]
     flows = build_cashflows(inputs.recurring, inputs.planned, schedules, payouts,
                             inputs.modifiers, start_date, end)

finance/tests/test_loans.py

@@ -27,3 +27,21 @@ def test_bullet_loan():
     assert all(i.principal == 0 for i in plan[:-1])
     assert plan[-1].principal == Decimal("10000")
     assert plan[-1].remaining == Decimal("0.00")
+
+
+def test_schedule_for_entspricht_loan_schedule():
+    from types import SimpleNamespace
+    from app.engine.loans import schedule_for
+    kredit = SimpleNamespace(principal="1200.00", annual_rate_pct="3.00", term_months=12,
+                             payout_date=date(2030, 1, 31), repayment_type="annuity")
+    assert schedule_for(kredit) == loan_schedule(Decimal("1200.00"), Decimal("3.00"), 12,
+                                                 date(2030, 1, 31), "annuity")
+
+
+def test_keine_manuelle_tilgungsplan_konvertierung_mehr():
+    from pathlib import Path
+    app_dir = Path(__file__).resolve().parent.parent / "app"
+    engine_loans = app_dir / "engine" / "loans.py"
+    treffer = [str(p.relative_to(app_dir)) for p in app_dir.rglob("*.py")
+               if p != engine_loans and "loan_schedule(Decimal(" in p.read_text()]
+    assert treffer == []

finance/tests/test_planning_api.py

@@ -2,6 +2,8 @@ from datetime import date
 from decimal import Decimal
 from itertools import count
 
+import pytest
+
 from app.models.tables import Account, Category, RecurringItem, Transaction
 from app.services.suggestions import _Series, _try_merge, suggest_recurring
 
@@ -368,3 +370,25 @@ def test_suggest_volatilitaetshinweis_bei_abgetrennter_neuester_buchung(db):
     assert len(out) == 1
     assert out[0]["amount"] == Decimal("-200.00")  # Betrag NICHT durch die 600er-Buchung verfaelscht
     assert "schwanken" in out[0]["hinweis"].lower()
+
+
+# ----------------------------------------------------------- Ausbaustufe 14: Task 5
+KREDIT = {"name": "Laufzeit-Test", "principal": "1000.00", "annual_rate_pct": "2.00",
+          "payout_date": "2030-01-01", "repayment_type": "annuity"}
+
+
+@pytest.mark.parametrize("laufzeit", [0, -5, 1201])
+def test_kredit_laufzeit_ausserhalb_1_bis_1200(client, laufzeit):
+    r = client.post("/api/loans", headers=H, json={**KREDIT, "term_months": laufzeit})
+    assert r.status_code == 422
+
+
+def test_kredit_laufzeit_grenzen_und_patch(client):
+    a = client.post("/api/loans", headers=H, json={**KREDIT, "term_months": 1})
+    b = client.post("/api/loans", headers=H, json={**KREDIT, "name": "L2", "term_months": 1200})
+    assert (a.status_code, b.status_code) == (201, 201)
+    url = f"/api/loans/{a.json()['id']}"
+    assert client.patch(url, headers=H, json={"term_months": 0}).status_code == 422
+    assert client.patch(url, headers=H, json={"term_months": 1201}).status_code == 422
+    r = client.patch(url, headers=H, json={"term_months": 1200})
+    assert r.status_code == 200 and r.json()["term_months"] == 1200