feat: API meldet mögliche Doppelzählung mit 409, Speichern nur mit Bestätigung (A12-T3)

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

finance/app/routers/planning.py

@@ -12,6 +12,10 @@ from app.db import get_session
 from app.engine.loans import loan_schedule
 from app.models.tables import (Category, Loan, PlannedItem, RecurringItem,
                                ScenarioLoan)
+from app.services.double_count import (CODE as DOPPELZAEHLUNG_CODE, Konflikt,
+                                       KreditDaten, PostenDaten,
+                                       conflicts_for_loan, conflicts_for_recurring,
+                                       kredit_aus, posten_aus)
 from app.services.suggestions import suggest_recurring
 
 router = APIRouter(prefix="/api", tags=["planning"],
@@ -36,6 +40,11 @@ class RecurringIn(BaseModel):
         return self
 
 
+class RecurringCreate(RecurringIn):
+    # Nur Anfrage: bestätigt eine erkannte Doppelzählung (nicht gespeichert).
+    doppelzaehlung_bestaetigt: bool = False
+
+
 class RecurringOut(RecurringIn):
     model_config = ConfigDict(from_attributes=True)
     id: int
@@ -49,6 +58,7 @@ class RecurringPatch(BaseModel):
     start_date: date | None = None
     end_date: date | None = None
     category_id: int | None = None
+    doppelzaehlung_bestaetigt: bool = False
 
 
 class SuggestionOut(BaseModel):
@@ -66,6 +76,26 @@ def _check_category(session: Session, category_id: int | None) -> None:
         raise HTTPException(404, "Kategorie nicht gefunden")
 
 
+_CENT = Decimal("0.01")
+_FLAG = "doppelzaehlung_bestaetigt"
+
+
+def _doppelzaehlung(konflikte: list[Konflikt]) -> HTTPException:
+    """409 mit strukturierter Erklärung; die GUI zeigt daraus das Warnfenster."""
+    return HTTPException(409, detail={
+        "code": DOPPELZAEHLUNG_CODE,
+        "meldung": ("Der Betrag entspricht vermutlich einer Kreditrate, die bereits "
+                    "über „Kredite“ eingeplant ist (oder umgekehrt). Beide zusammen "
+                    "zählen die Rate doppelt – Planung und Szenarien wären zu "
+                    "pessimistisch. Nur speichern, wenn das wirklich gewollt ist."),
+        "konflikte": [{"posten": k.posten_name,
+                       "posten_betrag": str(k.posten_betrag.quantize(_CENT)),
+                       "kredit": k.kredit_name,
+                       "kredit_rate": str(k.kredit_rate.quantize(_CENT))}
+                      for k in konflikte],
+    })
+
+
 @router.get("/recurring", response_model=list[RecurringOut])
 def list_recurring(session: Session = Depends(get_session)):
     return [RecurringOut.model_validate(r)
@@ -73,9 +103,16 @@ def list_recurring(session: Session = Depends(get_session)):
 
 
 @router.post("/recurring", response_model=RecurringOut, status_code=201)
-def create_recurring(data: RecurringIn, session: Session = Depends(get_session)):
+def create_recurring(data: RecurringCreate, session: Session = Depends(get_session)):
     _check_category(session, data.category_id)
-    item = RecurringItem(**data.model_dump())
+    fields = data.model_dump(exclude={_FLAG})
+    if not data.doppelzaehlung_bestaetigt:
+        konflikte = conflicts_for_recurring(session, PostenDaten(
+            None, fields["name"], fields["amount"], fields["rhythm"],
+            fields["start_date"], fields["end_date"]))
+        if konflikte:
+            raise _doppelzaehlung(konflikte)
+    item = RecurringItem(**fields)
     session.add(item)
     session.commit()
     session.refresh(item)
@@ -94,7 +131,8 @@ def patch_recurring(item_id: int, data: RecurringPatch,
     item = session.get(RecurringItem, item_id)
     if item is None:
         raise HTTPException(404, "Fixposten nicht gefunden")
-    fields = data.model_dump(exclude_unset=True)
+    vorher = {k.paar for k in conflicts_for_recurring(session, posten_aus(item))}
+    fields = data.model_dump(exclude_unset=True, exclude={_FLAG})
     if "category_id" in fields:
         _check_category(session, fields["category_id"])
     for key, value in fields.items():
@@ -103,6 +141,12 @@ def patch_recurring(item_id: int, data: RecurringPatch,
             and item.end_date < item.start_date):
         session.rollback()
         raise HTTPException(422, "Ende darf nicht vor Start liegen")
+    if not data.doppelzaehlung_bestaetigt:
+        neu = [k for k in conflicts_for_recurring(session, posten_aus(item))
+               if k.paar not in vorher]
+        if neu:
+            session.rollback()
+            raise _doppelzaehlung(neu)
     session.commit()
     session.refresh(item)
     return RecurringOut.model_validate(item)
@@ -188,6 +232,10 @@ class LoanIn(BaseModel):
     repayment_type: Literal["annuity", "bullet"] = "annuity"
 
 
+class LoanCreate(LoanIn):
+    doppelzaehlung_bestaetigt: bool = False
+
+
 class LoanOut(LoanIn):
     model_config = ConfigDict(from_attributes=True)
     id: int
@@ -200,6 +248,7 @@ class LoanPatch(BaseModel):
     term_months: int | None = None
     payout_date: date | None = None
     repayment_type: Literal["annuity", "bullet"] | None = None
+    doppelzaehlung_bestaetigt: bool = False
 
 
 class InstallmentOut(BaseModel):
@@ -217,8 +266,15 @@ def list_loans(session: Session = Depends(get_session)):
 
 
 @router.post("/loans", response_model=LoanOut, status_code=201)
-def create_loan(data: LoanIn, session: Session = Depends(get_session)):
-    loan = Loan(**data.model_dump())
+def create_loan(data: LoanCreate, session: Session = Depends(get_session)):
+    fields = data.model_dump(exclude={_FLAG})
+    if not data.doppelzaehlung_bestaetigt:
+        konflikte = conflicts_for_loan(session, KreditDaten(
+            None, fields["name"], fields["principal"], fields["annual_rate_pct"],
+            fields["term_months"], fields["payout_date"], fields["repayment_type"]))
+        if konflikte:
+            raise _doppelzaehlung(konflikte)
+    loan = Loan(**fields)
     session.add(loan)
     session.commit()
     session.refresh(loan)
@@ -230,8 +286,15 @@ def patch_loan(loan_id: int, data: LoanPatch, session: Session = Depends(get_ses
     loan = session.get(Loan, loan_id)
     if loan is None:
         raise HTTPException(404, "Kredit nicht gefunden")
-    for key, value in data.model_dump(exclude_unset=True).items():
+    vorher = {k.paar for k in conflicts_for_loan(session, kredit_aus(loan))}
+    for key, value in data.model_dump(exclude_unset=True, exclude={_FLAG}).items():
         setattr(loan, key, value)
+    if not data.doppelzaehlung_bestaetigt:
+        neu = [k for k in conflicts_for_loan(session, kredit_aus(loan))
+               if k.paar not in vorher]
+        if neu:
+            session.rollback()
+            raise _doppelzaehlung(neu)
     session.commit()
     session.refresh(loan)
     return LoanOut.model_validate(loan)