Tasa Cero: auto-detect 'CC ' vouchers + /installment-plans API

Ingestion auto-converts CC-prefixed credit-card purchases (default 3
cuotas, push note appended). CRUD endpoints cover manual convert (e.g.
ALMACENES SIMAN), edit-with-regeneration, and unconvert; anchor deletion
tears down the plan; cuotas cannot be deferred.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/api/v1/endpoints/transactions.py

@@ -21,9 +21,19 @@ from app.models.models import (
     TransactionUpdate,
 )
 
-from app.services.budget_projection import get_cycle_range, get_previous_cycle
+from app.services.budget_projection import (
+    NOT_INSTALLMENT_ANCHOR,
+    get_cycle_range,
+    get_previous_cycle,
+)
 from app.services.csv_export import build_transactions_csv
 from app.services.exchange_rate import get_converted_amount_expr
+from app.services.installments import (
+    DEFAULT_NUM_INSTALLMENTS,
+    create_plan,
+    is_tasa_cero_merchant,
+    teardown_plan_for_anchor,
+)
 
 router = APIRouter(prefix="/transactions", tags=["transactions"])
 
@@ -130,17 +140,22 @@ def bulk_action(
     txs = session.exec(
         select(Transaction).where(col(Transaction.id).in_(req.ids))
     ).all()
+    affected = 0
     for tx in txs:
         if req.action == "delete":
+            teardown_plan_for_anchor(session, tx)
             session.delete(tx)
         elif req.action == "set_category":
             tx.category_id = req.category_id
             session.add(tx)
         elif req.action == "set_deferred":
+            if tx.installment_plan_id:
+                continue  # cuotas of a plan cannot be deferred
             tx.deferred_to_next_cycle = bool(req.deferred)
             session.add(tx)
+        affected += 1
     session.commit()
-    return {"affected": len(txs)}
+    return {"affected": affected}
 
 
 @router.get("/export")
@@ -205,7 +220,9 @@ def list_billing_cycles(
         # Count transactions in this cycle
         count_result = session.exec(
             select(func.count(), func.coalesce(func.sum(amount_crc), 0)).where(
-                Transaction.date >= start, Transaction.date < end
+                Transaction.date >= start,
+                Transaction.date < end,
+                NOT_INSTALLMENT_ANCHOR,
             )
         ).first()
         count = count_result[0] if count_result else 0
@@ -268,6 +285,20 @@ def create_transaction(
     session.commit()
     session.refresh(tx)
 
+    # Tasa Cero auto-detection: BAC prefixes financed purchases with "CC ".
+    # Default 3 cuotas starting on the purchase date; editable afterwards via
+    # /installment-plans.
+    tasa_cero_note = ""
+    if (
+        tx.source == TransactionSource.CREDIT_CARD
+        and tx.transaction_type == TransactionType.COMPRA
+        and is_tasa_cero_merchant(tx.merchant)
+    ):
+        create_plan(session, tx, DEFAULT_NUM_INSTALLMENTS, tx.date)
+        session.commit()
+        session.refresh(tx)
+        tasa_cero_note = f" — Tasa Cero {DEFAULT_NUM_INSTALLMENTS} cuotas"
+
     # Send push notification
     symbols = {Currency.CRC: "₡", Currency.USD: "$", Currency.EUR: "€"}
     symbol = symbols.get(tx.currency, tx.currency.value)
@@ -278,7 +309,7 @@ def create_transaction(
     send_push_to_all(
         session,
         title=f"{'🏦' if is_income else '💳'} {tx.merchant}",
-        body=f"{amount_str} — {tx.bank.value} {label}",
+        body=f"{amount_str} — {tx.bank.value} {label}{tasa_cero_note}",
         url="/salarios" if is_income else "/budget",
     )
 
@@ -300,6 +331,11 @@ def update_transaction(
     if not tx:
         raise HTTPException(status_code=404, detail="Transaction not found")
     update_data = data.model_dump(exclude_unset=True)
+    if update_data.get("deferred_to_next_cycle") is not None and tx.installment_plan_id:
+        raise HTTPException(
+            status_code=400,
+            detail="Cuotas of an installment plan cannot be deferred",
+        )
     for key, value in update_data.items():
         setattr(tx, key, value)
     session.add(tx)
@@ -317,5 +353,6 @@ def delete_transaction(
     tx = session.get(Transaction, transaction_id)
     if not tx:
         raise HTTPException(status_code=404, detail="Transaction not found")
+    teardown_plan_for_anchor(session, tx)
     session.delete(tx)
     session.commit()