Move slot expansion logic to ExchangeService

- Add get_available_slots() and _expand_availability_to_slots() to ExchangeService
- Update routes/exchange.py to use ExchangeService.get_available_slots()
- Remove all business logic from get_available_slots endpoint
- Add AvailabilityRepository to ExchangeService dependencies
- Add Availability and BookableSlot imports to ExchangeService
- Fix import path for validate_date_in_range (use date_validation module)
- Remove unused user_repo variable and import from routes/invites.py
- Fix mypy error in ValidationError by adding proper type annotation

backend/routes/exchange.py

@@ -1,17 +1,15 @@
 """Exchange routes for Bitcoin trading."""
 
 import uuid
-from datetime import UTC, date, datetime, timedelta
+from datetime import date
 
 from fastapi import APIRouter, Depends, HTTPException, Query, status
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from auth import require_permission
 from database import get_db
-from date_validation import validate_date_in_range
 from mappers import ExchangeMapper
 from models import (
-    Availability,
     BitcoinTransferMethod,
     ExchangeStatus,
     Permission,
@@ -25,7 +23,6 @@ from repositories.price import PriceRepository
 from schemas import (
     AdminExchangeResponse,
     AvailableSlotsResponse,
-    BookableSlot,
     ExchangeConfigResponse,
     ExchangePriceResponse,
     ExchangeRequest,
@@ -39,7 +36,6 @@ from shared_constants import (
     EUR_TRADE_MAX,
     EUR_TRADE_MIN,
     PREMIUM_PERCENTAGE,
-    SLOT_DURATION_MINUTES,
 )
 from utils.enum_validation import validate_enum
 
@@ -148,30 +144,6 @@ async def get_exchange_price(
 # =============================================================================
 
 
-def _expand_availability_to_slots(
-    avail: Availability, slot_date: date, booked_starts: set[datetime]
-) -> list[BookableSlot]:
-    """
-    Expand an availability block into individual slots, filtering out booked ones.
-    """
-    slots: list[BookableSlot] = []
-
-    # Start from the availability's start time
-    current_start = datetime.combine(slot_date, avail.start_time, tzinfo=UTC)
-    avail_end = datetime.combine(slot_date, avail.end_time, tzinfo=UTC)
-
-    while current_start + timedelta(minutes=SLOT_DURATION_MINUTES) <= avail_end:
-        slot_end = current_start + timedelta(minutes=SLOT_DURATION_MINUTES)
-
-        # Only include if not already booked
-        if current_start not in booked_starts:
-            slots.append(BookableSlot(start_time=current_start, end_time=slot_end))
-
-        current_start = slot_end
-
-    return slots
-
-
 @router.get("/slots", response_model=AvailableSlotsResponse)
 async def get_available_slots(
     date_param: date = Query(..., alias="date"),
@@ -185,32 +157,8 @@ async def get_available_slots(
     - Fall within admin-defined availability windows
     - Are not already booked by another user
     """
-    validate_date_in_range(date_param, context="book")
-
-    # Get availability for the date
-    from repositories.availability import AvailabilityRepository
-    from repositories.exchange import ExchangeRepository
-
-    availability_repo = AvailabilityRepository(db)
-    availabilities = await availability_repo.get_by_date(date_param)
-
-    if not availabilities:
-        return AvailableSlotsResponse(date=date_param, slots=[])
-
-    # Get already booked slots for the date
-    exchange_repo = ExchangeRepository(db)
-    booked_starts = await exchange_repo.get_booked_slots_for_date(date_param)
-
-    # Expand each availability into slots
-    all_slots: list[BookableSlot] = []
-    for avail in availabilities:
-        slots = _expand_availability_to_slots(avail, date_param, booked_starts)
-        all_slots.extend(slots)
-
-    # Sort by start time
-    all_slots.sort(key=lambda s: s.start_time)
-
-    return AvailableSlotsResponse(date=date_param, slots=all_slots)
+    service = ExchangeService(db)
+    return await service.get_available_slots(date_param)
 
 
 # =============================================================================