feat: Add combined track functionality with repository and service layers

- Introduced CombinedTrackModel, CombinedTrackCreate, and CombinedTrackRepository for managing combined tracks.
- Implemented logic to create combined tracks based on existing tracks between two stations.
- Added methods to check for existing combined tracks and retrieve constituent track IDs.
- Enhanced TrackModel and TrackRepository to support OSM ID and track updates.
- Created migration scripts for adding combined tracks table and OSM ID to tracks.
- Updated services and API endpoints to handle combined track operations.
- Added tests for combined track creation, repository methods, and API interactions.

backend/app/services/tracks.py

@@ -0,0 +1,106 @@
+from __future__ import annotations
+
+"""Service layer for primary track management operations."""
+
+from typing import Iterable
+
+from sqlalchemy.exc import IntegrityError
+from sqlalchemy.orm import Session
+
+from backend.app.models import CombinedTrackModel, TrackCreate, TrackModel, TrackUpdate
+from backend.app.repositories import CombinedTrackRepository, TrackRepository
+
+
+def list_tracks(session: Session) -> list[TrackModel]:
+    repo = TrackRepository(session)
+    tracks = repo.list_all()
+    return [TrackModel.model_validate(track) for track in tracks]
+
+
+def get_track(session: Session, track_id: str) -> TrackModel | None:
+    repo = TrackRepository(session)
+    track = repo.get(track_id)
+    if track is None:
+        return None
+    return TrackModel.model_validate(track)
+
+
+def create_track(session: Session, payload: TrackCreate) -> TrackModel:
+    repo = TrackRepository(session)
+    try:
+        track = repo.create(payload)
+        session.commit()
+    except IntegrityError as exc:
+        session.rollback()
+        raise ValueError(
+            "Track with the same station pair already exists") from exc
+
+    return TrackModel.model_validate(track)
+
+
+def update_track(session: Session, track_id: str, payload: TrackUpdate) -> TrackModel | None:
+    repo = TrackRepository(session)
+    track = repo.get(track_id)
+    if track is None:
+        return None
+
+    repo.update(track, payload)
+    session.commit()
+
+    return TrackModel.model_validate(track)
+
+
+def delete_track(session: Session, track_id: str, regenerate: bool = False) -> bool:
+    repo = TrackRepository(session)
+    track = repo.get(track_id)
+    if track is None:
+        return False
+
+    start_station_id = str(track.start_station_id)
+    end_station_id = str(track.end_station_id)
+
+    session.delete(track)
+    session.commit()
+
+    if regenerate:
+        regenerate_combined_tracks(session, [start_station_id, end_station_id])
+
+    return True
+
+
+def regenerate_combined_tracks(session: Session, station_ids: Iterable[str]) -> list[CombinedTrackModel]:
+    combined_repo = CombinedTrackRepository(session)
+
+    station_id_set = set(station_ids)
+    if not station_id_set:
+        return []
+
+    # Remove combined tracks touching these stations
+    for combined in combined_repo.list_all():
+        if {str(combined.start_station_id), str(combined.end_station_id)} & station_id_set:
+            session.delete(combined)
+
+    session.commit()
+
+    # Rebuild combined tracks between affected station pairs
+    from backend.app.services.combined_tracks import create_combined_track
+
+    regenerated: list[CombinedTrackModel] = []
+    station_list = list(station_id_set)
+    for i in range(len(station_list)):
+        for j in range(i + 1, len(station_list)):
+            result = create_combined_track(
+                session, station_list[i], station_list[j])
+            if result is not None:
+                regenerated.append(result)
+    return regenerated
+
+
+__all__ = [
+    "list_tracks",
+    "get_track",
+    "create_track",
+    "update_track",
+    "delete_track",
+    "regenerate_combined_tracks",
+]