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/repositories/__init__.py

@@ -2,6 +2,7 @@
 
 from backend.app.repositories.stations import StationRepository
 from backend.app.repositories.tracks import TrackRepository
+from backend.app.repositories.combined_tracks import CombinedTrackRepository
 from backend.app.repositories.train_schedules import TrainScheduleRepository
 from backend.app.repositories.trains import TrainRepository
 from backend.app.repositories.users import UserRepository
@@ -10,6 +11,7 @@ __all__ = [
     "StationRepository",
     "TrainScheduleRepository",
     "TrackRepository",
+    "CombinedTrackRepository",
     "TrainRepository",
     "UserRepository",
 ]

backend/app/repositories/combined_tracks.py

@@ -0,0 +1,73 @@
+from __future__ import annotations
+
+import json
+from uuid import UUID
+
+import sqlalchemy as sa
+from geoalchemy2.elements import WKTElement
+from sqlalchemy.orm import Session
+
+from backend.app.db.models import CombinedTrack
+from backend.app.models import CombinedTrackCreate
+from backend.app.repositories.base import BaseRepository
+
+
+class CombinedTrackRepository(BaseRepository[CombinedTrack]):
+    model = CombinedTrack
+
+    def __init__(self, session: Session) -> None:
+        super().__init__(session)
+
+    def list_all(self) -> list[CombinedTrack]:
+        statement = sa.select(self.model)
+        return list(self.session.scalars(statement))
+
+    def exists_between_stations(self, start_station_id: str, end_station_id: str) -> bool:
+        """Check if a combined track already exists between two stations."""
+        statement = sa.select(sa.exists().where(
+            sa.and_(
+                self.model.start_station_id == start_station_id,
+                self.model.end_station_id == end_station_id
+            )
+        ))
+        return bool(self.session.scalar(statement))
+
+    def get_constituent_track_ids(self, combined_track: CombinedTrack) -> list[str]:
+        """Extract constituent track IDs from a combined track."""
+        try:
+            return json.loads(combined_track.constituent_track_ids)
+        except (json.JSONDecodeError, TypeError):
+            return []
+
+    @staticmethod
+    def _ensure_uuid(value: UUID | str) -> UUID:
+        if isinstance(value, UUID):
+            return value
+        return UUID(str(value))
+
+    @staticmethod
+    def _line_string(coordinates: list[tuple[float, float]]) -> WKTElement:
+        if len(coordinates) < 2:
+            raise ValueError(
+                "Combined track geometry requires at least two coordinate pairs")
+        parts = [f"{lon} {lat}" for lat, lon in coordinates]
+        return WKTElement(f"LINESTRING({', '.join(parts)})", srid=4326)
+
+    def create(self, data: CombinedTrackCreate) -> CombinedTrack:
+        coordinates = list(data.coordinates)
+        geometry = self._line_string(coordinates)
+        constituent_track_ids_json = json.dumps(data.constituent_track_ids)
+        
+        combined_track = CombinedTrack(
+            name=data.name,
+            start_station_id=self._ensure_uuid(data.start_station_id),
+            end_station_id=self._ensure_uuid(data.end_station_id),
+            length_meters=data.length_meters,
+            max_speed_kph=data.max_speed_kph,
+            is_bidirectional=data.is_bidirectional,
+            status=data.status,
+            combined_geometry=geometry,
+            constituent_track_ids=constituent_track_ids_json,
+        )
+        self.session.add(combined_track)
+        return combined_track

backend/app/repositories/tracks.py

@@ -7,7 +7,7 @@ from geoalchemy2.elements import WKTElement
 from sqlalchemy.orm import Session
 
 from backend.app.db.models import Track
-from backend.app.models import TrackCreate
+from backend.app.models import TrackCreate, TrackUpdate
 from backend.app.repositories.base import BaseRepository
 
 
@@ -21,6 +21,102 @@ class TrackRepository(BaseRepository[Track]):
         statement = sa.select(self.model)
         return list(self.session.scalars(statement))
 
+    def exists_by_osm_id(self, osm_id: str) -> bool:
+        statement = sa.select(sa.exists().where(self.model.osm_id == osm_id))
+        return bool(self.session.scalar(statement))
+
+    def find_path_between_stations(self, start_station_id: str, end_station_id: str) -> list[Track] | None:
+        """Find the shortest path between two stations using existing tracks.
+
+        Returns a list of tracks that form the path, or None if no path exists.
+        """
+        # Build adjacency list: station -> list of (neighbor_station, track)
+        adjacency = self._build_track_graph()
+
+        if start_station_id not in adjacency or end_station_id not in adjacency:
+            return None
+
+        # BFS to find shortest path
+        from collections import deque
+
+        # (current_station, path_so_far)
+        queue = deque([(start_station_id, [])])
+        visited = set([start_station_id])
+
+        while queue:
+            current_station, path = queue.popleft()
+
+            if current_station == end_station_id:
+                return path
+
+            for neighbor, track in adjacency[current_station]:
+                if neighbor not in visited:
+                    visited.add(neighbor)
+                    queue.append((neighbor, path + [track]))
+
+        return None  # No path found
+
+    def _build_track_graph(self) -> dict[str, list[tuple[str, Track]]]:
+        """Build a graph representation of tracks: station -> [(neighbor_station, track), ...]"""
+        tracks = self.list_all()
+        graph = {}
+
+        for track in tracks:
+            start_id = str(track.start_station_id)
+            end_id = str(track.end_station_id)
+
+            # Add bidirectional edges (assuming tracks are bidirectional)
+            if start_id not in graph:
+                graph[start_id] = []
+            if end_id not in graph:
+                graph[end_id] = []
+
+            graph[start_id].append((end_id, track))
+            graph[end_id].append((start_id, track))
+
+        return graph
+
+    def combine_track_geometries(self, tracks: list[Track]) -> list[tuple[float, float]]:
+        """Combine the geometries of multiple tracks into a single coordinate sequence.
+
+        Assumes tracks are in order and form a continuous path.
+        """
+        if not tracks:
+            return []
+
+        combined_coords = []
+
+        for i, track in enumerate(tracks):
+            # Extract coordinates from track geometry
+            coords = self._extract_coordinates_from_track(track)
+
+            if i == 0:
+                # First track: add all coordinates
+                combined_coords.extend(coords)
+            else:
+                # Subsequent tracks: skip the first coordinate (shared with previous track)
+                combined_coords.extend(coords[1:])
+
+        return combined_coords
+
+    def _extract_coordinates_from_track(self, track: Track) -> list[tuple[float, float]]:
+        """Extract coordinate list from a track's geometry."""
+        # Convert WKT string to WKTElement, then to shapely geometry
+        from geoalchemy2.elements import WKTElement
+        from geoalchemy2.shape import to_shape
+
+        try:
+            wkt_element = WKTElement(track.track_geometry)
+            geom = to_shape(wkt_element)
+            if hasattr(geom, 'coords'):
+                # For LineString, coords returns [(x, y), ...] where x=lon, y=lat
+                # Convert to (lat, lon)
+                return [(coord[1], coord[0]) for coord in geom.coords]
+        except Exception:
+            pass
+
+        return []
+
     @staticmethod
     def _ensure_uuid(value: UUID | str) -> UUID:
         if isinstance(value, UUID):
@@ -30,7 +126,8 @@ class TrackRepository(BaseRepository[Track]):
     @staticmethod
     def _line_string(coordinates: list[tuple[float, float]]) -> WKTElement:
         if len(coordinates) < 2:
-            raise ValueError("Track geometry requires at least two coordinate pairs")
+            raise ValueError(
+                "Track geometry requires at least two coordinate pairs")
         parts = [f"{lon} {lat}" for lat, lon in coordinates]
         return WKTElement(f"LINESTRING({', '.join(parts)})", srid=4326)
 
@@ -38,6 +135,7 @@ class TrackRepository(BaseRepository[Track]):
         coordinates = list(data.coordinates)
         geometry = self._line_string(coordinates)
         track = Track(
+            osm_id=data.osm_id,
             name=data.name,
             start_station_id=self._ensure_uuid(data.start_station_id),
             end_station_id=self._ensure_uuid(data.end_station_id),
@@ -49,3 +147,26 @@ class TrackRepository(BaseRepository[Track]):
         )
         self.session.add(track)
         return track
+
+    def update(self, track: Track, payload: TrackUpdate) -> Track:
+        if payload.start_station_id is not None:
+            track.start_station_id = self._ensure_uuid(
+                payload.start_station_id)
+        if payload.end_station_id is not None:
+            track.end_station_id = self._ensure_uuid(payload.end_station_id)
+        if payload.coordinates is not None:
+            track.track_geometry = self._line_string(
+                list(payload.coordinates))  # type: ignore[assignment]
+        if payload.osm_id is not None:
+            track.osm_id = payload.osm_id
+        if payload.name is not None:
+            track.name = payload.name
+        if payload.length_meters is not None:
+            track.length_meters = payload.length_meters
+        if payload.max_speed_kph is not None:
+            track.max_speed_kph = payload.max_speed_kph
+        if payload.is_bidirectional is not None:
+            track.is_bidirectional = payload.is_bidirectional
+        if payload.status is not None:
+            track.status = payload.status
+        return track