rail-game/backend/app/services/network.py

"""Domain services for railway network aggregation."""

from datetime import datetime, timezone
from decimal import Decimal
from typing import Iterable, cast

from geoalchemy2.elements import WKBElement, WKTElement
from geoalchemy2.shape import to_shape
try:  # pragma: no cover - optional dependency guard
    from shapely.geometry import Point  # type: ignore
except ImportError:  # pragma: no cover - allow running without shapely at import time
    Point = None  # type: ignore[assignment]

from sqlalchemy.orm import Session
from sqlalchemy.exc import SQLAlchemyError

from backend.app.models import StationModel, TrackModel, TrainModel
from backend.app.repositories import StationRepository, TrackRepository, TrainRepository


def _timestamp() -> datetime:
    return datetime.now(timezone.utc)


def _fallback_snapshot() -> dict[str, list[dict[str, object]]]:
    now = _timestamp()
    stations = [
        StationModel(
            id="station-1",
            name="Central",
            latitude=52.520008,
            longitude=13.404954,
            created_at=now,
            updated_at=now,
        ),
        StationModel(
            id="station-2",
            name="Harbor",
            latitude=53.551086,
            longitude=9.993682,
            created_at=now,
            updated_at=now,
        ),
    ]

    tracks = [
        TrackModel(
            id="track-1",
            start_station_id="station-1",
            end_station_id="station-2",
            length_meters=289000.0,
            max_speed_kph=230.0,
            created_at=now,
            updated_at=now,
        )
    ]

    trains = [
        TrainModel(
            id="train-1",
            designation="ICE 123",
            capacity=400,
            max_speed_kph=300.0,
            operating_track_ids=[track.id for track in tracks],
            created_at=now,
            updated_at=now,
        )
    ]

    return _serialize_snapshot(stations, tracks, trains)


def _serialize_snapshot(
    stations: Iterable[StationModel],
    tracks: Iterable[TrackModel],
    trains: Iterable[TrainModel],
) -> dict[str, list[dict[str, object]]]:
    return {
        "stations": [station.model_dump(by_alias=True) for station in stations],
        "tracks": [track.model_dump(by_alias=True) for track in tracks],
        "trains": [train.model_dump(by_alias=True) for train in trains],
    }


def _to_float(value: Decimal | float | int | None, default: float = 0.0) -> float:
    if value is None:
        return default
    if isinstance(value, Decimal):
        return float(value)
    return float(value)


def get_network_snapshot(session: Session) -> dict[str, list[dict[str, object]]]:
    station_repo = StationRepository(session)
    track_repo = TrackRepository(session)
    train_repo = TrainRepository(session)

    try:
        stations_entities = station_repo.list_active()
        tracks_entities = track_repo.list_all()
        trains_entities = train_repo.list_all()
    except SQLAlchemyError:
        session.rollback()
        return _fallback_snapshot()

    if not stations_entities and not tracks_entities and not trains_entities:
        return _fallback_snapshot()

    station_models: list[StationModel] = []
    for station in stations_entities:
        location = station.location
        geom = (
            to_shape(cast(WKBElement | WKTElement, location))
            if location is not None and Point is not None
            else None
        )
        if Point is not None and geom is not None and isinstance(geom, Point):
            latitude = float(geom.y)
            longitude = float(geom.x)
        else:
            latitude = 0.0
            longitude = 0.0
        station_models.append(
            StationModel(
                id=str(station.id),
                name=station.name,
                latitude=latitude,
                longitude=longitude,
                created_at=cast(datetime, station.created_at),
                updated_at=cast(datetime, station.updated_at),
            )
        )

    track_models: list[TrackModel] = []
    for track in tracks_entities:
        track_models.append(
            TrackModel(
                id=str(track.id),
                start_station_id=str(track.start_station_id),
                end_station_id=str(track.end_station_id),
                length_meters=_to_float(track.length_meters),
                max_speed_kph=_to_float(track.max_speed_kph),
                created_at=cast(datetime, track.created_at),
                updated_at=cast(datetime, track.updated_at),
            )
        )

    train_models: list[TrainModel] = []
    for train in trains_entities:
        train_models.append(
            TrainModel(
                id=str(train.id),
                designation=train.designation,
                capacity=train.capacity,
                max_speed_kph=_to_float(train.max_speed_kph),
                operating_track_ids=[],
                created_at=cast(datetime, train.created_at),
                updated_at=cast(datetime, train.updated_at),
            )
        )

    return _serialize_snapshot(station_models, track_models, train_models)