from __future__ import annotations

"""Application services for station CRUD operations."""

from datetime import datetime, timezone
from typing import cast
from uuid import UUID

from geoalchemy2.elements import WKBElement, WKTElement
from geoalchemy2.shape import to_shape
from sqlalchemy.orm import Session

from backend.app.db.models import Station
from backend.app.models import StationCreate, StationModel, StationUpdate
from backend.app.repositories import StationRepository

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]


def list_stations(
    session: Session, include_inactive: bool = False
) -> list[StationModel]:
    repo = StationRepository(session)
    if include_inactive:
        stations = repo.list()
    else:
        stations = repo.list_active()
    return [_to_station_model(station) for station in stations]


def get_station(session: Session, station_id: str) -> StationModel:
    repo = StationRepository(session)
    station = _resolve_station(repo, station_id)
    return _to_station_model(station)


def create_station(session: Session, payload: StationCreate) -> StationModel:
    name = payload.name.strip()
    if not name:
        raise ValueError("Station name must not be empty")
    _validate_coordinates(payload.latitude, payload.longitude)

    repo = StationRepository(session)
    station = repo.create(
        StationCreate(
            name=name,
            latitude=payload.latitude,
            longitude=payload.longitude,
            osm_id=_normalize_optional(payload.osm_id),
            code=_normalize_optional(payload.code),
            elevation_m=payload.elevation_m,
            is_active=payload.is_active,
        )
    )
    session.flush()
    session.refresh(station)
    session.commit()
    return _to_station_model(station)


def update_station(
    session: Session, station_id: str, payload: StationUpdate
) -> StationModel:
    repo = StationRepository(session)
    station = _resolve_station(repo, station_id)

    if payload.name is not None:
        name = payload.name.strip()
        if not name:
            raise ValueError("Station name must not be empty")
        station.name = name

    if payload.latitude is not None or payload.longitude is not None:
        if payload.latitude is None or payload.longitude is None:
            raise ValueError("Both latitude and longitude must be provided together")
        _validate_coordinates(payload.latitude, payload.longitude)
        station.location = repo._point(
            payload.latitude, payload.longitude
        )  # type: ignore[assignment]

    if payload.osm_id is not None:
        station.osm_id = _normalize_optional(payload.osm_id)

    if payload.code is not None:
        station.code = _normalize_optional(payload.code)

    if payload.elevation_m is not None:
        station.elevation_m = payload.elevation_m

    if payload.is_active is not None:
        station.is_active = payload.is_active

    session.flush()
    session.refresh(station)
    session.commit()
    return _to_station_model(station)


def archive_station(session: Session, station_id: str) -> StationModel:
    repo = StationRepository(session)
    station = _resolve_station(repo, station_id)
    if station.is_active:
        station.is_active = False
        session.flush()
        session.refresh(station)
        session.commit()
    return _to_station_model(station)


def _resolve_station(repo: StationRepository, station_id: str) -> Station:
    identifier = _parse_station_id(station_id)
    station = repo.get(identifier)
    if station is None:
        raise LookupError("Station not found")
    return station


def _parse_station_id(station_id: str) -> UUID:
    try:
        return UUID(station_id)
    except (ValueError, TypeError) as exc:  # pragma: no cover - simple validation
        raise ValueError("Invalid station identifier") from exc


def _validate_coordinates(latitude: float, longitude: float) -> None:
    if not (-90.0 <= latitude <= 90.0):
        raise ValueError("Latitude must be between -90 and 90 degrees")
    if not (-180.0 <= longitude <= 180.0):
        raise ValueError("Longitude must be between -180 and 180 degrees")


def _normalize_optional(value: str | None) -> str | None:
    if value is None:
        return None
    normalized = value.strip()
    return normalized or None


def _to_station_model(station: Station) -> StationModel:
    latitude, longitude = _extract_coordinates(station.location)
    created_at = station.created_at or datetime.now(timezone.utc)
    updated_at = station.updated_at or created_at
    return StationModel(
        id=str(station.id),
        name=station.name,
        latitude=latitude,
        longitude=longitude,
        code=station.code,
        osm_id=station.osm_id,
        elevation_m=station.elevation_m,
        is_active=station.is_active,
        created_at=cast(datetime, created_at),
        updated_at=cast(datetime, updated_at),
    )


def _extract_coordinates(location: object) -> tuple[float, float]:
    if location is None:
        raise ValueError("Station location is unavailable")

    # Attempt to leverage GeoAlchemy's shapely integration first.
    try:
        geometry = to_shape(cast(WKBElement | WKTElement, location))
        if Point is not None and isinstance(geometry, Point):
            return float(geometry.y), float(geometry.x)
    except Exception:  # pragma: no cover - fallback handles parsing
        pass

    if isinstance(location, WKTElement):
        return _parse_wkt_point(location.data)

    text = getattr(location, "desc", None)
    if isinstance(text, str):
        return _parse_wkt_point(text)

    raise ValueError("Unable to read station geometry")


def _parse_wkt_point(wkt: str) -> tuple[float, float]:
    marker = "POINT"
    if not wkt.upper().startswith(marker):
        raise ValueError("Unsupported geometry format")
    start = wkt.find("(")
    end = wkt.find(")", start)
    if start == -1 or end == -1:
        raise ValueError("Malformed POINT geometry")
    coordinates = wkt[start + 1 : end].strip().split()
    if len(coordinates) != 2:
        raise ValueError("POINT geometry must contain two coordinates")
    longitude, latitude = map(float, coordinates)
    _validate_coordinates(latitude, longitude)
    return latitude, longitude