# sn_basis/functions/ly_metadata_wrapper.py

from typing import Optional, List


LAYER_TYPE_VECTOR = "vector"
LAYER_TYPE_TABLE = "table"


def get_layer_type(layer) -> Optional[str]:
    """
    Gibt den Layer-Typ zurück.

    Rückgabewerte:
    - "vector"
    - "table"
    - None (unbekannt / nicht bestimmbar)
    """
    if layer is None:
        return None

    try:
        is_spatial = getattr(layer, "isSpatial", None)
        if callable(is_spatial):
            return LAYER_TYPE_VECTOR if is_spatial() else LAYER_TYPE_TABLE
    except Exception:
        pass

    return None


def get_layer_crs(layer) -> Optional[str]:
    """
    Gibt das CRS als AuthID zurück (z. B. 'EPSG:25833').
    """
    if layer is None:
        return None

    try:
        crs = layer.crs()
        authid = getattr(crs, "authid", None)
        if callable(authid):
            value = authid()
            if isinstance(value, str):
                return value
    except Exception:
        pass

    return None


def get_layer_fields(layer) -> List[str]:
    """
    Gibt die Feldnamen eines Layers zurück.
    """
    if layer is None:
        return []

    try:
        return list(layer.fields().names())
    except Exception:
        return []



def get_layer_source(layer) -> Optional[str]:
    """
    Gibt die Datenquelle eines Layers zurück.
    """
    if layer is None:
        return None

    try:
        value = layer.source()
        if isinstance(value, str) and value:
            return value
    except Exception:
        pass

    return None


def is_layer_editable(layer) -> bool:
    """
    Prüft, ob ein Layer editierbar ist.
    """
    if layer is None:
        return False

    try:
        is_editable = getattr(layer, "isEditable", None)
        if callable(is_editable):
            return bool(is_editable())
    except Exception:
        pass

    return False