Update regis.get_layer_names() to return pre 2.2.3 names (#433)

* Update regis.get_layer_names() to return pre 2.2.3 names

* Renaming regis layer names if version > 2.2.3

If regis version would receive a small version bump, the origional code would crash. With the proposed changes less likely so.

* formatting

* Refactor get_layer_names function to accept dataset as an argument and streamline layer name assignment in get_regis function.

* Remove unused import of 'get' from the arrow module in regis.py

* Removed trainling white space

Author: bdestombe

nlmod/read/regis.py

@@ -5,6 +5,7 @@
 import numpy as np
 import pandas as pd
 import xarray as xr
+from packaging.version import parse as parse_version
 
 from .. import cache
 from ..dims.layers import calculate_thickness, remove_layer_dim_from_top
@@ -163,18 +164,14 @@ def get_regis(
         msg = "No data found. Please supply valid extent in the Netherlands in RD-coordinates"
         raise (ValueError(msg))
 
-    # make sure layer names are regular strings
-    ds["layer"] = ds["layer"].astype(str)
+    ds["layer"] = get_layer_names(
+        ds=ds, rename_layers_to_version_2_2_2=rename_layers_to_version_2_2_2
+    )
 
     # make sure y is descending
     if (ds["y"].diff("y") > 0).all():
         ds = ds.isel(y=slice(None, None, -1))
 
-    if rename_layers_to_version_2_2_2 and ds.attrs["title"] == "REGIS v02r2s3":
-        df = get_table_name_changes()
-        layer = df.set_index("Nieuwe code")["Oude code"].loc[ds.layer]
-        ds = ds.assign_coords({"layer": layer})
-
     # slice layers
     if botm_layer is not None and botm_layer in ds.layer:
         ds = ds.sel(layer=slice(botm_layer))
@@ -345,17 +342,72 @@ def add_geotop_to_regis_layers(
     return rg
 
 
-def get_layer_names():
+def extract_version_from_title(version_string):
+    """
+    Extract version number in format X.Y.Z from a string like "REGIS vXXrYsZ".
+
+    Parameters
+    ----------
+    version_string : str
+        The input string containing version information in format "REGIS vXXrYsZ".
+
+    Returns
+    -------
+    packaging.version.Version
+        Extracted version in format "X.Y.Z".
+
+    Examples
+    --------
+    >>> extract_version("REGIS v02r2s3")
+    <Version('2.2.3')>
+    """
+    # Extract digits from the string after 'v', 'r', and 's'
+    parts = version_string.split()
+    code = parts[1]  # Get 'vXXrYsZ' part
+
+    # Extract the numbers after v, r, and s
+    major = (
+        code[1:3].lstrip("0") or "0"
+    )  # Remove leading zeros, but keep at least one digit
+    minor = code[code.find("r") + 1 : code.find("s")].lstrip("0") or "0"
+    patch = code[code.find("s") + 1 :].lstrip("0") or "0"
+
+    # Combine into version format
+    version = f"{major}.{minor}.{patch}"
+    return parse_version(version)
+
+
+def get_layer_names(ds=None, rename_layers_to_version_2_2_2=True):
     """Get all the available regis layer names.
 
+    Parameters
+    ----------
+    ds : xarray.Dataset, optional
+        The regis dataset. If None, a connection is made to the REGIS server.
+        The default is None.
+    rename_layers_to_version_2_2_2 : bool, optional
+        If True, the layer names are renamed to their pre-v2.2.3 names. The default is 
+        True.
+
     Returns
     -------
     layer_names : np.array
         array with names of all the regis layers.
     """
-    layer_names = xr.open_dataset(REGIS_URL).layer.astype(str).values
+    if ds is None:
+        ds = xr.open_dataset(REGIS_URL, decode_times=False, decode_coords=False)
+
+    regis_version = extract_version_from_title(ds.attrs["title"])
+
+    layer_names = ds.layer.values.astype(str)
 
-    return layer_names
+    if rename_layers_to_version_2_2_2 and regis_version >= parse_version("2.2.3"):
+        df = get_table_name_changes()
+        return (
+            df.set_index("Nieuwe code").loc[layer_names]["Oude code"].values.astype(str)
+        )
+    else:
+        return layer_names
 
 
 def get_legend(kind="REGIS"):
@@ -432,7 +484,7 @@ def read_voleg(fname):
 
 def get_table_name_changes():
     """
-    Get the table with name changes of REGIS
+    Get the table with name changes of REGIS.
 
     Returns
     -------