"""
Download geospatial entities' geometries and attributes from OpenStreetMap.

Retrieve points of interest, building footprints, or any other objects from
OSM, including their geometries and attribute data, and construct a
GeoDataFrame of them. You can use this module to query for nodes, ways, and
relations (the latter of type "multipolygon" or "boundary" only) by passing a
dictionary of desired tags/values.
"""

import logging as lg
import warnings

import geopandas as gpd
import numpy as np
import pandas as pd
from shapely.geometry import LineString
from shapely.geometry import MultiPolygon
from shapely.geometry import Point
from shapely.geometry import Polygon
from shapely.geos import TopologicalError
from shapely.ops import linemerge
from shapely.ops import polygonize

from . import downloader
from . import geocoder
from . import osm_xml
from . import settings
from . import utils
from . import utils_geo
from ._polygon_features import _polygon_features


def geometries_from_bbox(north, south, east, west, tags):
    """
    Create a GeoDataFrame of OSM entities within a N, S, E, W bounding box.

    Parameters
    ----------
    north : float
        northern latitude of bounding box
    south : float
        southern latitude of bounding box
    east : float
        eastern longitude of bounding box
    west : float
        western longitude of bounding box
    tags : dict
        Dict of tags used for finding objects in the selected area. Results
        returned are the union, not intersection of each individual tag.
        Each result matches at least one given tag. The dict keys should be
        OSM tags, (e.g., `building`, `landuse`, `highway`, etc) and the dict
        values should be either `True` to retrieve all items with the given
        tag, or a string to get a single tag-value combination, or a list of
        strings to get multiple values for the given tag. For example,
        `tags = {'building': True}` would return all building footprints in
        the area. `tags = {'amenity':True, 'landuse':['retail','commercial'],
        'highway':'bus_stop'}` would return all amenities, landuse=retail,
        landuse=commercial, and highway=bus_stop.

    Returns
    -------
    gdf : geopandas.GeoDataFrame

    Notes
    -----
    You can configure the Overpass server timeout, memory allocation, and
    other custom settings via ox.config().
    """
    # convert bounding box to a polygon
    polygon = utils_geo.bbox_to_poly(north, south, east, west)

    # create GeoDataFrame of geometries within this polygon
    gdf = geometries_from_polygon(polygon, tags)

    return gdf


def geometries_from_point(center_point, tags, dist=1000):
    """
    Create GeoDataFrame of OSM entities within some distance N, S, E, W of a point.

    Parameters
    ----------
    center_point : tuple
        the (lat, lng) center point around which to get the geometries
    tags : dict
        Dict of tags used for finding objects in the selected area. Results
        returned are the union, not intersection of each individual tag.
        Each result matches at least one given tag. The dict keys should be
        OSM tags, (e.g., `building`, `landuse`, `highway`, etc) and the dict
        values should be either `True` to retrieve all items with the given
        tag, or a string to get a single tag-value combination, or a list of
        strings to get multiple values for the given tag. For example,
        `tags = {'building': True}` would return all building footprints in
        the area. `tags = {'amenity':True, 'landuse':['retail','commercial'],
        'highway':'bus_stop'}` would return all amenities, landuse=retail,
        landuse=commercial, and highway=bus_stop.
    dist : numeric
        distance in meters

    Returns
    -------
    gdf : geopandas.GeoDataFrame

    Notes
    -----
    You can configure the Overpass server timeout, memory allocation, and
    other custom settings via ox.config().
    """
    # create bounding box from center point and distance in each direction
    north, south, east, west = utils_geo.bbox_from_point(center_point, dist)

    # convert the bounding box to a polygon
    polygon = utils_geo.bbox_to_poly(north, south, east, west)

    # create GeoDataFrame of geometries within this polygon
    gdf = geometries_from_polygon(polygon, tags)

    return gdf


def geometries_from_address(address, tags, dist=1000):
    """
    Create GeoDataFrame of OSM entities within some distance N, S, E, W of address.

    Parameters
    ----------
    address : string
        the address to geocode and use as the central point around which to
        get the geometries
    tags : dict
        Dict of tags used for finding objects in the selected area. Results
        returned are the union, not intersection of each individual tag.
        Each result matches at least one given tag. The dict keys should be
        OSM tags, (e.g., `building`, `landuse`, `highway`, etc) and the dict
        values should be either `True` to retrieve all items with the given
        tag, or a string to get a single tag-value combination, or a list of
        strings to get multiple values for the given tag. For example,
        `tags = {'building': True}` would return all building footprints in
        the area. `tags = {'amenity':True, 'landuse':['retail','commercial'],
        'highway':'bus_stop'}` would return all amenities, landuse=retail,
        landuse=commercial, and highway=bus_stop.
    dist : numeric
        distance in meters

    Returns
    -------
    gdf : geopandas.GeoDataFrame

    Notes
    -----
    You can configure the Overpass server timeout, memory allocation, and
    other custom settings via ox.config().
    """
    # geocode the address string to a (lat, lng) point
    center_point = geocoder.geocode(query=address)

    # create GeoDataFrame of geometries around this point
    gdf = geometries_from_point(center_point, tags, dist=dist)

    return gdf


def geometries_from_place(query, tags, which_result=None, buffer_dist=None):
    """
    Create GeoDataFrame of OSM entities within boundaries of geocodable place(s).

    The query must be geocodable and OSM must have polygon boundaries for the
    geocode result. If OSM does not have a polygon for this place, you can
    instead get geometries within it using the geometries_from_address
    function, which geocodes the place name to a point and gets the geometries
    within some distance of that point.

    If OSM does have polygon boundaries for this place but you're not finding
    it, try to vary the query string, pass in a structured query dict, or vary
    the which_result argument to use a different geocode result. If you know
    the OSM ID of the place, you can retrieve its boundary polygon using the
    geocode_to_gdf function, then pass it to the geometries_from_polygon
    function.

    Parameters
    ----------
    query : string or dict or list
        the query or queries to geocode to get place boundary polygon(s)
    tags : dict
        Dict of tags used for finding objects in the selected area. Results
        returned are the union, not intersection of each individual tag.
        Each result matches at least one given tag. The dict keys should be
        OSM tags, (e.g., `building`, `landuse`, `highway`, etc) and the dict
        values should be either `True` to retrieve all items with the given
        tag, or a string to get a single tag-value combination, or a list of
        strings to get multiple values for the given tag. For example,
        `tags = {'building': True}` would return all building footprints in
        the area. `tags = {'amenity':True, 'landuse':['retail','commercial'],
        'highway':'bus_stop'}` would return all amenities, landuse=retail,
        landuse=commercial, and highway=bus_stop.
    which_result : int
        which geocoding result to use. if None, auto-select the first
        (Multi)Polygon or raise an error if OSM doesn't return one.
    buffer_dist : float
        distance to buffer around the place geometry, in meters

    Returns
    -------
    gdf : geopandas.GeoDataFrame

    Notes
    -----
    You can configure the Overpass server timeout, memory allocation, and
    other custom settings via ox.config().
    """
    # create a GeoDataFrame with the spatial boundaries of the place(s)
    if isinstance(query, (str, dict)):
        # if it is a string (place name) or dict (structured place query),
        # then it is a single place
        gdf_place = geocoder.geocode_to_gdf(
            query, which_result=which_result, buffer_dist=buffer_dist
        )
    elif isinstance(query, list):
        # if it is a list, it contains multiple places to get
        gdf_place = geocoder.geocode_to_gdf(query, buffer_dist=buffer_dist)
    else:  # pragma: no cover
        raise TypeError("query must be dict, string, or list of strings")

    # extract the geometry from the GeoDataFrame to use in API query
    polygon = gdf_place["geometry"].unary_union
    utils.log("Constructed place geometry polygon(s) to query API")

    # create GeoDataFrame using this polygon(s) geometry
    gdf = geometries_from_polygon(polygon, tags)

    return gdf


def geometries_from_polygon(polygon, tags):
    """
    Create GeoDataFrame of OSM entities within boundaries of a (multi)polygon.

    Parameters
    ----------
    polygon : shapely.geometry.Polygon or shapely.geometry.MultiPolygon
        geographic boundaries to fetch geometries within
    tags : dict
        Dict of tags used for finding objects in the selected area. Results
        returned are the union, not intersection of each individual tag.
        Each result matches at least one given tag. The dict keys should be
        OSM tags, (e.g., `building`, `landuse`, `highway`, etc) and the dict
        values should be either `True` to retrieve all items with the given
        tag, or a string to get a single tag-value combination, or a list of
        strings to get multiple values for the given tag. For example,
        `tags = {'building': True}` would return all building footprints in
        the area. `tags = {'amenity':True, 'landuse':['retail','commercial'],
        'highway':'bus_stop'}` would return all amenities, landuse=retail,
        landuse=commercial, and highway=bus_stop.

    Returns
    -------
    gdf : geopandas.GeoDataFrame

    Notes
    -----
    You can configure the Overpass server timeout, memory allocation, and
    other custom settings via ox.config().
    """
    # verify that the geometry is valid and a Polygon/MultiPolygon
    if not polygon.is_valid:
        raise ValueError("The geometry of `polygon` is invalid")
    if not isinstance(polygon, (Polygon, MultiPolygon)):
        raise TypeError(
            "Boundaries must be a shapely Polygon or MultiPolygon. If you requested "
            "geometries from place name, make sure your query resolves to a Polygon or "
            "MultiPolygon, and not some other geometry, like a Point. See OSMnx "
            "documentation for details."
        )

    # download the geometry data from OSM
    response_jsons = downloader._osm_geometries_download(polygon, tags)

    # create GeoDataFrame from the downloaded data
    gdf = _create_gdf(response_jsons, polygon, tags)

    return gdf


def geometries_from_xml(filepath, polygon=None, tags=None):
    """
    Create a GeoDataFrame of OSM entities in an OSM-formatted XML file.

    Because this function creates a GeoDataFrame of geometries from an
    OSM-formatted XML file that has already been downloaded (i.e. no query is
    made to the Overpass API) the polygon and tags arguments are not required.
    If they are not supplied to the function, geometries_from_xml() will
    return geometries for all of the tagged elements in the file. If they are
    supplied they will be used to filter the final GeoDataFrame.

    Parameters
    ----------
    filepath : string or pathlib.Path
        path to file containing OSM XML data
    polygon : shapely.geometry.Polygon
        optional geographic boundary to filter objects
    tags : dict
        optional dict of tags for filtering objects from the XML. Results
        returned are the union, not intersection of each individual tag.
        Each result matches at least one given tag. The dict keys should be
        OSM tags, (e.g., `building`, `landuse`, `highway`, etc) and the dict
        values should be either `True` to retrieve all items with the given
        tag, or a string to get a single tag-value combination, or a list of
        strings to get multiple values for the given tag. For example,
        `tags = {'building': True}` would return all building footprints in
        the area. `tags = {'amenity':True, 'landuse':['retail','commercial'],
        'highway':'bus_stop'}` would return all amenities, landuse=retail,
        landuse=commercial, and highway=bus_stop.

    Returns
    -------
    gdf : geopandas.GeoDataFrame
    """
    # transmogrify file of OSM XML data into JSON
    response_jsons = [osm_xml._overpass_json_from_file(filepath)]

    # create GeoDataFrame using this response JSON
    gdf = _create_gdf(response_jsons, polygon=polygon, tags=tags)

    return gdf


def _create_gdf(response_jsons, polygon, tags):
    """
    Parse JSON responses from the Overpass API to a GeoDataFrame.

    Note: the `polygon` and `tags` arguments can both be `None` and the
    GeoDataFrame will still be created but it won't be filtered at the end
    i.e. the final GeoDataFrame will contain all tagged geometries in the
    `response_jsons`.

    Parameters
    ----------
    response_jsons : list
        list of JSON responses from from the Overpass API
    polygon : shapely.geometry.Polygon
        geographic boundary used for filtering the final GeoDataFrame
    tags : dict
        dict of tags used for filtering the final GeoDataFrame

    Returns
    -------
    gdf : geopandas.GeoDataFrame
        GeoDataFrame of geometries and their associated tags
    """
    elements_count = sum(len(rj["elements"]) for rj in response_jsons)

    # if there are no elements in the responses
    if elements_count == 0:
        # create an empty GeoDataFrame
        gdf = gpd.GeoDataFrame()
        gdf["geometry"] = np.nan
        gdf.set_geometry("geometry")
        gdf.crs = settings.default_crs

        # log a warning
        utils.log("No data elements: check query tags and location.", level=lg.WARNING)
        return gdf

    # else if there were elements in the response
    else:
        utils.log(f"Converting {elements_count} elements in JSON responses to geometries")

        # Dictionaries to hold nodes and complete geometries
        coords = dict()
        geometries = dict()

        # Set to hold the unique IDs of elements that do not have tags
        untagged_element_ids = set()

        # identify which relation types to parse to (multi)polygons
        relation_types = {"boundary", "multipolygon"}

        # extract geometries from the downloaded osm data
        for response_json in response_jsons:
            # Parses the JSON of OSM nodes, ways and (multipolygon) relations
            # to dictionaries of coordinates, Shapely Points, LineStrings,
            # Polygons and MultiPolygons
            for element in response_json["elements"]:

                # id numbers are only unique within element types
                # create unique id from combination of type and id
                unique_id = f"{element['type']}/{element['id']}"

                # add elements that are not nodes and that are without tags or
                # with empty tags to the untagged_element_ids set (untagged
                # nodes are not added to the geometries dict at all)
                if (element["type"] != "node") and (
                    ("tags" not in element) or (not element["tags"])
                ):
                    untagged_element_ids.add(unique_id)

                if element["type"] == "node":
                    # Parse all nodes to coords
                    coords[element["id"]] = _parse_node_to_coords(element=element)

                    # If the node has tags and the tags are not empty parse it
                    # to a Point. Empty check is necessary for JSONs created
                    # from XML where nodes without tags are assigned tags={}
                    if "tags" in element and len(element["tags"]) > 0:
                        point = _parse_node_to_point(element=element)
                        geometries[unique_id] = point

                elif element["type"] == "way":
                    # Parse all ways to linestrings or polygons
                    linestring_or_polygon = _parse_way_to_linestring_or_polygon(
                        element=element, coords=coords
                    )
                    geometries[unique_id] = linestring_or_polygon

                elif (
                    element["type"] == "relation"
                    and element.get("tags").get("type") in relation_types
                ):
                    # parse relations to (multi)polygons
                    multipolygon = _parse_relation_to_multipolygon(
                        element=element, geometries=geometries
                    )
                    geometries[unique_id] = multipolygon

        utils.log(f"{len(geometries)} geometries created in the dict")

        # remove untagged elements from the final dict of geometries
        for untagged_element_id in untagged_element_ids:
            geometries.pop(untagged_element_id, None)

        utils.log(f"{len(untagged_element_ids)} untagged geometries removed")

        # Create GeoDataFrame
        gdf = gpd.GeoDataFrame.from_dict(geometries, orient="index")

        # ensure gdf has a geometry col before assigning crs
        if "geometry" not in gdf.columns:
            # if there is no geometry column, create a null column
            gdf["geometry"] = np.nan
        gdf.set_geometry("geometry")

        # Set default crs
        gdf.crs = settings.default_crs

        # Apply .buffer(0) to any invalid geometries
        gdf = _buffer_invalid_geometries(gdf)

        # Filter final gdf to requested tags and query polygon
        gdf = _filter_gdf_by_polygon_and_tags(gdf, polygon=polygon, tags=tags)

        # bug in geopandas <0.9 raises a TypeError if trying to plot empty
        # geometries but missing geometries (gdf['geometry'] = None) cannot be
        # projected e.g. gdf.to_crs(). Remove rows with empty (e.g. Point())
        # or missing (e.g. None) geometry, and suppress gpd warning caused by
        # calling gdf["geometry"].isna() on GeoDataFrame with empty geometries
        if not gdf.empty:
            warnings.filterwarnings("ignore", "GeoSeries.isna", UserWarning)
            gdf = gdf[~(gdf["geometry"].is_empty | gdf["geometry"].isna())].copy()
            warnings.resetwarnings()

        utils.log(f"{len(gdf)} geometries in the final GeoDataFrame")
        return gdf


def _parse_node_to_coords(element):
    """
    Parse coordinates from a node in the overpass response.

    The coords are only used to create LineStrings and Polygons.

    Parameters
    ----------
    element : dict
        element type "node" from overpass response JSON

    Returns
    -------
    coords : dict
        dict of latitude/longitude coordinates
    """
    # return the coordinate of a single node element
    coords = {"lat": element["lat"], "lon": element["lon"]}
    return coords


def _parse_node_to_point(element):
    """
    Parse point from a tagged node in the overpass response.

    The points are geometries in their own right.

    Parameters
    ----------
    element : dict
        element type "node" from overpass response JSON

    Returns
    -------
    point : dict
        dict of OSM ID, OSM element type, tags and geometry
    """
    point = dict()
    point["osmid"] = element["id"]
    point["element_type"] = "node"

    if "tags" in element:
        for tag in element["tags"]:
            point[tag] = element["tags"][tag]

    point["geometry"] = Point(element["lon"], element["lat"])
    return point


def _parse_way_to_linestring_or_polygon(element, coords, polygon_features=_polygon_features):
    """
    Parse open LineString, closed LineString or Polygon from OSM 'way'.

    Please see https://wiki.openstreetmap.org/wiki/Overpass_turbo/Polygon_Features
    for more information on which tags should be parsed to polygons

    Parameters
    ----------
    element : dict
        element type "way" from overpass response JSON
    coords : dict
        dict of node IDs and their latitude/longitude coordinates
    polygon_features : dict
        dict for determining whether closed ways are LineStrings or Polygons

    Returns
    -------
    linestring_or_polygon : dict
        dict of OSM ID, OSM element type, nodes, tags and geometry
    """
    nodes = element["nodes"]

    linestring_or_polygon = dict()
    linestring_or_polygon["osmid"] = element["id"]
    linestring_or_polygon["element_type"] = "way"
    linestring_or_polygon["nodes"] = nodes

    # un-nest individual tags
    if "tags" in element:
        for tag in element["tags"]:
            linestring_or_polygon[tag] = element["tags"][tag]

    # if the OSM element is an open way (i.e. first and last nodes are not the
    # same) the geometry should be a Shapely LineString
    if element["nodes"][0] != element["nodes"][-1]:
        try:
            geometry = LineString([(coords[node]["lon"], coords[node]["lat"]) for node in nodes])
        except KeyError as e:  # pragma: no cover
            # XMLs may include geometries that are incomplete, in which case
            # return an empty geometry
            utils.log(
                f"node/{e} was not found in `coords`.\n"
                f"https://www.openstreetmap.org/{element['type']}/{element['id']} was not created."
            )
            geometry = LineString()

    # if the OSM element is a closed way (i.e. first and last nodes are the
    # same) depending upon the tags the geometry could be a Shapely LineString
    # or Polygon
    elif element["nodes"][0] == element["nodes"][-1]:

        # determine if closed way represents LineString or Polygon
        if _is_closed_way_a_polygon(element):
            # if it is a Polygon
            try:
                geometry = Polygon([(coords[node]["lon"], coords[node]["lat"]) for node in nodes])
            except ValueError as e:
                # XMLs may include geometries that are incomplete, in which
                # case return an empty geometry
                utils.log(
                    f"{e} . The geometry for "
                    f"https://www.openstreetmap.org/{element['type']}/{element['id']} was not created."
                )
                geometry = Polygon()
        else:
            # if it is a LineString
            try:
                geometry = LineString(
                    [(coords[node]["lon"], coords[node]["lat"]) for node in nodes]
                )
            except ValueError as e:
                # XMLs may include geometries that are incomplete, in which
                # case return an empty geometry
                utils.log(
                    f"{e} . The geometry for "
                    f"https://www.openstreetmap.org/{element['type']}/{element['id']} was not created."
                )
                geometry = LineString()

    linestring_or_polygon["geometry"] = geometry
    return linestring_or_polygon


def _is_closed_way_a_polygon(element, polygon_features=_polygon_features):
    """
    Determine whether a closed OSM way represents a Polygon, not a LineString.

    Closed OSM ways may represent LineStrings (e.g. a roundabout or hedge
    round a field) or Polygons (e.g. a building footprint or land use area)
    depending on the tags applied to them.

    The starting assumption is that it is not a polygon, however any polygon
    type tagging will return a polygon unless explicitly tagged with area:no.

    It is possible for a single closed OSM way to have both LineString and
    Polygon type tags (e.g. both barrier=fence and landuse=agricultural).
    OSMnx will return a single Polygon for elements tagged in this way.
    For more information see:
    https://wiki.openstreetmap.org/wiki/One_feature,_one_OSM_element)

    Parameters
    ----------
    element : dict
        closed element type "way" from overpass response JSON
    polygon_features : dict
        dict of tag keys with associated values and blocklist/passlist

    Returns
    -------
    is_polygon : bool
        True if the tags are for a polygon type geometry
    """
    # polygon_features dict is for determining which ways should become Polygons
    # therefore the starting assumption is that the geometry is a LineString
    is_polygon = False

    # get the element's tags
    element_tags = element.get("tags")

    # if the element doesn't have any tags leave it as a Linestring
    if element_tags is not None:

        # if the element is specifically tagged 'area':'no' -> LineString
        if element_tags.get("area") == "no":
            pass

        # if the element has tags and is not tagged 'area':'no'
        # compare its tags with the polygon_features dict
        else:
            # identify common keys in element's tags and polygon_features dict
            intersecting_keys = element_tags.keys() & polygon_features.keys()

            # for each key in the intersecting keys (if any found)
            for key in intersecting_keys:

                # Get the key's value from the element's tags
                key_value = element_tags.get(key)

                # Determine if the key is for a blocklist or passlist in
                # polygon_features dict
                blocklist_or_passlist = polygon_features.get(key).get("polygon")

                # Get values for the key from the polygon_features dict
                polygon_features_values = polygon_features.get(key).get("values")

                # if all features with that key should be polygons -> Polygon
                if blocklist_or_passlist == "all":
                    is_polygon = True

                # if the key is for a blocklist i.e. tags that should not
                # become Polygons
                elif blocklist_or_passlist == "blocklist":

                    # if the value for that key in the element is not in
                    # the blocklist -> Polygon
                    if key_value not in polygon_features_values:
                        is_polygon = True

                # if the key is for a passlist i.e. specific tags should
                # become Polygons
                elif blocklist_or_passlist == "passlist":

                    # if the value for that key in the element is in the
                    # passlist -> Polygon
                    if key_value in polygon_features_values:
                        is_polygon = True

    return is_polygon


def _parse_relation_to_multipolygon(element, geometries):
    """
    Parse multipolygon from OSM relation (type:MultiPolygon).

    See more information about relations from OSM documentation:
    http://wiki.openstreetmap.org/wiki/Relation

    Parameters
    ----------
    element : dict
        element type "relation" from overpass response JSON
    geometries : dict
        dict containing all linestrings and polygons generated from OSM ways

    Returns
    -------
    multipolygon : dict
        dict of tags and geometry for a single multipolygon
    """
    multipolygon = dict()
    multipolygon["osmid"] = element["id"]
    multipolygon["element_type"] = "relation"

    # Parse member 'way' ids
    member_way_refs = [member["ref"] for member in element["members"] if member["type"] == "way"]
    multipolygon["ways"] = member_way_refs

    # Add the tags
    if "tags" in element:
        for tag in element["tags"]:
            multipolygon[tag] = element["tags"][tag]

    # Extract the ways from the geometries dict using their unique id.
    # XMLs exported from the openstreetmap.org homepage with a bounding box
    # may include the relation but not the ways outside the bounding box.
    try:
        member_ways = [geometries[f"way/{member_way_ref}"] for member_way_ref in member_way_refs]
    except KeyError as e:  # pragma: no cover
        utils.log(
            f"{e} was not found in `geometries`.\nThe geometry for "
            f"https://www.openstreetmap.org/{element['type']}/{element['id']} was not created."
        )
        multipolygon["geometry"] = MultiPolygon()
        return multipolygon

    # Extract the nodes of those ways
    member_nodes = [[member_way["nodes"] for member_way in member_ways]]
    multipolygon["nodes"] = member_nodes

    # Assemble MultiPolygon component polygons from component LineStrings and
    # Polygons
    outer_polygons, inner_polygons = _assemble_multipolygon_component_polygons(element, geometries)

    # Subtract inner polygons from outer polygons
    geometry = _subtract_inner_polygons_from_outer_polygons(element, outer_polygons, inner_polygons)

    multipolygon["geometry"] = geometry
    return multipolygon


def _assemble_multipolygon_component_polygons(element, geometries):
    """
    Assemble a MultiPolygon from its component LineStrings and Polygons.

    The OSM wiki suggests an algorithm for assembling multipolygon geometries
    https://wiki.openstreetmap.org/wiki/Relation:multipolygon/Algorithm.
    This method takes a simpler approach relying on the accurate tagging
    of component ways with 'inner' and 'outer' roles as required on this page
    https://wiki.openstreetmap.org/wiki/Relation:multipolygon.

    Parameters
    ----------
    element : dict
        element type "relation" from overpass response JSON
    geometries : dict
        dict containing all linestrings and polygons generated from OSM ways

    Returns
    -------
    geometry : shapely.geometry.MultiPolygon
        a single MultiPolygon object
    """
    outer_polygons = []
    inner_polygons = []
    outer_linestrings = []
    inner_linestrings = []

    # get the linestrings and polygons that make up the multipolygon
    for member in element["members"]:
        if member.get("type") == "way":
            # get the member's geometry from linestrings_and_polygons
            linestring_or_polygon = geometries.get(f"way/{member['ref']}")
            # sort it into one of the lists according to its role and geometry
            if (member.get("role") == "outer") and (
                linestring_or_polygon["geometry"].geom_type == "Polygon"
            ):
                outer_polygons.append(linestring_or_polygon["geometry"])
            elif (member.get("role") == "inner") and (
                linestring_or_polygon["geometry"].geom_type == "Polygon"
            ):
                inner_polygons.append(linestring_or_polygon["geometry"])
            elif (member.get("role") == "outer") and (
                linestring_or_polygon["geometry"].geom_type == "LineString"
            ):
                outer_linestrings.append(linestring_or_polygon["geometry"])
            elif (member.get("role") == "inner") and (
                linestring_or_polygon["geometry"].geom_type == "LineString"
            ):
                inner_linestrings.append(linestring_or_polygon["geometry"])

    # Merge outer linestring fragments.
    # Returns a single LineString or MultiLineString collection
    merged_outer_linestrings = linemerge(outer_linestrings)

    # polygonize each linestring separately and append to list of outer polygons
    if merged_outer_linestrings.geom_type == "LineString":
        outer_polygons += polygonize(merged_outer_linestrings)
    elif merged_outer_linestrings.geom_type == "MultiLineString":
        for merged_outer_linestring in list(merged_outer_linestrings):
            outer_polygons += polygonize(merged_outer_linestring)

    # Merge inner linestring fragments.
    # Returns a single LineString or MultiLineString collection
    merged_inner_linestrings = linemerge(inner_linestrings)

    # polygonize each linestring separately and append to list of inner polygons
    if merged_inner_linestrings.geom_type == "LineString":
        inner_polygons += polygonize(merged_inner_linestrings)
    elif merged_inner_linestrings.geom_type == "MultiLineString":
        for merged_inner_linestring in merged_inner_linestrings.geoms:
            inner_polygons += polygonize(merged_inner_linestring)

    if not outer_polygons:
        utils.log(
            "No outer polygons were created for"
            f" https://www.openstreetmap.org/{element['type']}/{element['id']}"
        )

    return outer_polygons, inner_polygons


def _subtract_inner_polygons_from_outer_polygons(element, outer_polygons, inner_polygons):
    """
    Subtract inner polygons from outer polygons.

    Creates a Polygon or MultiPolygon with holes.

    Parameters
    ----------
    element : dict
        element type "relation" from overpass response JSON
    outer_polygons : list
        list of outer polygons that are part of a multipolygon
    inner_polygons : list
        list of inner polygons that are part of a multipolygon

    Returns
    -------
    geometry : shapely.geometry.Polygon or shapely.geometry.MultiPolygon
        a single Polygon or MultiPolygon
    """
    # create a new list to hold the outer polygons with the inner polygons
    # subtracted
    outer_polygons_with_holes = []

    # loop through the outer polygons subtracting the inner polygons and
    # appending to the list
    for outer_polygon in outer_polygons:
        for inner_polygon in inner_polygons:
            if inner_polygon.within(outer_polygon):
                try:
                    outer_polygon = outer_polygon.difference(inner_polygon)
                except TopologicalError:  # pragma: no cover
                    utils.log(
                        f"relation https://www.openstreetmap.org/relation/{element['id']} caused"
                        " a TopologicalError, trying with zero buffer."
                    )
                    outer_polygon = outer_polygon.buffer(0).difference(inner_polygon.buffer(0))

        # note: .buffer(0) can return either a Polygon or MultiPolygon
        # if it returns a MultiPolygon we need to extract the component
        # sub Polygons to add to outer_polygons_with_holes
        if outer_polygon.geom_type == "Polygon":
            outer_polygons_with_holes.append(outer_polygon)
        elif outer_polygon.geom_type == "MultiPolygon":
            outer_polygons_with_holes.extend(list(outer_polygon))

    # if only one polygon with holes was created, return that single polygon
    if len(outer_polygons_with_holes) == 1:
        geometry = outer_polygons_with_holes[0]
    # otherwise create a multipolygon from list of outer polygons with holes
    else:
        geometry = MultiPolygon(outer_polygons_with_holes)

    return geometry


def _buffer_invalid_geometries(gdf):
    """
    Buffer any invalid geometries remaining in the GeoDataFrame.

    Invalid geometries in the GeoDataFrame (which may accurately reproduce
    invalid geometries in OpenStreetMap) can cause the filtering to the query
    polygon and other subsequent geometric operations to fail. This function
    logs the ids of the invalid geometries and applies a buffer of zero to try
    to make them valid.

    Note: the resulting geometries may differ from the originals - please
    check them against OpenStreetMap

    Parameters
    ----------
    gdf : geopandas.GeoDataFrame
        a GeoDataFrame with possibly invalid geometries

    Returns
    -------
    gdf : geopandas.GeoDataFrame
        the GeoDataFrame with .buffer(0) applied to invalid geometries
    """
    # only apply the filters if the GeoDataFrame is not empty
    if not gdf.empty:

        # create a filter for rows with invalid geometries
        invalid_geometry_filter = ~gdf["geometry"].is_valid

        # if there are invalid geometries
        if invalid_geometry_filter.any():

            # get their unique_ids from the index
            invalid_geometry_ids = gdf.loc[invalid_geometry_filter].index.to_list()

            # create a list of their urls and log them
            osm_url = "https://www.openstreetmap.org/"
            invalid_geom_urls = [osm_url + unique_id for unique_id in invalid_geometry_ids]
            utils.log(
                f"{len(invalid_geometry_ids)} invalid geometries"
                f".buffer(0) applied to {invalid_geom_urls}",
                level=lg.WARNING,
            )

            # apply .buffer(0)
            gdf.loc[invalid_geometry_filter, "geometry"] = gdf.loc[
                invalid_geometry_filter, "geometry"
            ].buffer(0)

    return gdf


def _filter_gdf_by_polygon_and_tags(gdf, polygon, tags):
    """
    Filter the GeoDataFrame to the requested bounding polygon and tags.

    Filters GeoDataFrame to query polygon and tags. Removes columns of all
    NaNs (that held values only in rows removed by the filters). Resets the
    index of GeoDataFrame, writing it into a new column called 'unique_id'.

    Parameters
    ----------
    gdf : geopandas.GeoDataFrame
        the GeoDataFrame to filter
    polygon : shapely.geometry.Polygon
        polygon defining the boundary of the requested area
    tags : dict
        the tags requested

    Returns
    -------
    gdf : geopandas.GeoDataFrame
        final filtered GeoDataFrame
    """
    # only apply the filters if the GeoDataFrame is not empty
    if not gdf.empty:

        # create two filters, initially all True
        polygon_filter = pd.Series(True, index=gdf.index)
        combined_tag_filter = pd.Series(True, index=gdf.index)

        # if a polygon was supplied, create a filter that is True for
        # geometries that intersect with the polygon
        if polygon:
            # get set of index labels of geometries that intersect polygon
            gdf_indices_in_polygon = utils_geo._intersect_index_quadrats(gdf, polygon)
            # create boolean series, True for geometries whose index is in set
            polygon_filter = gdf.index.isin(gdf_indices_in_polygon)

            utils.log(f"{sum(~polygon_filter)} geometries removed by the polygon filter")

        # if tags were supplied, create filter that is True for geometries
        # that have at least one of the requested tags
        if tags:
            # Reset all values in the combined_tag_filter to False
            combined_tag_filter[:] = False

            # reduce the tags to those that are actually present in the
            # GeoDataFrame columns
            tags_in_columns = {key: tags[key] for key in tags if key in gdf.columns}

            for key, value in tags_in_columns.items():
                if value is True:
                    tag_filter = gdf[key].notna()
                elif isinstance(value, str):
                    tag_filter = gdf[key] == value
                elif isinstance(value, list):
                    tag_filter = gdf[key].isin(value)

                combined_tag_filter = combined_tag_filter | tag_filter

            utils.log(f"{sum(~combined_tag_filter)} geometries removed by the tag filter")

        # apply the filters
        gdf = gdf[polygon_filter & combined_tag_filter].copy()

        # remove columns of all nulls (created by discarded component geometries)
        gdf.dropna(axis="columns", how="all", inplace=True)

    # multi-index gdf by element_type and osmid then return
    idx_cols = ["element_type", "osmid"]
    if all(c in gdf.columns for c in idx_cols):
        gdf = gdf.set_index(idx_cols)
    return gdf
