'''
Download ST_LUCAS samples based on built request.
'''

import os
import logging
import tempfile
import json
import requests
from pathlib import Path
from shutil import copy
from requests.exceptions import HTTPError, ConnectionError, InvalidSchema, InvalidURL, MissingSchema
from osgeo import gdal, ogr

gdal.UseExceptions()

from owslib.wfs import WebFeatureService
from owslib.util import ServiceException
from owslib import __version__ as owslib_version

from .logger import Logger
from .exceptions import LucasDownloadError, LucasDataError

__version__ = '1.0'

class LucasIO:
    """
    LUCAS features input / output class.

    :param str url: WFS endpoint
    :param str version: WFS version to be used
    """

    def __init__(self,
                 url='https://geoforall.fsv.cvut.cz/st_lucas',
                 version='1.1.0'):
        Logger.debug(f"Using owslib version {owslib_version}")
        self._wfs_url = url + "/geoserver/wfs"
        self._wfs_version = version

        self._mtd_url = url + "/st_lucas_metadata.json"
        self._request = None

        self._path = None # path to GPKG file

    @property
    def data(self):
        return self._path

    @data.setter
    def data(self, path):
        """Set data property from existing GPKG file.

        :param str path: path to existing GPKG file
        """
        try:
            ds = gdal.OpenEx(path, gdal.OF_VECTOR | gdal.OF_READONLY)
            driver = ds.GetDriver().ShortName
            if driver != "GPKG":
                raise LucasDataError(f"Unexpected input file: {driver}")
            del ds
        except RuntimeError as e:
            raise LucasDataError(f"Unable to open input file: {e}")

        self._path = path

    @property
    def metadata(self):
        """Get metadata.

        :return dict: metadata dictionary
        """
        try:
            ds = gdal.OpenEx(self._path, gdal.OF_VECTOR | gdal.OF_READONLY)
            md = ds.GetMetadata()
            del ds
        except RuntimeError as e:
            raise LucasDataError(f"Unable to get metadata: {e}")

        return md

    @staticmethod
    def __get_tempfile_name(extension):
        return os.path.join(tempfile.gettempdir(),
                            "st_lucas_{n}.{e}".format(
                                n=next(tempfile._get_candidate_names()),
                                e=extension)
                            )

    def download(self, request):
        """
        Download LUCAS features from dedicated WFS server based on
        specified request :class:`.request.LucasRequest`.

        :param LucasRequest: request
        """
        try:
            wfs = WebFeatureService(url=self._wfs_url, version=self._wfs_version)
        except (HTTPError, ConnectionError, InvalidSchema, InvalidURL, MissingSchema, AttributeError, UnicodeError) as e:
            raise LucasDownloadError(f"Cannot connect to server: {e}")


        Logger.debug(f"Connected to {self._wfs_url}")

        # collect getfeature() arguments
        args = {
            'srsname': "http://www.opengis.net/gml/srs/epsg.xml#3035"
        }
        args.update(request.build())
        Logger.debug(f"Request: {args}")

        try:
            response = wfs.getfeature(**args)
        except (ServiceException, AttributeError, TypeError) as e:
            raise LucasDownloadError(f"Unable to get features from WFS server: {e}")


        gml = response.read()
        Logger.info(
            "Download process successfuly finished. Size of downloaded data: {}kb".format(
                int(len(gml) / 1000)
            ))

        self._request = request

        self._path = self._load(gml)
        self._postprocessing(self._path)

    def _load(self, gml):
        """Load features from GML string and creates temporary GPKG file.

        :param str gml: GML string to be loaded

        :return str: path to temporary GPKG file
        """

        # 1. store GML string into temporary file
        path_gml = self.__get_tempfile_name("gml")
        Logger.debug(f"WFS GML path: {path_gml}")
        with open(path_gml, 'wb') as f:
            f.write(gml)

        # 2. convert GML to GPKG
        path_gpkg = self.__get_tempfile_name("gpkg")
        try:
            gdal.VectorTranslate(path_gpkg, path_gml, dstSRS="EPSG:3035")
        except RuntimeError as e:
            raise LucasDataError(f"Unable to translate into GPKG: {e}")

        return path_gpkg

    def _postprocessing(self, path):
        """Delete gml_id column. If data are space time aggregated, delete columns which aren't required

        :param str path: path to GPKG file
        """
        def _group(name):
            return {
                "LC_LU": "LAND COVER,LAND USE",
                "LC_LU_SO": "LAND COVER,LAND USE,SOIL",
                "FO": "FORESTRY",
                "CO": "COPERNICUS",
                "IN": "INSPIRE"
            }[name]

        try:
            ds = gdal.OpenEx(path, gdal.OF_VECTOR | gdal.OF_UPDATE)
            layer = ds.GetLayer()
            defn = layer.GetLayerDefn()
            layer.DeleteField(defn.GetFieldIndex('gml_id'))
            if self._request.st_aggregated and self._request.years is not None:
                driver = ogr.GetDriverByName("GPKG")
                gpkg = driver.Open(path)
                layer1 = gpkg.GetLayer()
                layer_definition = layer1.GetLayerDefn()
                for i in range(layer_definition.GetFieldCount()):
                    attr = layer_definition.GetFieldDefn(i).GetName()
                    try:
                        if int(attr[-4:]) not in self._request.years:
                            layer.DeleteField(defn.GetFieldIndex(attr))
                    except ValueError:
                        # some attributes are timeless (eg. point_id, ..., count_survey)
                        pass

            # read LUCAS JSON metadata from server
            try:
                r = requests.get(self._mtd_url)
                lucas_metadata = json.loads(r.content)
            except (HTTPError, json.decoder.JSONDecodeError) as e:
                raise LucasDataError(f"Postprocessing failed: {e}")

            # write metadata into GPKG
            # note:
            #  values are provided as strings due to GDAL < 3.3 limitation
            #  -> Dictionary must contain tuples of strings
            metadata = ({
                "LUCAS_TABLE": self._request.typename.split(":")[1],
                "LUCAS_ST": str(int(self._request.st_aggregated)),
                "LUCAS_CLIENT_VERSION": __version__,
                "LUCAS_DB_VERSION": str(lucas_metadata["version"]),
                "LUCAS_MAX_FEATURES": str(lucas_metadata["max_features"]),
            })
            if self._request.group is not None:
                metadata["LUCAS_GROUP"] = _group(self._request.group.upper())
            ds.SetMetadata(metadata)

            del ds
        except RuntimeError as e:
            raise LucasDataError(f"Postprocessing failed: {e}")

    def __check_data(self):
        """Check whether LUCAS features are downloaded.

        Raise LucasDownloadError of failure
        """
        if self._path is None:
            raise LucasDownloadError("No LUCAS features downloaded")

    def to_gml(self, epsg=3035):
        """Get downloaded LUCAS features as `OGC GML
        <https://www.ogc.org/standards/gml>`__ string.

        :param int epsg: target EPSG code

        :return str: GML string
        """
        self.__check_data()

        path_gml = self.__get_tempfile_name("gml")

        try:
            gdal.VectorTranslate(path_gml, self._path,
                                 dstSRS=f"EPSG:{epsg}",
                                 format="GML")
        except RuntimeError as e:
            raise LucasDataError(f"Unable to translate into GML: {e}")

        with open(path_gml) as fd:
            data = fd.read()

        return data

    def to_gpkg(self, output_path, epsg=3035):
        """Save downloaded LUCAS features into `OGC GeoPackage
        <https://www.ogc.org/standards/gml>`__ file.

        Raises LucasDataError on failure.

        :param str output_path: path to the output OGC GeoPackage file
        :param int epsg: target EPSG code
        """
        self.__check_data()

        out_path = Path(output_path)

        # Delete file if exists
        if out_path.exists():
            try:
                out_path.unlink()
            except PermissionError as e:
                raise LucasDataError(f"Unable to overwrite existing file: {e}")

        if epsg != 3035:
            try:
                gdal.VectorTranslate(output_path, self._path, dstSRS=f"EPSG:{epsg}")
            except RuntimeError as e:
                raise LucasDataError(f"Unable to translate into GPKG: {e}")
        else:
            # Copy file from temporary directory
            if Path(self._path).parent != out_path.parent:
                try:
                    copy(self._path, out_path.parent)
                except PermissionError as e:
                    raise LucasDataError(f"Permission denied: {e}")

            # Rename file
            path = Path(out_path.parent) / Path(self._path).name
            path.rename(out_path)

    def to_geopandas(self, epsg=3035):
        """Get downloaded LUCAS features as GeoPandas `GeoDataFrame
        <https://geopandas.org/docs/reference/api/geopandas.GeoDataFrame.html>`__
        structure.

        :param int epsg: target EPSG code

        :return GeoDataFrame:

        """
        from geopandas import read_file

        self.__check_data()

        if epsg != 3035:
            try:
                _path = self.__get_tempfile_name("gpkg")
                gdal.VectorTranslate(_path, self._path, dstSRS=f"EPSG:{epsg}")
            except RuntimeError as e:
                raise LucasDataError(f"Unable to translate into GPKG: {e}")
        else:
            _path = self._path

        return read_file(_path)

    def count(self):
        """Get number of downloaded LUCAS features.

        :return int: number of downloaded features
        """
        self.__check_data()

        try:
            ds = gdal.OpenEx(self._path, gdal.OF_VECTOR | gdal.OF_READONLY)
            layer = ds.GetLayer()
            nop = layer.GetFeatureCount()
            del ds
        except RuntimeError as e:
            raise LucasDataError(f"Postprocessing failed: {e}")

        return nop

    def is_empty(self):
        """Check whether downloaded LUCAS feature collection is empty.

        :return bool: True for empty collection otherwise False
        """
        return self.count() < 1

    def get_images(self, year, point_id):
        """Get images of selected point and its surroundings from Eurostat FTP server.

        :param int year: year of the measurement
        :param int point_id: id of the LUCAS point

        :return images: dictionary of images (URL)
        """
        try:
            ds = gdal.OpenEx(self._path, gdal.OF_VECTOR | gdal.OF_READONLY)
            layer = ds.GetLayer(0).GetName()
            point_layer = ds.ExecuteSQL(
                f"SELECT * FROM {layer} WHERE point_id={point_id} AND survey_year={year}"
            )
            num_points = point_layer.GetFeatureCount()
            if num_points != 1:
                raise LucasDataError(f"Unexpected number of selected points: {num_points}")
            nuts0 = point_layer.GetNextFeature().GetFieldAsString("nuts0")
            del ds
        except RuntimeError as e:
            raise LucasDataError(f"Unable to get images: {e}")

        images = {}
        url = f'https://gisco-services.ec.europa.eu/lucas/photos/{str(year)}/{nuts0}/{str(point_id)[0:3]}/{str(point_id)[3:6]}/{str(point_id)}'
        for i in ("P", "S", "N", "E", "W"):
            images[i] = f"{url}{i}.jpg"

        return images
