"""!
@brief WMS, WMTS and NASA OnEarth drivers implemented in GRASS using GDAL Python bindings.

List of classes:
 - wms_drv::WMSDrv
 - wms_drv::BaseRequestMgr
 - wms_drv::WMSRequestMgr
 - wms_drv::WMTSRequestMgr
 - wms_drv::OnEarthRequestMgr

(C) 2012 by the GRASS Development Team

This program is free software under the GNU General Public License
(>=v2). Read the file COPYING that comes with GRASS for details.

@author Stepan Turek <stepan.turek seznam.cz> (Mentor: Martin Landa)
"""

import socket
import grass.script as grass

from time import sleep

try:
    from osgeo import gdal
except:
    grass.fatal(
        _(
            "Unable to load GDAL Python bindings (requires package 'python-gdal' being installed)"
        )
    )

import numpy as Numeric

Numeric.arrayrange = Numeric.arange

from math import pi, floor

try:
    from urllib2 import HTTPError
    from httplib import HTTPException
except ImportError:
    # python3
    from urllib.error import HTTPError
    from http.client import HTTPException

try:
    from xml.etree.ElementTree import ParseError
except ImportError:  # < Python 2.7
    from xml.parsers.expat import ExpatError as ParseError

from wms_base import GetEpsg, GetSRSParamVal, WMSBase

from wms_cap_parsers import WMTSCapabilitiesTree, OnEarthCapabilitiesTree
from srs import Srs


class WMSDrv(WMSBase):
    def _download(self):
        """!Downloads data from WMS server using own driver

        @return temp_map with downloaded data
        """
        grass.message(_("Downloading data from WMS server..."))
        server_url = self.params["url"]

        if "?" in self.params["url"]:
            self.params["url"] += "&"
        else:
            self.params["url"] += "?"

        if not self.params["capfile"]:
            self.cap_file = self._fetchCapabilities(self.params)
        else:
            self.cap_file = self.params["capfile"]

        # initialize correct manager according to chosen OGC service
        if self.params["driver"] == "WMTS_GRASS":
            req_mgr = WMTSRequestMgr(
                self.params, self.bbox, self.region, self.proj_srs, self.cap_file
            )
        elif self.params["driver"] == "WMS_GRASS":
            req_mgr = WMSRequestMgr(
                self.params, self.bbox, self.region, self.tile_size, self.proj_srs
            )
        elif self.params["driver"] == "OnEarth_GRASS":
            req_mgr = OnEarthRequestMgr(
                self.params, self.bbox, self.region, self.proj_srs, self.cap_file
            )

        # get information about size in pixels and bounding box of raster, where
        # all tiles will be joined
        map_region = req_mgr.GetMapRegion()

        init = True
        temp_map = None

        fetch_try = 0

        # iterate through all tiles and download them
        while True:

            if fetch_try == 0:
                # get url for request the tile and information for placing the tile into
                # raster with other tiles
                tile = req_mgr.GetNextTile()

            # if last tile has been already downloaded
            if not tile:
                break

            # url for request the tile
            query_url = tile[0]

            # the tile size and offset in pixels for placing it into raster where tiles are joined
            tile_ref = tile[1]
            grass.debug(query_url, 2)
            try:
                wms_data = self._fetchDataFromServer(
                    query_url, self.params["username"], self.params["password"]
                )
            except (IOError, HTTPException) as e:
                if isinstance(e, HTTPError) and e.code == 401:
                    grass.fatal(
                        _("Authorization failed to '%s' when fetching data.\n%s")
                        % (self.params["url"], str(e))
                    )
                else:
                    grass.fatal(
                        _("Unable to fetch data from: '%s'\n%s")
                        % (self.params["url"], str(e))
                    )

            temp_tile = self._tempfile()

            # download data into temporary file
            try:
                temp_tile_opened = open(temp_tile, "wb")
                temp_tile_opened.write(wms_data.read())
            except IOError as e:
                # some servers are not happy with many subsequent requests for tiles done immediately,
                # if immediate request was unsuccessful, try to repeat the request after 5s and 30s breaks
                # TODO probably servers can return more kinds of errors related to this
                # problem (not only 104)
                if isinstance(e, socket.error) and e[0] == 104 and fetch_try < 2:
                    fetch_try += 1

                    if fetch_try == 1:
                        sleep_time = 5
                    elif fetch_try == 2:
                        sleep_time = 30

                    grass.warning(
                        _(
                            "Server refused to send data for a tile.\nRequest will be repeated after %d s."
                        )
                        % sleep_time
                    )

                    sleep(sleep_time)
                    continue
                else:
                    grass.fatal(_("Unable to write data into tempfile.\n%s") % str(e))
            finally:
                temp_tile_opened.close()

            fetch_try = 0

            tile_dataset_info = gdal.Open(temp_tile, gdal.GA_ReadOnly)
            if tile_dataset_info is None:
                # print error xml returned from server
                try:
                    error_xml_opened = open(temp_tile, "rb")
                    err_str = error_xml_opened.read()
                except IOError as e:
                    grass.fatal(_("Unable to read data from tempfile.\n%s") % str(e))
                finally:
                    error_xml_opened.close()

                if err_str is not None:
                    grass.fatal(_("WMS server error: %s") % err_str)
                else:
                    grass.fatal(_("WMS server unknown error"))

            temp_tile_pct2rgb = None
            if tile_dataset_info.RasterCount < 1:
                grass.fatal(
                    _(
                        "WMS server error: no band(s) received. Is server URL correct? <%s>"
                    )
                    % server_url
                )
            if (
                tile_dataset_info.RasterCount == 1
                and tile_dataset_info.GetRasterBand(1).GetRasterColorTable() is not None
            ):
                # expansion of color table into bands
                temp_tile_pct2rgb = self._tempfile()
                tile_dataset = self._pct2rgb(temp_tile, temp_tile_pct2rgb)
            else:
                tile_dataset = tile_dataset_info

            # initialization of temp_map_dataset, where all tiles are merged
            if init:
                temp_map = self._tempfile()

                driver = gdal.GetDriverByName(self.gdal_drv_format)
                metadata = driver.GetMetadata()
                if (
                    gdal.DCAP_CREATE not in metadata
                    or metadata[gdal.DCAP_CREATE] == "NO"
                ):
                    grass.fatal(
                        _("Driver %s does not supports Create() method")
                        % self.gdal_drv_format
                    )
                self.temp_map_bands_num = tile_dataset.RasterCount
                temp_map_dataset = driver.Create(
                    temp_map,
                    map_region["cols"],
                    map_region["rows"],
                    self.temp_map_bands_num,
                    tile_dataset.GetRasterBand(1).DataType,
                )
                init = False

            # tile is written into temp_map
            tile_to_temp_map = tile_dataset.ReadRaster(
                0,
                0,
                tile_ref["sizeX"],
                tile_ref["sizeY"],
                tile_ref["sizeX"],
                tile_ref["sizeY"],
            )

            temp_map_dataset.WriteRaster(
                tile_ref["t_cols_offset"],
                tile_ref["t_rows_offset"],
                tile_ref["sizeX"],
                tile_ref["sizeY"],
                tile_to_temp_map,
            )

            tile_dataset = None
            tile_dataset_info = None
            grass.try_remove(temp_tile)
            grass.try_remove(temp_tile_pct2rgb)

        if not temp_map:
            return temp_map
        # georeferencing and setting projection of temp_map
        projection = grass.read_command(
            "g.proj", flags="wf", epsg=GetEpsg(self.params["srs"])
        )
        projection = projection.rstrip("\n")
        temp_map_dataset.SetProjection(projection)

        pixel_x_length = (map_region["maxx"] - map_region["minx"]) / int(
            map_region["cols"]
        )
        pixel_y_length = (map_region["miny"] - map_region["maxy"]) / int(
            map_region["rows"]
        )

        geo_transform = [
            map_region["minx"],
            pixel_x_length,
            0.0,
            map_region["maxy"],
            0.0,
            pixel_y_length,
        ]
        temp_map_dataset.SetGeoTransform(geo_transform)
        temp_map_dataset = None

        return temp_map

    def _pct2rgb(self, src_filename, dst_filename):
        """!Create new dataset with data in dst_filename with bands according to src_filename
        raster color table - modified code from gdal utility pct2rgb

        @return new dataset
        """
        out_bands = 4
        band_number = 1

        # open source file
        src_ds = gdal.Open(src_filename)
        if src_ds is None:
            grass.fatal(_("Unable to open %s " % src_filename))

        src_band = src_ds.GetRasterBand(band_number)

        # Build color table
        lookup = [
            Numeric.arrayrange(256),
            Numeric.arrayrange(256),
            Numeric.arrayrange(256),
            Numeric.ones(256) * 255,
        ]

        ct = src_band.GetRasterColorTable()
        if ct is not None:
            for i in range(min(256, ct.GetCount())):
                entry = ct.GetColorEntry(i)
                for c in range(4):
                    lookup[c][i] = entry[c]

        # create the working file
        gtiff_driver = gdal.GetDriverByName(self.gdal_drv_format)
        tif_ds = gtiff_driver.Create(
            dst_filename, src_ds.RasterXSize, src_ds.RasterYSize, out_bands
        )

        # do the processing one scanline at a time
        for iY in range(src_ds.RasterYSize):
            src_data = src_band.ReadAsArray(0, iY, src_ds.RasterXSize, 1)

            for iBand in range(out_bands):
                band_lookup = lookup[iBand]

                dst_data = Numeric.take(band_lookup, src_data)
                tif_ds.GetRasterBand(iBand + 1).WriteArray(dst_data, 0, iY)

        return tif_ds


class BaseRequestMgr:
    """!Base class for request managers."""

    def _computeRequestData(self, bbox, tl_corner, tile_span, tile_size, mat_num_bbox):
        """!Initialize data needed for iteration through tiles. Used by WMTS_GRASS and OnEarth_GRASS drivers."""
        epsilon = 1e-15

        # request data bbox specified in row and col number
        self.t_num_bbox = {}

        self.t_num_bbox["min_col"] = int(
            floor((bbox["minx"] - tl_corner["minx"]) / tile_span["x"] + epsilon)
        )
        self.t_num_bbox["max_col"] = int(
            floor((bbox["maxx"] - tl_corner["minx"]) / tile_span["x"] - epsilon)
        )

        self.t_num_bbox["min_row"] = int(
            floor((tl_corner["maxy"] - bbox["maxy"]) / tile_span["y"] + epsilon)
        )
        self.t_num_bbox["max_row"] = int(
            floor((tl_corner["maxy"] - bbox["miny"]) / tile_span["y"] - epsilon)
        )

        # Does required bbox intersects bbox of data available on server?
        self.intersects = False
        for col in ["min_col", "max_col"]:
            for row in ["min_row", "max_row"]:
                if (
                    self.t_num_bbox["min_row"] <= self.t_num_bbox[row]
                    and self.t_num_bbox[row] <= mat_num_bbox["max_row"]
                ) and (
                    self.t_num_bbox["min_col"] <= self.t_num_bbox[col]
                    and self.t_num_bbox[col] <= mat_num_bbox["max_col"]
                ):
                    self.intersects = True

        if not self.intersects:
            grass.warning(_("Region is out of server data extend."))
            self.map_region = None
            return

        # crop request bbox to server data bbox extend
        if self.t_num_bbox["min_col"] < (mat_num_bbox["min_col"]):
            self.t_num_bbox["min_col"] = int(mat_num_bbox["min_col"])

        if self.t_num_bbox["max_col"] > (mat_num_bbox["max_col"]):
            self.t_num_bbox["max_col"] = int(mat_num_bbox["max_col"])

        if self.t_num_bbox["min_row"] < (mat_num_bbox["min_row"]):
            self.t_num_bbox["min_row"] = int(mat_num_bbox["min_row"])

        if self.t_num_bbox["max_row"] > (mat_num_bbox["max_row"]):
            self.t_num_bbox["max_row"] = int(mat_num_bbox["max_row"])

        grass.debug(
            "t_num_bbox: min_col:%d max_col:%d min_row:%d max_row:%d"
            % (
                self.t_num_bbox["min_col"],
                self.t_num_bbox["max_col"],
                self.t_num_bbox["min_row"],
                self.t_num_bbox["max_row"],
            ),
            3,
        )

        num_tiles = (self.t_num_bbox["max_col"] - self.t_num_bbox["min_col"] + 1) * (
            self.t_num_bbox["max_row"] - self.t_num_bbox["min_row"] + 1
        )
        grass.message(
            _("Fetching %d tiles with %d x %d pixel size per tile...")
            % (num_tiles, tile_size["x"], tile_size["y"])
        )

        # georeference of raster, where tiles will be merged
        self.map_region = {}
        self.map_region["minx"] = (
            self.t_num_bbox["min_col"] * tile_span["x"] + tl_corner["minx"]
        )
        self.map_region["maxy"] = (
            tl_corner["maxy"] - (self.t_num_bbox["min_row"]) * tile_span["y"]
        )

        self.map_region["maxx"] = (self.t_num_bbox["max_col"] + 1) * tile_span[
            "x"
        ] + tl_corner["minx"]
        self.map_region["miny"] = (
            tl_corner["maxy"] - (self.t_num_bbox["max_row"] + 1) * tile_span["y"]
        )

        # size of raster, where tiles will be merged
        self.map_region["cols"] = int(
            tile_size["x"]
            * (self.t_num_bbox["max_col"] - self.t_num_bbox["min_col"] + 1)
        )
        self.map_region["rows"] = int(
            tile_size["y"]
            * (self.t_num_bbox["max_row"] - self.t_num_bbox["min_row"] + 1)
        )

        # hold information about current column and row during iteration
        self.i_col = self.t_num_bbox["min_col"]
        self.i_row = self.t_num_bbox["min_row"]

        # bbox for first tile request
        self.query_bbox = {
            "minx": tl_corner["minx"],
            "maxy": tl_corner["maxy"],
            "maxx": tl_corner["minx"] + tile_span["x"],
            "miny": tl_corner["maxy"] - tile_span["y"],
        }

        self.tile_ref = {"sizeX": tile_size["x"], "sizeY": tile_size["y"]}

    def _isGeoProj(self, proj):
        """!Is it geographic projection?"""
        if proj.find("+proj=latlong") != -1 or proj.find("+proj=longlat") != -1:

            return True
        return False


class WMSRequestMgr(BaseRequestMgr):
    def __init__(self, params, bbox, region, tile_size, proj_srs, cap_file=None):
        """!Initialize data needed for iteration through tiles."""
        self.version = params["wms_version"]
        self.srs_param = params["srs"]

        proj = params["proj_name"] + "=" + GetSRSParamVal(params["srs"])
        self.url = params["url"] + (
            "SERVICE=WMS&REQUEST=GetMap&VERSION=%s&LAYERS=%s&WIDTH=%s&HEIGHT=%s&STYLES=%s&TRANSPARENT=%s"
            % (
                params["wms_version"],
                params["layers"],
                tile_size["cols"],
                tile_size["rows"],
                params["styles"],
                params["transparent"],
            )
        )

        if params["bgcolor"]:
            self.url += "&BGCOLOR=" + params["bgcolor"]

        self.url += "&" + proj + "&" + "FORMAT=" + params["format"]

        self.bbox = bbox
        self.proj_srs = proj_srs
        self.tile_rows = tile_size["rows"]
        self.tile_cols = tile_size["cols"]

        if params["urlparams"] != "":
            self.url += "&" + params["urlparams"]

        cols = int(region["cols"])
        rows = int(region["rows"])

        # computes parameters of tiles
        self.num_tiles_x = cols // self.tile_cols
        self.last_tile_x_size = cols % self.tile_cols
        self.tile_length_x = (
            float(self.tile_cols)
            / float(cols)
            * (self.bbox["maxx"] - self.bbox["minx"])
        )

        self.last_tile_x = False
        if self.last_tile_x_size != 0:
            self.last_tile_x = True
            self.num_tiles_x = self.num_tiles_x + 1

        self.num_tiles_y = rows // self.tile_rows
        self.last_tile_y_size = rows % self.tile_rows
        self.tile_length_y = (
            float(self.tile_rows)
            / float(rows)
            * (self.bbox["maxy"] - self.bbox["miny"])
        )

        self.last_tile_y = False
        if self.last_tile_y_size != 0:
            self.last_tile_y = True
            self.num_tiles_y = self.num_tiles_y + 1

        self.tile_bbox = dict(self.bbox)
        self.tile_bbox["maxx"] = self.bbox["minx"] + self.tile_length_x

        self.i_x = 0
        self.i_y = 0

        self.map_region = self.bbox
        self.map_region["cols"] = cols
        self.map_region["rows"] = rows

    def GetMapRegion(self):
        """!Get size in pixels and bounding box of raster where all tiles will be merged."""
        return self.map_region

    def GetNextTile(self):
        """!Get url for tile request from server and information for merging the tile with other tiles"""

        tile_ref = {}

        if self.i_x >= self.num_tiles_x:
            return None

        tile_ref["sizeX"] = self.tile_cols
        if self.i_x == self.num_tiles_x - 1 and self.last_tile_x:
            tile_ref["sizeX"] = self.last_tile_x_size

        # set bbox for tile (N, S)
        if self.i_y != 0:
            self.tile_bbox["miny"] -= self.tile_length_y
            self.tile_bbox["maxy"] -= self.tile_length_y
        else:
            self.tile_bbox["maxy"] = self.bbox["maxy"]
            self.tile_bbox["miny"] = self.bbox["maxy"] - self.tile_length_y

        tile_ref["sizeY"] = self.tile_rows
        if self.i_y == self.num_tiles_y - 1 and self.last_tile_y:
            tile_ref["sizeY"] = self.last_tile_y_size

        query_bbox = self._getQueryBbox(
            self.tile_bbox, self.proj_srs, self.srs_param, self.version
        )
        query_url = (
            self.url
            + "&"
            + "BBOX=%s,%s,%s,%s"
            % (
                query_bbox["minx"],
                query_bbox["miny"],
                query_bbox["maxx"],
                query_bbox["maxy"],
            )
        )

        tile_ref["t_cols_offset"] = int(self.tile_cols * self.i_x)
        tile_ref["t_rows_offset"] = int(self.tile_rows * self.i_y)

        if self.i_y >= self.num_tiles_y - 1:
            self.i_y = 0
            self.i_x += 1
            # set bbox for next tile (E, W)
            self.tile_bbox["maxx"] += self.tile_length_x
            self.tile_bbox["minx"] += self.tile_length_x
        else:
            self.i_y += 1

        return query_url, tile_ref

    def _getQueryBbox(self, bbox, proj, srs_param, version):
        """!Creates query bbox (used in request URL)

        Mostly bbox is not modified but if WMS standard is 1.3.0 and
        projection is geographic, the bbox x and y are in most cases flipped.
        """
        # CRS:84 and CRS:83 are exception (CRS:83 and CRS:27 need to be tested)
        if srs_param in [84, 83] or version != "1.3.0":
            return bbox
        elif Srs(GetSRSParamVal(srs_param)).axisorder == "yx":
            return self._flipBbox(bbox)

        return bbox

    def _flipBbox(self, bbox):
        """
        Flips bbox values between this keys:
        maxy -> maxx
        maxx -> maxy
        miny -> minx
        minx -> miny
        @return copy of bbox with flipped coordinates
        """

        temp_bbox = dict(bbox)
        new_bbox = {}
        new_bbox["maxy"] = temp_bbox["maxx"]
        new_bbox["miny"] = temp_bbox["minx"]
        new_bbox["maxx"] = temp_bbox["maxy"]
        new_bbox["minx"] = temp_bbox["miny"]

        return new_bbox


class WMTSRequestMgr(BaseRequestMgr):
    def __init__(self, params, bbox, region, proj_srs, cap_file=None):
        """!Initializes data needed for iteration through tiles."""

        self.proj_srs = proj_srs
        self.meters_per_unit = None

        # constant defined in WMTS standard (in meters)
        self.pixel_size = 0.00028

        # parse capabilities file
        try:
            # checks all elements needed by this class,
            # invalid elements are removed
            cap_tree = WMTSCapabilitiesTree(cap_file)
        except ParseError as error:
            grass.fatal(_("Unable to parse tile service file.\n%s\n") % str(error))
        self.xml_ns = cap_tree.getxmlnshandler()

        root = cap_tree.getroot()

        # get layer tile matrix sets with required projection
        # [[TileMatrixSet, TileMatrixSetLink], ....]
        mat_sets = self._getMatSets(root, params["layers"], params["srs"])

        # TODO: what if more tile matrix sets have required srs (returned more than 1)?
        mat_set = mat_sets[0][0]
        mat_set_link = mat_sets[0][1]
        params["tile_matrix_set"] = mat_set.find(self.xml_ns.NsOws("Identifier")).text

        # find tile matrix with resolution closest and smaller to wanted resolution
        tile_mat = self._findTileMats(
            mat_set.findall(self.xml_ns.NsWmts("TileMatrix")), region, bbox
        )

        # get extend of data available on server expressed in max/min rows and cols of tile matrix
        mat_num_bbox = self._getMatSize(tile_mat, mat_set_link)

        # initialize data needed for iteration through tiles
        self._computeRequestData(
            tile_mat, params, bbox, mat_num_bbox, self._getMatSetSrs(mat_set)
        )

    def GetMapRegion(self):
        """!Get size in pixels and bounding box of raster where all tiles will be merged."""
        return self.map_region

    def _getMatSets(self, root, layer_name, srs):
        """!Get matrix sets which are available for chosen layer and have required EPSG."""

        contents = root.find(self.xml_ns.NsWmts("Contents"))
        layers = contents.findall(self.xml_ns.NsWmts("Layer"))

        ch_layer = None
        for layer in layers:
            layer_id = layer.find(self.xml_ns.NsOws("Identifier")).text
            if layer_id == layer_name:
                ch_layer = layer
                break

        if ch_layer is None:
            grass.fatal(_("Layer '%s' was not found in capabilities file") % layer_name)

        mat_set_links = ch_layer.findall(self.xml_ns.NsWmts("TileMatrixSetLink"))

        suitable_mat_sets = []
        tileMatrixSets = contents.findall(self.xml_ns.NsWmts("TileMatrixSet"))

        for link in mat_set_links:
            mat_set_link_id = link.find(self.xml_ns.NsWmts("TileMatrixSet")).text
            for mat_set in tileMatrixSets:
                mat_set_id = mat_set.find(self.xml_ns.NsOws("Identifier")).text
                if mat_set_id != mat_set_link_id:
                    continue
                mat_set_srs = self._getMatSetSrs(mat_set)
                if Srs(mat_set_srs).getcode() == (GetSRSParamVal(srs)).upper():
                    suitable_mat_sets.append([mat_set, link])

        if not suitable_mat_sets:
            grass.fatal(
                _("Layer '%s' is not available with %s code.")
                % (layer_name, "EPSG:" + str(srs))
            )

        return suitable_mat_sets  # [[TileMatrixSet, TileMatrixSetLink], ....]

    def _getMatSetSrs(self, mat_set):

        return mat_set.find(self.xml_ns.NsOws("SupportedCRS")).text

    def _findTileMats(self, tile_mats, region, bbox):
        """!Find best tile matrix set for requested resolution."""
        scale_dens = []

        scale_dens.append(
            (bbox["maxy"] - bbox["miny"])
            / region["rows"]
            * self._getMetersPerUnit()
            / self.pixel_size
        )
        scale_dens.append(
            (bbox["maxx"] - bbox["minx"])
            / region["cols"]
            * self._getMetersPerUnit()
            / self.pixel_size
        )

        scale_den = min(scale_dens)

        first = True
        for t_mat in tile_mats:
            mat_scale_den = float(
                t_mat.find(self.xml_ns.NsWmts("ScaleDenominator")).text
            )
            if first:
                best_scale_den = mat_scale_den
                best_t_mat = t_mat
                first = False
                continue

            best_diff = best_scale_den - scale_den
            mat_diff = mat_scale_den - scale_den
            if (best_diff < mat_diff and mat_diff < 0) or (
                best_diff > mat_diff and best_diff > 0
            ):
                best_t_mat = t_mat
                best_scale_den = mat_scale_den

        return best_t_mat

    def _getMetersPerUnit(self):
        """!Get coefficient which allows converting units of request projection into meters."""
        if self.meters_per_unit:
            return self.meters_per_unit

        # for geographic projection
        if self._isGeoProj(self.proj_srs):
            proj_params = self.proj_srs.split(" ")
            for param in proj_params:
                if "+a" in param:
                    a = float(param.split("=")[1])
                    break
            equator_perim = 2 * pi * a
            # meters per degree on equator
            self.meters_per_unit = equator_perim / 360

        # other units
        elif "+to_meter" in self.proj_srs:
            proj_params = self.proj_srs.split(" ")
            for param in proj_params:
                if "+to_meter" in param:
                    self.meters_per_unit = 1 / float(param.split("=")[1])
                    break
        # coordinate system in meters
        else:
            self.meters_per_unit = 1

        return self.meters_per_unit

    def _getMatSize(self, tile_mat, mat_set_link):
        """!Get rows and cols extend of data available on server for chosen layer and tile matrix."""

        # general tile matrix size
        mat_num_bbox = {}
        mat_num_bbox["min_col"] = mat_num_bbox["min_row"] = 0
        mat_num_bbox["max_col"] = (
            int(tile_mat.find(self.xml_ns.NsWmts("MatrixWidth")).text) - 1
        )
        mat_num_bbox["max_row"] = (
            int(tile_mat.find(self.xml_ns.NsWmts("MatrixHeight")).text) - 1
        )

        # get extend restriction in TileMatrixSetLink for the tile matrix, if exists
        tile_mat_set_limits = mat_set_link.find(
            (self.xml_ns.NsWmts("TileMatrixSetLimits"))
        )
        if tile_mat_set_limits is None:
            return mat_num_bbox

        tile_mat_id = tile_mat.find(self.xml_ns.NsOws("Identifier")).text
        tile_mat_limits = tile_mat_set_limits.findall(
            self.xml_ns.NsWmts("TileMatrixLimits")
        )

        for limit in tile_mat_limits:
            limit_tile_mat = limit.find(self.xml_ns.NsWmts("TileMatrix"))
            limit_id = limit_tile_mat.text

            if limit_id == tile_mat_id:
                for i in [
                    ["min_row", "MinTileRow"],
                    ["max_row", "MaxTileRow"],
                    ["min_col", "MinTileCol"],
                    ["max_col", "MaxTileCol"],
                ]:
                    i_tag = limit.find(self.xml_ns.NsWmts(i[1]))

                    mat_num_bbox[i[0]] = int(i_tag.text)

                    if i[0] in ("max_row", "max_col"):
                        mat_num_bbox[i[0]] = mat_num_bbox[i[0]] - 1

                break
        return mat_num_bbox

    def _computeRequestData(self, tile_mat, params, bbox, mat_num_bbox, mat_set_srs):
        """!Initialize data needed for iteration through tiles."""
        scale_den = float(tile_mat.find(self.xml_ns.NsWmts("ScaleDenominator")).text)

        pixel_span = scale_den * self.pixel_size / self._getMetersPerUnit()

        tl_str = tile_mat.find(self.xml_ns.NsWmts("TopLeftCorner")).text.split(" ")

        tl_corner = {}
        tl_corner["minx"] = float(tl_str[0])
        tl_corner["maxy"] = float(tl_str[1])

        # TODO do it more generally WMS cap parser may use it in future(not needed now)???
        s = Srs(
            mat_set_srs
        )  # NOTE not used params['srs'], it is just number, encoding needed
        # TODO needs to be tested, tried only on
        # http://www.landesvermessung.sachsen.de/geoserver/gwc/service/wmts?:
        if s.getcode() == "EPSG:4326" and s.encoding in ("uri", "urn"):
            grass.warning("switch")
            (tl_corner["minx"], tl_corner["maxy"]) = (
                tl_corner["maxy"],
                tl_corner["minx"],
            )
        else:
            grass.warning("no switch")

        tile_span = {}
        self.tile_size = {}

        self.tile_size["x"] = int(tile_mat.find(self.xml_ns.NsWmts("TileWidth")).text)
        tile_span["x"] = pixel_span * self.tile_size["x"]

        self.tile_size["y"] = int(tile_mat.find(self.xml_ns.NsWmts("TileHeight")).text)
        tile_span["y"] = pixel_span * self.tile_size["y"]

        self.url = params["url"] + (
            "SERVICE=WMTS&REQUEST=GetTile&VERSION=1.0.0&"
            "LAYER=%s&STYLE=%s&FORMAT=%s&TILEMATRIXSET=%s&TILEMATRIX=%s"
            % (
                params["layers"],
                params["styles"],
                params["format"],
                params["tile_matrix_set"],
                tile_mat.find(self.xml_ns.NsOws("Identifier")).text,
            )
        )

        BaseRequestMgr._computeRequestData(
            self, bbox, tl_corner, tile_span, self.tile_size, mat_num_bbox
        )

    def GetNextTile(self):
        """!Get url for tile request from server and information for merging the tile with other tiles."""
        if not self.intersects or self.i_col > self.t_num_bbox["max_col"]:
            return None

        query_url = self.url + "&TILECOL=%i&TILEROW=%i" % (
            int(self.i_col),
            int(self.i_row),
        )

        self.tile_ref["t_cols_offset"] = int(
            self.tile_size["x"] * (self.i_col - self.t_num_bbox["min_col"])
        )
        self.tile_ref["t_rows_offset"] = int(
            self.tile_size["y"] * (self.i_row - self.t_num_bbox["min_row"])
        )

        if self.i_row >= self.t_num_bbox["max_row"]:
            self.i_row = self.t_num_bbox["min_row"]
            self.i_col += 1
        else:
            self.i_row += 1

        return query_url, self.tile_ref


class OnEarthRequestMgr(BaseRequestMgr):
    def __init__(self, params, bbox, region, proj_srs, tile_service):
        """!Initializes data needed for iteration through tiles."""
        try:
            # checks all elements needed by this class,
            # invalid elements are removed
            self.cap_tree = OnEarthCapabilitiesTree(tile_service)
        except ParseError as error:
            grass.fatal(_("Unable to parse tile service file.\n%s\n") % str(error))

        root = self.cap_tree.getroot()

        # parse tile service file and get needed data for making tile requests
        url, self.tile_span, t_patt_bbox, self.tile_size = self._parseTileService(
            root, bbox, region, params
        )
        self.url = url
        self.url[0] = params["url"] + url[0]
        # initialize data needed for iteration through tiles
        self._computeRequestData(bbox, t_patt_bbox, self.tile_span, self.tile_size)

    def GetMapRegion(self):
        """!Get size in pixels and bounding box of raster where all tiles will be merged."""
        return self.map_region

    def _parseTileService(self, root, bbox, region, params):
        """!Get data from tile service file"""
        tiled_patterns = root.find("TiledPatterns")
        tile_groups = self._getAllTiledGroup(tiled_patterns)
        if not tile_groups:
            grass.fatal(
                _("Unable to parse tile service file. \n No tag '%s' was found.")
                % "TiledGroup"
            )

        req_group = None
        for group in tile_groups:
            name = group.find("Name")
            if name.text == params["layers"]:
                req_group = group
                break

        if req_group is None:
            grass.fatal(
                _("Tiled group '%s' was not found in tile service file")
                % params["layers"]
            )

        group_t_patts = req_group.findall("TilePattern")
        best_patt = self._parseTilePattern(group_t_patts, bbox, region)

        urls = best_patt.text.split("\n")
        if params["urlparams"]:
            url = self._insTimeToTilePatternUrl(params["urlparams"], urls)
        else:
            url = urls[0]
            for u in urls:
                if "time=${" not in u:
                    url = u

        url, t_bbox, width, height = self.cap_tree.gettilepatternurldata(url)
        tile_span = {}
        tile_span["x"] = abs(t_bbox[0] - t_bbox[2])
        tile_span["y"] = abs(t_bbox[1] - t_bbox[3])

        tile_pattern_bbox = req_group.find("LatLonBoundingBox")

        t_patt_bbox = {}
        for s in ["minx", "miny", "maxx", "maxy"]:
            t_patt_bbox[s] = float(tile_pattern_bbox.get(s))

        tile_size = {}
        tile_size["x"] = width
        tile_size["y"] = height

        return url, tile_span, t_patt_bbox, tile_size

    def _getAllTiledGroup(self, parent, tiled_groups=None):
        """!Get all 'TileGroup' elements"""
        if not tiled_groups:
            tiled_groups = []

        tiled_groups += parent.findall("TiledGroup")
        new_groups = parent.findall("TiledGroups")

        for group in new_groups:
            self._getAllTiledGroup(group, tiled_groups)
        return tiled_groups

    def _parseTilePattern(self, group_t_patts, bbox, region):
        """!Find best tile pattern for requested resolution."""
        res = {}
        res["y"] = (bbox["maxy"] - bbox["miny"]) / region["rows"]
        res["x"] = (bbox["maxx"] - bbox["minx"]) / region["cols"]

        if res["x"] < res["y"]:
            comp_res = "x"
        else:
            comp_res = "y"

        t_res = {}
        best_patt = None
        for pattern in group_t_patts:
            url, t_bbox, width, height = self.cap_tree.gettilepatternurldata(
                pattern.text.split("\n")[0]
            )

            t_res["x"] = abs(t_bbox[0] - t_bbox[2]) / width
            t_res["y"] = abs(t_bbox[1] - t_bbox[3]) / height

            if best_patt is None:
                best_res = t_res[comp_res]
                best_patt = pattern
                continue

            best_diff = best_res - res[comp_res]
            tile_diff = t_res[comp_res] - res[comp_res]

            if (best_diff < tile_diff and tile_diff < 0) or (
                best_diff > tile_diff and best_diff > 0
            ):

                best_res = t_res[comp_res]
                best_patt = pattern

        return best_patt

    def _insTimeToTilePatternUrl(self, url_params, urls):
        """!Time can be variable in some urls in OnEarth TMS.
        Insert requested time from 'urlparams' into the variable if any url of urls contains the variable.
        """
        url = None
        not_sup_params = []
        url_params_list = url_params.split("&")

        for param in url_params_list:
            try:
                k, v = param.split("=")
            except ValueError:
                grass.warning(
                    _(
                        "Wrong form of parameter '%s' in '%s'. \n \
                                 The parameter was ignored."
                    )
                    % (param, "urlparams")
                )

            if k != "time":
                not_sup_params.append(k)
                continue

            has_time_var = False
            for url in urls:
                url_p_idxs = self.geturlparamidxs(url, k)
                if not url_p_idxs:
                    continue

                url_p_value = url[url_p_idxs[0] + len(k + "=") : url_p_idxs[1]]

                if url_p_value[:2] == "${" and url_p_value[len(url_p_value) - 1] == "}":
                    url = url[: url_p_idxs[0]] + param + url[url_p_idxs[1] :]
                    has_time_var = True
                    break

            if not has_time_var:
                grass.warning(
                    _("Parameter '%s' in '%s' is not variable in tile pattern url.")
                    % (k, "urlparams")
                )

        if not_sup_params:
            grass.warning(
                _(
                    "%s driver supports only '%s' parameter in '%s'. Other parameters are ignored."
                )
                % ("OnEarth GRASS", "time", "urlparams")
            )

        return url

    def _computeRequestData(self, bbox, t_patt_bbox, tile_span, tile_size):
        """!Initialize data needed for iteration through tiles."""
        epsilon = 1e-15
        mat_num_bbox = {}

        mat_num_bbox["min_row"] = mat_num_bbox["min_col"] = 0
        mat_num_bbox["max_row"] = floor(
            (t_patt_bbox["maxy"] - t_patt_bbox["miny"]) / tile_span["y"] + epsilon
        )
        mat_num_bbox["max_col"] = floor(
            (t_patt_bbox["maxx"] - t_patt_bbox["minx"]) / tile_span["x"] + epsilon
        )

        BaseRequestMgr._computeRequestData(
            self, bbox, t_patt_bbox, self.tile_span, self.tile_size, mat_num_bbox
        )

    def GetNextTile(self):
        """!Get url for tile request from server and information for merging the tile with other tiles"""
        if self.i_col > self.t_num_bbox["max_col"]:
            return None

        x_offset = self.tile_span["x"] * self.i_col
        y_offset = self.tile_span["y"] * self.i_row

        query_url = (
            self.url[0]
            + "&"
            + "bbox=%s,%s,%s,%s"
            % (
                float(self.query_bbox["minx"] + x_offset),
                float(self.query_bbox["miny"] - y_offset),
                float(self.query_bbox["maxx"] + x_offset),
                float(self.query_bbox["maxy"] - y_offset),
            )
            + self.url[1]
        )

        self.tile_ref["t_cols_offset"] = int(
            self.tile_size["y"] * (self.i_col - self.t_num_bbox["min_col"])
        )
        self.tile_ref["t_rows_offset"] = int(
            self.tile_size["x"] * (self.i_row - self.t_num_bbox["min_row"])
        )

        if self.i_row >= self.t_num_bbox["max_row"]:
            self.i_row = self.t_num_bbox["min_row"]
            self.i_col += 1
        else:
            self.i_row += 1

        return query_url, self.tile_ref