fgmeta/ws30/calc_tile.py

# -*- coding: utf-8 -*-
"""
shamelessly translated from calc-tile.pl
"""
import logging
from math import floor
import os
from typing import List, Tuple
import unittest

import numpy as np


def bucket_span(lat: float) -> float:
    """Latitude Range -> Tile Width (deg)"""
    abs_lat = abs(lat)
    if abs_lat >= 89:
        return 360
    elif abs_lat >= 88:
        return 8
    elif abs_lat >= 86:
        return 4
    elif abs_lat >= 83:
        return 2
    elif abs_lat >= 76:
        return 1
    elif abs_lat >= 62:
        return .5
    elif abs_lat >= 22:
        return .25
    elif abs_lat >= 0:
        return .125
    return 360


def format_lon(lon):
    """Format longitude as e/w."""
    if lon < 0.:
        return "w%03d" % int(0. - lon)
    else:
        return "e%03d" % int(lon)


def format_lat(lat):
    """Format latitude as n/s."""
    if lat < 0.:
        return "s%02d" % int(0. - lat)
    else:
        return "n%02d" % int(lat)


def directory_name(lon_lat: Tuple[float, float], separator: str = None) -> str:
    """Generate the directory name for a location."""
    (lon, lat) = lon_lat
    lon_floor = floor(lon)
    lat_floor = floor(lat)
    lon_chunk = floor(lon/10.0) * 10
    lat_chunk = floor(lat/10.0) * 10
    if separator:
        return '{}{}{}{}{}'.format(format_lon(lon_chunk), format_lat(lat_chunk), separator,
                                   format_lon(lon_floor), format_lat(lat_floor))
    return os.path.join(format_lon(lon_chunk) + format_lat(lat_chunk), format_lon(lon_floor) + format_lat(lat_floor))


def calc_tile_index(lon_lat: Tuple[float, float], x: int = 0, y: int = 0) -> int:
    """See  http://wiki.flightgear.org/Tile_Index_Scheme"""
    (lon, lat) = lon_lat
    if x == 0 and y == 0:
        y = calc_y(lat)
        x = calc_x(lon, lat)

    index = (int(floor(lon)) + 180) << 14
    index += (int(floor(lat)) + 90) << 6
    index += y << 3
    index += x
    return index


def calc_tile_location(tile_index: int) -> Tuple[Tuple[float, float], Tuple[float, float]]:
    """The lon/lat as well as x/y tuples for the location of a tile by its index"""
    lon = tile_index >> 14
    index = tile_index - (lon << 14)
    lon = lon - 180

    lat = index >> 6
    index = index - (lat << 6)
    lat = lat - 90

    y = index >> 3
    index = index - (y << 3)
    x = index

    return (lon, lat), (x, y)


def log_tile_info(tile_index: int) -> None:
    """logs information about the tile to logging.debug."""
    (lon, lat), (x, y) = calc_tile_location(tile_index)
    center_lat = lat + y / 8.0 + 0.0625
    center_lon = bucket_span(center_lat)
    if center_lon >= 1.0:
        center_lon = lon + center_lon / 2.0
    else:
        center_lon = lon + x * center_lon + center_lon / 2.0

    tile_info = 'Tile location: {}; lon: {}, lat: {}; x: {}, y: {}; tile span degrees: {}; center lon/lat: {}/{}.'
    logging.debug(tile_info.format(tile_index, lon, lat, x, y, bucket_span(lat), center_lon, center_lat))


def construct_path_to_files(base_directory: str, scenery_type: str, center_global: Tuple[float, float]) -> str:
    """Returns the path to the stg-files in a FG scenery directory hierarchy at a given global lat/lon location.
    The scenery type is e.g. 'Terrain', 'Object', 'Buildings'."""
    return os.path.join(base_directory, scenery_type, directory_name(center_global))


def construct_stg_file_name(center_global: Tuple[float, float]) -> str:
    """Returns the file name of the stg-file at a given global lat/lon location"""
    return construct_stg_file_name_from_tile_index(calc_tile_index(center_global))


def construct_stg_file_name_from_tile_index(tile_idx: int) -> str:
    return str(tile_idx) + '.stg'


def construct_btg_file_name_from_tile_index(tile_idx: int) -> str:
    return str(tile_idx) + '.btg.gz'


def construct_btg_file_name_from_airport_code(airport_code: str) -> str:
    return airport_code + '.btg.gz'


def get_north_lat(lat, y):
    return float(floor(lat)) + y / 8.0 + .125


def get_south_lat(lat, y):
    return float(floor(lat)) + y / 8.0


def get_west_lon(lon, lat, x):
    if x == 0:
        return float(floor(lon))
    else: 
        return float(floor(lon)) + x * (bucket_span(lat))


def get_east_lon(lon, lat, x):
    if x == 0:
        return float(floor(lon)) + (bucket_span(lat))
    else: 
        return float(floor(lon)) + x * (bucket_span(lat)) + (bucket_span(lat))


def calc_x(lon: float, lat: float) -> int:
    """
    FIXME: is this correct? Also: some returns do not take calculations into account.
    """
    epsilon = 0.0000001
    span = bucket_span(lat)
    if span < epsilon:
        lon = 0
        return 0
    elif span <= 1.0:
        return int((lon - floor(lon)) / span)
    else:
        if lon >= 0:
            lon = int(int(lon/span) * span)
        else:
            lon = int(int((lon+1)/span) * span - span)
            if lon < -180:
                lon = -180
        return 0


def calc_y(lat: float) -> int:
    return int((lat - floor(lat)) * 8)
    

def get_stg_files_in_boundary(boundary_west: float, boundary_south: float, boundary_east: float, boundary_north: float,
                              path_to_scenery: str, scenery_type: str) -> List[str]:
    """Based on boundary rectangle returns a list of stg-files (incl. full path) to be found within the boundary of
    the scenery"""
    stg_files = []
    for my_lat in np.arange(boundary_south, boundary_north, 0.125):  # latitude; 0.125 as there are always 8 tiles
        for my_lon in np.arange(boundary_west, boundary_east, bucket_span(my_lat)):  # longitude
            coords = (my_lon, my_lat)
            stg_files.append(os.path.join(construct_path_to_files(path_to_scenery, scenery_type, coords),
                             construct_stg_file_name(coords)))
    return stg_files


# ================ UNITTESTS =======================


class TestCalcTiles(unittest.TestCase):
    def test_calc_tiles(self):
        self.assertEqual(5760, calc_tile_index((-179.9, 0.1)))
        self.assertEqual(5752, calc_tile_index((-179.9, -0.1)))
        self.assertEqual(5887623, calc_tile_index((179.9, 0.1)))
        self.assertEqual(5887615, calc_tile_index((179.9, -0.1)))
        self.assertEqual(2954880, calc_tile_index((0.0, 0.0)))
        self.assertEqual(2938495, calc_tile_index((-0.1, -0.1)))

    def test_file_name(self):
        self.assertEqual("3088961.stg", construct_stg_file_name((8.29, 47.08)))