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geo_hash.py
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geo_hash.py
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from math import ceil
from typing import List, Optional
class GeoHash:
def __init__(self) -> None:
self.__base32_lookup_table = {
0: "0", 1: "1", 2: "2", 3: "3", 4: "4", 5: "5", 6: "6",
7: "7", 8: "8", 9: "9", 10: "b", 11: "c", 12: "d",
13: "e", 14: "f", 15: "g", 16: "h", 17: "j", 18: "k",
19: "m", 20: "n", 21: "p", 22: "q", 23: "r", 24: "s",
25: "t", 26: "u", 27: "v", 28: "w", 29: "x", 30: "y",
31: "z",
}
self.__inverted_base32_lookup_table = {
value: key for key, value in self.__base32_lookup_table.items()
}
def __to_base_32(self, binary_str: str) -> str:
chunked_str = [
binary_str[i:i+5] for i in range(0, len(binary_str), 5)
]
return "".join(
[
self.__base32_lookup_table[int(chunk, base=2)] for chunk in chunked_str
if len(chunk) == 5 # Drop chunk falling short of 5 chars
]
)
def __encode_to_binary(self, number: float, bit_len: int, _range: List[float]) -> str:
bin_string_list = []
for _ in range(bit_len):
if number < _range[1]:
bin_string_list.append("0")
_range[2] = _range[1]
else:
bin_string_list.append("1")
_range[0] = _range[1]
_range[1] = (_range[0] + _range[2]) / 2
return "".join(bin_string_list)
def __longitude_to_binary(self, longitude: float, bit_len: int) -> str:
_range = [-180, 0, 180] # [low, mid, high]
return self.__encode_to_binary(longitude, bit_len, _range)
def __latitude_to_binary(self, latitude: float, bit_len: int) -> str:
_range = [-90, 0, 90] # [low, mid, high]
return self.__encode_to_binary(latitude, bit_len, _range)
def __binary_to_latitude(self, binary_stream: str) -> float:
_range = [-90, 0, 90]
return self.__decode_from_binary(binary_stream, _range)
def __binary_to_longitude(self, binary_stream: str) -> float:
_range = [-180, 0, 180]
return self.__decode_from_binary(binary_stream, _range)
def __decode_from_binary(self, binary_stream: str, _range: List[float]) -> float:
for digit in binary_stream:
if digit == "1":
_range[0] = _range[1]
else:
_range[2] = _range[1]
_range[1] = (_range[0] + _range[2]) / 2
return _range[1]
def get_geohash(self, longitude: float, latitude: float, precision: Optional[int]) -> str:
# TODO: Validate lat, long
if not precision: precision = 12
total_bits = precision * 5
longitude_bin: str = self.__longitude_to_binary(longitude, ceil(total_bits / 2))
latitude_bin: str = self.__latitude_to_binary(latitude, ceil(total_bits / 2))
interleaved_binary_str = "".join("".join(entry) for entry in list(zip(longitude_bin, latitude_bin)))
return self.__to_base_32(interleaved_binary_str)
def get_coordinates(self, geohash) -> tuple[float, float]:
decoded_base32 = [self.__inverted_base32_lookup_table[char] for char in geohash]
binary_str = "".join([bin(number).replace("0b", "").zfill(5) for number in decoded_base32])
longitude_bin_str = "".join([char for index, char in enumerate(binary_str) if index % 2 == 0])
latitude_bin_str = "".join([char for index, char in enumerate(binary_str) if index % 2 == 1])
return self.__binary_to_longitude(longitude_bin_str), self.__binary_to_latitude(latitude_bin_str)