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# -*- coding: utf-8 -*- 

 

u'''Classes L{Garef} and L{GARSError} and several functions to encode, 

decode and inspect I{Global Area Reference System} (GARS) references. 

 

Transcribed from C++ class U{GARS 

<https://GeographicLib.SourceForge.io/html/classGeographicLib_1_1GARS.html>} 

by I{Charles Karney}. See also U{Global Area Reference System 

<https://WikiPedia.org/wiki/Global_Area_Reference_System>} and U{NGA (GARS) 

<https://Earth-Info.NGA.mil/GandG/coordsys/grids/gars.html>}. 

 

@newfield example: Example, Examples 

''' 

 

from pygeodesy.basics import isstr, property_RO 

from pygeodesy.dms import parse3llh # parseDMS2 

from pygeodesy.errors import _ValueError 

from pygeodesy.interns import EPS1_2, NN, _item_sq, _0_5, _90_0 

from pygeodesy.interns import _1_0 # PYCHOK used! 

from pygeodesy.lazily import _ALL_LAZY, _ALL_OTHER 

from pygeodesy.named import nameof, _xnamed 

from pygeodesy.namedTuples import LatLon2Tuple, LatLonPrec3Tuple 

from pygeodesy.units import Int_, Lat, Lon, Precision_, Scalar_, \ 

Str, _xStrError 

 

from math import floor 

 

__all__ = _ALL_LAZY.gars 

__version__ = '20.09.27' 

 

_Digits = '0123456789' 

_LatLen = 2 

_LatOrig = -90 

_Letters = 'ABCDEFGHJKLMNPQRSTUVWXYZ' 

_LonLen = 3 

_LonOrig = -180 

_MaxPrec = 2 

 

_MinLen = _LonLen + _LatLen 

_MaxLen = _MinLen + _MaxPrec 

 

_M1 = 2 

_M2 = 2 

_M3 = 3 

_M_ = _M1 * _M2 * _M3 

 

_LatOrig_M_ = _LatOrig * _M_ 

_LonOrig_M_ = _LonOrig * _M_ 

 

_LatOrig_M1 = _LatOrig * _M1 

_LonOrig_M1_1 = _LonOrig * _M1 - 1 

 

_Resolutions = tuple(_1_0 / _ for _ in (_M1, _M1 * _M2, _M_)) 

 

 

def _2divmod2(ll, Orig_M_): 

x = int(floor(ll * _M_)) - Orig_M_ 

i = (x * _M1) // _M_ 

x -= i * _M_ // _M1 

return i, x 

 

 

def _2fll(lat, lon, *unused): 

'''(INTERNAL) Convert lat, lon. 

''' 

# lat, lon = parseDMS2(lat, lon) 

return (Lat(lat, Error=GARSError), 

Lon(lon, Error=GARSError)) 

 

 

# def _2Garef(garef): 

# '''(INTERNAL) Check or create a L{Garef} instance. 

# ''' 

# if not isinstance(garef, Garef): 

# try: 

# garef = Garef(garef) 

# except (TypeError, ValueError): 

# raise _xStrError(Garef, Str, garef=garef) 

# return garef 

 

 

def _2garstr2(garef): 

'''(INTERNAL) Check a garef string. 

''' 

try: 

n, garstr = len(garef), garef.upper() 

if n < _MinLen or n > _MaxLen \ 

or garstr[:3] == 'INV' \ 

or not garstr.isalnum(): 

raise ValueError 

return garstr, _2Precision(n - _MinLen) 

 

except (AttributeError, TypeError, ValueError) as x: 

raise GARSError(Garef.__name__, garef, txt=str(x)) 

 

 

def _2Precision(precision): 

'''(INTERNAL) Return a L{Precision_} instance. 

''' 

return Precision_(precision, Error=GARSError, low=0, high=_MaxPrec) 

 

 

class GARSError(_ValueError): 

'''Global Area Reference System (GARS) encode, decode or other L{Garef} issue. 

''' 

pass 

 

 

class Garef(Str): 

'''Garef class, a named C{str}. 

''' 

_latlon = None # cached latlon property 

_precision = None 

 

# no str.__init__ in Python 3 

def __new__(cls, cll, precision=1, name=NN): 

'''New L{Garef} from an other L{Garef} instance or garef 

C{str} or from a C{LatLon} instance or lat-/longitude C{str}. 

 

@arg cll: Cell or location (L{Garef} or C{str}, C{LatLon} 

or C{str}). 

@kwarg precision: Optional, the desired garef resolution 

and length (C{int} 0..2), see function 

L{gars.encode} for more details. 

@kwarg name: Optional name (C{str}). 

 

@return: New L{Garef}. 

 

@raise RangeError: Invalid B{C{cll}} lat- or longitude. 

 

@raise TypeError: Invalid B{C{cll}}. 

 

@raise GARSError: INValid or non-alphanumeric B{C{cll}}. 

''' 

if isinstance(cll, Garef): 

g, p = _2garstr2(str(cll)) 

self = Str.__new__(cls, g) 

self._latlon = LatLon2Tuple(*cll._latlon) 

self._name = cll._name 

self._precision = p # cll._precision 

 

elif isstr(cll): 

if ',' in cll: 

lat, lon = _2fll(*parse3llh(cll)) 

cll = encode(lat, lon, precision=precision) # PYCHOK false 

self = Str.__new__(cls, cll) 

self._latlon = LatLon2Tuple(lat, lon) 

else: 

self = Str.__new__(cls, cll.upper()) 

self._decode() 

 

else: # assume LatLon 

try: 

lat, lon = _2fll(cll.lat, cll.lon) 

except AttributeError: 

raise _xStrError(Garef, cll=cll) # Error=GARSError 

cll = encode(lat, lon, precision=precision) # PYCHOK false 

self = Str.__new__(cls, cll) 

self._latlon = LatLon2Tuple(lat, lon) 

 

if self._precision is None: 

self._precision = _2Precision(precision) 

 

if name: 

self.name = name 

return self 

 

def _decode(self): 

# cache all decoded attrs 

lat, lon, p = decode3(self) 

if self._latlon is None: 

self._latlon = LatLon2Tuple(lat, lon) 

if self._precision is None: 

self._precision = p 

 

@property_RO 

def latlon(self): 

'''Get this garef's (center) lat- and longitude (L{LatLon2Tuple}). 

''' 

if self._latlon is None: 

self._decode() 

return self._latlon 

 

@property_RO 

def precision(self): 

'''Get this garef's precision (C{int}). 

''' 

if self._precision is None: 

self._decode() 

return self._precision 

 

def toLatLon(self, LatLon, **kwds): 

'''Return (the center of) this garef cell as an instance 

of the supplied C{LatLon} class. 

 

@arg LatLon: Class to use (C{LatLon}). 

@kwarg kwds: Optional keyword arguments for B{C{LatLon}}. 

 

@return: This garef location (B{C{LatLon}}). 

 

@raise GARSError: Invalid B{C{LatLon}}. 

''' 

if LatLon is None: 

raise GARSError(LatLon=LatLon) 

 

return self._xnamed(LatLon(*self.latlon, **kwds)) 

 

 

def decode3(garef, center=True): 

'''Decode a C{garef} to lat-, longitude and precision. 

 

@arg garef: To be decoded (L{Garef} or C{str}). 

@kwarg center: If C{True} the center, otherwise the south-west, 

lower-left corner (C{bool}). 

 

@return: A L{LatLonPrec3Tuple}C{(lat, lon, precision)}. 

 

@raise GARSError: Invalid B{C{garef}}, INValid, non-alphanumeric 

or bad length B{C{garef}}. 

''' 

def _Error(i): 

return GARSError(garef=_item_sq(repr(garef), i)) 

 

def _ll(chars, g, i, j, lo, hi): 

ll, b = 0, len(chars) 

for i in range(i, j): 

d = chars.find(g[i]) 

if d < 0: 

raise _Error(i) 

ll = ll * b + d 

if ll < lo or ll > hi: 

raise _Error(j) 

return ll 

 

def _ll2(lon, lat, g, i, m): 

d = _Digits.find(g[i]) 

if d < 1 or d > m * m: 

raise _Error(i) 

d, r = divmod(d - 1, m) 

lon = lon * m + r 

lat = lat * m + (m - 1 - d) 

return lon, lat 

 

g, precision = _2garstr2(garef) 

 

lon = _ll(_Digits, g, 0, _LonLen, 1, 720) + _LonOrig_M1_1 

lat = _ll(_Letters, g, _LonLen, _MinLen, 0, 359) + _LatOrig_M1 

if precision > 0: 

lon, lat = _ll2(lon, lat, g, _MinLen, _M2) 

if precision > 1: 

lon, lat = _ll2(lon, lat, g, _MinLen + 1, _M3) 

 

if center: # ll = (ll * 2 + 1) / 2 

lon += _0_5 

lat += _0_5 

 

r = _Resolutions[precision] # == 1.0 / unit 

r = LatLonPrec3Tuple(Lat(lat * r, Error=GARSError), 

Lon(lon * r, Error=GARSError), precision) 

return _xnamed(r, nameof(garef)) 

 

 

def encode(lat, lon, precision=1): # MCCABE 14 

'''Encode a lat-/longitude as a C{garef} of the given precision. 

 

@arg lat: Latitude (C{degrees}). 

@arg lon: Longitude (C{degrees}). 

@kwarg precision: Optional, the desired C{garef} resolution 

and length (C{int} 0..2). 

 

@return: The C{garef} (C{str}). 

 

@raise RangeError: Invalid B{C{lat}} or B{C{lon}}. 

 

@raise GARSError: Invalid B{C{precision}}. 

 

@note: The C{garef} length is M{precision + 5} and the C{garef} 

resolution is B{30′} for B{C{precision}} 0, B{15′} for 1 

and B{5′} for 2, respectively. 

''' 

def _digit(x, y, m): 

return _Digits[m * (m - y - 1) + x + 1], 

 

def _str(chars, x, n): 

s, b = [], len(chars) 

for i in range(n): 

x, i = divmod(x, b) 

s.append(chars[i]) 

return tuple(reversed(s)) 

 

p = _2Precision(precision) 

 

lat, lon = _2fll(lat, lon) 

if lat == _90_0: 

lat *= EPS1_2 

 

ix, x = _2divmod2(lon, _LonOrig_M_) 

iy, y = _2divmod2(lat, _LatOrig_M_) 

 

g = _str(_Digits, ix + 1, _LonLen) + _str(_Letters, iy, _LatLen) 

if p > 0: 

ix, x = divmod(x, _M3) 

iy, y = divmod(y, _M3) 

g += _digit(ix, iy, _M2) 

if p > 1: 

g += _digit(x, y, _M3) 

 

return NN.join(g) 

 

 

def precision(res): 

'''Determine the L{Garef} precision to meet a required (geographic) 

resolution. 

 

@arg res: The required resolution (C{degrees}). 

 

@return: The L{Garef} precision (C{int} 0..2). 

 

@raise ValueError: Invalid B{C{res}}. 

 

@see: Function L{gars.encode} for more C{precision} details. 

''' 

r = Scalar_(res=res) 

for p in range(_MaxPrec): 

if resolution(p) <= r: 

return p 

return _MaxPrec 

 

 

def resolution(prec): 

'''Determine the (geographic) resolution of a given L{Garef} precision. 

 

@arg prec: The given precision (C{int}). 

 

@return: The (geographic) resolution (C{degrees}). 

 

@raise GARSError: Invalid B{C{prec}}. 

 

@see: Function L{gars.encode} for more C{precision} details. 

''' 

p = Int_(prec=prec, Error=GARSError, low=-1, high=_MaxPrec + 1) 

return _Resolutions[max(0, min(p, _MaxPrec))] 

 

 

__all__ += _ALL_OTHER(decode3, # functions 

encode, precision, resolution) 

 

# **) MIT License 

# 

# Copyright (C) 2016-2020 -- mrJean1 at Gmail -- All Rights Reserved. 

# 

# Permission is hereby granted, free of charge, to any person obtaining a 

# copy of this software and associated documentation files (the "Software"), 

# to deal in the Software without restriction, including without limitation 

# the rights to use, copy, modify, merge, publish, distribute, sublicense, 

# and/or sell copies of the Software, and to permit persons to whom the 

# Software is furnished to do so, subject to the following conditions: 

# 

# The above copyright notice and this permission notice shall be included 

# in all copies or substantial portions of the Software. 

# 

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 

# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 

# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 

# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 

# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 

# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 

# OTHER DEALINGS IN THE SOFTWARE.