/**
 * \file Geohash.cpp
 * \brief Implementation for GeographicLib::Geohash class
 *
 * Copyright (c) Charles Karney (2012-2017) <charles@karney.com> and licensed
 * under the MIT/X11 License. For more information, see
 * https://geographiclib.sourceforge.io/
 **********************************************************************/

#include <GeographicLib/Geohash.hpp>
#include <GeographicLib/Utility.hpp>

namespace GeographicLib {

 using namespace std;

 const char* const Geohash::lcdigits_ = "0123456789bcdefghjkmnpqrstuvwxyz";
 const char* const Geohash::ucdigits_ = "0123456789BCDEFGHJKMNPQRSTUVWXYZ";

 void Geohash::Forward(real lat, real lon, int len, std::string& geohash) {
 static const real shift = ldexp(real(1), 45);
 static const real loneps = 180 / shift;
 static const real lateps = 90 / shift;
 if (abs(lat) > 90)
 throw GeographicErr("Latitude " + Utility::str(lat)
 + "d not in [-90d, 90d]");
 if (Math::isnan(lat) || Math::isnan(lon)) {
 geohash = "invalid";
 return;
 }
 if (lat == 90) lat -= lateps / 2;
 lon = Math::AngNormalize(lon); // lon in [-180,180)
 // lon/loneps in [-2^45,2^45); lon/loneps + shift in [0,2^46)
 // similarly for lat
 len = max(0, min(int(maxlen_), len));
 unsigned long long
 ulon = (unsigned long long)(floor(lon/loneps) + shift),
 ulat = (unsigned long long)(floor(lat/lateps) + shift);
 char geohash1[maxlen_];
 unsigned byte = 0;
 for (unsigned i = 0; i < 5 * unsigned(len);) {
 if ((i & 1) == 0) {
 byte = (byte << 1) + unsigned((ulon & mask_) != 0);
 ulon <<= 1;
 } else {
 byte = (byte << 1) + unsigned((ulat & mask_) != 0);
 ulat <<= 1;
 }
 ++i;
 if (i % 5 == 0) {
 geohash1[(i/5)-1] = lcdigits_[byte];
 byte = 0;
 }
 }
 geohash.resize(len);
 copy(geohash1, geohash1 + len, geohash.begin());
 }

 void Geohash::Reverse(const std::string& geohash, real& lat, real& lon,
 int& len, bool centerp) {
 static const real shift = ldexp(real(1), 45);
 static const real loneps = 180 / shift;
 static const real lateps = 90 / shift;
 int len1 = min(int(maxlen_), int(geohash.length()));
 if (len1 >= 3 &&
 ((toupper(geohash[0]) == 'I' &&
 toupper(geohash[1]) == 'N' &&
 toupper(geohash[2]) == 'V') ||
 // Check A first because it is not in a standard geohash
 (toupper(geohash[1]) == 'A' &&
 toupper(geohash[0]) == 'N' &&
 toupper(geohash[2]) == 'N'))) {
 lat = lon = Math::NaN();
 return;
 }
 unsigned long long ulon = 0, ulat = 0;
 for (unsigned k = 0, j = 0; k < unsigned(len1); ++k) {
 int byte = Utility::lookup(ucdigits_, geohash[k]);
 if (byte < 0)
 throw GeographicErr("Illegal character in geohash " + geohash);
 for (unsigned m = 16; m; m >>= 1) {
 if (j == 0)
 ulon = (ulon << 1) + unsigned((byte & m) != 0);
 else
 ulat = (ulat << 1) + unsigned((byte & m) != 0);
 j ^= 1;
 }
 }
 ulon <<= 1; ulat <<= 1;
 if (centerp) {
 ulon += 1;
 ulat += 1;
 }
 int s = 5 * (maxlen_ - len1);
 ulon <<= (s / 2);
 ulat <<= s - (s / 2);
 lon = ulon * loneps - 180;
 lat = ulat * lateps - 90;
 len = len1;
 }

} // namespace GeographicLib