location.py

#Copyright 2011 Do@. All rights reserved.
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from .countries import countries

from geohasher import hasher
import math
import struct
import base64
import logging

class Location(object):
    """
    This is the base class for all location subclasses
    """
    
    __spec__ = ['lat', 'lon', 'name']
    __keyspec__ = None
    
    #keys should be named so we can query by the key names
    _keys = {}
    
    def __init__(self, **kwargs):

        self.lat = float(kwargs.get('lat', None))
        self.lon = float(kwargs.get('lon', None))
        self.name = kwargs.get('name', '').strip()
        

    @classmethod
    def _key(cls, _valdict):
        
        h = hash(':'.join((str(_valdict.get(x)) for x in cls.__keyspec__ or cls.__spec__)))
        return '%s:%s' % (cls.__name__,  base64.b64encode(struct.pack('q', h).strip('=')))
        
    def getId(self):

        #h = hash(':'.join((str(getattr(self, x)) for x in self.__keyspec__ or self.__spec__)))
        #'%s:%s' % (self.__class__.__name__,  base64.b64encode(struct.pack('q', h).strip('=')))
        return self._key(self.__dict__)

    def get(self, prop):

        return getattr(self, prop)


    @classmethod
    def getGeohashIndexKey(cls):

        return '%s:geohash' % cls.__name__

    def save(self, redisConn):

        
        #save all properties
        redisConn.hmset(self.getId(), dict(((k, getattr(self, k)) for k in \
                                        self.__spec__)))

        self._indexGeohash(redisConn)

        for k in self._keys.values():
            k.save(self, redisConn)

    def _indexGeohash(self, redisConn):
        """
        Save the key of the object into the goehash index for this object type
        """

        redisConn.zadd(self.getGeohashIndexKey(), self.getId(), hasher.encode(self.lat, self.lon))


    def __str__(self):
        return "%s: %s" % (self.__class__.__name__, self.__dict__)

    def __repr__(self):
        return "%s: %s" % (self.__class__.__name__, self.__dict__)
    
    @classmethod
    def load(cls, key, redisConn):
        """
        a Factory function to load a location from a given location key
        """
        
        d = redisConn.hgetall(str(key))
        
        if not d:
            return None
        
        #build a new object based on the loaded dict
        return cls(**d)
    
    def score(self, refLat, refLon):
        """
        To be implemented by child classes
        """
        return 1
    
    
    
    @classmethod
    def multiLoad(cls, keys, redisConn):
        """
        a Factory function to load a location from a given location key
        """
        
        p = redisConn.pipeline()
        [p.hgetall(str(key)) for key in keys]
        rx = p.execute()
        
        
        #build a new object based on the loaded dict
        return [cls(**d) for d in rx if d is not None]
    
    @classmethod
    def getIdsByNamedKey(cls, keyName, redisConn, *args, **kwargs):
        k = cls._keys[keyName]
        
        return k.getIds(redisConn, *args, **kwargs)
        
    @classmethod
    def loadByNamedKey(cls, keyName, redisConn, *args, **kwargs):
        """
        Load a class by a named key indexing some if its fields
        """
         
        k = cls._keys[keyName]
        
        ids = k.getIds(redisConn, *args, **kwargs)
        
        logging.info("Found %d ids for %s",len(ids or []), keyName)
        p  = redisConn.pipeline(False)
        [p.hgetall(id) for id in ids]
        rx = p.execute()
        
        ret = [cls(**d) for d in filter(None, rx)]
        
#        for id in ids:
#            ret.append(cls.load(id, redisConn))
            
        return ret
    
    
    
    @classmethod
    def getByKey(cls, redisConn, **kwargs):
        """
        Load an object by combining data from kwargs to create the unique key for this object
        useful for loading ZIP codes with only the known zip
        """
        key = cls._key(kwargs)
        
        return cls.load(key, redisConn)


    @classmethod
    def getByLatLon(cls, lat, lon, redisConn):
        
        geoKey = hasher.encode(lat, lon)
        
        return cls.getByGeohash(geoKey, redisConn)

    @staticmethod
    def getDistance(geoHash1, geoHash2):
        """
        Estimate the distance between 2 geohashes in uint64 format
        """

#        return abs(geoHash1 - geoHash2)
        
        try:
            coords1 = hasher.decode(geoHash1)
            coords2 = hasher.decode(geoHash2)
            return Location.getLatLonDistance(coords1, coords2)
            #return math.sqrt(math.pow(coords1[0] - coords2[0], 2) +
            #math.pow(coords1[1] - coords2[1], 2))
        except Exception as e:
            print(e)
            return None

        
    @staticmethod
    def getLatLonDistance(x, y):
        
        
        R = 6371
        dLat = math.radians(y[0]-x[0])
        dLon = math.radians(y[1]-x[1])
        a = math.sin(dLat/2) * math.sin(dLat/2) + \
            math.cos( math.radians(x[0])) * math.cos( math.radians(y[0])) * \
            math.sin(dLon/2) * math.sin(dLon/2);
        
        c = 2 * math.atan2(math.sqrt(a), math.sqrt(1-a))
        return R * c



    @classmethod
    def getByGeohash(cls, geoKey, redisConn):
        """
        Get a location (used directly on a subclass only!) according to a geohash key
        """


        key = cls.getGeohashIndexKey()
        tx = redisConn.pipeline()
        tx.zrangebyscore(key, geoKey, 'inf', 0, 10, True)
        tx.zrevrangebyscore(key, geoKey, '-inf', 0, 10, True)
        ret = tx.execute()

        #find the two closest locations to the left and to the right of us
        candidates = filter(None, ret[0]) + filter(None, ret[1])
        
        closestDist = None
        selected = None
        if not candidates :
            return None
        
        for i in range(len(candidates)):
            
            gk = long(candidates[i][1])
            
            dist = Location.getDistance(geoKey, gk)
            if dist is None:
                continue
            
            if not closestDist or dist < closestDist:
                closestDist = dist
                selected = i
            
            
        if selected is None:
            return None

        
        return cls.load(str(candidates[selected][0]), redisConn)