"""

 This object provides quoting for GEOS geometries into PostgreSQL/PostGIS.

"""

from django.contrib.gis.db.backend.postgis.query import GEOM_FROM_WKB

from psycopg2 import Binary

from psycopg2.extensions import ISQLQuote

class PostGISAdaptor(object):

    def __init__(self, geom):

        "Initializes on the geometry."

        # Getting the WKB (in string form, to allow easy pickling of

        # the adaptor) and the SRID from the geometry.

        self.wkb = str(geom.wkb)

        self.srid = geom.srid

    def __conform__(self, proto):

        # Does the given protocol conform to what Psycopg2 expects?

        if proto == ISQLQuote:

            return self

        else:

            raise Exception('Error implementing psycopg2 protocol. Is psycopg2 installed?')

    def __eq__(self, other):

        return (self.wkb == other.wkb) and (self.srid == other.srid)

    def __str__(self):

        return self.getquoted()

    def getquoted(self):

        "Returns a properly quoted string for use in PostgreSQL/PostGIS."

        # Want to use WKB, so wrap with psycopg2 Binary() to quote properly.

        return "%s(%s, %s)" % (GEOM_FROM_WKB, Binary(self.wkb), self.srid or -1)

    def prepare_database_save(self, unused):

        return self