from django.db import connection

from django.db.backends.util import truncate_name

from django.db.models.fields import Field # Django base Field class

from django.contrib.gis.db.backend.util import gqn

from django.contrib.gis.db.backend.oracle.query import TRANSFORM

# Quotename & geographic quotename, respectively.

qn = connection.ops.quote_name

class OracleSpatialField(Field):

    """

    The backend-specific geographic field for Oracle Spatial.

    """

    empty_strings_allowed = False

    def __init__(self, extent=(-180.0, -90.0, 180.0, 90.0), tolerance=0.05, **kwargs):

        """

        Oracle Spatial backend needs to have the extent -- for projected coordinate

        systems _you must define the extent manually_, since the coordinates are

        for geodetic systems.  The `tolerance` keyword specifies the tolerance

        for error (in meters), and defaults to 0.05 (5 centimeters).

        """

        # Oracle Spatial specific keyword arguments.

        self._extent = extent

        self._tolerance = tolerance

        # Calling the Django field initialization.

        super(OracleSpatialField, self).__init__(**kwargs)

    def _add_geom(self, style, db_table):

        """

        Adds this geometry column into the Oracle USER_SDO_GEOM_METADATA

        table.

        """

        # Checking the dimensions.

        # TODO: Add support for 3D geometries.

        if self._dim != 2:

            raise Exception('3D geometries not yet supported on Oracle Spatial backend.')

        # Constructing the SQL that will be used to insert information about

        # the geometry column into the USER_GSDO_GEOM_METADATA table.

        meta_sql = style.SQL_KEYWORD('INSERT INTO ') + \

                   style.SQL_TABLE('USER_SDO_GEOM_METADATA') + \

                   ' (%s, %s, %s, %s)\n  ' % tuple(map(qn, ['TABLE_NAME', 'COLUMN_NAME', 'DIMINFO', 'SRID'])) + \

                   style.SQL_KEYWORD(' VALUES ') + '(\n    ' + \

                   style.SQL_TABLE(gqn(db_table)) + ',\n    ' + \

                   style.SQL_FIELD(gqn(self.column)) + ',\n    ' + \

                   style.SQL_KEYWORD("MDSYS.SDO_DIM_ARRAY") + '(\n      ' + \

                   style.SQL_KEYWORD("MDSYS.SDO_DIM_ELEMENT") + \

                   ("('LONG', %s, %s, %s),\n      " % (self._extent[0], self._extent[2], self._tolerance)) + \

                   style.SQL_KEYWORD("MDSYS.SDO_DIM_ELEMENT") + \

                   ("('LAT', %s, %s, %s)\n    ),\n" % (self._extent[1], self._extent[3], self._tolerance)) + \

                   '    %s\n  );' % self._srid

        return meta_sql

    def _geom_index(self, style, db_table):

        "Creates an Oracle Geometry index (R-tree) for this geometry field."

        # Getting the index name, Oracle doesn't allow object

        # names > 30 characters.

        idx_name = truncate_name('%s_%s_id' % (db_table, self.column), 30)

        sql = style.SQL_KEYWORD('CREATE INDEX ') + \

              style.SQL_TABLE(qn(idx_name)) + \

              style.SQL_KEYWORD(' ON ') + \

              style.SQL_TABLE(qn(db_table)) + '(' + \

              style.SQL_FIELD(qn(self.column)) + ') ' + \

              style.SQL_KEYWORD('INDEXTYPE IS ') + \

              style.SQL_TABLE('MDSYS.SPATIAL_INDEX') + ';'

        return sql

    def post_create_sql(self, style, db_table):

        """

        Returns SQL that will be executed after the model has been

        created.

        """

        # Getting the meta geometry information.

        post_sql = self._add_geom(style, db_table)

        # Getting the geometric index for this Geometry column.

        if self._index:

            return (post_sql, self._geom_index(style, db_table))

        else:

            return (post_sql,)

    def db_type(self):

        "The Oracle geometric data type is MDSYS.SDO_GEOMETRY."

        return 'MDSYS.SDO_GEOMETRY'

    def get_placeholder(self, value):

        """

        Provides a proper substitution value for Geometries that are not in the

        SRID of the field.  Specifically, this routine will substitute in the

        SDO_CS.TRANSFORM() function call.

        """

        if value is None:

            return '%s'

        elif value.srid != self._srid:

            # Adding Transform() to the SQL placeholder.

            return '%s(SDO_GEOMETRY(%%s, %s), %s)' % (TRANSFORM, value.srid, self._srid)

        else:

            return 'SDO_GEOMETRY(%%s, %s)' % self._srid