"""

 Utilities for manipulating Geometry WKT.

"""

def precision_wkt(geom, prec):

    """

    Returns WKT text of the geometry according to the given precision (an 

    integer or a string).  If the precision is an integer, then the decimal

    places of coordinates WKT will be truncated to that number:

     >>> pnt = Point(5, 23)

     >>> pnt.wkt

     'POINT (5.0000000000000000 23.0000000000000000)'

     >>> precision(geom, 1)

     'POINT (5.0 23.0)'

    If the precision is a string, it must be valid Python format string 

    (e.g., '%20.7f') -- thus, you should know what you're doing.

    """

    if isinstance(prec, int):

        num_fmt = '%%.%df' % prec

    elif isinstance(prec, basestring):

        num_fmt = prec

    else:

        raise TypeError

    # TODO: Support 3D geometries.

    coord_fmt = ' '.join([num_fmt, num_fmt])

    def formatted_coords(coords):

        return ','.join([coord_fmt % c[:2] for c in coords])

    def formatted_poly(poly):

        return ','.join(['(%s)' % formatted_coords(r) for r in poly])

    def formatted_geom(g):

        gtype = str(g.geom_type).upper()

        yield '%s(' % gtype

        if gtype == 'POINT':

            yield formatted_coords((g.coords,))

        elif gtype in ('LINESTRING', 'LINEARRING'):

            yield formatted_coords(g.coords)

        elif gtype in ('POLYGON', 'MULTILINESTRING'):

            yield formatted_poly(g)

        elif gtype == 'MULTIPOINT':

            yield formatted_coords(g.coords)

        elif gtype == 'MULTIPOLYGON':

            yield ','.join(['(%s)' % formatted_poly(p) for p in g])

        elif gtype == 'GEOMETRYCOLLECTION':

            yield ','.join([''.join([wkt for wkt in formatted_geom(child)]) for child in g])

        else:

            raise TypeError

        yield ')'

    return ''.join([wkt for wkt in formatted_geom(geom)])