"""

  This utility module is for obtaining information about the PostGIS

   installation.

  See PostGIS docs at Ch. 6.2.1 for more information on these functions.

"""

import re

def _get_postgis_func(func):

    "Helper routine for calling PostGIS functions and returning their result."

    from django.db import connection

    cursor = connection.cursor()

    cursor.execute('SELECT %s()' % func)

    row = cursor.fetchone()

    cursor.close()

    return row[0]

### PostGIS management functions ###

def postgis_geos_version():

    "Returns the version of the GEOS library used with PostGIS."

    return _get_postgis_func('postgis_geos_version')

def postgis_lib_version():

    "Returns the version number of the PostGIS library used with PostgreSQL."

    return _get_postgis_func('postgis_lib_version')

def postgis_proj_version():

    "Returns the version of the PROJ.4 library used with PostGIS."

    return _get_postgis_func('postgis_proj_version')

def postgis_version():

    "Returns PostGIS version number and compile-time options."

    return _get_postgis_func('postgis_version')

def postgis_full_version():

    "Returns PostGIS version number and compile-time options."

    return _get_postgis_func('postgis_full_version')

### Routines for parsing output of management functions. ###

version_regex = re.compile('^(?P<major>\d)\.(?P<minor1>\d)\.(?P<minor2>\d+)')

def postgis_version_tuple():

    "Returns the PostGIS version as a tuple."

    # Getting the PostGIS version

    version = postgis_lib_version()

    m = version_regex.match(version)

    if m:

        major = int(m.group('major'))

        minor1 = int(m.group('minor1'))

        minor2 = int(m.group('minor2'))

    else:

        raise Exception('Could not parse PostGIS version string: %s' % version)

    return (version, major, minor1, minor2)