import os, sys

from ctypes import c_char_p, CDLL

from ctypes.util import find_library

from django.contrib.gis.gdal.error import OGRException

# Custom library path set?

try:

    from django.conf import settings

    lib_path = settings.GDAL_LIBRARY_PATH

except (AttributeError, EnvironmentError, ImportError):

    lib_path = None

if lib_path:

    lib_names = None

elif os.name == 'nt':

    # Windows NT shared library

    lib_names = ['gdal16', 'gdal15']

elif os.name == 'posix':

    # *NIX library names.

    lib_names = ['gdal', 'GDAL', 'gdal1.6.0', 'gdal1.5.0', 'gdal1.4.0']

else:

    raise OGRException('Unsupported OS "%s"' % os.name)

# Using the ctypes `find_library` utility  to find the 

# path to the GDAL library from the list of library names.

if lib_names:

    for lib_name in lib_names:

        lib_path = find_library(lib_name)

        if not lib_path is None: break

if lib_path is None:

    raise OGRException('Could not find the GDAL library (tried "%s"). '

                       'Try setting GDAL_LIBRARY_PATH in your settings.' % 

                       '", "'.join(lib_names))

# This loads the GDAL/OGR C library

lgdal = CDLL(lib_path)

# On Windows, the GDAL binaries have some OSR routines exported with 

# STDCALL, while others are not.  Thus, the library will also need to 

# be loaded up as WinDLL for said OSR functions that require the 

# different calling convention.

if os.name == 'nt':

    from ctypes import WinDLL

    lwingdal = WinDLL(lib_path)

def std_call(func):

    """

    Returns the correct STDCALL function for certain OSR routines on Win32

    platforms.

    """

    if os.name == 'nt':

        return lwingdal[func]

    else:

        return lgdal[func]

#### Version-information functions. ####

# Returns GDAL library version information with the given key.

_version_info = std_call('GDALVersionInfo')

_version_info.argtypes = [c_char_p]

_version_info.restype = c_char_p

def gdal_version():

    "Returns only the GDAL version number information."

    return _version_info('RELEASE_NAME')

def gdal_full_version(): 

    "Returns the full GDAL version information."

    return _version_info('')

def gdal_release_date(date=False): 

    """

    Returns the release date in a string format, e.g, "2007/06/27".

    If the date keyword argument is set to True, a Python datetime object

    will be returned instead.

    """

    from datetime import date as date_type

    rel = _version_info('RELEASE_DATE')

    yy, mm, dd = map(int, (rel[0:4], rel[4:6], rel[6:8]))

    d = date_type(yy, mm, dd)

    if date: return d

    else: return d.strftime('%Y/%m/%d')