"""

 This module contains functions that generate ctypes prototypes for the

 GDAL routines.

"""

from ctypes import c_char_p, c_double, c_int, c_void_p

from django.contrib.gis.gdal.prototypes.errcheck import \

    check_arg_errcode, check_errcode, check_geom, check_geom_offset, \

    check_pointer, check_srs, check_str_arg, check_string, check_const_string

def double_output(func, argtypes, errcheck=False, strarg=False):

    "Generates a ctypes function that returns a double value."

    func.argtypes = argtypes

    func.restype = c_double

    if errcheck: func.errcheck = check_arg_errcode

    if strarg: func.errcheck = check_str_arg

    return func

def geom_output(func, argtypes, offset=None):

    """

    Generates a function that returns a Geometry either by reference

    or directly (if the return_geom keyword is set to True).

    """

    # Setting the argument types

    func.argtypes = argtypes

    if not offset:

        # When a geometry pointer is directly returned.

        func.restype = c_void_p

        func.errcheck = check_geom

    else:

        # Error code returned, geometry is returned by-reference.

        func.restype = c_int

        def geomerrcheck(result, func, cargs):

            return check_geom_offset(result, func, cargs, offset)

        func.errcheck = geomerrcheck

    return func

def int_output(func, argtypes):

    "Generates a ctypes function that returns an integer value."

    func.argtypes = argtypes

    func.restype = c_int

    return func

def srs_output(func, argtypes):

    """

    Generates a ctypes prototype for the given function with

    the given C arguments that returns a pointer to an OGR

    Spatial Reference System.

    """

    func.argtypes = argtypes

    func.restype = c_void_p

    func.errcheck = check_srs

    return func

def const_string_output(func, argtypes, offset=None):

    func.argtypes = argtypes

    if offset:

        func.restype = c_int

    else:

        func.restype = c_char_p

    def _check_const(result, func, cargs):

        return check_const_string(result, func, cargs, offset=offset)

    func.errcheck = _check_const

    return func

def string_output(func, argtypes, offset=-1, str_result=False):

    """

    Generates a ctypes prototype for the given function with the

    given argument types that returns a string from a GDAL pointer.

    The `const` flag indicates whether the allocated pointer should 

    be freed via the GDAL library routine VSIFree -- but only applies

    only when `str_result` is True.

    """

    func.argtypes = argtypes

    if str_result:

        # String is the result, don't explicitly define

        # the argument type so we can get the pointer.

        pass

    else:

        # Error code is returned

        func.restype = c_int

    # Dynamically defining our error-checking function with the

    # given offset.

    def _check_str(result, func, cargs):

        return check_string(result, func, cargs,

                            offset=offset, str_result=str_result)

    func.errcheck = _check_str

    return func

def void_output(func, argtypes, errcheck=True):

    """

    For functions that don't only return an error code that needs to

    be examined.

    """

    if argtypes: func.argtypes = argtypes

    if errcheck:

        # `errcheck` keyword may be set to False for routines that

        # return void, rather than a status code.

        func.restype = c_int

        func.errcheck = check_errcode

    else:

        func.restype = None

    return func

def voidptr_output(func, argtypes):

    "For functions that return c_void_p."

    func.argtypes = argtypes

    func.restype = c_void_p

    func.errcheck = check_pointer

    return func