from rpython.rtyper.lltypesystem import rffi, lltype
from pypy.module.cpyext.api import (PyObjectFields, bootstrap_function,
    cpython_struct,
    CANNOT_FAIL, cpython_api, PyObject, build_type_checkers, CONST_STRING)
from pypy.module.cpyext.pyobject import (
    make_typedescr, track_reference, from_ref)
from pypy.interpreter.error import OperationError
from rpython.rlib.rstruct import runpack
from pypy.objspace.std.floatobject import W_FloatObject

PyFloatObjectStruct = lltype.ForwardReference()
PyFloatObject = lltype.Ptr(PyFloatObjectStruct)
PyFloatObjectFields = PyObjectFields + \
    (("ob_fval", rffi.DOUBLE),)
cpython_struct("PyFloatObject", PyFloatObjectFields, PyFloatObjectStruct)

@bootstrap_function
def init_floatobject(space):
    "Type description of PyFloatObject"
    make_typedescr(space.w_float.layout.typedef,
                   basestruct=PyFloatObject.TO,
                   attach=float_attach,
                   realize=float_realize)

def float_attach(space, py_obj, w_obj, w_userdata=None):
    """
    Fills a newly allocated PyFloatObject with the given float object. The
    value must not be modified.
    """
    py_float = rffi.cast(PyFloatObject, py_obj)
    py_float.c_ob_fval = space.float_w(w_obj)

def float_realize(space, obj):
    floatval = rffi.cast(lltype.Float, rffi.cast(PyFloatObject, obj).c_ob_fval)
    w_type = from_ref(space, rffi.cast(PyObject, obj.c_ob_type))
    w_obj = space.allocate_instance(W_FloatObject, w_type)
    w_obj.__init__(floatval)
    track_reference(space, obj, w_obj)
    return w_obj

PyFloat_Check, PyFloat_CheckExact = build_type_checkers("Float")

@cpython_api([lltype.Float], PyObject)
def PyFloat_FromDouble(space, value):
    return space.newfloat(value)

@cpython_api([PyObject], lltype.Float, error=-1)
def PyFloat_AsDouble(space, w_obj):
    return space.float_w(space.float(w_obj))

@cpython_api([rffi.VOIDP], lltype.Float, error=CANNOT_FAIL)
def PyFloat_AS_DOUBLE(space, w_float):
    """Return a C double representation of the contents of w_float, but
    without error checking."""
    return space.float_w(w_float)

@cpython_api([PyObject], PyObject)
def PyNumber_Float(space, w_obj):
    """
    Returns the o converted to a float object on success, or NULL on failure.
    This is the equivalent of the Python expression float(o)."""
    return space.call_function(space.w_float, w_obj)

@cpython_api([PyObject], PyObject)
def PyFloat_FromString(space, w_obj):
    """
    Create a PyFloatObject object based on the string value in str, or
    NULL on failure.
    """
    return space.call_function(space.w_float, w_obj)

UCHARP = lltype.Ptr(lltype.Array(
    rffi.UCHAR, hints={'nolength':True, 'render_as_const':True}))
@cpython_api([UCHARP, rffi.INT_real], rffi.DOUBLE, error=-1.0)
def _PyFloat_Unpack4(space, ptr, le):
    input = rffi.charpsize2str(rffi.cast(CONST_STRING, ptr), 4)
    if rffi.cast(lltype.Signed, le):
        return runpack.runpack("<f", input)
    else:
        return runpack.runpack(">f", input)

@cpython_api([UCHARP, rffi.INT_real], rffi.DOUBLE, error=-1.0)
def _PyFloat_Unpack8(space, ptr, le):
    input = rffi.charpsize2str(rffi.cast(CONST_STRING, ptr), 8)
    if rffi.cast(lltype.Signed, le):
        return runpack.runpack("<d", input)
    else:
        return runpack.runpack(">d", input)
