import os
from OCC.Core.STEPControl import STEPControl_Reader, STEPControl_Writer, STEPControl_AsIs
from OCC.Core.STEPCAFControl import STEPCAFControl_Writer

from OCC.Core.Interface import Interface_Static_SetCVal
from OCC.Core.IFSelect import IFSelect_RetDone, IFSelect_ItemsByEntity
from OCC.Core.TDocStd import TDocStd_Document
from OCC.Core.TCollection import TCollection_ExtendedString

try:
    import svgwrite
    HAVE_SVGWRITE = True
except ImportError:
    HAVE_SVGWRITE = False

def write_step_file(a_shape, filename, application_protocol="AP242DIS"):
    """ exports a shape to a STEP file
    a_shape: the topods_shape to export (a compound, a solid etc.)
    filename: the filename
    application protocol: "AP203" or "AP214IS" or "AP242DIS"
    """
    # a few checks
    #if a_shape.IsNull():
    #    raise AssertionError("Shape %s is null." % a_shape)
    if application_protocol not in ["AP203", "AP214IS", "AP242DIS"]:
        raise AssertionError("application_protocol must be either AP203 or AP214IS. You passed %s." % application_protocol)
    if os.path.isfile(filename):
        print("Warning: %s file already exists and will be replaced" % filename)
    # creates and initialise the step exporter
    step_writer = STEPCAFControl_Writer()
    Interface_Static_SetCVal("write.step.schema", application_protocol)

    # transfer shapes and write file
    step_writer.Transfer(a_shape, STEPControl_AsIs)
    status = step_writer.Write(filename)

    if not status == IFSelect_RetDone:
        raise IOError("Error while writing shape to STEP file.")
    if not os.path.isfile(filename):
        raise IOError("File %s was not saved to filesystem." % filename)