import bpy
from bpy_extras.io_utils import ExportHelper


class ExportFoobar(bpy.types.Operator, ExportHelper):
    bl_idname = "export_scene.foobar"
    bl_label = 'Export Foobar'
    bl_options = {'PRESET'}

    filename_ext = ''
    filter_glob: bpy.props.StringProperty(default='*.foo;*.bar', options={'HIDDEN'})

    extension: bpy.props.EnumProperty(
        name='Extension',
        items=(('FOO', '.foo', '.foo'), ('BAR', '.bar', '.bar')),
        default='FOO',
    )

    def execute(self, context):
        print(self.filepath)
        return {'FINISHED'}

    def check(self, context):
        print('check called')

        import os
        changed = False

        filepath = self.filepath
        if os.path.basename(filepath):
            filepath = bpy.path.ensure_ext(
                filepath,
                '.foo' if self.extension == 'FOO' else '.bar',
            )
            changed = (filepath != self.filepath)
            self.filepath = filepath

        return changed

    def draw(self, context):
        pass
        # NOTE!: if the prop is drawn here instead of in a panel, check is
        # called automatically without having to do anything special


class FOOBAR_PT_export_main(bpy.types.Panel):
    bl_space_type = 'FILE_BROWSER'
    bl_region_type = 'TOOL_PROPS'
    bl_label = ""
    bl_parent_id = "FILE_PT_operator"
    bl_options = {'HIDE_HEADER'}

    @classmethod
    def poll(cls, context):
        sfile = context.space_data
        operator = sfile.active_operator

        return operator.bl_idname == "EXPORT_SCENE_OT_foobar"

    def draw(self, context):
        layout = self.layout
        layout.use_property_split = True
        layout.use_property_decorate = False  # No animation.

        sfile = context.space_data
        operator = sfile.active_operator

        layout.prop(operator, 'extension')


classes = (ExportFoobar, FOOBAR_PT_export_main)


def menu_func_export(self, context):
    self.layout.operator(ExportFoobar.bl_idname, text="Export foobar")


def register():
    for cls in classes: bpy.utils.register_class(cls)
    bpy.types.TOPBAR_MT_file_export.append(menu_func_export)


def unregister():
    bpy.types.TOPBAR_MT_file_export.remove(menu_func_export)
    for cls in classes: bpy.utils.unregister_class(cls)


if __name__ == "__main__":
    register()