Perform command and return the appropriate exit code.

        :rtype: int

def perform_command(self):
        """
        Perform command and return the appropriate exit code.

        :rtype: int
        """
        if len(self.actual_arguments) < 2:
            return self.print_help()
        input_file_path = self.actual_arguments[0]
        output_file_path = self.actual_arguments[1]
        output_html = self.has_option(u"--output-html")

        if not self.check_input_file(input_file_path):
            return self.ERROR_EXIT_CODE
        input_sm_format = self.has_option_with_value(u"--input-format")
        if input_sm_format is None:
            input_sm_format = gf.file_extension(input_file_path)
        if not self.check_format(input_sm_format):
            return self.ERROR_EXIT_CODE

        if not self.check_output_file(output_file_path):
            return self.ERROR_EXIT_CODE

        if output_html:
            if len(self.actual_arguments) < 3:
                return self.print_help()
            audio_file_path = self.actual_arguments[2]
            if not self.check_input_file(audio_file_path):
                return self.ERROR_EXIT_CODE
        else:
            output_sm_format = self.has_option_with_value(u"--output-format")
            if output_sm_format is None:
                output_sm_format = gf.file_extension(output_file_path)
            if not self.check_format(output_sm_format):
                return self.ERROR_EXIT_CODE

        # TODO add a way to specify a text file for input formats like SMIL
        #      that do not carry the source text
        language = self.has_option_with_value(u"--language")
        audio_ref = self.has_option_with_value(u"--audio-ref")
        page_ref = self.has_option_with_value(u"--page-ref")
        parameters = {
            gc.PPN_SYNCMAP_LANGUAGE: language,
            gc.PPN_TASK_OS_FILE_SMIL_AUDIO_REF: audio_ref,
            gc.PPN_TASK_OS_FILE_SMIL_PAGE_REF: page_ref
        }

        try:
            self.print_info(u"Reading sync map in '%s' format from file '%s'" % (input_sm_format, input_file_path))
            self.print_info(u"Reading sync map...")
            syncmap = SyncMap(logger=self.logger)
            syncmap.read(input_sm_format, input_file_path, parameters)
            self.print_info(u"Reading sync map... done")
            self.print_info(u"Read %d sync map fragments" % (len(syncmap)))
        except Exception as exc:
            self.print_error(u"An unexpected error occurred while reading the input sync map:")
            self.print_error(u"%s" % (exc))
            return self.ERROR_EXIT_CODE

        if output_html:
            try:
                self.print_info(u"Writing HTML file...")
                syncmap.output_html_for_tuning(audio_file_path, output_file_path, parameters)
                self.print_info(u"Writing HTML file... done")
                self.print_success(u"Created HTML file '%s'" % (output_file_path))
                return self.NO_ERROR_EXIT_CODE
            except Exception as exc:
                self.print_error(u"An unexpected error occurred while writing the output HTML file:")
                self.print_error(u"%s" % (exc))
        else:
            try:
                self.print_info(u"Writing sync map...")
                syncmap.write(output_sm_format, output_file_path, parameters)
                self.print_info(u"Writing sync map... done")
                self.print_success(u"Created '%s' sync map file '%s'" % (output_sm_format, output_file_path))
                return self.NO_ERROR_EXIT_CODE
            except Exception as exc:
                self.print_error(u"An unexpected error occurred while writing the output sync map:")
                self.print_error(u"%s" % (exc))

        return self.ERROR_EXIT_CODE