import gdb

from .error_code import KstdErrorCodePrinter


class KstdResultPrinter(gdb.ValuePrinter):
    def __init__(self, val):
        self.__val = val
        self.__has_value = bool(val["_M_has_value"])
        try:
            t = val.type.template_argument(0)
            self.__is_void = t.code == gdb.TYPE_CODE_VOID
        except (gdb.error, AttributeError):
            self.__is_void = False

    @property
    def _error_code(self):
        return self.__val["_M_unex"]

    @property
    def _value(self):
        return self.__val["_M_val"]

    def _format_value(self, gdb_value):
        printer = gdb.default_visualizer(gdb_value)
        if printer is not None:
            return printer.to_string()
        s = str(gdb_value)
        if s.startswith("{"):
            return str(gdb_value.type.strip_typedefs())
        return s

    def _format_error(self, error_code_val):
        printer = KstdErrorCodePrinter(error_code_val)
        return printer.to_string()

    def to_string(self):
        if not self.__has_value:
            return f"failure: {self._format_error(self._error_code)}"
        if self.__is_void:
            return "success"
        return f"success: {self._format_value(self._value)}"

    def children(self):
        if not self.__has_value:
            yield ("error", self._error_code)
        elif not self.__is_void:
            yield ("value", self._value)

    def display_hint(self):
        return None