import gdb


class KstdFlatMapPrinter(gdb.ValuePrinter):
    class _Iterator:
        def __init__(self, keys_ptr, vals_ptr, size):
            self._keys = keys_ptr
            self._vals = vals_ptr
            self._size = size
            self._count = 0

        def __iter__(self):
            return self

        def __next__(self):
            index = self._count // 2
            if index >= self._size:
                raise StopIteration

            if self._count % 2 == 0:
                item = (self._keys + index).dereference()
            else:
                item = (self._vals + index).dereference()

            result = (f"[{self._count}]", item)
            self._count += 1
            return result

    def __init__(self, val):
        self.__val = val
        containers = val["m_containers"]
        keys_vector = containers["keys"]
        vals_vector = containers["values"]
        self.__size = int(keys_vector["m_size"])
        self.__keys_ptr = keys_vector["m_data"]
        self.__vals_ptr = vals_vector["m_data"]
        self.__key_type = val.type.template_argument(0)
        self.__val_type = val.type.template_argument(1)

    def to_string(self):
        return f"flat_map<{self.__key_type}, {self.__val_type}> with {self.__size} entries"

    def children(self):
        return self._Iterator(self.__keys_ptr, self.__vals_ptr, self.__size)

    def display_hint(self):
        return "map"

    def num_children(self):
        return self.__size * 2