class Node:
    def _pos_str(self):
        start_pos_str = "?"
        if self.pos is not None:
            start_pos_str = f"{self.pos[0]}:{self.pos[1]}"
        end_pos_str = "?"
        if self.end_pos is not None:
            end_pos_str = f"{self.end_pos[0]}:{self.end_pos[1]}"

        return f"  # {start_pos_str}-{end_pos_str}"

    def _make_str(self, indent=None, positions=False):
        if indent is not None:
            s = "  " * indent
        else:
            s = ""

        s += self.__class__.__name__
        s += "("

        if self.value:
            s += repr(self.value)
            if self.children:
                s += ", "

        if positions and self.children:
            s += self._pos_str()

        for i, child in enumerate(self.children):
            if indent is not None:
                s += "\n"
            s += child._make_str(
                indent=None if indent is None else indent + 1, positions=positions
            )
            if i < len(self.children) - 1:
                s += ", "
        s += ")"

        if positions and not self.children:
            s += self._pos_str()

        return s

    def pretty(self, positions=False):
        return self._make_str(indent=0, positions=positions)

    def accept(self, visitor):
        raise NotImplementedError()


class Script(Node):
    def __init__(self, statements):
        self.statements = statements

    def accept(self, visitor):
        return visitor.visit_script(self)


class ProcDef(Node):
    def __init__(self, name, args, body):
        self.name = name
        self.args = args
        self.body = body

    def accept(self, visitor):
        return visitor.visit_proc(self)


class SetStmt(Node):
    def __init__(self, varname, value):
        self.varname = varname
        self.value = value

    def accept(self, visitor):
        return visitor.visit_set(self)


class Namespace(Node):
    def __init__(self, name, body):
        self.name = name
        self.body = body

    def accept(self, visitor):
        return visitor.visit_namespace(self)


class CommandSubst(Node):
    def __init__(self, name, args):
        self.name = name
        self.args = args

    def accept(self, visitor):
        return visitor.visit_command(self)