"""Base class for pluggable defect mutation rules."""

from abc import ABC, abstractmethod
from dataclasses import dataclass
from typing import List, Optional


@dataclass
class Mutation:
    defect_type: str
    language: str
    line_start: int
    line_end: int
    mutated_source: str
    reference_fix: str
    description: str


class MutationRule(ABC):
    name: str = ""
    language: str = ""
    defect_type: str = ""

    @abstractmethod
    def detect_and_mutate(self, source: str, filename: str = "") -> Optional[Mutation]:
        """Return a mutation if the rule can introduce a defect, else None."""
        ...

    def _line_for_position(self, source: str, position: int) -> int:
        return source[:position].count("\n") + 1