"""AI 教师：基于题目讲解与知识点状态生成即时反馈。

当前为本地规则式实现，不依赖外部模型：能够给出“为什么对/为什么错”的
讲解与后续建议；若配置了 OPENAI_API_KEY，可在此基础上扩展为真实模型调用。
"""
from __future__ import annotations

from models import Question, UserKnowledge
from services.mastery_engine import action_for


def explain(
    question: Question,
    selected: int,
    correct: bool,
    knowledge: UserKnowledge | None,
) -> str:
    head = "回答正确。" if correct else "回答错误。"
    base = question.explanation or "结合定义与图像性质重新判断。"

    mastery_hint = ""
    if knowledge is not None:
        mastery_hint = (
            f" 该知识点当前掌握度为 {knowledge.mastery}%，"
            f"建议{action_for(knowledge.mastery)}。"
        )

    if correct:
        return f"{head} 考点「{question.knowledge_name}」：{base}{mastery_hint}"
    return f"{head} 你选择了选项 {chr(65 + selected)}。正确思路：{base}{mastery_hint}"