"""
历史知识问答引擎 — 七年级中国历史背诵题库
从 data/历史背诵题库.json 加载题目，支持随机出题、答题判断、进度追踪
"""

import json
import random
import os
from pathlib import Path
from datetime import datetime

QUIZ_FILE = Path(os.environ.get(
    "HISTORY_QUIZ_FILE",
    os.path.join(os.path.dirname(__file__), "..", "data", "历史背诵题库.json")
))

# 单元别名映射（用于前端显示）
UNIT_ALIASES = {
    "U1": "七上·第一单元 史前时期",
    "U2": "七上·第二单元 夏商周时期",
    "U3": "七上·第三单元 秦汉时期",
    "U4": "七上·第四单元 三国两晋南北朝",
    "U5": "七下·第一单元 隋唐时期",
    "U6": "七下·第二单元 辽宋夏金元",
    "U7": "七下·第三单元 明清时期",
}


class HistoryQuiz:
    """历史题库引擎"""

    def __init__(self):
        self.data = self._load_quiz()
        self.units = {u["unit_id"]: u for u in self.data.get("units", [])}
        self.all_questions = []
        for unit in self.data.get("units", []):
            for q in unit.get("questions", []):
                q["unit_id"] = unit["unit_id"]
                q["unit_title"] = unit.get("title", "")
                self.all_questions.append(q)

    def _load_quiz(self) -> dict:
        if QUIZ_FILE.exists():
            return json.loads(QUIZ_FILE.read_text(encoding="utf-8"))
        # 降级：空题库
        return {"metadata": {}, "units": []}

    def get_units(self) -> list:
        """获取所有单元信息（含题目数量）"""
        result = []
        for unit in self.data.get("units", []):
            uid = unit["unit_id"]
            result.append({
                "unit_id": uid,
                "title": unit.get("title", ""),
                "grade": unit.get("grade", ""),
                "alias": UNIT_ALIASES.get(uid, uid),
                "question_count": len(unit.get("questions", [])),
                "lessons": unit.get("lessons", []),
            })
        return result

    def get_random_question(self, unit_id: str = None, question_type: str = None) -> dict:
        """随机获取一道题，可选按单元/题型过滤"""
        pool = self.all_questions
        if unit_id:
            pool = [q for q in pool if q.get("unit_id") == unit_id]
        if question_type:
            pool = [q for q in pool if q.get("type") == question_type]
        if not pool:
            return {"error": "该条件下没有题目"}
        q = random.choice(pool)
        return {
            "id": q["id"],
            "type": q["type"],
            "question": q["question"],
            "answer": q["answer"],
            "unit_id": q["unit_id"],
            "unit_title": q.get("unit_title", ""),
            "unit_alias": UNIT_ALIASES.get(q["unit_id"], q["unit_id"]),
            "source": q.get("source", ""),
        }

    def get_batch(self, count: int = 10, unit_id: str = None, question_type: str = None) -> list:
        """批量获取题目（不重复）"""
        pool = list(self.all_questions)
        if unit_id:
            pool = [q for q in pool if q.get("unit_id") == unit_id]
        if question_type:
            pool = [q for q in pool if q.get("type") == question_type]
        random.shuffle(pool)
        selected = pool[:count]
        return [{
            "id": q["id"],
            "type": q["type"],
            "question": q["question"],
            "answer": q["answer"],
            "unit_id": q["unit_id"],
            "unit_title": q.get("unit_title", ""),
            "unit_alias": UNIT_ALIASES.get(q["unit_id"], q["unit_id"]),
        } for q in selected]

    def check_answer(self, question_id: str, student_answer: str) -> dict:
        """检查答案 — 模糊匹配（关键词匹配）"""
        q = next((q for q in self.all_questions if q["id"] == question_id), None)
        if not q:
            return {"correct": False, "error": "题目不存在"}

        correct = q["answer"].strip()
        student = student_answer.strip()

        # 精确匹配
        if student == correct:
            return {
                "correct": True,
                "question_id": question_id,
                "student_answer": student,
                "correct_answer": correct,
                "match_type": "exact"
            }

        # 包含匹配（学生答案包含在标准答案中，或反之）
        if len(student) >= 2 and (student in correct or correct in student):
            return {
                "correct": True,
                "question_id": question_id,
                "student_answer": student,
                "correct_answer": correct,
                "match_type": "partial"
            }

        # 关键词匹配（答案拆分为关键词，匹配度>60%算对）
        keywords = set(correct.replace("，", " ").replace("、", " ").replace("；", " ").split())
        student_words = set(student.replace("，", " ").replace("、", " ").replace("；", " ").split())
        if keywords and student_words:
            overlap = len(keywords & student_words) / len(keywords)
            if overlap >= 0.6:
                return {
                    "correct": True,
                    "question_id": question_id,
                    "student_answer": student,
                    "correct_answer": correct,
                    "match_type": "keyword",
                    "keyword_match": f"{overlap:.0%}"
                }

        return {
            "correct": False,
            "question_id": question_id,
            "student_answer": student,
            "correct_answer": correct,
            "hint": self._generate_hint(correct)
        }

    def _generate_hint(self, answer: str) -> str:
        """生成提示（显示答案首字+长度）"""
        if len(answer) <= 1:
            return "答案很短，再想想？"
        first_char = answer[0]
        return f"提示：答案以「{first_char}」开头，共{len(answer)}个字"

    def get_stats(self) -> dict:
        """题库统计"""
        type_counts = {}
        for q in self.all_questions:
            t = q.get("type", "unknown")
            type_counts[t] = type_counts.get(t, 0) + 1

        return {
            "total_questions": len(self.all_questions),
            "total_units": len(self.units),
            "by_type": type_counts,
            "by_unit": {uid: len(u.get("questions", [])) for uid, u in self.units.items()},
        }


# 全局单例
_quiz_instance = None

def get_quiz() -> HistoryQuiz:
    global _quiz_instance
    if _quiz_instance is None:
        _quiz_instance = HistoryQuiz()
    return _quiz_instance