"""练习：章节组卷与提交判分（学习数据按用户隔离）。"""
from __future__ import annotations

import json

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session

from database import get_db
from dependencies import require_learning_user
from models import (
    AttemptItem,
    AttemptSession,
    Chapter,
    ErrorEntry,
    Knowledge,
    Question,
    Textbook,
    UserKnowledge,
    User,
)
from schemas import (
    AnswerIn,
    KnowledgeOut,
    PerQuestionOut,
    PracticeSessionOut,
    QuestionOut,
    SubmitIn,
    SubmitResultOut,
)
from services.ai_teacher import explain as teacher_explain
from services.mastery_engine import apply_answers, snapshot, status_for
from services.question_engine import chapter_question_ids, load_questions
from services.knowledge_service import question_knowledge_names


router = APIRouter(prefix="/practice", tags=["practice"])


def _to_question_out(q: Question) -> QuestionOut:
    return QuestionOut(
        id=q.id,
        stem=q.stem,
        options=json.loads(q.options),
        knowledge_name=q.knowledge_name,
    )


@router.get("/chapter/{chapter_id}", response_model=PracticeSessionOut)
def chapter_session(
    chapter_id: int,
    limit: int = 5,
    variant: int = 0,
    db: Session = Depends(get_db),
    user: User = Depends(require_learning_user),
):
    chapter = db.get(Chapter, chapter_id)
    if chapter is None:
        raise HTTPException(status_code=404, detail="章节不存在")
    textbook = db.get(Textbook, chapter.textbook_id)
    question_ids = chapter_question_ids(
        db, user.id, chapter.id, limit=max(1, min(limit, 10)), variant=variant
    )
    questions = load_questions(db, question_ids)
    return PracticeSessionOut(
        mode="chapter",
        title=f"{textbook.name if textbook else '教材'} · {chapter.name}",
        chapter_id=chapter.id,
        questions=[_to_question_out(q) for q in questions],
    )


@router.post("/submit", response_model=SubmitResultOut)
def submit_answers(
    payload: SubmitIn,
    db: Session = Depends(get_db),
    user: User = Depends(require_learning_user),
):
    mode = payload.mode
    if mode != "chapter":
        raise HTTPException(status_code=400, detail="未知的练习模式")

    seen: set[int] = set()
    for answer in payload.answers:
        if answer.question_id in seen:
            raise HTTPException(status_code=400, detail="同一道题提交了多次")
        seen.add(answer.question_id)

    questions = load_questions(db, list(seen))
    by_id = {q.id: q for q in questions}
    if len(by_id) != len(seen):
        raise HTTPException(status_code=400, detail="部分题目不存在")

    knowledge_map = {
        knowledge.name: user_knowledge
        for user_knowledge, knowledge in (
            db.query(UserKnowledge, Knowledge)
            .join(Knowledge, Knowledge.id == UserKnowledge.knowledge_id)
            .filter(UserKnowledge.user_id == user.id)
            .all()
        )
    }
    if payload.chapter_id is None:
        raise HTTPException(status_code=400, detail="章节测试需要指定 chapter_id")
    chapter = db.get(Chapter, payload.chapter_id)
    if chapter is None:
        raise HTTPException(status_code=404, detail="章节不存在")
    textbook = db.get(Textbook, chapter.textbook_id)
    title = f"{textbook.name if textbook else '教材'} · {chapter.name}"
    if any(q.chapter_id != chapter.id for q in questions):
        raise HTTPException(
            status_code=400,
            detail="提交的题目不属于所选章节，请重新开始测试",
        )
    score = 0
    answered_mastery: list[tuple[str, bool]] = []
    per_question: list[PerQuestionOut] = []

    attempt = AttemptSession(
        user_id=user.id,
        mode=mode,
        title=title,
        total=len(payload.answers),
        correct=0,
        chapter_id=chapter.id,
    )
    db.add(attempt)
    db.flush()

    for index, answer in enumerate(payload.answers, start=1):
        q = by_id[answer.question_id]
        correct = answer.selected == q.correct_index
        if correct:
            score += 1
        tags = question_knowledge_names(db, q)
        for tag in tags:
            answered_mastery.append((tag, correct))

        teacher_text = teacher_explain(
            q,
            answer.selected,
            correct,
            knowledge_map.get(q.knowledge_name),
        )
        q.used_count = (q.used_count or 0) + 1
        db.add(
            AttemptItem(
                attempt_id=attempt.id,
                user_id=user.id,
                question_index=index,
                question_id=q.id,
                stem=q.stem,
                options=q.options,
                correct_index=q.correct_index,
                selected=answer.selected,
                correct=correct,
                knowledge_name=tags[0] if tags else q.knowledge_name,
                knowledge_names=json.dumps(tags or [q.knowledge_name], ensure_ascii=False),
                explanation=teacher_text,
            )
        )
        if not correct:
            diagnosis = q.explanation or "需要复习该知识点"
            db.add(
                ErrorEntry(
                    user_id=user.id,
                    attempt_id=attempt.id,
                    source_label=f"{title} · {index}",
                    knowledge_name=tags[0] if tags else q.knowledge_name,
                    knowledge_names=json.dumps(
                        tags or [q.knowledge_name], ensure_ascii=False
                    ),
                    diagnosis=diagnosis,
                    question_id=q.id,
                    stem=q.stem,
                    options=q.options,
                    selected=answer.selected,
                    correct_index=q.correct_index,
                    explanation=teacher_text,
                )
            )
        per_question.append(
            PerQuestionOut(
                question_id=q.id,
                correct=correct,
                selected=answer.selected,
                correct_index=q.correct_index,
                explanation=teacher_text,
            )
        )

    apply_answers(db, user.id, mode, answered_mastery)
    attempt.correct = score
    db.commit()

    accuracy = score / len(payload.answers) * 100 if payload.answers else 0.0
    return SubmitResultOut(
        mode=mode,
        title=title,
        total=len(payload.answers),
        score=score,
        accuracy=round(accuracy, 1),
        per_question=per_question,
        knowledge=[
            KnowledgeOut(
                id=k.id,
                knowledge_id=k.knowledge_id,
                name=k.name,
                mastery=k.mastery,
                position=k.position,
                status=status_for(k.mastery),
                domain=k.domain,
                category=k.category,
            )
            for k in snapshot(db, user.id)
        ],
    )