import json
import uuid

from fastapi import APIRouter, Depends, HTTPException, Query, status
from sqlalchemy.orm import Session, joinedload

from app.core.database import get_db
from app.core.deps import get_current_user
from app.models.user import ExamRecord, SubjectScore, User
from app.schemas import (
    ExamCreate,
    ExamOut,
    ExamReviewUpdate,
    ExamUpdate,
    ReviewStatusEnum,
    ScoreOut,
    TrendResponse,
)
from app.services.score_trend import build_trend
from app.services.student_access import get_student_for_user

router = APIRouter(tags=["exams"])


def _parse_review_statuses(raw: str | None) -> list[ReviewStatusEnum]:
    if not raw:
        return []
    try:
        data = json.loads(raw)
    except json.JSONDecodeError:
        return []
    if not isinstance(data, list):
        return []
    result: list[ReviewStatusEnum] = []
    for item in data:
        try:
            result.append(ReviewStatusEnum(str(item)))
        except ValueError:
            continue
    return result


def _serialize_review_statuses(statuses: list[ReviewStatusEnum] | None) -> str | None:
    if not statuses:
        return None
    values: list[str] = []
    for item in statuses:
        if isinstance(item, ReviewStatusEnum):
            values.append(item.value)
        else:
            values.append(str(item))
    return json.dumps(values, ensure_ascii=False)


def _score_to_out(score: SubjectScore) -> ScoreOut:
    return ScoreOut(
        id=score.id,
        subject_id=score.subject_id,
        subject_name=score.subject.name if score.subject else None,
        total_score=float(score.total_score),
        obtained_score=float(score.obtained_score),
        ratio=float(score.ratio),
        review_statuses=_parse_review_statuses(score.review_statuses_json),
    )


def _exam_to_out(exam: ExamRecord) -> ExamOut:
    return ExamOut(
        id=exam.id,
        exam_type=exam.exam_type,
        exam_date=exam.exam_date,
        title=exam.title,
        created_at=exam.created_at,
        scores=[_score_to_out(s) for s in exam.scores],
    )


def _apply_scores(db: Session, exam: ExamRecord, scores_data):
    existing_by_subject = {s.subject_id: s for s in list(exam.scores)}
    keep_subject_ids: set[int] = set()

    for item in scores_data:
        keep_subject_ids.add(item.subject_id)
        ratio = round(item.obtained_score / item.total_score, 4)
        review_json = _serialize_review_statuses(item.review_statuses)
        existing = existing_by_subject.get(item.subject_id)
        if existing is not None:
            existing.total_score = item.total_score
            existing.obtained_score = item.obtained_score
            existing.ratio = ratio
            existing.review_statuses_json = review_json
        else:
            exam.scores.append(
                SubjectScore(
                    subject_id=item.subject_id,
                    total_score=item.total_score,
                    obtained_score=item.obtained_score,
                    ratio=ratio,
                    review_statuses_json=review_json,
                )
            )

    for subject_id, score in existing_by_subject.items():
        if subject_id not in keep_subject_ids:
            exam.scores.remove(score)
            db.delete(score)


@router.get("/students/{student_id}/exams", response_model=list[ExamOut])
def list_exams(
    student_id: uuid.UUID,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    get_student_for_user(db, student_id, current_user.id)
    exams = (
        db.query(ExamRecord)
        .options(joinedload(ExamRecord.scores).joinedload(SubjectScore.subject))
        .filter(ExamRecord.student_id == student_id)
        .order_by(ExamRecord.exam_date.desc(), ExamRecord.created_at.desc())
        .all()
    )
    return [_exam_to_out(e) for e in exams]


@router.post("/students/{student_id}/exams", response_model=ExamOut, status_code=status.HTTP_201_CREATED)
def create_exam(
    student_id: uuid.UUID,
    data: ExamCreate,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    get_student_for_user(db, student_id, current_user.id)
    exam = ExamRecord(
        student_id=student_id,
        exam_type=data.exam_type,
        exam_date=data.exam_date,
        title=data.title,
    )
    db.add(exam)
    db.flush()
    if data.scores:
        _apply_scores(db, exam, data.scores)
    db.commit()
    db.refresh(exam)
    exam = (
        db.query(ExamRecord)
        .options(joinedload(ExamRecord.scores).joinedload(SubjectScore.subject))
        .filter(ExamRecord.id == exam.id)
        .first()
    )
    return _exam_to_out(exam)


@router.get("/exams/{exam_id}", response_model=ExamOut)
def get_exam(
    exam_id: uuid.UUID,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    exam = (
        db.query(ExamRecord)
        .options(joinedload(ExamRecord.scores).joinedload(SubjectScore.subject))
        .join(ExamRecord.student)
        .filter(ExamRecord.id == exam_id)
        .first()
    )
    if exam is None or exam.student.user_id != current_user.id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="考试记录不存在")
    return _exam_to_out(exam)


@router.patch("/exams/{exam_id}", response_model=ExamOut)
def update_exam(
    exam_id: uuid.UUID,
    data: ExamUpdate,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    exam = (
        db.query(ExamRecord)
        .options(joinedload(ExamRecord.scores).joinedload(SubjectScore.subject))
        .join(ExamRecord.student)
        .filter(ExamRecord.id == exam_id)
        .first()
    )
    if exam is None or exam.student.user_id != current_user.id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="考试记录不存在")

    if data.exam_type is not None:
        exam.exam_type = data.exam_type
    if data.exam_date is not None:
        exam.exam_date = data.exam_date
    if data.title is not None:
        exam.title = data.title
    if data.scores is not None:
        _apply_scores(db, exam, data.scores)

    db.commit()
    db.refresh(exam)
    exam = (
        db.query(ExamRecord)
        .options(joinedload(ExamRecord.scores).joinedload(SubjectScore.subject))
        .filter(ExamRecord.id == exam.id)
        .first()
    )
    return _exam_to_out(exam)


@router.patch("/exams/{exam_id}/review", response_model=ExamOut)
def update_exam_review(
    exam_id: uuid.UUID,
    data: ExamReviewUpdate,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    exam = (
        db.query(ExamRecord)
        .options(joinedload(ExamRecord.scores).joinedload(SubjectScore.subject))
        .join(ExamRecord.student)
        .filter(ExamRecord.id == exam_id)
        .first()
    )
    if exam is None or exam.student.user_id != current_user.id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="考试记录不存在")

    by_subject = {s.subject_id: s for s in exam.scores}
    for item in data.reviews:
        score = by_subject.get(item.subject_id)
        if score is None:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=f"科目 {item.subject_id} 不在该次考试中",
            )
        score.review_statuses_json = _serialize_review_statuses(item.review_statuses)

    db.commit()
    db.refresh(exam)
    exam = (
        db.query(ExamRecord)
        .options(joinedload(ExamRecord.scores).joinedload(SubjectScore.subject))
        .filter(ExamRecord.id == exam.id)
        .first()
    )
    return _exam_to_out(exam)


@router.delete("/exams/{exam_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_exam(
    exam_id: uuid.UUID,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    exam = (
        db.query(ExamRecord)
        .join(ExamRecord.student)
        .filter(ExamRecord.id == exam_id)
        .first()
    )
    if exam is None or exam.student.user_id != current_user.id:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="考试记录不存在")
    db.delete(exam)
    db.commit()


@router.get("/students/{student_id}/scores/trend", response_model=TrendResponse)
def get_score_trend(
    student_id: uuid.UUID,
    subject_id: int = Query(...),
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    get_student_for_user(db, student_id, current_user.id)
    try:
        return build_trend(db, student_id, subject_id)
    except ValueError as exc:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(exc)) from exc