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, ExamUpdate, 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 _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),
    )


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):
    exam.scores.clear()
    for item in scores_data:
        ratio = round(item.obtained_score / item.total_score, 4)
        exam.scores.append(
            SubjectScore(
                subject_id=item.subject_id,
                total_score=item.total_score,
                obtained_score=item.obtained_score,
                ratio=ratio,
            )
        )


@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.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