import csv
import json
from io import StringIO

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

from backend.auth import get_current_user
from backend.database import get_db
from backend.models import Question
from backend.services.excel_service import export_excel_bytes

router = APIRouter(dependencies=[Depends(get_current_user)])


def _filter_questions(
    db: Session, chapter: str = "", question_type: str = "", difficulty: str = ""
) -> list[Question]:
    query = db.query(Question)
    if chapter:
        query = query.filter(Question.chapter == chapter)
    if question_type:
        query = query.filter(Question.question_type == question_type)
    if difficulty:
        query = query.filter(Question.difficulty == difficulty)
    return query.order_by(Question.id.desc()).all()


@router.get("")
def export_questions(
    format: str = Query(default="json", pattern="^(json|csv|xlsx)$"),
    chapter: str = "",
    question_type: str = "",
    difficulty: str = "",
    db: Session = Depends(get_db),
) -> dict:
    items = _filter_questions(db, chapter, question_type, difficulty)
    rows = [
        {
            "id": i.id,
            "chapter": i.chapter,
            "primary_knowledge": i.primary_knowledge,
            "secondary_knowledge": i.secondary_knowledge,
            "question_type": i.question_type,
            "difficulty": i.difficulty,
            "stem": i.stem,
            "option_a": i.option_a,
            "option_b": i.option_b,
            "option_c": i.option_c,
            "option_d": i.option_d,
            "answer": i.answer,
            "explanation": i.explanation,
            "notes": i.notes,
            "source_file": i.source_file,
        }
        for i in items
    ]
    if format == "json":
        return {"format": "json", "content": json.dumps(rows, ensure_ascii=False)}
    if format == "csv":
        out = StringIO()
        writer = csv.DictWriter(out, fieldnames=rows[0].keys() if rows else ["id"])
        writer.writeheader()
        for row in rows:
            writer.writerow(row)
        return {"format": "csv", "content": out.getvalue()}
    xlsx_bytes = export_excel_bytes(rows)
    return {"format": "xlsx", "content_base64": xlsx_bytes.hex()}