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

from backend.auth import get_current_user
from backend.database import get_db
from backend.models import Category, Question
from backend.schemas import CategoryCreate, CategoryOut

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


def _build_tree(rows: list[Category], counts: dict[str, int]) -> list[dict]:
    nodes = {
        row.id: {
            "id": row.id,
            "name": row.name,
            "level": row.level,
            "parent_id": row.parent_id,
            "count": counts.get(row.name, 0),
            "children": [],
        }
        for row in rows
    }
    tree = []
    for node in nodes.values():
        pid = node["parent_id"]
        if pid and pid in nodes:
            nodes[pid]["children"].append(node)
        else:
            tree.append(node)
    return tree


@router.get("")
def list_categories(db: Session = Depends(get_db)) -> dict:
    rows = db.query(Category).order_by(Category.level.asc(), Category.id.asc()).all()
    counts = dict(db.query(Question.chapter, func.count(Question.id)).group_by(Question.chapter).all())
    return {"items": _build_tree(rows, counts)}


@router.post("", response_model=CategoryOut)
def create_category(payload: CategoryCreate, db: Session = Depends(get_db)) -> CategoryOut:
    if payload.parent_id:
        parent = db.get(Category, payload.parent_id)
        if not parent:
            raise HTTPException(status_code=404, detail="父分类不存在")
    item = Category(**payload.model_dump())
    db.add(item)
    db.commit()
    db.refresh(item)
    return CategoryOut.model_validate(item)


@router.put("/{category_id}", response_model=CategoryOut)
def update_category(category_id: int, payload: CategoryCreate, db: Session = Depends(get_db)) -> CategoryOut:
    item = db.get(Category, category_id)
    if not item:
        raise HTTPException(status_code=404, detail="分类不存在")
    for key, value in payload.model_dump().items():
        setattr(item, key, value)
    db.commit()
    db.refresh(item)
    return CategoryOut.model_validate(item)


@router.delete("/{category_id}")
def delete_category(category_id: int, db: Session = Depends(get_db)) -> dict:
    item = db.get(Category, category_id)
    if not item:
        raise HTTPException(status_code=404, detail="分类不存在")
    db.delete(item)
    db.commit()
    return {"ok": True}