import uuid

from fastapi import HTTPException, status
from sqlalchemy import func, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.security import hash_password
from app.models.user import User


async def list_users(db: AsyncSession, limit: int = 50, offset: int = 0) -> tuple[list[User], int]:
    total = await db.scalar(select(func.count()).select_from(User))
    result = await db.execute(
        select(User).order_by(User.created_at.desc()).limit(limit).offset(offset)
    )
    return list(result.scalars().all()), total or 0


async def get_user(db: AsyncSession, user_id: uuid.UUID) -> User:
    result = await db.execute(select(User).where(User.id == user_id))
    user = result.scalar_one_or_none()
    if not user:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
    return user


async def create_user(
    db: AsyncSession, email: str, username: str, password: str,
    full_name: str | None = None, role: str = "user", max_chats: int = 10,
) -> User:
    existing = await db.execute(
        select(User).where((User.email == email) | (User.username == username))
    )
    if existing.scalar_one_or_none():
        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="User already exists")

    user = User(
        email=email,
        username=username,
        hashed_password=hash_password(password),
        full_name=full_name,
        role=role,
        max_chats=max_chats,
    )
    db.add(user)
    await db.flush()
    return user


async def update_user(db: AsyncSession, user_id: uuid.UUID, **kwargs) -> User:
    user = await get_user(db, user_id)
    allowed = {"role", "is_active", "max_chats", "full_name"}
    for key, value in kwargs.items():
        if key in allowed and value is not None:
            setattr(user, key, value)
    await db.flush()
    return user