from datetime import datetime
from typing import Any, Dict, List, Optional, Union

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.security import get_password_hash, verify_password
from app.models.user import User
from app.schemas.user import UserCreate, UserUpdate


async def get_by_id(db: AsyncSession, user_id: str) -> Optional[User]:
    """
    Get a user by ID.
    """
    result = await db.execute(select(User).filter(User.id == user_id))
    return result.scalars().first()


async def get_by_email(db: AsyncSession, email: str) -> Optional[User]:
    """
    Get a user by email.
    """
    result = await db.execute(select(User).filter(User.email == email))
    return result.scalars().first()


async def get_users(db: AsyncSession, skip: int = 0, limit: int = 100) -> List[User]:
    """
    Get a list of users with pagination.
    """
    result = await db.execute(select(User).offset(skip).limit(limit))
    return result.scalars().all()


async def create(db: AsyncSession, *, obj_in: UserCreate) -> User:
    """
    Create a new user.
    """
    db_obj = User(
        email=obj_in.email,
        hashed_password=get_password_hash(obj_in.password),
        full_name=obj_in.full_name,
        is_active=True,
        is_superuser=False,
        email_verified=False,
    )
    db.add(db_obj)
    await db.commit()
    await db.refresh(db_obj)
    return db_obj


async def update(
    db: AsyncSession, *, db_obj: User, obj_in: Union[UserUpdate, Dict[str, Any]]
) -> User:
    """
    Update a user.
    """
    if isinstance(obj_in, dict):
        update_data = obj_in
    else:
        update_data = obj_in.dict(exclude_unset=True)

    if "password" in update_data and update_data["password"]:
        hashed_password = get_password_hash(update_data["password"])
        del update_data["password"]
        update_data["hashed_password"] = hashed_password

    for field in update_data:
        if hasattr(db_obj, field):
            setattr(db_obj, field, update_data[field])

    db.add(db_obj)
    await db.commit()
    await db.refresh(db_obj)
    return db_obj


async def remove(db: AsyncSession, *, id: str) -> Optional[User]:
    """
    Delete a user.
    """
    user = await get_by_id(db, id)
    if user:
        await db.delete(user)
        await db.commit()
    return user


async def authenticate(
    db: AsyncSession, *, email: str, password: str
) -> Optional[User]:
    """
    Authenticate a user by email and password.
    """
    user = await get_by_email(db, email=email)
    if not user:
        return None
    if not verify_password(password, user.hashed_password):
        return None
    return user


async def update_last_login(db: AsyncSession, *, user: User) -> User:
    """
    Update the last login timestamp for a user.
    """
    user.last_login = datetime.utcnow()
    db.add(user)
    await db.commit()
    await db.refresh(user)
    return user