from datetime import datetime, timezone

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

from app.users.models import User


async def create_user(db: AsyncSession, *, email: str, name: str, username: str, password_hash: str) -> User:
    user = User(email=email, name=name, username=username, password_hash=password_hash, email_verified=False)
    db.add(user)
    await db.flush()
    return user


async def get_user_by_id(db: AsyncSession, user_id: int) -> User | None:
    result = await db.execute(select(User).where(User.id == user_id))
    return result.scalar_one_or_none()


async def get_user_by_email(db: AsyncSession, email: str) -> User | None:
    result = await db.execute(select(User).where(User.email == email))
    return result.scalar_one_or_none()


async def get_user_by_username(db: AsyncSession, username: str) -> User | None:
    result = await db.execute(select(User).where(User.username == username))
    return result.scalar_one_or_none()


async def list_users_by_ids(db: AsyncSession, user_ids: list[int]) -> list[User]:
    if not user_ids:
        return []
    result = await db.execute(select(User).where(User.id.in_(user_ids)))
    return list(result.scalars().all())


async def search_users_by_username(
    db: AsyncSession,
    *,
    query: str,
    limit: int = 20,
    exclude_user_id: int | None = None,
) -> list[User]:
    normalized = query.lower().strip().lstrip("@")
    stmt = select(User).where(func.lower(User.username).like(f"%{normalized}%"))
    if exclude_user_id is not None:
        stmt = stmt.where(User.id != exclude_user_id)
    stmt = stmt.order_by(User.username.asc()).limit(limit)
    result = await db.execute(stmt)
    return list(result.scalars().all())


async def update_user_last_seen_now(db: AsyncSession, *, user_id: int) -> User | None:
    user = await get_user_by_id(db, user_id)
    if not user:
        return None
    user.last_seen_at = datetime.now(timezone.utc)
    await db.flush()
    return user