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

from app.chats.models import Chat, ChatMember, ChatMemberRole, ChatType


async def create_chat(db: AsyncSession, *, chat_type: ChatType, title: str | None) -> Chat:
    chat = Chat(type=chat_type, title=title)
    db.add(chat)
    await db.flush()
    return chat


async def add_chat_member(db: AsyncSession, *, chat_id: int, user_id: int, role: ChatMemberRole) -> ChatMember:
    member = ChatMember(chat_id=chat_id, user_id=user_id, role=role)
    db.add(member)
    await db.flush()
    return member


def _user_chats_query(user_id: int) -> Select[tuple[Chat]]:
    return (
        select(Chat)
        .join(ChatMember, ChatMember.chat_id == Chat.id)
        .where(ChatMember.user_id == user_id)
        .order_by(Chat.id.desc())
    )


async def list_user_chats(db: AsyncSession, *, user_id: int, limit: int = 50, before_id: int | None = None) -> list[Chat]:
    query = _user_chats_query(user_id).limit(limit)
    if before_id is not None:
        query = query.where(Chat.id < before_id)
    result = await db.execute(query)
    return list(result.scalars().all())


async def get_chat_by_id(db: AsyncSession, chat_id: int) -> Chat | None:
    result = await db.execute(select(Chat).where(Chat.id == chat_id))
    return result.scalar_one_or_none()


async def get_chat_member(db: AsyncSession, *, chat_id: int, user_id: int) -> ChatMember | None:
    result = await db.execute(
        select(ChatMember).where(
            ChatMember.chat_id == chat_id,
            ChatMember.user_id == user_id,
        )
    )
    return result.scalar_one_or_none()


async def list_chat_members(db: AsyncSession, *, chat_id: int) -> list[ChatMember]:
    result = await db.execute(select(ChatMember).where(ChatMember.chat_id == chat_id).order_by(ChatMember.id.asc()))
    return list(result.scalars().all())


async def list_user_chat_ids(db: AsyncSession, *, user_id: int) -> list[int]:
    result = await db.execute(
        select(ChatMember.chat_id).where(ChatMember.user_id == user_id).order_by(ChatMember.chat_id.asc())
    )
    return list(result.scalars().all())