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

from app.chats import repository
from app.chats.models import Chat, ChatMemberRole, ChatType
from app.chats.schemas import ChatCreateRequest
from app.users.repository import get_user_by_id


async def create_chat_for_user(db: AsyncSession, *, creator_id: int, payload: ChatCreateRequest) -> Chat:
    member_ids = list(dict.fromkeys(payload.member_ids))
    member_ids = [member_id for member_id in member_ids if member_id != creator_id]

    if payload.type == ChatType.PRIVATE and len(member_ids) != 1:
        raise HTTPException(
            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
            detail="Private chat requires exactly one target user.",
        )
    if payload.type in {ChatType.GROUP, ChatType.CHANNEL} and not payload.title:
        raise HTTPException(
            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
            detail="Group and channel chats require title.",
        )

    for member_id in member_ids:
        user = await get_user_by_id(db, member_id)
        if not user:
            raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=f"User {member_id} not found")

    chat = await repository.create_chat(db, chat_type=payload.type, title=payload.title)
    await repository.add_chat_member(db, chat_id=chat.id, user_id=creator_id, role=ChatMemberRole.OWNER)

    default_role = ChatMemberRole.MEMBER
    for member_id in member_ids:
        await repository.add_chat_member(db, chat_id=chat.id, user_id=member_id, role=default_role)

    await db.commit()
    return chat


async def get_chats_for_user(db: AsyncSession, *, user_id: int, limit: int = 50, before_id: int | None = None) -> list[Chat]:
    safe_limit = max(1, min(limit, 100))
    return await repository.list_user_chats(db, user_id=user_id, limit=safe_limit, before_id=before_id)


async def get_chat_for_user(db: AsyncSession, *, chat_id: int, user_id: int) -> tuple[Chat, list]:
    chat = await repository.get_chat_by_id(db, chat_id)
    if not chat:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Chat not found")

    membership = await repository.get_chat_member(db, chat_id=chat_id, user_id=user_id)
    if not membership:
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="You are not a member of this chat")

    members = await repository.list_chat_members(db, chat_id=chat_id)
    return chat, members


async def ensure_chat_membership(db: AsyncSession, *, chat_id: int, user_id: int) -> None:
    membership = await repository.get_chat_member(db, chat_id=chat_id, user_id=user_id)
    if not membership:
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="You are not a member of this chat")