from __future__ import annotations

from app.core.exceptions import AppError
from app.modules.api.infrastructure.streaming.sse_encoder import SseEncoder
from app.modules.api.infrastructure.streaming.sse_event_channel import SseEventChannel
from app.schemas.common import ModuleName


class StreamService:
    def __init__(self, channel: SseEventChannel, request_exists, encoder: SseEncoder | None = None) -> None:
        self._channel = channel
        self._request_exists = request_exists
        self._encoder = encoder or SseEncoder()

    async def subscribe(self, request_id: str):
        if not self._request_exists(request_id):
            raise AppError("request_not_found", f"Agent request not found: {request_id}", ModuleName.BACKEND)
        return await self._channel.subscribe(request_id, replay=True)

    async def unsubscribe(self, request_id: str, queue) -> None:
        await self._channel.unsubscribe(request_id, queue)

    def encode(self, event) -> str:
        return self._encoder.encode(event)