from __future__ import annotations

from dataclasses import dataclass
from enum import StrEnum

from slack_sdk.errors import SlackApiError
from slack_sdk.web.async_client import AsyncWebClient

from yuxi.channels.models import DeliveryResult
from yuxi.utils.logging_config import logger


class StreamState(StrEnum):
    INIT = "init"
    STREAMING = "streaming"
    STOPPED = "stopped"
    ERROR = "error"


_BENIGN_FINALIZE_ERRORS = frozenset(
    {
        "user_not_found",
        "team_not_found",
        "missing_recipient_user_id",
        "not_in_channel",
        "channel_not_found",
    }
)


class SlackStreamNotDeliveredError(Exception):
    pass


@dataclass
class NativeStreamSession:
    channel: str
    team_id: str = ""
    user_id: str = ""
    message_ts: str = ""
    accumulated_text: str = ""
    state: StreamState = StreamState.INIT
    error: str = ""


_MISSING_OVERRIDE = object()


class NativeStreamManager:
    def __init__(self, client: AsyncWebClient):
        self._client = client
        self._sessions: dict[str, NativeStreamSession] = {}

    async def start_stream(
        self,
        channel: str,
        *,
        team_id: str = "",
        user_id: str = "",
        text: str = "",
    ) -> DeliveryResult:
        session_key = f"{channel}:{team_id}:{user_id}"
        existing = self._sessions.get(session_key)
        if existing and existing.state == StreamState.STREAMING:
            return await self.append_stream(channel, text, team_id=team_id, user_id=user_id)

        try:
            params: dict = {
                "channel": channel,
                "text": text or "...",
            }
            if user_id:
                params["user_id"] = user_id
            if team_id:
                params["team_id"] = team_id

            result = await self._client.api_call(
                api_method="chat.startStream",
                http_verb="POST",
                params=params,
            )
            ok = result.get("ok", False)
            ts = result.get("ts", "")

            session = NativeStreamSession(
                channel=channel,
                team_id=team_id,
                user_id=user_id,
                message_ts=ts,
                accumulated_text=text,
                state=StreamState.STREAMING if ok else StreamState.ERROR,
                error=result.get("error", ""),
            )
            self._sessions[session_key] = session

            if ok:
                logger.debug(f"Native stream started: channel={channel}, ts={ts}")
                return DeliveryResult(success=True, message_id=ts)

            logger.warning(f"Native stream start failed: {result.get('error')}")
            return DeliveryResult(success=False, error=result.get("error", "Unknown error"))

        except SlackApiError as e:
            err = e.response.get("error", str(e))
            logger.error(f"Native stream start error: {err}")
            return DeliveryResult(success=False, error=err)

    async def append_stream(
        self,
        channel: str,
        text: str,
        *,
        team_id: str = "",
        user_id: str = "",
        ts: str = "",
    ) -> DeliveryResult:
        session_key = f"{channel}:{team_id}:{user_id}"
        session = self._sessions.get(session_key)
        if not session or session.state != StreamState.STREAMING:
            return await self.start_stream(channel, team_id=team_id, user_id=user_id, text=text)

        try:
            result = await self._client.api_call(
                api_method="chat.appendStream",
                http_verb="POST",
                params={
                    "channel": channel,
                    "ts": ts or session.message_ts,
                    "text": text,
                },
            )
            ok = result.get("ok", False)
            if ok:
                session.accumulated_text = text
            return DeliveryResult(
                success=ok,
                error=result.get("error") if not ok else None,
            )

        except SlackApiError as e:
            err = e.response.get("error", str(e))
            logger.error(f"Native stream append error: {err}")
            return DeliveryResult(success=False, error=err)

    async def stop_stream(
        self,
        channel: str,
        *,
        team_id: str = "",
        user_id: str = "",
        ts: str = "",
        final_text: str = _MISSING_OVERRIDE,
    ) -> DeliveryResult:
        session_key = f"{channel}:{team_id}:{user_id}"
        session = self._sessions.pop(session_key, None)

        try:
            result = await self._client.api_call(
                api_method="chat.stopStream",
                http_verb="POST",
                params={
                    "channel": channel,
                    "ts": ts or (session.message_ts if session else ""),
                    "text": final_text
                    if final_text is not _MISSING_OVERRIDE
                    else (session.accumulated_text if session else ""),
                },
            )
            ok = result.get("ok", False)
            err = result.get("error", "")

            if not ok and not _is_benign_stop_error(err):
                logger.error(f"Native stream stop error: {err}")
                raise SlackStreamNotDeliveredError(f"Stream not delivered: {err}")

            return DeliveryResult(
                success=True,
                error=err if err and err not in _BENIGN_FINALIZE_ERRORS else None,
            )

        except SlackApiError as e:
            err = e.response.get("error", str(e))
            if _is_benign_stop_error(err):
                return DeliveryResult(success=True)
            logger.error(f"Native stream stop API error: {err}")
            raise SlackStreamNotDeliveredError(f"Stream not delivered: {err}") from e


def _is_benign_stop_error(error: str) -> bool:
    return error in _BENIGN_FINALIZE_ERRORS