from __future__ import annotations

import asyncio
import logging
from typing import TYPE_CHECKING, Any, Callable, Awaitable

from telegram import Update
from telegram.ext import Application, ApplicationBuilder, MessageHandler, filters

from channels.base import BaseChannel
from config import settings

if TYPE_CHECKING:
    pass

logger = logging.getLogger(__name__)


class TelegramChannel(BaseChannel):
    """Telegram-Kanal via python-telegram-bot (Long-Polling)."""

    def __init__(self) -> None:
        self._app: Application | None = None
        self._inbound_callback: Callable[[dict[str, Any]], Awaitable[None]] | None = None

    def set_inbound_callback(self, cb: Callable[[dict[str, Any]], Awaitable[None]]) -> None:
        """Callback, der bei eingehenden Nachrichten aufgerufen wird."""
        self._inbound_callback = cb

    # ── BaseChannel interface ──────────────────────────────────────────────────

    async def send_message(
        self,
        recipient: str,
        text: str,
        reply_to_id: str | None = None,
    ) -> dict[str, Any]:
        if not self._app:
            return {"success": False, "channel_message_id": None, "error": "Telegram not initialized"}
        try:
            kwargs: dict[str, Any] = {"chat_id": recipient, "text": text}
            if reply_to_id:
                kwargs["reply_to_message_id"] = int(reply_to_id)
            msg = await self._app.bot.send_message(**kwargs)
            return {"success": True, "channel_message_id": str(msg.message_id), "error": None}
        except Exception as exc:
            logger.error("Telegram send error: %s", exc)
            return {"success": False, "channel_message_id": None, "error": str(exc)}

    async def check_connection(self) -> tuple[bool, str]:
        if not self._app:
            return False, "Not initialized"
        try:
            me = await self._app.bot.get_me()
            return True, f"@{me.username}"
        except Exception as exc:
            return False, str(exc)

    async def start(self) -> None:
        if not settings.telegram_enabled:
            logger.info("Telegram disabled (no token configured)")
            return

        self._app = ApplicationBuilder().token(settings.telegram_token).build()
        self._app.add_handler(MessageHandler(~filters.COMMAND, self._handle_message))

        await self._app.initialize()
        await self._app.start()
        # Long-Polling als Background-Task
        asyncio.create_task(self._polling_loop(), name="telegram-polling")
        logger.info("Telegram channel started (long-polling)")

    async def stop(self) -> None:
        if self._app:
            # Korrekte PTB v20+ Shutdown-Reihenfolge:
            # Erst Updater stoppen, dann Application stoppen/shutdown
            try:
                if self._app.updater.running:
                    await self._app.updater.stop()
            except Exception:
                pass
            await self._app.stop()
            await self._app.shutdown()
            logger.info("Telegram channel stopped")

    # ── Interner Handler ───────────────────────────────────────────────────────

    async def _polling_loop(self) -> None:
        """Endlos-Polling im Hintergrund."""
        try:
            await self._app.updater.start_polling(allowed_updates=["message"])
            # In PTB v20+ läuft der Updater als eigener asyncio-Task weiter –
            # wir warten hier einfach, bis der Task abgebrochen wird.
            await asyncio.Event().wait()
        except asyncio.CancelledError:
            pass
        except Exception as exc:
            logger.error("Telegram polling error: %s", exc)

    async def _handle_message(self, update: Update, context: Any) -> None:
        if not update.message or not self._inbound_callback:
            return
        msg = update.message
        payload: dict[str, Any] = {
            "channel": "telegram",
            "channel_message_id": str(msg.message_id),
            "sender_telegram_id": str(msg.from_user.id) if msg.from_user else None,
            "sender_name": (
                (msg.from_user.full_name or msg.from_user.username)
                if msg.from_user
                else "Unknown"
            ),
            "chat_id": str(msg.chat.id),
            "text": msg.text or msg.caption or "",
            "reply_to_id": (
                str(msg.reply_to_message.message_id) if msg.reply_to_message else None
            ),
        }
        await self._inbound_callback(payload)