from __future__ import annotations

from dataclasses import dataclass
from typing import TYPE_CHECKING, Any

from aiogram.types import MessageEntity

from session_bot.html_entities import html_to_text_entities
from session_bot.render import build_channel_text

if TYPE_CHECKING:
    from session_bot.config import BotSettings
    from session_bot.storage import JsonStateStorage


@dataclass(slots=True)
class TelethonPublisher:
    settings: "BotSettings"
    _client: Any = None
    _peer: Any = None

    @property
    def enabled(self) -> bool:
        return self.settings.telethon_enabled

    async def start(self) -> None:
        if not self.enabled or self._client is not None:
            return

        try:
            from telethon import TelegramClient
            from telethon.sessions import StringSession
        except ImportError as exc:
            raise RuntimeError(
                "Telethon is not installed. Add it to the runtime environment to use channel editing via MTProto."
            ) from exc

        self._client = TelegramClient(
            StringSession(self.settings.telethon_session_string),
            self.settings.telethon_api_id,
            self.settings.telethon_api_hash,
        )
        await self._client.connect()
        if not await self._client.is_user_authorized():
            raise RuntimeError("Telethon session is not authorized. Generate a valid StringSession first.")

    async def close(self) -> None:
        if self._client is None:
            return
        await self._client.disconnect()
        self._client = None
        self._peer = None

    async def edit_channel_post(self, app_config: dict, state_storage: "JsonStateStorage", message_id: int) -> None:
        await self.start()
        html_text = build_channel_text(app_config, state_storage.load(), include_hidden_link=True)
        text, bot_entities = html_to_text_entities(html_text)
        entities = self._convert_entities(bot_entities)
        peer = await self._resolve_peer()
        await self._client.edit_message(
            peer,
            message_id,
            text=text,
            formatting_entities=entities,
            link_preview=bool(app_config.get("hidden_link_url", "").strip()),
        )

    async def _resolve_peer(self) -> Any:
        if self._peer is not None:
            return self._peer
        if self._client is None:
            raise RuntimeError("Telethon client is not started.")

        candidates: list[Any] = []
        channel_ref = self.settings.telethon_channel.strip()
        if channel_ref:
            candidates.extend(self._candidate_refs(channel_ref))
        else:
            candidates.extend(self._candidate_refs(self.settings.channel_id))

        last_error: Exception | None = None
        seen: set[str] = set()
        for candidate in candidates:
            key = repr(candidate)
            if key in seen:
                continue
            seen.add(key)
            try:
                self._peer = await self._client.get_entity(candidate)
                return self._peer
            except Exception as exc:  # pragma: no cover - depends on runtime Telegram session
                last_error = exc

        raise RuntimeError(
            "Unable to resolve TELETHON_CHANNEL. Set TELETHON_CHANNEL to @username, t.me link, or numeric channel id."
        ) from last_error

    def _candidate_refs(self, value: str | int) -> list[Any]:
        candidates: list[Any] = [value]
        raw = str(value).strip()
        if not raw:
            return candidates
        if raw.lstrip("-").isdigit():
            numeric = int(raw)
            candidates.append(numeric)
            if raw.startswith("-100"):
                candidates.append(int(raw[4:]))
            try:
                from telethon import utils

                resolved_id, _ = utils.resolve_id(numeric)
                candidates.append(resolved_id)
            except Exception:  # pragma: no cover - best effort normalization
                pass
        return candidates

    def _convert_entities(self, entities: list[MessageEntity]) -> list[Any]:
        try:
            from telethon.tl import types
        except ImportError as exc:
            raise RuntimeError(
                "Telethon is not installed. Add it to the runtime environment to use channel editing via MTProto."
            ) from exc

        converted: list[Any] = []
        for entity in entities:
            item = self._convert_entity(entity, types)
            if item is not None:
                converted.append(item)
        return converted

    @staticmethod
    def _convert_entity(entity: MessageEntity, types: Any) -> Any | None:
        kwargs = {"offset": entity.offset, "length": entity.length}

        if entity.type == "bold":
            return types.MessageEntityBold(**kwargs)
        if entity.type == "italic":
            return types.MessageEntityItalic(**kwargs)
        if entity.type == "underline":
            return types.MessageEntityUnderline(**kwargs)
        if entity.type == "strikethrough":
            return types.MessageEntityStrike(**kwargs)
        if entity.type == "code":
            return types.MessageEntityCode(**kwargs)
        if entity.type == "pre":
            return types.MessageEntityPre(language=entity.language or "", **kwargs)
        if entity.type == "text_link":
            return types.MessageEntityTextUrl(url=entity.url or "", **kwargs)
        if entity.type == "spoiler":
            return types.MessageEntitySpoiler(**kwargs)
        if entity.type == "blockquote" and hasattr(types, "MessageEntityBlockquote"):
            try:
                return types.MessageEntityBlockquote(collapsed=False, **kwargs)
            except TypeError:
                return types.MessageEntityBlockquote(**kwargs)
        if entity.type == "custom_emoji" and entity.custom_emoji_id:
            return types.MessageEntityCustomEmoji(document_id=int(entity.custom_emoji_id), **kwargs)
        return None