import asyncio
import logging
from types import SimpleNamespace
from typing import Iterable

from aiogram import Bot
from aiogram.exceptions import TelegramBadRequest
from aiogram.types import InlineKeyboardButton, InlineKeyboardMarkup
from sqlalchemy import and_, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.config import settings
from app.database.crud.user import add_user_balance
from app.database.models import (
    Poll,
    PollOption,
    PollQuestion,
    PollResponse,
    TransactionType,
    User,
)
from app.localization.texts import get_texts

logger = logging.getLogger(__name__)


def _build_poll_invitation_text(poll: Poll, language: str) -> str:
    texts = get_texts(language)

    lines: list[str] = [f"🗳️ <b>{poll.title}</b>"]
    if poll.description:
        lines.append(poll.description)

    if poll.reward_enabled and poll.reward_amount_kopeks > 0:
        reward_line = texts.t(
            "POLL_INVITATION_REWARD",
            "🎁 За участие вы получите {amount}.",
        ).format(amount=settings.format_price(poll.reward_amount_kopeks))
        lines.append(reward_line)

    lines.append(
        texts.t(
            "POLL_INVITATION_START",
            "Нажмите кнопку ниже, чтобы пройти опрос.",
        )
    )

    return "\n\n".join(lines)


def build_start_keyboard(response_id: int, language: str) -> InlineKeyboardMarkup:
    texts = get_texts(language)
    return InlineKeyboardMarkup(
        inline_keyboard=[
            [
                InlineKeyboardButton(
                    text=texts.t("POLL_START_BUTTON", "📝 Пройти опрос"),
                    callback_data=f"poll_start:{response_id}",
                )
            ]
        ]
    )


async def send_poll_to_users(
    bot: Bot,
    db: AsyncSession,
    poll: Poll,
    users: Iterable[User],
) -> dict:
    from app.database.database import AsyncSessionLocal
    
    sent = 0
    failed = 0
    skipped = 0

    poll_id = poll.id

    user_snapshots = [
        SimpleNamespace(
            id=user.id,
            telegram_id=user.telegram_id,
            language=user.language,
        )
        for user in users
    ]

    # Получаем список пользователей, которые уже прошли опрос, за один запрос
    user_ids = [user_snapshot.id for user_snapshot in user_snapshots]
    existing_responses_result = await db.execute(
        select(PollResponse.user_id).where(
            and_(
                PollResponse.poll_id == poll_id,
                PollResponse.user_id.in_(user_ids)
            )
        )
    )
    existing_user_ids = set(existing_responses_result.scalars().all())

    # Используем умеренный семафор, чтобы не превышать лимиты подключений к БД
    semaphore = asyncio.Semaphore(30)  # Баланс между производительностью и нагрузкой на БД

    # Создаем отдельную функцию для создания отдельной сессии для каждой отправки
    async def send_poll_invitation(user_snapshot):
        """Отправляет приглашение к опросу одному пользователю"""
        async with semaphore:
            # Пропускаем пользователей, которые уже прошли опрос
            if user_snapshot.id in existing_user_ids:
                return "skipped"
                
            # Создаем новую сессию для изоляции транзакции
            async with AsyncSessionLocal() as new_db:
                try:
                    # Проверяем еще раз в новой сессии на случай гонки
                    existing_response = await new_db.execute(
                        select(PollResponse.id).where(
                            and_(
                                PollResponse.poll_id == poll_id,
                                PollResponse.user_id == user_snapshot.id,
                            )
                        )
                    )
                    existing_id = existing_response.scalar_one_or_none()
                    if existing_id:
                        return "skipped"

                    response = PollResponse(
                        poll_id=poll_id,
                        user_id=user_snapshot.id,
                    )
                    new_db.add(response)

                    await new_db.flush()

                    text = _build_poll_invitation_text(poll, user_snapshot.language)
                    keyboard = build_start_keyboard(response.id, user_snapshot.language)

                    await bot.send_message(
                        chat_id=user_snapshot.telegram_id,
                        text=text,
                        reply_markup=keyboard,
                        parse_mode="HTML",
                        disable_web_page_preview=True,
                    )

                    await new_db.commit()
                    return "sent"
                except TelegramBadRequest as error:
                    error_text = str(error).lower()
                    if "chat not found" in error_text or "bot was blocked by the user" in error_text:
                        await new_db.rollback()
                        return "skipped"
                    else:  # pragma: no cover - unexpected telegram error
                        await new_db.rollback()
                        return "failed"
                except Exception as error:  # pragma: no cover - defensive logging
                    await new_db.rollback()
                    # Проверяем, является ли ошибка связанной с лимитом подключений
                    if "too many clients" in str(error).lower():
                        logger.warning(
                            "⚠️ Ограничение на количество подключений к БД: %s пользователю %s",
                            poll_id,
                            user_snapshot.telegram_id,
                        )
                        # Уменьшаем вероятность переполнения, делая небольшую задержку
                        await asyncio.sleep(0.1)
                    else:
                        logger.error(
                            "❌ Ошибка отправки опроса %s пользователю %s: %s",
                            poll_id,
                            user_snapshot.telegram_id,
                            error,
                        )
                    return "failed"

    # Отправляем все приглашения одновременно без задержек для максимальной скорости
    tasks = [send_poll_invitation(user_snapshot) for user_snapshot in user_snapshots]
    results = await asyncio.gather(*tasks, return_exceptions=True)

    for result in results:
        if isinstance(result, str):  # Успешно выполненная задача
            if result == "sent":
                sent += 1
            elif result == "failed":
                failed += 1
            elif result == "skipped":
                skipped += 1
        elif isinstance(result, Exception):  # Ошибка выполнения задачи
            failed += 1

    return {
        "sent": sent,
        "failed": failed,
        "skipped": skipped,
        "total": sent + failed + skipped,
    }


async def reward_user_for_poll(
    db: AsyncSession,
    response: PollResponse,
) -> int:
    await db.refresh(response, with_for_update=True)

    poll = response.poll
    if not poll.reward_enabled or poll.reward_amount_kopeks <= 0:
        return 0

    if response.reward_given:
        return response.reward_amount_kopeks

    user = response.user
    description = f"Награда за участие в опросе \"{poll.title}\""

    response.reward_given = True
    response.reward_amount_kopeks = poll.reward_amount_kopeks

    success = await add_user_balance(
        db,
        user,
        poll.reward_amount_kopeks,
        description,
        transaction_type=TransactionType.POLL_REWARD,
    )

    if not success:
        return 0

    await db.refresh(
        response,
        attribute_names=["reward_given", "reward_amount_kopeks"],
    )

    return poll.reward_amount_kopeks


async def get_next_question(response: PollResponse) -> tuple[int | None, PollQuestion | None]:
    if not response.poll or not response.poll.questions:
        return None, None

    answered_question_ids = {answer.question_id for answer in response.answers}
    ordered_questions = sorted(response.poll.questions, key=lambda q: q.order)

    for index, question in enumerate(ordered_questions, start=1):
        if question.id not in answered_question_ids:
            return index, question

    return None, None


async def get_question_option(question: PollQuestion, option_id: int) -> PollOption | None:
    for option in question.options:
        if option.id == option_id:
            return option
    return None