from datetime import UTC, datetime, timedelta

import structlog
from sqlalchemy import and_, func, select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.database.models import PromoCode, PromoCodeType, PromoCodeUse, User


logger = structlog.get_logger(__name__)


async def get_promocode_by_code(db: AsyncSession, code: str) -> PromoCode | None:
    result = await db.execute(
        select(PromoCode)
        .options(selectinload(PromoCode.uses), selectinload(PromoCode.promo_group))
        .where(PromoCode.code == code.upper())
    )
    return result.scalar_one_or_none()


async def get_promocode_by_id(db: AsyncSession, promo_id: int) -> PromoCode | None:
    """
    Получает промокод по ID с eager loading всех связанных данных.
    Используется для избежания lazy loading в async контексте.
    """
    result = await db.execute(
        select(PromoCode)
        .options(selectinload(PromoCode.uses), selectinload(PromoCode.promo_group))
        .where(PromoCode.id == promo_id)
    )
    return result.scalar_one_or_none()


async def check_promocode_validity(db: AsyncSession, code: str) -> dict:
    """
    Проверяет существование и валидность промокода без активации.
    Возвращает словарь с информацией о промокоде.
    """
    promocode = await get_promocode_by_code(db, code)

    if not promocode:
        return {'valid': False, 'error': 'not_found', 'promocode': None}

    if not promocode.is_valid:
        if promocode.current_uses >= promocode.max_uses:
            return {'valid': False, 'error': 'used', 'promocode': None}
        return {'valid': False, 'error': 'expired', 'promocode': None}

    return {'valid': True, 'error': None, 'promocode': promocode}


async def create_promocode(
    db: AsyncSession,
    code: str,
    type: PromoCodeType,
    balance_bonus_kopeks: int = 0,
    subscription_days: int = 0,
    max_uses: int = 1,
    valid_until: datetime | None = None,
    created_by: int | None = None,
    promo_group_id: int | None = None,
) -> PromoCode:
    promocode = PromoCode(
        code=code.upper(),
        type=type.value,
        balance_bonus_kopeks=balance_bonus_kopeks,
        subscription_days=subscription_days,
        max_uses=max_uses,
        valid_until=valid_until,
        created_by=created_by,
        promo_group_id=promo_group_id,
    )

    db.add(promocode)
    await db.commit()
    await db.refresh(promocode)

    if promo_group_id:
        logger.info('✅ Создан промокод: с промогруппой ID', code=code, promo_group_id=promo_group_id)
    else:
        logger.info('✅ Создан промокод', code=code)
    return promocode


async def check_user_promocode_usage(db: AsyncSession, user_id: int, promocode_id: int) -> bool:
    result = await db.execute(
        select(PromoCodeUse).where(and_(PromoCodeUse.user_id == user_id, PromoCodeUse.promocode_id == promocode_id))
    )
    return result.scalar_one_or_none() is not None


async def create_promocode_use(db: AsyncSession, promocode_id: int, user_id: int) -> PromoCodeUse | None:
    from sqlalchemy.exc import IntegrityError

    promocode_use = PromoCodeUse(promocode_id=promocode_id, user_id=user_id, used_at=datetime.now(UTC))

    try:
        async with db.begin_nested():
            db.add(promocode_use)
            await db.flush()
    except IntegrityError:
        logger.warning(
            '⚠️ Дублирующая запись использования промокода (race condition)',
            promocode_id=promocode_id,
            user_id=user_id,
        )
        return None

    logger.info('📝 Записано использование промокода пользователем', promocode_id=promocode_id, user_id=user_id)
    return promocode_use


async def get_promocode_use_by_user_and_code(db: AsyncSession, user_id: int, promocode_id: int) -> PromoCodeUse | None:
    result = await db.execute(
        select(PromoCodeUse).where(and_(PromoCodeUse.user_id == user_id, PromoCodeUse.promocode_id == promocode_id))
    )
    return result.scalar_one_or_none()


async def count_user_recent_activations(db: AsyncSession, user_id: int, hours: int = 24) -> int:
    """Подсчитывает количество активаций промокодов пользователем за последние N часов."""
    cutoff = datetime.now(UTC) - timedelta(hours=hours)
    result = await db.execute(
        select(func.count(PromoCodeUse.id)).where(and_(PromoCodeUse.user_id == user_id, PromoCodeUse.used_at >= cutoff))
    )
    return result.scalar() or 0


async def get_user_promocodes(db: AsyncSession, user_id: int) -> list[PromoCodeUse]:
    result = await db.execute(
        select(PromoCodeUse).where(PromoCodeUse.user_id == user_id).order_by(PromoCodeUse.used_at.desc())
    )
    return result.scalars().all()


async def get_promocodes_list(
    db: AsyncSession, offset: int = 0, limit: int = 50, is_active: bool | None = None
) -> list[PromoCode]:
    query = select(PromoCode).options(selectinload(PromoCode.uses), selectinload(PromoCode.promo_group))

    if is_active is not None:
        query = query.where(PromoCode.is_active == is_active)

    query = query.order_by(PromoCode.created_at.desc()).offset(offset).limit(limit)

    result = await db.execute(query)
    return result.scalars().all()


async def get_promocodes_count(db: AsyncSession, is_active: bool | None = None) -> int:
    query = select(func.count(PromoCode.id))

    if is_active is not None:
        query = query.where(PromoCode.is_active == is_active)

    result = await db.execute(query)
    return result.scalar()


async def update_promocode(db: AsyncSession, promocode: PromoCode, **kwargs) -> PromoCode:
    for field, value in kwargs.items():
        if hasattr(promocode, field):
            setattr(promocode, field, value)

    promocode.updated_at = datetime.now(UTC)
    await db.commit()
    await db.refresh(promocode)

    return promocode


async def delete_promocode(db: AsyncSession, promocode: PromoCode) -> bool:
    try:
        from sqlalchemy import delete as sql_delete

        await db.execute(sql_delete(PromoCodeUse).where(PromoCodeUse.promocode_id == promocode.id))

        await db.delete(promocode)
        await db.commit()

        logger.info('🗑️ Удален промокод', code=promocode.code)
        return True

    except Exception as e:
        logger.error('Ошибка удаления промокода', error=e)
        await db.rollback()
        return False


async def get_active_discount_promocode_for_user(
    db: AsyncSession, user_id: int
) -> tuple[PromoCode | None, PromoCodeUse | None]:
    """
    Находит активный промокод на скидку, который сейчас действует у пользователя.
    Ищет по source-полю пользователя (формат 'promocode:CODE').

    Returns:
        Кортеж (PromoCode, PromoCodeUse) или (None, None) если ничего не найдено.
    """
    from app.database.models import User as UserModel

    user_result = await db.execute(select(UserModel).where(UserModel.id == user_id))
    user = user_result.scalar_one_or_none()
    if not user:
        return None, None

    source = getattr(user, 'promo_offer_discount_source', None)
    if not source or not source.startswith('promocode:'):
        return None, None

    code = source.split(':', 1)[1]
    promocode = await get_promocode_by_code(db, code)
    if not promocode:
        return None, None

    use = await get_promocode_use_by_user_and_code(db, user_id, promocode.id)
    return promocode, use


async def get_promocode_statistics(db: AsyncSession, promocode_id: int) -> dict:
    total_uses_result = await db.execute(
        select(func.count(PromoCodeUse.id)).where(PromoCodeUse.promocode_id == promocode_id)
    )
    total_uses = total_uses_result.scalar()

    today = datetime.now(UTC).date()
    today_uses_result = await db.execute(
        select(func.count(PromoCodeUse.id)).where(
            and_(PromoCodeUse.promocode_id == promocode_id, PromoCodeUse.used_at >= today)
        )
    )
    today_uses = today_uses_result.scalar()

    recent_uses_result = await db.execute(
        select(PromoCodeUse, User)
        .join(User, PromoCodeUse.user_id == User.id)
        .where(PromoCodeUse.promocode_id == promocode_id)
        .order_by(PromoCodeUse.used_at.desc())
        .limit(10)
    )
    recent_uses_data = recent_uses_result.all()

    recent_uses = []
    for use, user in recent_uses_data:
        use.user_username = user.username
        use.user_full_name = user.full_name
        use.user_telegram_id = user.telegram_id
        recent_uses.append(use)

    return {'total_uses': total_uses, 'today_uses': today_uses, 'recent_uses': recent_uses}