from __future__ import annotations

from collections import Counter
from datetime import datetime
from decimal import Decimal

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.enums.credit_balance import CreditAllocationAction, CreditBalanceStatus, CreditScope
from app.enums.credit_record import CreditRecordBillingScene, CreditRecordType
from app.models.credit.allocation import CreditRecordAllocation
from app.models.credit.balance import UserCreditBalance
from app.models.credit.subscription import UserCreditSubscription
from app.models.credit_record import CreditRecord
from app.services.credit.locking import acquire_user_credit_lock
from app.services.credit.query_service import get_available_credits
from app.services.credit.utils import to_credit_decimal, utc_now
from app.utils.id_gen import generate_id


async def archive_expired_user_balances(
    db: AsyncSession,
    *,
    user_id: str,
    request_time: datetime | None = None,
    limit: int = 500,
) -> int:
    checked_at = request_time or utc_now()
    await acquire_user_credit_lock(db, user_id)
    result = await db.execute(
        select(UserCreditBalance)
        .where(
            UserCreditBalance.user_id == user_id,
            UserCreditBalance.expires_at <= checked_at,
            UserCreditBalance.unspent_amount > 0,
            UserCreditBalance.expired_processed_at.is_(None),
            UserCreditBalance.revoked_at.is_(None),
        )
        .order_by(UserCreditBalance.expires_at.asc(), UserCreditBalance.id.asc())
        .limit(max(1, limit))
        .with_for_update()
    )
    balances = list(result.scalars().all())
    if not balances:
        return 0

    current_available = await get_available_credits(db, user_id, request_time=checked_at)
    subscription_ids = [item.subscription_id for item in balances if item.subscription_id]
    manager_map: dict[str, str | None] = {}
    if subscription_ids:
        sub_result = await db.execute(
            select(UserCreditSubscription.id, UserCreditSubscription.team_manager_id_snapshot)
            .where(UserCreditSubscription.id.in_(subscription_ids))
        )
        manager_map = {str(row.id): row.team_manager_id_snapshot for row in sub_result.all()}
    for balance in balances:
        amount = to_credit_decimal(balance.unspent_amount)
        if amount <= 0:
            continue
        before_consumed = to_credit_decimal(balance.consumed_amount)
        record = CreditRecord(
            id=generate_id(),
            user_id=user_id,
            type=CreditRecordType.EXPIRE.value,
            amount=-amount,
            balance_delta=Decimal("0.00"),
            expired_amount=amount,
            balance_after=current_available,
            description=f"积分到期：{float(amount):.2f}",
            related_id=balance.id,
            request_time=checked_at,
            biz_key=f"credit-balance:{balance.id}:expire",
            billing_scene=CreditRecordBillingScene.CREDIT_EXPIRE.value,
            credit_level_snapshot=balance.credit_level,
        )
        db.add(record)
        await db.flush()
        db.add(
            CreditRecordAllocation(
                id=generate_id(),
                credit_record_id=record.id,
                credit_balance_id=balance.id,
                user_id=user_id,
                allocation_action=CreditAllocationAction.EXPIRE.value,
                amount=amount,
                request_time=checked_at,
                credit_level_snapshot=balance.credit_level,
                credit_scope_snapshot=balance.credit_scope or CreditScope.PERSONAL.value,
                source_type_snapshot=balance.source_type,
                source_id_snapshot=balance.source_id,
                team_id_snapshot=balance.team_id,
                team_manager_id_snapshot=manager_map.get(balance.subscription_id or ""),
                subscription_id_snapshot=balance.subscription_id,
                subscription_period_id_snapshot=balance.subscription_period_id,
                seat_id_snapshot=None,
                valid_from_snapshot=balance.valid_from,
                expires_at_snapshot=balance.expires_at,
                unspent_before=amount,
                unspent_after=Decimal("0.00"),
                consumed_before=before_consumed,
                consumed_after=before_consumed,
            )
        )
        balance.unspent_amount = Decimal("0.00")
        balance.expired_amount = to_credit_decimal(balance.expired_amount) + amount
        balance.expired_processed_at = checked_at
        balance.status = CreditBalanceStatus.EXPIRED.value
    await db.flush()
    return len(balances)


async def list_expired_balance_user_limits(
    db: AsyncSession,
    *,
    request_time: datetime,
    batch_size: int = 500,
) -> list[tuple[str, int]]:
    result = await db.execute(
        select(UserCreditBalance.id, UserCreditBalance.user_id)
        .where(
            UserCreditBalance.expires_at <= request_time,
            UserCreditBalance.unspent_amount > 0,
            UserCreditBalance.expired_processed_at.is_(None),
            UserCreditBalance.revoked_at.is_(None),
        )
        .order_by(UserCreditBalance.expires_at.asc(), UserCreditBalance.id.asc())
        .limit(max(1, batch_size))
    )
    selected = [(str(row.id), str(row.user_id)) for row in result.all()]
    per_user_limit = Counter(user_id for _, user_id in selected)
    return sorted(per_user_limit.items(), key=lambda item: item[0])


async def archive_expired_balances_batch(
    db: AsyncSession,
    *,
    request_time: datetime | None = None,
    batch_size: int = 500,
) -> int:
    checked_at = request_time or utc_now()
    user_limits = await list_expired_balance_user_limits(
        db, request_time=checked_at, batch_size=batch_size
    )
    processed = 0
    for user_id, user_limit in user_limits:
        processed += await archive_expired_user_balances(
            db,
            user_id=user_id,
            request_time=checked_at,
            limit=user_limit,
        )
    return processed