"""资金池：划额度、派单扣减。"""
from decimal import Decimal

from django.db import transaction
from django.db.models import F

from merchant_ops.constants import WALLET_ALLOCATE, WALLET_DISPATCH_CONFIRM
from merchant_ops.models import MerchantStaffWallet, MerchantStaffWalletLedger


def get_or_create_wallet(member):
    wallet, _ = MerchantStaffWallet.objects.get_or_create(
        merchant_id=member.merchant_id,
        staff_user_id=member.staff_user_id,
        defaults={'member': member},
    )
    return wallet


def allocate_quota(member, amount, operator_id, remark=''):
    amount = Decimal(str(amount))
    if amount <= 0:
        raise ValueError('划额度必须大于0')

    with transaction.atomic():
        wallet = MerchantStaffWallet.objects.select_for_update().get(
            merchant_id=member.merchant_id,
            staff_user_id=member.staff_user_id,
        )
        wallet.quota_total = F('quota_total') + amount
        wallet.save(update_fields=['quota_total'])
        wallet.refresh_from_db()
        MerchantStaffWalletLedger.objects.create(
            wallet=wallet,
            merchant_id=member.merchant_id,
            staff_user_id=member.staff_user_id,
            change_type=WALLET_ALLOCATE,
            amount=amount,
            balance_after=wallet.quota_available,
            operator_id=operator_id,
            remark=remark,
        )
    return wallet


def check_wallet_available(member, amount):
    amount = Decimal(str(amount))
    wallet = get_or_create_wallet(member)
    if amount > wallet.quota_available:
        raise ValueError('客服可用额度不足')


def confirm_dispatch_deduct(member, amount, order_id, operator_id):
    """派单成功：扣客服额度。"""
    amount = Decimal(str(amount))
    with transaction.atomic():
        wallet = MerchantStaffWallet.objects.select_for_update().get(
            merchant_id=member.merchant_id,
            staff_user_id=member.staff_user_id,
        )
        available = wallet.quota_total - wallet.quota_used - wallet.quota_frozen
        if amount > available:
            raise ValueError('客服可用额度不足')
        wallet.quota_used = F('quota_used') + amount
        wallet.save(update_fields=['quota_used'])
        wallet.refresh_from_db()
        MerchantStaffWalletLedger.objects.create(
            wallet=wallet,
            merchant_id=member.merchant_id,
            staff_user_id=member.staff_user_id,
            change_type=WALLET_DISPATCH_CONFIRM,
            amount=-amount,
            balance_after=wallet.quota_available,
            related_order_id=order_id,
            operator_id=operator_id,
            remark='派单扣额度',
        )