from . import models
from django.db.models import Sum
from django.utils import timezone
import logging


logger = logging.getLogger(__name__)


def find_inventory(product_id: int, warehouse_id: int) -> models.Inventory | None:
    """根据产品ID和仓库ID查找库存记录"""

    try:
        inventory = models.Inventory.objects.get(
            product_id=product_id,
            warehouse_id=warehouse_id,
        )
        return inventory
    except models.Inventory.DoesNotExist:
        return None


def create_stock_snapshot(stock_change_detail: models.StockChangeDetail, inventory: models.Inventory) -> models.StockSnapshot:
    """创建库存快照记录"""

    if not stock_change_detail or stock_change_detail.id is None:
        raise ValueError("无效的库存变动明细记录")

    delta = stock_change_detail.quantity if stock_change_detail.stock_change_record.is_incoming else -stock_change_detail.quantity
    rolls_delta = 1 if stock_change_detail.stock_change_record.is_incoming else -1

    # 必须在库存变动发生后创建快照
    snapshot = models.StockSnapshot(
        merchant_id=stock_change_detail.merchant_id,
        product_id=inventory.product_id,
        warehouse_id=inventory.warehouse_id,
        delta=delta,
        quantity_before=inventory.quantity - delta,
        quantity_after=inventory.quantity,
        stock_change_record_id=stock_change_detail.stock_change_record.id,
        unit=stock_change_detail.unit,
        num_of_rolls=inventory.num_of_rolls + rolls_delta,
    )
    snapshot.save()
    logger.info(
        f'创建库存快照，库存ID: {inventory.id}, 数量: {inventory.quantity}, '
        f'匹数: {inventory.num_of_rolls}'
    )
    return snapshot


def make_stock_change_completed(stock_change_record: models.StockChangeRecord) -> bool:
    """处理库存变动完成后的逻辑, 实际扣减库存也在这里发生"""
    # TODO: 这里可以添加事务处理以确保数据一致性

    if not stock_change_record or stock_change_record.id is None:
        # 无效的库存变动记录
        return False

    if stock_change_record.is_finished:
        return True


    # TODO: 逻辑更改 = 出入库单现在不记录库存总量了
    # 需要根据产品分别统计变动数量（要考虑不同单位）

    for detail in stock_change_record.details.all():
        detail: models.StockChangeDetail

        logger.info(
            f'处理库存变动明细，产品ID: {detail.product_id}, '
            f'数量: {detail.quantity}, 单位: {detail.get_unit_display()}'
        )

        inventory_record = find_inventory(
            product_id=detail.product_id,
            warehouse_id=stock_change_record.warehouse_id,
        )

        # 确定方向
        positive = 1 if stock_change_record.is_incoming else -1

        if inventory_record:
            # 更新现有库存记录
            inventory_record.quantity += detail.quantity * positive
            inventory_record.num_of_rolls += positive
            
            logger.info(
                f'更新库存记录 {inventory_record.id}，新数量: {inventory_record.quantity}, '
                f'新匹数: {inventory_record.num_of_rolls}'
            )

            inventory_record.save()
        else:
            # 创建新库存记录
            inventory_record = models.Inventory(
                merchant_id=stock_change_record.merchant_id,
                product_id=detail.product_id,
                warehouse_id=stock_change_record.warehouse_id,
                quantity=detail.quantity * positive,
                num_of_rolls=1 if stock_change_record.is_incoming else -1,
            )
            inventory_record.save()
            logger.info(
                f'创建新库存记录 {inventory_record.id}，数量: {inventory_record.quantity}, '
                f'匹数: {inventory_record.num_of_rolls}'
            )

        # 无论库存记录原本是否存在都创建库存快照
        create_stock_snapshot(detail, inventory_record)

    # 所有明细处理完毕，标记库存变动记录为已完成
    stock_change_record.is_finished = True
    stock_change_record.finished_at = timezone.now()
    stock_change_record.save()
    logger.info(
        f'库存变动记录 {stock_change_record.id} 标记为已完成。'
    )
    return True


def get_frozen_stock_count(product_id: int, warehouse_id: int) -> int:
    """获取指定产品在指定仓库的冻结库存数量"""
    total_frozen = models.StockFreeze.objects.filter(
        product_id=product_id,
        warehouse_id=warehouse_id,
        status=models.StockFreezeStatusEnum.FROZEN
    ).aggregate(total=Sum('quantity'))['total'] or 0
    return total_frozen