from app.extensions import db
from app.models.stock import StockBuy
from app.models.material import MaterialBase
from sqlalchemy.exc import SQLAlchemyError


class StockService:
    @staticmethod
    def create_inbound(data):
        """
        处理入库逻辑：
        1. 根据 SKU 查找物料。
        2. 如果没找到，创建新物料 (MaterialBase)。
        3. 创建入库单 (StockBuy)。
        """
        try:
            sku = data.get('sku_code')
            material_id = data.get('material_id')

            # --- 第一步：确定 material_id ---

            # 如果前端没传 ID，或者传了但我们想二次确认，都通过 SKU 查一遍
            existing_material = MaterialBase.query.filter_by(sku_code=sku).first()

            if existing_material:
                # 场景 A: 物料已存在 -> 直接使用其 ID
                material_id = existing_material.id
            else:
                # 场景 B: 物料不存在 -> 自动创建新物料
                if not data.get('material_name'):
                    raise ValueError(f"SKU [{sku}] 是新物料，必须填写【物料名称】才能入库。")

                new_material = MaterialBase(
                    sku_code=sku,
                    name=data.get('material_name'),
                    spec_model=data.get('spec_model'),
                    unit=data.get('unit'),
                    category=data.get('category')
                )
                db.session.add(new_material)
                db.session.flush()  # 关键：将对象刷入暂存区，以获取自增的 ID
                material_id = new_material.id

            # --- 第二步：创建入库单 ---

            qty = data.get('qty_inbound')
            price = data.get('price_unit', 0)

            new_stock = StockBuy(
                material_id=material_id,
                inbound_date=data.get('inbound_date'),
                batch_no=data.get('batch_no'),
                warehouse_loc=data.get('warehouse_loc'),
                supplier_name=data.get('supplier_name'),

                # 数量逻辑：初始时，当前量 = 可用量 = 入库量
                qty_inbound=qty,
                qty_current=qty,
                qty_available=qty,

                # 财务逻辑
                price_unit=price,
                price_total=float(qty) * float(price) if qty else 0
            )

            db.session.add(new_stock)
            db.session.commit()  # 统一提交事务

            return new_stock

        except SQLAlchemyError as e:
            db.session.rollback()  # 数据库报错回滚
            raise e
        except ValueError as e:
            db.session.rollback()  # 业务报错回滚
            raise e

    @staticmethod
    def get_list(page, per_page):
        """获取分页列表"""
        pagination = StockBuy.query.order_by(StockBuy.inbound_date.desc()).paginate(
            page=page, per_page=per_page, error_out=False
        )
        return {
            'items': [item.to_dict() for item in pagination.items],
            'total': pagination.total,
            'pages': pagination.pages,
            'current_page': pagination.page
        }

    @staticmethod
    def update_inbound(stock_id, data):
        """更新入库单信息 (通常不允许改物料本身，只改入库相关)"""
        stock = StockBuy.query.get_or_404(stock_id)

        if 'warehouse_loc' in data: stock.warehouse_loc = data['warehouse_loc']
        if 'supplier_name' in data: stock.supplier_name = data['supplier_name']
        if 'batch_no' in data: stock.batch_no = data['batch_no']
        if 'price_unit' in data: stock.price_unit = data['price_unit']

        # 如果修改了数量，需要级联更新当前库存
        if 'qty_inbound' in data:
            old_qty = float(stock.qty_inbound)
            new_qty = float(data['qty_inbound'])
            diff = new_qty - old_qty

            stock.qty_inbound = new_qty
            stock.qty_current = float(stock.qty_current) + diff
            stock.qty_available = float(stock.qty_available) + diff

        db.session.commit()
        return stock

    @staticmethod
    def delete_inbound(stock_id):
        """删除入库单"""
        stock = StockBuy.query.get_or_404(stock_id)
        db.session.delete(stock)
        db.session.commit()