from sqlalchemy import (

Table, MetaData, Column, Integer, String, Date, ForeignKey,

event,

)

from sqlalchemy.orm import mapper, relationship

from allocation import model

metadata = MetaData()

order_lines = Table(

'order_lines', metadata,

Column('id', Integer, primary_key=True, autoincrement=True),

Column('sku', String(255)),

Column('qty', Integer, nullable=False),

Column('orderid', String(255)),

)

products = Table(

'products', metadata,

Column('sku', String(255), primary_key=True),

Column('version_number', Integer, nullable=False, server_default='0'),

)

batches = Table(

'batches', metadata,

Column('id', Integer, primary_key=True, autoincrement=True),

Column('reference', String(255)),

Column('sku', ForeignKey('products.sku')),

Column('_purchased_quantity', Integer, nullable=False),

Column('eta', Date, nullable=True),

)

allocations = Table(

'allocations', metadata,

Column('id', Integer, primary_key=True, autoincrement=True),

Column('orderline_id', ForeignKey('order_lines.id')),

Column('batch_id', ForeignKey('batches.id')),

)

def start_mappers():

lines_mapper = mapper(model.OrderLine, order_lines)

batches_mapper = mapper(model.Batch, batches, properties={

'_allocations': relationship(

lines_mapper,

secondary=allocations,

collection_class=set,

)

})

mapper(model.Product, products, properties={

'batches': relationship(batches_mapper)

})

@event.listens_for(model.Product, 'load')

def receive_load(product, _):

product.events = []