乡镇即时配送系统怎么选：四端订单与结算状态机验收

import sqlite3
from decimal import Decimal, ROUND_HALF_UP

def money(value):
    return Decimal(value).quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)

def init(conn):
    conn.executescript('''
    CREATE TABLE orders(
      order_id TEXT PRIMARY KEY,
      status TEXT NOT NULL,
      goods_cents INTEGER NOT NULL,
      delivery_cents INTEGER NOT NULL
    );
    CREATE TABLE ledger(
      order_id TEXT NOT NULL,
      party TEXT NOT NULL,
      kind TEXT NOT NULL,
      amount_cents INTEGER NOT NULL,
      note TEXT NOT NULL
    );
    ''')

def add_order(conn, order_id, goods_cents, delivery_cents):
    conn.execute(
        'INSERT INTO orders VALUES (?, ?, ?, ?)',
        (order_id, 'PAID', goods_cents, delivery_cents)
    )

def deliver_with_commission(conn, order_id, commission_rate):
    row = conn.execute(
        'SELECT goods_cents, delivery_cents FROM orders WHERE order_id = ? AND status = ?',
        (order_id, 'PAID')
    ).fetchone()
    if not row:
        raise ValueError('order not payable')
    goods, delivery = row
    commission = int(money(goods) * money(str(commission_rate)))
    merchant = goods - commission + delivery
    rider = delivery
    platform = commission
    conn.execute('UPDATE orders SET status = ? WHERE order_id = ?', ('DELIVERED', order_id))
    conn.executemany(
        'INSERT INTO ledger VALUES (?, ?, ?, ?, ?)',
        [
            (order_id, 'merchant', 'SALE', merchant, 'goods minus commission plus delivery'),
            (order_id, 'rider', 'DELIVERY', rider, 'delivery income'),
            (order_id, 'platform', 'COMMISSION', platform, 'commission income'),
        ]
    )

def refund_partial(conn, order_id, refund_cents, commission_refund_cents):
    row = conn.execute(
        'SELECT status FROM orders WHERE order_id = ?', (order_id,)
    ).fetchone()
    if not row:
        raise ValueError('unknown order')
    conn.execute('UPDATE orders SET status = ? WHERE order_id = ?', ('PARTIAL_REFUNDED', order_id))
    conn.executemany(
        'INSERT INTO ledger VALUES (?, ?, ?, ?, ?)',
        [
            (order_id, 'merchant', 'REFUND', -refund_cents, 'partial refund'),
            (order_id, 'platform', 'COMMISSION_REFUND', -commission_refund_cents, 'commission reversal'),
        ]
    )

def balances(conn):
    return conn.execute(
        'SELECT party, SUM(amount_cents) FROM ledger GROUP BY party ORDER BY party'
    ).fetchall()

if __name__ == '__main__':
    conn = sqlite3.connect(':memory:')
    init(conn)
    add_order(conn, 'A1001', 5000, 600)
    deliver_with_commission(conn, 'A1001', 0.08)
    refund_partial(conn, 'A1001', 1000, 80)
    print(balances(conn))