不懂技术做校园配送系统：SaaS试跑与订单状态机验收

from dataclasses import dataclass
from enum import Enum

class Status(Enum):
    PAID = 'paid'
    ACCEPTED = 'accepted'
    PICKED_UP = 'picked_up'
    GATE_RECEIVED = 'gate_received'
    SORTED = 'sorted'
    DELIVERING = 'delivering'
    DELIVERED = 'delivered'
    REFUNDING = 'refunding'
    REFUNDED = 'refunded'
    EXCEPTION = 'exception'

ALLOWED = {
    Status.PAID: {Status.ACCEPTED, Status.REFUNDING, Status.EXCEPTION},
    Status.ACCEPTED: {Status.PICKED_UP, Status.REFUNDING, Status.EXCEPTION},
    Status.PICKED_UP: {Status.GATE_RECEIVED, Status.REFUNDING, Status.EXCEPTION},
    Status.GATE_RECEIVED: {Status.SORTED, Status.EXCEPTION},
    Status.SORTED: {Status.DELIVERING, Status.EXCEPTION},
    Status.DELIVERING: {Status.DELIVERED, Status.EXCEPTION},
    Status.DELIVERED: {Status.REFUNDING},
    Status.REFUNDING: {Status.REFUNDED, Status.EXCEPTION},
    Status.REFUNDED: set(),
    Status.EXCEPTION: {Status.ACCEPTED, Status.PICKED_UP, Status.GATE_RECEIVED, Status.SORTED, Status.DELIVERING, Status.REFUNDING},
}

@dataclass
class Order:
    order_id: str
    building: str
    amount_cents: int
    status: Status = Status.PAID
    refunded_cents: int = 0

def move(order, target):
    if order.status == target:
        return 'skipped_idempotent'
    if target not in ALLOWED[order.status]:
        raise ValueError(f'{order.order_id}: {order.status.value} -> {target.value} not allowed')
    order.status = target
    return 'moved'

def batch_move(orders, target):
    report = {'moved': [], 'skipped': [], 'failed': []}
    for order in orders:
        try:
            result = move(order, target)
            report['moved' if result == 'moved' else 'skipped'].append(order.order_id)
        except ValueError as exc:
            report['failed'].append(str(exc))
    return report

def refund(order, cents):
    if cents <= 0:
        raise ValueError('refund cents must be positive')
    if order.refunded_cents + cents > order.amount_cents:
        raise ValueError('refund exceeds paid amount')
    order.refunded_cents += cents
    if order.refunded_cents == order.amount_cents:
        order.status = Status.REFUNDED
    else:
        order.status = Status.REFUNDING
    return order.refunded_cents

orders = [
    Order('A1001', '1号楼', 1800, Status.GATE_RECEIVED),
    Order('A1002', '2号楼', 2200, Status.GATE_RECEIVED),
    Order('A1003', '1号楼', 1500, Status.PAID),
]
print(batch_move(orders, Status.SORTED))
print(batch_move(orders, Status.SORTED))
try:
    refund(orders[0], 20000)
except ValueError as exc:
    print('refund rejected:', exc)