乡镇本地外卖系统怎么起步：从人工试跑到订单验收的技术清单

CREATE TABLE platform_order (
  id BIGINT PRIMARY KEY,
  order_no VARCHAR(32) NOT NULL UNIQUE,
  order_type VARCHAR(16) NOT NULL,
  merchant_id BIGINT,
  customer_id BIGINT NOT NULL,
  pricing_zone_id BIGINT NOT NULL,
  address_zone_id BIGINT NOT NULL,
  distance_m INT NOT NULL,
  goods_amount DECIMAL(10,2) NOT NULL,
  delivery_fee DECIMAL(10,2) NOT NULL,
  discount_amount DECIMAL(10,2) NOT NULL DEFAULT 0,
  payable_amount DECIMAL(10,2) NOT NULL,
  refund_amount DECIMAL(10,2) NOT NULL DEFAULT 0,
  status VARCHAR(16) NOT NULL,
  fee_rule_version VARCHAR(32) NOT NULL,
  idempotency_key VARCHAR(64) NOT NULL UNIQUE,
  created_at DATETIME NOT NULL
);
CREATE TABLE settlement_ledger (
  id BIGINT PRIMARY KEY,
  order_id BIGINT NOT NULL,
  business_key VARCHAR(96) NOT NULL UNIQUE,
  account_type VARCHAR(16) NOT NULL,
  amount DECIMAL(10,2) NOT NULL,
  direction VARCHAR(8) NOT NULL,
  status VARCHAR(16) NOT NULL
);

ALLOWED = {
    '待支付': {'已支付', '已取消'},
    '已支付': {'商家接单', '已取消'},
    '商家接单': {'骑手接单', '退款中'},
    '骑手接单': {'配送中', '转单中'},
    '配送中': {'已送达', '异常'},
    '已送达': {'已完成'},
    '异常': {'配送中', '退款中', '已取消'},
    '退款中': {'已退款'},
    '转单中': {'骑手接单', '异常'},
}
def transit(current, target):
    if target not in ALLOWED.get(current, set()):
        raise ValueError('illegal_transition: %s -> %s' % (current, target))
    return target

from decimal import Decimal, ROUND_HALF_UP
class OutOfRange(Exception): pass
class ZoneMismatch(Exception): pass

def delivery_fee(base_fee, base_km, per_km_fee, max_km, distance_m, remote=False):
    km = Decimal(distance_m) / Decimal(1000)
    if km > Decimal(str(max_km)):
        raise OutOfRange('out_of_range: %sm exceeds %skm' % (distance_m, max_km))
    fee = Decimal(str(base_fee))
    if km > Decimal(str(base_km)):
        fee += (km - Decimal(str(base_km))) * Decimal(str(per_km_fee))
    if remote:
        fee += Decimal('2.00')
    return fee.quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)

def check_zone(order_zone, address_zone, rider_zones):
    if order_zone != address_zone:
        raise ZoneMismatch('order_zone %s != address_zone %s' % (order_zone, address_zone))
    if order_zone not in rider_zones:
        raise ZoneMismatch('%s not in rider zones' % order_zone)

-- 结算流水幂等示例
INSERT INTO settlement_ledger (order_id, business_key, account_type, amount, direction, status)
VALUES (1001, '1001:merchant:2026-01', 'merchant', 84.60, 'credit', 'settled');
-- 重复执行同一 business_key 会触发唯一约束，由应用层转为幂等响应