accordian api change

01 sample_api.py

Namespace
    .signal(name) -> Signal

Signal
    .connect(async fn) -> async fn
    .send(*a, **kw) -> Set[Task]
    async .join(*a, **kw) -> List[Any]

_global = Namespace()
signal = _global.Signal

02 sample_receivers.py

import math
from sample_api import signal

check_price = signal("check-price")


@check_price.connect
async def recent_check(prod, qty):
    return "recent", await db.get("recent", prod)


@check_price.connect
async def minimum_check(prod, qty):
    return "min", 0.01


@check_price.connect
async def bulk_check(prod, qty):
    _, recent = await recent_check(prod, qty)
    discount = [0, 3, 7, 11, 15]
    i = int(math.log10(qty))
    i = min(i, len(discount))
    return "bulk", recent * (1 - discount[i]/100)

03 sample_webhook_handler.py

from sample_receivers import check_price


async def price_check_handler(prod, qty):
    prices = await check_price.join(prod, qty)
    return [(src, p*qty) for (src, p) in prices]