"""An SNMP poll collects on schedule while the database hangs, and what it
held is stored oldest first, each at its own time, once it answers (#5995)."""
import asyncio
from contextlib import asynccontextmanager
from types import SimpleNamespace as NS

import plugins.snmp.scheduler as scheduler
import plugins.snmp.service as service
from plugins.snmp.poller import Credentials, PollResult


def _device():
    return NS(id="d1", name="nas", address="10.0.0.5", port=161, version="2c", presets=["system"],
              interfaces="", custom=None, tables={}, tables_at=None, last_error=None, texts={})


def test_polls_go_on_while_the_database_hangs_and_are_stored_in_order_after(monkeypatch):
    async def main():
        stalled = asyncio.Event()

        @asynccontextmanager
        async def hung_session():
            await stalled.wait()                         # the storage under Postgres has stalled
            yield None

        app = NS(db_sessionmaker=hung_session)
        gate, stored = asyncio.Event(), []

        async def store(app_, rounds):
            await gate.wait()
            stored.extend(rounds)

        uptimes = iter([100.0, 200.0])

        async def poll(address, port, creds, oids):
            return PollResult(readings={"uptime": next(uptimes)})

        monkeypatch.setattr(scheduler, "DEVICES", [_device()])
        monkeypatch.setattr(scheduler, "DEVICES_READ_S", 0.05)
        monkeypatch.setattr(scheduler, "STORE_WAIT_S", 0.05)
        monkeypatch.setattr(scheduler, "_store", store)
        monkeypatch.setattr(service, "credentials", lambda d: Credentials(community="public"))
        scheduler.RATES = None

        await scheduler._do_poll(app, poll=poll)         # the device list is the last one read
        await asyncio.sleep(0.01)
        await scheduler._do_poll(app, poll=poll)         # the first store hasn't returned: polled anyway
        gate.set()
        await app._holdings["SNMP poll"].flush(1.0)
        return stored

    rounds = asyncio.run(main())
    assert [[(p.name, p.values) for p in r] for r in rounds] == [
        [("nas", [("uptime", 100.0)])], [("nas", [("uptime", 200.0)])]]
    assert rounds[0][0].at < rounds[1][0].at              # each stored at the time it was collected