"""Region coverage comes from the provider, not from a list in Helix.

A hardcoded region list is wrong in the one direction that matters: a
machine created in a region nobody thought to add is invisible forever,
and invisible reads exactly like "we have no servers there".

Prod Tencent was pinned to three regions (guangzhou / shanghai /
beijing) out of the 19 the account can use. Enumerating all 19 by hand
on 2026-08-12 found genuinely zero CVM instances — which is the point:
that zero is now confirmed rather than assumed, and it stays confirmed
as regions come and go.
"""
from __future__ import annotations

from unittest.mock import patch

from app.domains.cmdb.providers.base import ProviderCredentials
from app.domains.cmdb.providers.tencent import TencentProvider


class _Resp:
    def __init__(self, **kw):
        for k, v in kw.items():
            setattr(self, k, v)


class _Client:
    def __getattr__(self, name):
        return lambda *a, **kw: None


def _provider(regions: str | None = None) -> TencentProvider:
    fields = {"secret_id": "AKIDtest", "secret_key": "sk-test"}
    if regions is not None:
        fields["regions"] = regions
    return TencentProvider(ProviderCredentials(
        provider_id="tc-test", provider_type="tencent",
        account_alias="腾讯云", fields=fields,
    ))


def _with_regions(provider, regions, *, raises=False):
    def _call(fn, req, **_kw):
        if req.__class__.__name__ == "DescribeRegionsRequest":
            if raises:
                raise RuntimeError("DescribeRegions exploded")
            return _Resp(RegionSet=[_Resp(Region=r) for r in regions])
        return _Resp()

    return (
        patch(
            "app.domains.cmdb.providers.tencent._make_tc_client",
            return_value=_Client(),
        ),
        patch.object(provider, "_call", side_effect=_call),
    )


def test_regions_are_discovered_when_none_configured() -> None:
    provider = _provider()
    discovered = ["ap-guangzhou", "ap-nanjing", "eu-frankfurt"]
    p1, p2 = _with_regions(provider, discovered)
    with p1, p2:
        assert provider._regions == discovered


def test_an_explicit_list_stays_an_explicit_narrowing() -> None:
    """An admin who typed three regions meant three regions."""
    provider = _provider("ap-guangzhou, ap-shanghai")
    p1, p2 = _with_regions(provider, ["ap-guangzhou", "ap-nanjing"])
    with p1, p2:
        assert provider._regions == ["ap-guangzhou", "ap-shanghai"]


def test_discovery_failure_falls_back_to_the_static_list() -> None:
    """A transient API error must degrade to the previous behaviour, not
    to syncing nothing — an empty region list would silently report an
    empty fleet."""
    provider = _provider()
    p1, p2 = _with_regions(provider, [], raises=True)
    with p1, p2:
        regions = provider._regions
    assert "ap-guangzhou" in regions
    assert len(regions) > 3


def test_an_empty_region_set_falls_back_rather_than_syncing_nothing() -> None:
    provider = _provider()
    p1, p2 = _with_regions(provider, [])
    with p1, p2:
        regions = provider._regions
    assert "ap-guangzhou" in regions


def test_discovery_runs_once_per_provider_instance() -> None:
    """One extra API call per sync, not one per capability."""
    provider = _provider()
    calls: list[str] = []

    def _call(fn, req, **_kw):
        calls.append(req.__class__.__name__)
        return _Resp(RegionSet=[_Resp(Region="ap-guangzhou")])

    with (
        patch(
            "app.domains.cmdb.providers.tencent._make_tc_client",
            return_value=_Client(),
        ),
        patch.object(provider, "_call", side_effect=_call),
    ):
        provider._regions
        provider._regions
        provider._regions

    assert calls.count("DescribeRegionsRequest") == 1