# coding=utf-8
"""
@Time   :2026/6/24
@Author :tao.chen

Regression tests for gunicorn.conf.py.

The MCP session-affinity constraint is documented in gunicorn.conf.py: the
mcp library stores each session in a per-process dict, so a multi-worker
gunicorn deploy returns "Session not found" ~50% of the time. The fix in
this config is an `on_starting` hook that warns loudly when workers > 1.

These tests assert that:
  1. The hook exists and is wired up.
  2. workers == 1 is silent (no false alarms in the default single-worker
     mode people use after reading the comment).
  3. workers > 1 emits a WARNING that mentions the symptom and the fix.

If anyone ever "cleans up" the hook, these tests fail — that's the point.
"""
import importlib.util
import sys
from pathlib import Path

import pytest

REPO_ROOT = Path(__file__).resolve().parents[2]
GUNICORN_CONF = REPO_ROOT / "gunicorn.conf.py"


def _load_gunicorn_conf():
    """Import gunicorn.conf.py as a module (not a package member).

    The file lives at the repo root and is loaded by gunicorn via exec();
    we use importlib so the test can introspect `on_starting` and mutate
    `workers` between cases.
    """
    spec = importlib.util.spec_from_file_location("gunicorn_conf_under_test", GUNICORN_CONF)
    assert spec is not None and spec.loader is not None, f"cannot load {GUNICORN_CONF}"
    module = importlib.util.module_from_spec(spec)
    # Make sure repo root is on sys.path so the module's `import os` etc. work.
    if str(REPO_ROOT) not in sys.path:
        sys.path.insert(0, str(REPO_ROOT))
    spec.loader.exec_module(module)
    return module


class _FakeServer:
    """Minimal stand-in for gunicorn's `server` argument to on_starting.

    gunicorn passes a `gunicorn.arbiter.Arbiter`-like object that exposes
    `server.log.warning(...)`. We only need the .log.warning sink.
    """

    def __init__(self):
        self.warnings: list[str] = []

    class _Log:
        def __init__(self, sink):
            self._sink = sink

        def warning(self, fmt: str, *args) -> None:  # noqa: A002 - matches gunicorn API
            self._sink.append(fmt % args if args else fmt)

    @property
    def log(self) -> "_FakeServer._Log":
        return self._Log(self.warnings)


@pytest.fixture
def gunicorn_conf():
    """Load gunicorn.conf.py once per test, then reset `workers` to the
    project default so other tests in the suite are not affected by us
    mutating the module global."""
    mod = _load_gunicorn_conf()
    yield mod
    # Restore the env-driven default so a stale value doesn't leak out.
    import os
    mod.workers = int(os.environ.get("GUNICORN_WORKERS", "2"))


def test_on_starting_hook_is_defined(gunicorn_conf):
    """The hook must exist — the bug fix lives here."""
    assert callable(getattr(gunicorn_conf, "on_starting", None)), (
        "gunicorn.conf.py is missing the on_starting hook. The MCP session-"
        "affinity warning is the only thing that keeps a multi-worker deploy "
        "from silently returning 'Session not found' for half its requests."
    )


def test_on_starting_silent_for_single_worker(gunicorn_conf):
    """workers == 1 is the safe config; no warning should fire."""
    gunicorn_conf.workers = 1
    server = _FakeServer()
    gunicorn_conf.on_starting(server)
    assert server.warnings == [], (
        f"workers=1 should be silent (no MCP session affinity issue), got: {server.warnings}"
    )


def test_on_starting_warns_for_multi_worker(gunicorn_conf):
    """workers > 1 must produce a warning that names the symptom and the fix.

    The point of the hook is to be loud at deploy time, not at request time.
    """
    gunicorn_conf.workers = 4
    server = _FakeServer()
    gunicorn_conf.on_starting(server)
    assert len(server.warnings) == 1, (
        f"expected exactly one warning when workers=4, got {len(server.warnings)}: {server.warnings}"
    )
    msg = server.warnings[0]
    assert "GUNICORN_WORKERS=4" in msg, "warning should name the offending worker count"
    assert "Session not found" in msg, "warning should name the symptom users actually see"
    assert "GUNICORN_WORKERS=1" in msg, "warning should point at the easy fix"
    assert "sticky-session" in msg, "warning should mention the load-balancer escape hatch"