"""Unit tests: conditional debugpy gating (PLAN anchor A14).

Rules under test:
* DEBUGPY unset or 0 -> configure_debugging() is False, debugpy NOT imported.
* DEBUGPY=1          -> configure_debugging() is True, listener on DEBUGPY_PORT.
"""
from __future__ import annotations

import socket
import sys

import pytest

import app.core.debugging as dbg


@pytest.fixture()
def free_port() -> int:
    with socket.socket() as s:
        s.bind(("127.0.0.1", 0))
        return s.getsockname()[1]


def test_disabled_by_default(monkeypatch) -> None:
    monkeypatch.delenv("DEBUGPY", raising=False)
    monkeypatch.delenv("DEBUGPY_PORT", raising=False)
    sys.modules.pop("debugpy", None)
    assert dbg.configure_debugging() is False
    assert "debugpy" not in sys.modules  # zero overhead: never imported


def test_explicit_zero(monkeypatch) -> None:
    monkeypatch.setenv("DEBUGPY", "0")
    sys.modules.pop("debugpy", None)
    assert dbg.configure_debugging() is False
    assert "debugpy" not in sys.modules


def test_invalid_value_treated_as_disabled(monkeypatch) -> None:
    monkeypatch.setenv("DEBUGPY", "yes-please")
    assert dbg.configure_debugging() is False


def test_enabled_starts_listener(monkeypatch, free_port) -> None:
    monkeypatch.setenv("DEBUGPY", "1")
    monkeypatch.setenv("DEBUGPY_PORT", str(free_port))
    try:
        assert dbg.configure_debugging() is True
        assert "debugpy" in sys.modules
    finally:
        dbg.shutdown_debugpy()


def test_port_falls_back_on_invalid_value(monkeypatch) -> None:
    monkeypatch.setenv("DEBUGPY_PORT", "not-a-port")
    assert dbg._port() == 5678


def test_shutdown_is_idempotent_when_disabled() -> None:
    dbg.shutdown_debugpy()  # no listener → no-op, no error