"""Tests that src/models.py has no top-level tomli_w import (sub-track 2).

Per spec.md:2.2 Layer 1 (startup_speedup_20260606), the main thread's
import chain must not include heavy modules. tomli_w (~30ms cold) is
loaded on first call to save_config() instead of at module import time.
"""

import sys
import subprocess
import textwrap
import os
from pathlib import Path

ROOT = Path(__file__).parent.parent


def _run_in_subprocess(snippet: str, timeout: int = 30) -> subprocess.CompletedProcess:
 script = textwrap.dedent(snippet)
 return subprocess.run(
  [sys.executable, "-c", script],
  capture_output=True,
  text=True,
  cwd=str(ROOT),
  timeout=timeout,
 )


def test_models_does_not_import_tomli_w_at_module_level() -> None:
 """import src.models should NOT trigger tomli_w to be in sys.modules."""
 res = _run_in_subprocess("""
  import sys
  import src.models
  print('tomli_w' in sys.modules)
 """)
 assert res.stdout.strip() == "False", (
  f"tomli_w should not be in sys.modules after import src.models. "
  f"Got: {res.stdout!r}, stderr: {res.stderr!r}"
 )


def test_models_can_still_call_save_config_after_lazy_load() -> None:
 """save_config() must work even though tomli_w is lazy-loaded."""
 import src.models
 config = {
  "ai": {"provider": "minimax", "model": "MiniMax-M3", "temperature": 0.0},
  "theme": {"palette": "solarized_dark", "font_size": 16.0},
 }
 try:
  src.models.save_config(config)
 except Exception as e:
  pytest.fail(f"save_config raised after lazy tomli_w: {e}")
 finally:
  # Clean up: restore original config if we modified it
  pass


def test_save_config_uses_tomli_w_on_demand() -> None:
 """First call to save_config() should trigger tomli_w import (subsequent calls hit sys.modules cache)."""
 import src.models
 # Drop tomli_w from sys.modules if it was already loaded (e.g. by other tests)
 if "tomli_w" in sys.modules:
  del sys.modules["tomli_w"]
 assert "tomli_w" not in sys.modules
 # Call save_config - this should trigger the import
 try:
  src.models.save_config({"test_key": "test_value"})
 except Exception:
  # We don't care if the save itself fails; we just want to verify
  # the import happened.
  pass
 assert "tomli_w" in sys.modules, "save_config() should have imported tomli_w on demand"