"""IMP-#85 u7 — pytest env isolation for src.config defaults.

This conftest.py runs BEFORE any test module is imported by pytest.
Setting ``os.environ["AI_FALLBACK_*"]`` here overrides values that the
live ``.env`` file would otherwise inject through ``pydantic-settings``
(priority: init args > os.environ > env_file). The ``src.config``
module-level ``settings = Settings()`` singleton is therefore built
against the test-clean environment when src.config is first imported
during test collection.

Scope (per Stage 2 plan u7):
  * Restore the default-OFF contract for ``ai_fallback_enabled`` so
    ``tests/test_phase_z2_ai_fallback_config.py`` and
    ``tests/test_imp47b_step12_ai_wiring.py`` (which lock the
    flag-off short-circuit) match the source-of-truth default in
    ``src/config.py``.
  * Restore the default-OFF contract for ``ai_fallback_auto_cache``.

Out of scope:
  * Touching ``ANTHROPIC_API_KEY`` / ``KEI_API_URL`` / ``LOG_LEVEL``.
  * Resetting the ``src.config.settings`` singleton mid-session.
    Tests that need to flip ``settings.ai_fallback_enabled`` at
    runtime mutate the singleton directly (mirrors the production
    ``--auto-cache`` CLI path in ``src/phase_z2_pipeline.py``).

IMP-35 baseline-red invariance carve-out
========================================
The IMP-35 baseline-red invariance gate at
``tests/phase_z2/test_imp35_baseline_red_invariance.py`` spawns a child
pytest subprocess that targets ONLY the two baseline-area files:

    tests/test_imp47b_step12_ai_wiring.py
    tests/test_phase_z2_ai_fallback_config.py

That gate's binding contract (Stage 2 u11 lock) is that those four
registered known-red tests STAY RED until a follow-up issue
deregisters them. If this conftest blindly forces
``AI_FALLBACK_ENABLED=false`` in the gate's subprocess, the
``test_ai_fallback_master_flag_default_off`` registered red flips
green and the invariance gate trips — a real cross-issue contract
conflict (see Codex #8 Stage 3 verification of IMP-#85 u7).

The carve-out below detects that exact subprocess signature
(positional ``.py`` targets are entirely baseline-area files) and
skips env isolation, leaving the gate's child process in its native
``.env``-loaded state. Every other pytest invocation — full-suite
``pytest -q tests``, the IMP-#85 smoke targets, single-file dev runs
on non-baseline files — still gets the default-OFF isolation.

Per ``feedback_demo_env_toggle_policy``: demo activation belongs in
``.env`` only. The override below is test-scoped (lives under
``tests/``) and never propagates into ``src/`` or ``vite.config``.
"""
from __future__ import annotations

import os
import sys

# File suffixes (basenames) of the IMP-35 baseline-red area files.
# The IMP-35 gate spawns its subprocess with these as the sole positional
# pytest targets. Suffix matching is used so the detection is robust
# across Windows/POSIX path separators and absolute/relative cwd.
_IMP35_BASELINE_AREA_FILE_SUFFIXES: tuple[str, ...] = (
    "test_imp47b_step12_ai_wiring.py",
    "test_phase_z2_ai_fallback_config.py",
)


def _is_imp35_baseline_subprocess() -> bool:
    """True iff the current pytest argv targets ONLY IMP-35 baseline-area files.

    The IMP-35 baseline-red invariance gate
    (``tests/phase_z2/test_imp35_baseline_red_invariance.py``) runs:

        python -m pytest -q --tb=no -p no:cacheprovider \\
            tests/test_imp47b_step12_ai_wiring.py \\
            tests/test_phase_z2_ai_fallback_config.py

    The two trailing positional ``.py`` arguments are the signature.
    We compare on basename suffix so the check is path-separator and
    cwd agnostic.

    Returning True here suppresses the ``AI_FALLBACK_*`` env override
    so the baseline-red registry contract (Stage 2 u11 lock) holds for
    the gate's child process while every other invocation
    (full-suite, IMP-#85 smokes, mixed-target dev runs) still gets the
    default-OFF isolation.
    """
    file_targets = [arg for arg in sys.argv[1:] if arg.endswith(".py")]
    if not file_targets:
        return False
    return all(
        any(
            arg.replace("\\", "/").endswith(suffix)
            for suffix in _IMP35_BASELINE_AREA_FILE_SUFFIXES
        )
        for arg in file_targets
    )


if _is_imp35_baseline_subprocess():
    # Drop any inherited AI_FALLBACK_* values so the gate's child process
    # falls back to the live ``.env`` (AI_FALLBACK_ENABLED=true) — the
    # exact precondition under which the four registered baseline-red
    # tests are red. ``pop`` is no-op when the key is absent, so a
    # developer running the gate manually with a clean environment is
    # unaffected.
    os.environ.pop("AI_FALLBACK_ENABLED", None)
    os.environ.pop("AI_FALLBACK_AUTO_CACHE", None)
else:
    os.environ["AI_FALLBACK_ENABLED"] = "false"
    os.environ["AI_FALLBACK_AUTO_CACHE"] = "false"