"""IMP-38 U1 — v4_fallback_policy.yaml loader test.

Verify:
  - load_v4_fallback_policy() returns dict with expected keys
  - yaml parsed correctly (usable_threshold, default_max_rank, extended_max_rank, policy_type)
  - graceful fallback when yaml missing → _V4_FALLBACK_POLICY_DEFAULT
  - _V4_FALLBACK_POLICY_CACHE pattern (lazy load, mirror of _CATALOG_CACHE)
  - load_frame_contracts() shape unchanged (separate yaml, catalog 오염 X)

4 round 합의 (#67):
  - Codex #1: separate yaml (not frame_contracts.yaml top-level)
  - Codex #3: load_frame_contracts() shape 변경 X
"""
from __future__ import annotations

import importlib
from pathlib import Path
from unittest.mock import patch

import pytest


PROJECT_ROOT = Path(__file__).parent.parent
V4_POLICY_PATH = PROJECT_ROOT / "templates" / "phase_z2" / "catalog" / "v4_fallback_policy.yaml"
CATALOG_PATH = PROJECT_ROOT / "templates" / "phase_z2" / "catalog" / "frame_contracts.yaml"


def _reset_caches():
    """Reset module-level caches for test isolation."""
    import src.phase_z2_mapper as mapper
    mapper._V4_FALLBACK_POLICY_CACHE = None
    mapper._CATALOG_CACHE = None


@pytest.fixture(autouse=True)
def clean_caches():
    _reset_caches()
    yield
    _reset_caches()


def test_v4_fallback_policy_yaml_exists():
    """IMP-38 U1 — separate yaml file must exist."""
    assert V4_POLICY_PATH.exists(), (
        f"v4_fallback_policy.yaml not found at {V4_POLICY_PATH}. "
        "IMP-38 U1 expects separate yaml (Codex #1 corr — not frame_contracts.yaml top-level)."
    )


def test_load_v4_fallback_policy_returns_dict_with_expected_keys():
    """load_v4_fallback_policy() must return dict with policy keys."""
    from src.phase_z2_mapper import load_v4_fallback_policy
    policy = load_v4_fallback_policy()
    assert isinstance(policy, dict)
    expected_keys = {"policy_type", "usable_threshold", "default_max_rank", "extended_max_rank"}
    missing = expected_keys - set(policy.keys())
    assert not missing, f"missing keys in v4_fallback_policy: {missing}"


def test_load_v4_fallback_policy_values_match_yaml():
    """Loaded policy values must match v4_fallback_policy.yaml (initial commit)."""
    from src.phase_z2_mapper import load_v4_fallback_policy
    policy = load_v4_fallback_policy()
    assert policy["policy_type"] == "dynamic_usable_count_based"
    assert policy["usable_threshold"] == 1
    assert policy["default_max_rank"] == 3
    assert policy["extended_max_rank"] == 32


def test_load_v4_fallback_policy_cache_pattern():
    """_V4_FALLBACK_POLICY_CACHE pattern — second call returns same dict (lazy load)."""
    from src.phase_z2_mapper import load_v4_fallback_policy
    policy_a = load_v4_fallback_policy()
    policy_b = load_v4_fallback_policy()
    assert policy_a is policy_b, "cache pattern violated (should return same dict instance)"


def test_load_v4_fallback_policy_graceful_when_yaml_missing():
    """yaml 파일 없을 시 → _V4_FALLBACK_POLICY_DEFAULT (extended_max_rank=3, byte-identical pre-IMP-38)."""
    import src.phase_z2_mapper as mapper
    with patch.object(mapper, "V4_FALLBACK_POLICY_PATH", PROJECT_ROOT / "tests" / "__nonexistent_policy.yaml"):
        # reset cache to force reload via patched path
        mapper._V4_FALLBACK_POLICY_CACHE = None
        policy = mapper.load_v4_fallback_policy()
        assert policy["default_max_rank"] == 3
        assert policy["extended_max_rank"] == 3, (
            "graceful fallback must keep extended==default (byte-identical pre-IMP-38)"
        )


def test_load_frame_contracts_shape_unchanged():
    """Codex #3 LOCK — load_frame_contracts() must still return template_id → entry dict."""
    from src.phase_z2_mapper import load_frame_contracts, load_v4_fallback_policy
    catalog = load_frame_contracts()
    policy = load_v4_fallback_policy()

    # catalog 의 key 가 모두 frame entry (dict with template_id/frame_id) 여야 함
    for key, entry in catalog.items():
        assert isinstance(entry, dict), f"catalog entry {key} should be dict"
        assert "template_id" in entry, f"catalog entry {key} missing template_id (policy bleed?)"

    # policy keys 는 catalog 에 안 들어감
    policy_keys = {"policy_type", "usable_threshold", "default_max_rank", "extended_max_rank"}
    catalog_top_keys = set(catalog.keys())
    bleed = policy_keys & catalog_top_keys
    assert not bleed, (
        f"policy keys leaked into frame_contracts.yaml: {bleed}. "
        "Codex #1 corr violated — policy must stay in separate v4_fallback_policy.yaml."
    )