"""IMP-09 PR 1 — fixture-driven regression checks.

Loads the YAML snapshots under tests/phase_z2/fixtures/ and exercises
build_layout_css + _attempt_zone_ratio_retry against them. Any drift
in IMP-09 output forces a fixture refresh, which is the lock surface
called out in Stage 3 round 4 §5.
"""
from __future__ import annotations

from pathlib import Path

import pytest
import yaml

from src.phase_z2_pipeline import _attempt_zone_ratio_retry, build_layout_css


FIXTURES_DIR = Path(__file__).parent / "fixtures"


def _load_yaml(path: Path) -> dict:
    with path.open(encoding="utf-8") as f:
        return yaml.safe_load(f)


# ──────────────────────── build_layout_css fixtures ────────────────────────


_BUILD_DIR = FIXTURES_DIR / "build_layout_css"
_BUILD_FIXTURES = sorted(_BUILD_DIR.glob("*.yaml")) if _BUILD_DIR.exists() else []


@pytest.mark.parametrize(
    "fixture_path",
    _BUILD_FIXTURES,
    ids=[p.stem for p in _BUILD_FIXTURES],
)
def test_build_layout_css_matches_fixture(fixture_path: Path):
    payload = _load_yaml(fixture_path)
    inp = payload["input"]
    expected = payload["expected_layout_css"]

    result = build_layout_css(
        inp["layout_preset"],
        inp["zones_data"],
        override_zone_geometries=inp.get("override_zone_geometries"),
    )
    # raw_zone_layout is intentionally not snapshotted (contains
    # solver internals); compare the rest.
    actual = {k: v for k, v in result.items() if k != "raw_zone_layout"}
    assert actual == expected, (
        f"layout_css drift in fixture {fixture_path.name}:\n"
        f"  expected={expected}\n  actual={actual}"
    )


# ────────────────────────── retry_gate fixtures ──────────────────────────


_RETRY_DIR = FIXTURES_DIR / "retry_gate"
_RETRY_FIXTURES = sorted(_RETRY_DIR.glob("*.yaml")) if _RETRY_DIR.exists() else []


@pytest.mark.parametrize(
    "fixture_path",
    _RETRY_FIXTURES,
    ids=[p.stem for p in _RETRY_FIXTURES],
)
def test_retry_gate_matches_fixture(fixture_path: Path, tmp_path: Path):
    payload = _load_yaml(fixture_path)
    layout_css = payload["input_layout_css"]
    router_decision = payload["router_decision"]
    expected = payload["expected_gate"]

    trace = _attempt_zone_ratio_retry(
        run_dir=tmp_path,
        out_path=tmp_path / "final.html",
        slide_title="fixture",
        slide_footer=None,
        zones_data=[],
        debug_zones=[],
        layout_preset="fixture",
        layout_css=layout_css,
        overflow={},
        fit_classification={},
        router_decision=router_decision,
        gap_px=14,
    )

    assert trace["retry_attempted"] == expected["retry_attempted"]
    skip_reason = trace.get("retry_skipped_reason")
    for needle in expected.get("retry_skipped_reason_contains", []):
        assert skip_reason is not None and needle in skip_reason, (
            f"expected {needle!r} in retry_skipped_reason, got {skip_reason!r}"
        )
    for forbidden in expected.get("retry_skipped_reason_excludes", []):
        if skip_reason is not None:
            assert forbidden not in skip_reason, (
                f"forbidden {forbidden!r} found in retry_skipped_reason {skip_reason!r}"
            )