"""Tests for perfxpert.tools.regression — with Gate 4 'hot kernel' definition."""

from pathlib import Path

import pytest

from perfxpert.tools import regression
from perfxpert.tools._class import ToolClass


FIX = Path(__file__).parent.parent / "fixtures"
BASELINE = FIX / "regression_baseline.db"
IMPROVED = FIX / "regression_improved.db"
TAIL_HURT = FIX / "regression_tail_hurt.db"


def test_compare_detects_improvement():
    r = regression.compare_runs(str(BASELINE), str(IMPROVED), threshold_pct=3.0)
    assert r["verdict"] == "improved"
    # matmul was 70% of runtime and got 20% faster → total ~14% speedup.
    # total_delta_pct is a fraction (negative = improvement); -0.14 ≈ -14%.
    assert r["total_delta_pct"] < -0.10


def test_compare_detects_tail_hurt():
    """Small kernels regressing 15% individually trigger weighted-geomean fail.

    Spec §5 Gate 4: hot = top-K covering 80% cumulative OR ≥ 3% individually.
    conv2d is 20% of runtime → hot. It regressed 15% → > 10% threshold → fail.
    """
    r = regression.compare_runs(str(BASELINE), str(TAIL_HURT), threshold_pct=3.0)
    assert r["verdict"] == "regressed"
    assert any(k["kernel"] == "conv2d" and k["delta_pct"] > 0.10 for k in r["per_kernel_deltas"])


def test_hot_kernel_definition():
    """Explicit: hot = top-K where K covers 80% cumulative OR kernel ≥ 3% individually."""
    hot = regression.identify_hot_kernels(str(BASELINE))
    names = {k["name"] for k in hot}
    # matmul (70%) and conv2d (20%) together cover 90% > 80% → both hot
    # add (10%) is individually ≥ 3% → also hot
    assert "matmul" in names
    assert "conv2d" in names
    assert "add" in names  # because 10% ≥ 3%


def test_noise_threshold():
    """Baseline vs itself → verdict = neutral."""
    r = regression.compare_runs(str(BASELINE), str(BASELINE), threshold_pct=3.0)
    assert r["verdict"] == "neutral"


def test_is_read_only_class():
    assert regression.compare_runs.__tool_class__ == ToolClass.READ_ONLY
    assert regression.identify_hot_kernels.__tool_class__ == ToolClass.READ_ONLY