import json
import pytest

from perfkit.memtrend import slope_per_cycle, main


def test_slope_linear():
    assert slope_per_cycle([10, 11, 12, 13]) == pytest.approx(1.0)


def test_slope_flat():
    assert slope_per_cycle([5, 5, 5]) == 0.0


def test_slope_noisy_is_least_squares():
    # y = 2x + шум; МНК, а не (last-first)/n
    assert slope_per_cycle([0, 3, 3, 7, 8]) == pytest.approx(2.0)


def test_slope_needs_two_points():
    with pytest.raises(ValueError):
        slope_per_cycle([1.0])
    with pytest.raises(ValueError):
        slope_per_cycle([])


def test_cli_prints_three_slopes(tmp_path, capsys):
    rows = [
        {"scenario": "memory", "repeat": 0, "metrics": {"cycle": c, "heap_used_mb": 100 + 2 * c, "nodes": 1000 + 5 * c, "js_event_listeners": 50}}
        for c in range(4)
    ]
    # записи могут идти не по порядку и вперемешку с чужим сценарием
    lines = [json.dumps(r) for r in reversed(rows)] + [json.dumps({"scenario": "other", "metrics": {"cycle": 0}})]
    (tmp_path / "memory.jsonl").write_text("\n".join(lines) + "\n")
    assert main([str(tmp_path)]) == 0
    out = capsys.readouterr().out
    assert "heap_used_mb" in out and "nodes" in out and "js_event_listeners" in out
    assert "2.000" in out and "5.000" in out and "0.000" in out


def _write(tmp_path, heap):
    rows = [{"scenario": "memory", "metrics": {"cycle": c, "heap_used_mb": h, "nodes": 350 if c else 289, "js_event_listeners": 336 if c else 322}} for c, h in enumerate(heap)]
    (tmp_path / "memory.jsonl").write_text("\n".join(json.dumps(r) for r in rows) + "\n")


def test_cli_skips_baseline_step_by_default(tmp_path, capsys):
    # ступенька на цикле 0 (7 -> 11), дальше +1 на цикл, 0 для nodes/listeners
    _write(tmp_path, [7, 11, 12, 13, 14, 15, 16])
    assert main([str(tmp_path)]) == 0
    out = capsys.readouterr().out
    assert "циклы 1-6" in out and "6 точек" in out
    assert "heap_used_mb: 1.000" in out
    assert "nodes: 0.000" in out and "js_event_listeners: 0.000" in out


def test_cli_from_cycle_zero_includes_step(tmp_path, capsys):
    _write(tmp_path, [7, 11, 12, 13, 14, 15, 16])
    assert main([str(tmp_path), "--from-cycle", "0"]) == 0
    out = capsys.readouterr().out
    assert "циклы 0-6" in out and "7 точек" in out
    assert "heap_used_mb: 1.000" not in out.split("вторая половина")[0]


def test_cli_second_half_slope(tmp_path, capsys):
    # рост до цикла 10, потом плато: вторая половина (циклы 11-20) = 0
    _write(tmp_path, [7] + [11 + min(c, 10) for c in range(0, 20)])
    assert main([str(tmp_path)]) == 0
    out = capsys.readouterr().out
    assert "вторая половина (циклы 11-20)" in out
    assert "heap_used_mb: 0.000" in out.split("вторая половина")[1]