"""Pins for the diagnostic trace hook in pure_root (diag_model_order.py relies on it)."""
from __future__ import annotations

import math

import pytest

from simroot.pure import pure_root

PROBS = (
    (lambda t: t ** 3 - 2.0 * t - 5.0, 1.0, 4.0),
    (lambda t: math.exp(t) - 2.0, 0.0, 3.0),
    (lambda t: (t - 3.0) ** 3, 0.0, 10.0),
)
CFG = dict(similarity="ratio", scale="derived3", guard="safe", prestep="slope",
           direction="dissimilar")


@pytest.mark.parametrize("f,a,b", PROBS)
def test_trace_is_behaviour_neutral(f, a, b):
    """Asking for a trace must not change a single evaluation."""
    plain = pure_root(f, a, b, 1e-12, 200, **CFG)
    st = {"trace": []}
    traced = pure_root(f, a, b, 1e-12, 200, stats=st, **CFG)
    assert plain == traced


@pytest.mark.parametrize("f,a,b", PROBS)
def test_trace_records_every_similarity_step(f, a, b):
    st = {"trace": []}
    _x, n, ok = pure_root(f, a, b, 1e-12, 200, stats=st, **CFG)
    assert ok and 0 < len(st["trace"]) < n
    for s in st["trace"]:
        lo, hi = min(s["A"], s["B"]), max(s["A"], s["B"])
        assert lo <= s["x"] <= hi
        assert s["far"] in (s["A"], s["B"])


def test_no_trace_key_means_no_trace():
    st = {}
    pure_root(lambda t: t - 1.0, 0.0, 3.0, 1e-10, 100, stats=st, **CFG)
    assert "trace" not in st