"""Act identity must never be decided on a thin margin.

Bug 28: detect_current_act committed to whatever town marker won, and in Act 4
the A5_TOWN_1 template scored 0.636 on corner scenery while the genuine
A4_TOWN_5 scored 0.619. A 1.7pp gap decided the act, and the bot ran A5 pathing
inside Act 4 after every Halbu repair trip.

That was fixed in detect_current_act and NOT in wait_for_town_spawn, which runs
first every game and sets the act for everything after it. On 2026-08-28 the
character spawned in Harrogath and it reported a4_town_start every game.

These tests pin the invariant for BOTH, because the bug has now been the same
twice: a fix applied to one call site while its twin kept the defect.
"""
import inspect

import pytest


ACT_DECIDING_FUNCS = ["detect_current_act", "wait_for_town_spawn"]


@pytest.mark.parametrize("func_name", ACT_DECIDING_FUNCS)
def test_act_decision_requires_a_margin(func_name):
    from town.town_manager import TownManager

    src = inspect.getsource(getattr(TownManager, func_name))
    assert "_ACT_DETECT_MARGIN" in src, (
        f"{func_name} decides an act without requiring a margin over the best "
        "marker from another act — a marginal winner is not evidence"
    )
    assert "TOWN_MARKERS_ACT" in src, f"{func_name} does not separate own-act from rival markers"


@pytest.mark.parametrize("func_name", ACT_DECIDING_FUNCS)
def test_act_decision_scores_both_sides_on_one_image(func_name):
    """Comparing scores from two different grabs is not a comparison.

    The character can move between them, so the margin becomes meaningless.
    """
    from town.town_manager import TownManager

    src = inspect.getsource(getattr(TownManager, func_name))
    grabs = src.count("grab(force_new=True)") + src.count("grab()")
    assert grabs <= 1, (
        f"{func_name} grabs {grabs} images; own-act and rival scores must come "
        "from the same frame to be comparable"
    )


def test_margin_is_meaningfully_large():
    from town.town_manager import TownManager

    assert TownManager._ACT_DETECT_MARGIN >= 0.03, "margin too small to separate a phantom from a real marker"


def test_ambiguous_detection_returns_none_not_a_guess():
    """Refusing to answer is the safe outcome.

    Callers treat None as "keep the assumed act", which makes go_to_act actually
    travel rather than wrongly early-returning. A confident wrong answer skips
    the recovery path entirely.
    """
    from town.town_manager import TownManager

    src = inspect.getsource(TownManager.detect_current_act)
    assert "refusing to guess" in src
    assert src.rstrip().endswith("return None")