"""IMP-09 PR 1 — _parse_fr_string tests.

Catalog presets only use `1fr` / `1fr 1fr` specs (verified
templates/phase_z2/layouts/layouts.yaml). The helper must reject
non-fr tokens and round to integer pixel sizes summing to `total`.
"""
from __future__ import annotations

import pytest

from src.phase_z2_pipeline import _parse_fr_string


def test_single_fr_returns_full_total():
    assert _parse_fr_string("1fr", 585) == [585]


def test_two_equal_fr_splits_evenly():
    result = _parse_fr_string("1fr 1fr", 1180)
    assert result == [590, 590]
    assert sum(result) == 1180


def test_unequal_fr_distributes_by_ratio():
    result = _parse_fr_string("2fr 1fr", 300)
    assert sum(result) == 300
    assert result[0] > result[1]


def test_rounding_absorbed_by_last_track():
    # 1fr 1fr 1fr / total=100 -> 33,33,33 + diff 1 absorbed by last.
    result = _parse_fr_string("1fr 1fr 1fr", 100)
    assert sum(result) == 100
    assert result == [33, 33, 34]


def test_non_fr_token_raises():
    with pytest.raises(ValueError, match="non-fr token"):
        _parse_fr_string("200px 1fr", 1000)


def test_empty_spec_raises():
    with pytest.raises(ValueError, match="empty spec"):
        _parse_fr_string("", 1000)


def test_zero_fr_raises():
    with pytest.raises(ValueError, match="total fr"):
        _parse_fr_string("0fr 0fr", 1000)