"""Unit tests for automatic brightness limiting (ABL) current estimation."""

import numpy as np
import pytest

from ledgrab.core.processing.power_limit import (
    DEFAULT_MILLIAMPS_PER_LED,
    estimate_current_ma,
    power_limit_scale,
)


def test_default_ma_per_led_constant():
    assert DEFAULT_MILLIAMPS_PER_LED == 55


def test_full_white_draws_ma_per_led_times_count():
    colors = np.full((100, 3), 255, dtype=np.uint8)
    assert estimate_current_ma(colors, 55) == pytest.approx(100 * 55)


def test_black_draws_zero():
    colors = np.zeros((100, 3), dtype=np.uint8)
    assert estimate_current_ma(colors, 55) == 0.0


def test_half_white_is_half_current():
    full = estimate_current_ma(np.full((100, 3), 255, dtype=np.uint8), 55)
    half = estimate_current_ma(np.full((100, 3), 128, dtype=np.uint8), 55)
    assert half == pytest.approx(full * 128 / 255, rel=1e-6)


def test_zero_ma_per_led_draws_zero():
    colors = np.full((100, 3), 255, dtype=np.uint8)
    assert estimate_current_ma(colors, 0) == 0.0


def test_empty_frame_is_safe():
    colors = np.zeros((0, 3), dtype=np.uint8)
    assert estimate_current_ma(colors, 55) == 0.0
    assert power_limit_scale(colors, 1000, 55) == 1.0


def test_scale_is_one_when_disabled():
    colors = np.full((100, 3), 255, dtype=np.uint8)
    assert power_limit_scale(colors, 0, 55) == 1.0
    assert power_limit_scale(colors, -1, 55) == 1.0


def test_scale_is_one_within_budget():
    colors = np.full((100, 3), 255, dtype=np.uint8)  # 5500 mA at 55 mA/LED
    assert power_limit_scale(colors, 6000, 55) == 1.0
    assert power_limit_scale(colors, 5500, 55) == 1.0  # exactly on budget


def test_scale_brings_full_white_to_budget():
    colors = np.full((100, 3), 255, dtype=np.uint8)  # 5500 mA
    scale = power_limit_scale(colors, 2750, 55)  # half budget
    assert scale == pytest.approx(0.5, rel=1e-6)


def test_applying_scale_lands_within_budget():
    colors = np.full((100, 3), 255, dtype=np.uint8)  # 5500 mA
    budget = 2750
    scale = power_limit_scale(colors, budget, 55)
    # Mirror the processor's fixed-point application (factor/256).
    factor = int(scale * 256)
    scaled = ((colors.astype(np.uint16) * factor) >> 8).astype(np.uint8)
    # Fixed-point rounding can only ever round DOWN, so we never exceed budget.
    assert estimate_current_ma(scaled, 55) <= budget