"""Tests for the composite renderer.

The blending in ``merger_FITS`` is the product's visual identity -- years of tuning
that no test can meaningfully assert the *correctness* of.  What these tests protect
is that it does not change: it was lifted out of a worker loop so the bench could
render reconstructed frames, and the only thing that makes such a refactor safe is
proof the pixels came out the same.
"""

import numpy as np
import pytest

import merger_FITS as M
from conftest import solar_disc


@pytest.fixture
def six_bands():
    """Six distinct 1280x1280 bands, bright enough to exercise every blend stage."""
    return [
        solar_disc(peak=peak, radius=386, active_region=True)
        for peak in (0.06, 0.12, 1.2, 1.6, 1.2, 3.0)
    ]


def test_renders_a_composite_of_the_expected_shape(six_bands):
    img = M.composite_from_arrays(six_bands, 1715212800)
    # 1280 trimmed by 2*64 in x and 2*100 in y, then padded by a third either side.
    assert img.size == (1920, 1080)
    assert img.mode == "RGB"


def test_rendering_is_deterministic(six_bands):
    first = M.composite_from_arrays(six_bands, 1715212800).tobytes()
    second = M.composite_from_arrays(six_bands, 1715212800).tobytes()
    assert first == second


def test_the_timestamp_is_drawn_on_the_image(six_bands):
    """Two timestamps must differ only where the caption is."""
    a = np.asarray(M.composite_from_arrays(six_bands, 1715212800))
    b = np.asarray(M.composite_from_arrays(six_bands, 1715299200))
    assert not np.array_equal(a, b)
    # The caption sits in the top strip; everything below it is identical.
    assert np.array_equal(a[60:], b[60:])


def test_every_band_contributes(six_bands):
    """Changing any one band must change the output.

    Guards against an indexing slip in the extracted function silently dropping a
    band -- the composite would still render, and still look plausible.
    """
    reference = np.asarray(M.composite_from_arrays(six_bands, 1715212800))
    for index in range(6):
        altered = list(six_bands)
        altered[index] = altered[index] * 1.5
        assert not np.array_equal(
            np.asarray(M.composite_from_arrays(altered, 1715212800)), reference
        ), f"band {index} made no difference to the composite"


def test_band_order_matters(six_bands):
    """The six arrays are positional; a caller passing them shuffled must not match."""
    shuffled = [six_bands[i] for i in (5, 4, 3, 2, 1, 0)]
    assert not np.array_equal(
        np.asarray(M.composite_from_arrays(shuffled, 1715212800)),
        np.asarray(M.composite_from_arrays(six_bands, 1715212800)),
    )


def test_render_assets_are_built_once():
    """The first four colormaps are mutated in place, so building twice would
    re-apply the mutation to already-mutated objects."""
    first = M._render_assets()
    second = M._render_assets()
    assert first is second
    assert first["cmaps"][0] is second["cmaps"][0]


def test_tolerates_a_filled_frame_containing_no_signal(six_bands):
    """Reconstructed frames can be blank; rendering must not raise on them."""
    blanked = list(six_bands)
    blanked[2] = np.zeros_like(blanked[2])
    img = M.composite_from_arrays(blanked, 1715212800)
    assert img.size == (1920, 1080)


def test_mapping_constants_line_up_with_the_bands():
    assert len(M.VMINS) == len(M.VMAXS) == len(M.GAMMAS) == len(M.image_names) == 6