"""app.html_render's shared ordered-dithering primitives -- ordered_dither
and ordered_dither_regions -- exercised directly against synthetic
images, no Chromium/Playwright involved (these two functions run purely
on whatever Image render_html_to_image already handed back)."""

from __future__ import annotations

from PIL import Image

from app import html_render
from app.image_pipeline import DEFAULT_PALETTE_RGB

_PALETTE = set(DEFAULT_PALETTE_RGB)
# A muddy hue nowhere near any of the 6 exact palette colors -- at the
# "modern" style's tuned default amplitude (48), this should still snap
# flatly to a single nearest ink (see theme_tokens.py's module docstring
# for why 48 was chosen for icon/text legibility); only a much higher
# amplitude (as a rich theme's accent_amplitude would use) stipples it
# into a multi-ink approximation.
_RICH_HUE = (168, 75, 42)  # a terracotta-ish RGB, not one of the 6 inks


def test_ordered_dither_output_is_exact_palette_colors():
    img = Image.new("RGB", (40, 30), (128, 128, 128))
    dithered = html_render.ordered_dither(img, None)
    assert set(dithered.getdata()) <= _PALETTE


def test_ordered_dither_regions_outside_the_region_matches_plain_dither():
    """Pixels outside every accent_regions rect must come out identical
    to a plain ordered_dither call at base_amplitude -- the region-aware
    variant must not perturb anything it wasn't asked to."""
    img = Image.new("RGB", (100, 80), (90, 140, 200))
    base_only = html_render.ordered_dither(img, None, amplitude=48.0)
    regions = html_render.ordered_dither_regions(
        img, None, base_amplitude=48.0, accent_regions=[((10, 10, 40, 30), 130.0)]
    )
    for x in range(100):
        for y in range(80):
            if 10 <= x < 40 and 10 <= y < 30:
                continue  # inside the accent region -- expected to differ
            assert regions.getpixel((x, y)) == base_only.getpixel((x, y))


def test_ordered_dither_regions_stipples_a_rich_hue_the_base_amplitude_would_flatten():
    """The whole reason ordered_dither_regions exists: a rich accent hue
    dithered at the base (icon/text-safe) amplitude just snaps to one
    nearest ink, but the same hue in an accent region at a theme's higher
    accent_amplitude resolves to a believable multi-ink stipple instead --
    assert that difference directly, not just "some image came back"."""
    img = Image.new("RGB", (60, 60), _RICH_HUE)
    rect = (0, 0, 60, 60)

    flat = html_render.ordered_dither(img, None, amplitude=48.0)
    richer = html_render.ordered_dither_regions(img, None, base_amplitude=48.0, accent_regions=[(rect, 130.0)])

    assert len(set(flat.getdata())) == 1
    assert len(set(richer.getdata())) > 1
    assert set(richer.getdata()) <= _PALETTE


def test_ordered_dither_regions_with_no_accent_regions_matches_plain_dither():
    img = Image.new("RGB", (30, 30), (50, 60, 70))
    assert list(html_render.ordered_dither_regions(img, None, base_amplitude=48.0).getdata()) == \
        list(html_render.ordered_dither(img, None, amplitude=48.0).getdata())