"""Icon normalization — anything decodable becomes a 256x256 PNG."""
from __future__ import annotations

import io

import pytest
from PIL import Image

from imptune.services.image_utils import ICON_SIZE, ImageError, normalize_icon


def _png(width: int, height: int, mode: str = "RGBA") -> bytes:
    buf = io.BytesIO()
    Image.new(mode, (width, height), color="red").save(buf, format="PNG")
    return buf.getvalue()


def _jpeg(width: int, height: int) -> bytes:
    buf = io.BytesIO()
    Image.new("RGB", (width, height), color="blue").save(buf, format="JPEG")
    return buf.getvalue()


def test_exact_png_passes_through_byte_identical():
    """The icon store is content-addressed — re-encoding would move the file."""
    data = _png(*ICON_SIZE)
    assert normalize_icon(data) is data


@pytest.mark.parametrize(
    "source",
    [_png(64, 64), _png(1024, 1024), _png(1024, 128), _jpeg(300, 200)],
    ids=["small", "large", "wide", "jpeg"],
)
def test_everything_else_becomes_a_256_png(source):
    out = normalize_icon(source)
    with Image.open(io.BytesIO(out)) as img:
        assert img.format == "PNG"
        assert img.size == ICON_SIZE


def test_aspect_ratio_is_kept_not_stretched():
    """A 400x100 source keeps its 4:1 shape, letterboxed in a square canvas.

    Checked through the alpha channel: the padding stays fully transparent, so
    the opaque band is 64px tall in a 256px canvas.
    """
    out = normalize_icon(_png(400, 100))
    with Image.open(io.BytesIO(out)) as img:
        alpha = img.convert("RGBA").split()[3]
        opaque_rows = [
            y for y in range(256) if any(alpha.getpixel((x, y)) for x in range(256))
        ]
    assert len(opaque_rows) == 64
    # ...and it is centered, not flush to the top.
    assert opaque_rows[0] == 96


def test_undecodable_bytes_raise():
    with pytest.raises(ImageError):
        normalize_icon(b"this is not an image")


def test_empty_bytes_raise():
    with pytest.raises(ImageError):
        normalize_icon(b"")