"""Atari GR.15 (ANTIC mode E): 160x192, 4 colours chosen globally from 256.

No per-cell colour limit, so this is a clean 4-colour dithered image.
"""

from __future__ import annotations

import numpy as np

from ... import palette as c64pal       # for srgb_to_lab (shared)
from ...convert.base import (Conversion, mean_error, perceptual_error,
                             DIFFUSION_DITHERS)
from .. import palette as apal
from . import _common

WIDTH, HEIGHT = 160, 192
PIXEL_ASPECT = 2.0


def convert(img_rgb, palette_name="ntsc", dither_mode="floyd",
            intensive=False, base_color=None):
    plab = apal.palette_lab(palette_name)
    prgb = apal.get_palette(palette_name).astype(np.uint8)
    img_lab = c64pal.srgb_to_lab(img_rgb)

    # Dither-aware palette for error-diffusion modes: pick 4 colours whose blends
    # span the image gamut (so dithering reproduces saturated/intermediate shades)
    # instead of k-means centroids the dither can't reach.
    if dither_mode in DIFFUSION_DITHERS:
        colors = _common.choose_palette_dither(img_lab, plab, k=4)
    else:
        colors = _common.choose_palette(img_lab, plab, k=4)
    colors.sort(key=lambda c: plab[c, 0])       # value 0 = darkest (background)

    idx = _common.quantize_global(img_lab, plab, colors, dither_mode)
    value_of = {c: v for v, c in enumerate(colors)}
    val_image = np.vectorize(value_of.get)(idx).astype(np.uint8)

    lines = _common.pack_2bpp(val_image)
    data = _common.split_screen(lines) + bytes(colors)   # 4 colour regs at $6000

    preview = np.repeat(prgb[idx], int(PIXEL_ASPECT), axis=1)

    err = (perceptual_error if dither_mode in DIFFUSION_DITHERS else mean_error)
    return Conversion(
        mode="gr15", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
        index_image=idx.astype(np.uint16), data=data, data_addr=_common.DATA_ADDR,
        viewer="gr15", preview_rgb=preview,
        error=err(idx, img_lab, plab),
        meta={"palette": palette_name, "dither": dither_mode, "colors": colors},
    )