"""Atari 7800 monochrome / tinted-mono (MARIA 160A restricted to one hue).

Reuses the c160 machinery but restricts the colour pool to the 16 luminances of a
single hue (hue 0 = greyscale), so the 8 palettes become up to ~16 grey levels and
the per-segment palette choice yields a smooth, detailed luminance image.
"""
from __future__ import annotations

import numpy as np

from ... import palette as c64pal
from ...convert.base import DIFFUSION_DITHERS, perceptual_error
from ...atari import palette as apal
from . import c160

WIDTH, HEIGHT, PIXEL_ASPECT = c160.WIDTH, c160.HEIGHT, c160.PIXEL_ASPECT


def convert(img_rgb, palette_name="ntsc", dither_mode="floyd",
            intensive=False, base_color=None):
    # mono is carried by dithering -> needs error diffusion
    if dither_mode not in DIFFUSION_DITHERS:
        dither_mode = "floyd"
    hue = 0 if base_color is None else (int(base_color) & 0x0F)
    candidates = list(range(hue * 16, hue * 16 + 16))     # 16 lums of this hue
    conv = c160.convert(img_rgb, palette_name, dither_mode, intensive,
                        base_color=base_color, candidates=candidates, _mode="mono")
    # report error in LUMINANCE space (a greyscale image must not be scored
    # against the colour original, as the colour modes are)
    plab = apal.palette_lab("ntsc").copy()
    plab[:, 1:] = 0.0
    img_l = c64pal.srgb_to_lab(img_rgb)
    img_l[..., 1:] = 0.0
    conv.error = perceptual_error(np.asarray(conv.index_image), img_l, plab)
    conv.meta["base_color"] = base_color
    return conv