"""ZX Spectrum monochrome / tinted-mono mode.

256x192 matched by luminance.  The Spectrum has no grey, so greyscale is a 2-level
black/white halftone (bright black + bright white) -- which at 256x192 with
dithering is a crisp, high-detail image free of attribute clash.  A base colour
gives a 3-level tinted ramp (black -> colour -> white), all within one brightness
group so the per-cell BRIGHT constraint is satisfied.  Reuses the hires packing.
"""

from __future__ import annotations

import numpy as np

from ...convert import base
from .. import palette as spal
from . import hires


def _ramp(base_color):
    """Luminance ramp kept inside ONE brightness group (shared BRIGHT bit)."""
    if base_color is None:
        return [8, 15]                       # bright black + bright white
    c = base_color & 7                        # base hue 0-7
    if c in (0, 7):
        return [8, 15]
    return [8, 8 | c, 15]                      # bright black, bright hue, bright white


def convert(img_rgb, palette_name="spectrum", dither_mode="atkinson",
            intensive=False, base_color=None):
    plab = spal.palette_lab()
    prgb = spal.get_palette().astype(np.uint8)
    ramp = _ramp(base_color)

    idx, sets, rows, cols, err = base.mono_render(
        img_rgb, plab, ramp, hires.WIDTH, hires.HEIGHT,
        hires.CELL_W, hires.CELL_H, dither_mode, n_free=2)

    scr = hires._encode(idx, sets, rows, cols)

    return base.Conversion(
        mode="mono", width=hires.WIDTH, height=hires.HEIGHT,
        pixel_aspect=hires.PIXEL_ASPECT, index_image=idx.astype(np.uint16),
        data=bytes(scr), data_addr=0x4000, viewer="spectrum", preview_rgb=prgb[idx],
        error=err,
        meta={"palette": "spectrum", "dither": dither_mode, "base_color": base_color},
    )