"""CoCo PMODE 3: 128x192, 4 colours from one MC6847 colour set.

128 wide on a 4:3 screen -> 2:1 pixels (like C64 multicolor).  The 4 colours are
fixed per CSS set (green/yellow/blue/red or buff/cyan/magenta/orange); we dither
to whichever set reproduces the image with lower error and tell the viewer which.
"""

from __future__ import annotations

import numpy as np

from ... import dither
from ...convert.base import Conversion, perceptual_error
from ...palette import srgb_to_lab
from .. import palette as cpal

WIDTH, HEIGHT = 128, 192
PIXEL_ASPECT = 2.0


def convert(img_rgb, palette_name="mc6847", dither_mode="floyd",
            intensive=False, base_color=None):
    img_lab = srgb_to_lab(img_rgb)
    allowed = np.tile(np.array([0, 1, 2, 3]), (HEIGHT, WIDTH, 1))

    best = None
    for vdg, rgb in cpal.PMODE3_SETS.items():
        plab = srgb_to_lab(rgb)
        idx = dither.quantize(img_lab, allowed, plab, dither_mode).astype(np.uint8)
        err = perceptual_error(idx, img_lab, plab)
        if best is None or err < best[0]:
            best = (err, vdg, rgb, plab, idx)

    err, vdg, rgb, plab, idx = best
    data = cpal.pack_pmode3(idx)                 # 6144-byte video buffer
    preview = rgb.astype(np.uint8)[idx]

    return Conversion(
        mode="pmode3", width=WIDTH, height=HEIGHT, pixel_aspect=PIXEL_ASPECT,
        index_image=idx.astype(np.uint16), data=data, data_addr=0,
        viewer="pmode3", preview_rgb=preview,
        error=err,
        meta={"palette": "mc6847", "dither": dither_mode, "vdg": vdg},
    )