"""Commodore Amiga (OCS/ECS) colour palette.

12-bit colour: 4 bits per channel (x17 -> 0..255), 4096 colours.  A colour
register value is %0000 RRRR GGGG BBBB.  We index the master palette by the
packed 12-bit key (R<<8)|(G<<4)|B, which is also the register word.
"""
from __future__ import annotations

import numpy as np

from ..palette import srgb_to_lab

_r = (np.arange(4096) >> 8) & 0xF
_g = (np.arange(4096) >> 4) & 0xF
_b = np.arange(4096) & 0xF
PALETTE = (np.stack([_r, _g, _b], axis=1) * 17).astype(np.float64)   # 4096 x 3

GREYS = [(v << 8) | (v << 4) | v for v in range(16)]    # 16 grey keys


def color_word(key: int) -> int:
    return key & 0x0FFF


def get_palette() -> np.ndarray:
    return PALETTE


def palette_lab() -> np.ndarray:
    return srgb_to_lab(PALETTE)