"""Sinclair ZX Spectrum colour palette.

The ULA has 8 base colours, each in a normal and a BRIGHT version (component
value 0xD7 normal, 0xFF bright; black is the same in both).  Crucially the BRIGHT
bit is per 8x8 *cell*, shared by that cell's ink and paper -- so a cell's two
colours must both be normal or both be bright (they can't mix).  We model this as
a 16-entry palette: indices 0-7 = normal, 8-15 = bright, where index & 7 is the
ink/paper colour number and index >> 3 is the BRIGHT bit.
"""

from __future__ import annotations

import numpy as np

from ..palette import srgb_to_lab

_N = 0xD7   # normal-brightness component
_B = 0xFF   # bright component


def _ramp(v):
    # colour order matches the Spectrum's INK/PAPER numbering 0..7
    return [
        (0, 0, 0),     # 0 black
        (0, 0, v),     # 1 blue
        (v, 0, 0),     # 2 red
        (v, 0, v),     # 3 magenta
        (0, v, 0),     # 4 green
        (0, v, v),     # 5 cyan
        (v, v, 0),     # 6 yellow
        (v, v, v),     # 7 white
    ]


SPECTRUM = np.array(_ramp(_N) + _ramp(_B), dtype=np.float64)

# Cell colour pairs must come from one brightness group (shared BRIGHT bit).
NORMAL_GROUP = list(range(0, 8))
BRIGHT_GROUP = list(range(8, 16))


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


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