"""Commodore PET / CBM monochrome display.

The PET has no bitmap or colour -- a 40- or 80-column text screen of a fixed
character ROM on a monochrome (green P1 phosphor) monitor.  Images are rendered
with the PETSCII 2x2 quadrant-block graphics characters, giving an effective
80x50 (40-col) or 160x50 (80-col) one-bit pixel grid.
"""
from __future__ import annotations

import numpy as np

from ..palette import srgb_to_lab

# 0 = background (dark), 1 = foreground (lit phosphor).  Green to match the
# classic PET monitor; the signal is one bit, so only luminance matters.
PALETTE = np.array([(0, 0, 0), (0x40, 0xE0, 0x40)], dtype=np.float64)


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


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


# screen (poke) code for each 2x2 quadrant pattern, bits TL<<3|TR<<2|BL<<1|BR.
# Derived from the PET character ROM: 8 blocks exist directly, the other 8 are
# their reverse-video forms (screen code | $80).
QUAD = [32, 108, 123, 98, 124, 225, 255, 254, 126, 127, 97, 252, 226, 251, 236, 160]