"""Sprite rendering: master-palette index grids -> RGBA -> PNG."""
import sys
from pathlib import Path

import numpy as np
from PIL import Image

sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "src"))
from pxg_tiny.config import PALETTE, IMG  # noqa: E402


def grid_to_rgba(grid: np.ndarray) -> np.ndarray:
    """(16,16) index grid -> (16,16,4) uint8 RGBA. Index 0 = transparent."""
    out = np.zeros((IMG, IMG, 4), dtype=np.uint8)
    for idx, rgba in PALETTE.items():
        mask = grid == idx
        out[mask] = rgba + (255,)
    return out


def save_png(grid: np.ndarray, path: Path, scale: int = 8) -> Path:
    rgba = grid_to_rgba(np.asarray(grid))
    im = Image.fromarray(rgba, "RGBA")
    im = im.resize((IMG * scale, IMG * scale), Image.NEAREST)
    path = Path(path)
    path.parent.mkdir(parents=True, exist_ok=True)
    im.save(path)
    return path