import type { Palette } from "../world/types";

/** Decode Game Boy planar pixels directly to RGBA; no display hardware emulation. */
export function drawTile(
  target: Uint8ClampedArray,
  width: number,
  height: number,
  graphics: Uint8Array,
  tile: number,
  x: number,
  y: number,
  palette: Palette,
  options: {
    transparent?: boolean;
    flipX?: boolean;
    flipY?: boolean;
    /** Background color indices per pixel: a background tile records them;
     * an OAM_PRIO sprite (`behind`) only draws over color 0. */
    indices?: Uint8Array;
    behind?: boolean;
  } = {},
) {
  const offset = tile * 16;
  if (offset < 0 || offset + 16 > graphics.length) return;
  for (let row = 0; row < 8; row++) {
    const sourceRow = options.flipY ? 7 - row : row;
    const lo = graphics[offset + sourceRow * 2],
      hi = graphics[offset + sourceRow * 2 + 1];
    for (let col = 0; col < 8; col++) {
      const bit = options.flipX ? col : 7 - col;
      const index = ((lo >> bit) & 1) | (((hi >> bit) & 1) << 1);
      if (options.transparent && index === 0) continue;
      const px = x + col,
        py = y + row;
      if (px < 0 || py < 0 || px >= width || py >= height) continue;
      if (options.indices) {
        if (options.behind) {
          if (options.indices[py * width + px]) continue;
        } else if (!options.transparent) options.indices[py * width + px] = index;
      }
      const destination = (py * width + px) * 4,
        color = palette[index];
      target[destination] = color[0];
      target[destination + 1] = color[1];
      target[destination + 2] = color[2];
      target[destination + 3] = 255;
    }
  }
}