import { readFile } from 'node:fs/promises';
import path from 'node:path';

/**
 * The 1-bit wordmark, inlined as a data URI.
 *
 * Read from the committed `public/brand/logo-eink.png` and embedded in the
 * SVG rather than linked: the renderer must not depend on the network, and an
 * image the rasteriser silently failed to fetch would leave a hole in the shop
 * window. Regenerate the file with `npm run brand`.
 *
 * Its dimensions are read from the file rather than kept as constants beside
 * it. The letter-spacing of the wordmark is adjustable, and every adjustment
 * changes the height — a number copied here would drift and squash the logo
 * without anything failing.
 */

export type Logo = { dataUri: string; width: number; height: number };

let cached: Logo | null | undefined;

export async function loadLogo(): Promise<Logo | null> {
  if (cached !== undefined) {
    return cached;
  }
  try {
    const file = path.join(process.cwd(), 'public', 'brand', 'logo-eink.png');
    const bytes = await readFile(file);
    cached = {
      dataUri: `data:image/png;base64,${bytes.toString('base64')}`,
      ...readPngSize(bytes),
    };
  } catch {
    // Not fatal: the header falls back to the shop name from the settings,
    // which is plainer but still a working screen.
    cached = null;
  }
  return cached;
}

/** A PNG states its size in the IHDR chunk, at a fixed offset. */
export function readPngSize(bytes: Buffer): { width: number; height: number } {
  return { width: bytes.readUInt32BE(16), height: bytes.readUInt32BE(20) };
}