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

import type { Font } from 'satori';

import { SANS, SERIF } from './layout';

/**
 * Font binaries for the panel renderer, read from `public/fonts` rather than
 * from `node_modules`.
 *
 * The rendered pixels feed a content hash that decides whether the e-ink panel
 * redraws, so they have to be reproducible. Vendored files make that true; an
 * install tree or a CDN would not.
 */
const FILES: { file: string; name: string; weight: Font['weight'] }[] = [
  { file: 'inter-400.woff', name: SANS, weight: 400 },
  { file: 'inter-600.woff', name: SANS, weight: 600 },
  { file: 'inter-700.woff', name: SANS, weight: 700 },
  { file: 'source-serif-600.woff', name: SERIF, weight: 600 },
];

let cached: Font[] | null = null;

export async function loadScreenFonts(): Promise<Font[]> {
  if (cached) {
    return cached;
  }
  const directory = path.join(process.cwd(), 'public', 'fonts');
  cached = await Promise.all(
    FILES.map(async ({ file, name, weight }) => ({
      name,
      data: await readFile(path.join(directory, file)),
      weight,
      style: 'normal' as const,
    })),
  );
  return cached;
}