import { initSkia, hasGpu } from './skiaShim';
import type { RenderAssets } from './exportEngine';

// One CanvasKit instance per page, one copy of the render assets. The wasm file
// is served from /wasm/ (scripts/copy-wasm.mjs puts it there at build time); the
// fonts and the wall-frame artwork are in public/assets.
let assets: RenderAssets | null = null;

// The faces the watermarks' FONT option offers beside DEFAULT. There is no OS
// font service in a browser, so the list is exactly what the bundle carries —
// and each family is ONE file, because drawText has no glyph fallback: a name
// mapped to only the latin subset would print a Vietnamese place name as tofu.
// The two here are the site's own self-hosted faces (styles/fonts.css, SIL OFL),
// with their latin / latin-ext / vietnamese woff2 subsets decompressed, pinned
// to weight 400 @ opsz 14 and merged into one TTF per family (fontTools).
export const MARK_FACES: { family: string; file: string }[] = [
  { family: 'Inter', file: '/assets/Inter-Regular.ttf' },
  { family: 'Fraunces', file: '/assets/Fraunces-Regular.ttf' },
];

async function buf(url: string): Promise<ArrayBuffer> {
  const res = await fetch(url);
  if (!res.ok) throw new Error(`fetch ${url}: ${res.status}`);
  return res.arrayBuffer();
}

// The engine is only usable on a WebGL-backed surface (see skiaShim.ts), so the
// app has to know whether it got one: reporting "no WebGL" beats silently
// spending minutes per photo on the raster fallback.
export function probeGpu(): boolean {
  return hasGpu();
}

export async function loadEngine(): Promise<{ assets: RenderAssets; gpu: boolean }> {
  await initSkia({ locateFile: (file) => `/wasm/${file}` });
  if (!assets) {
    const [textFont, emojiFont, wallframePng, markFonts] = await Promise.all([
      buf('/assets/Cousine-Regular.ttf'),
      buf('/assets/NotoEmoji-GPS.ttf'),
      buf('/assets/wallframe.png'),
      Promise.all(MARK_FACES.map(async (face) => ({ family: face.family, bytes: await buf(face.file) }))),
    ]);
    assets = { textFont, emojiFont, wallframe: new Uint8Array(wallframePng), markFonts };
  }
  return { assets, gpu: probeGpu() };
}