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 first two 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).
// The rest come from google/fonts (SIL OFL), subset to the same latin /
// latin-ext / vietnamese ranges with pyftsubset (fontTools); the variable ones
// (Hahmlet, Dancing Script @ wght 400, Tilt Warp @ XROT 0 YROT 0) are pinned to
// that one named instance first. Every file keeps whatever glyph its source had
// inside those ranges — no invented ones: Tilt Warp has no U+0111, the rest do.
export const MARK_FACES: { family: string; file: string }[] = [
  { family: 'Inter', file: '/assets/Inter-Regular.ttf' },
  { family: 'Fraunces', file: '/assets/Fraunces-Regular.ttf' },
  { family: 'VT323', file: '/assets/VT323-Regular.ttf' },
  { family: 'Alex Brush', file: '/assets/AlexBrush-Regular.ttf' },
  { family: 'Tilt Warp', file: '/assets/TiltWarp-Regular.ttf' },
  { family: 'Hahmlet', file: '/assets/Hahmlet-Regular.ttf' },
  { family: 'Pinyon Script', file: '/assets/PinyonScript-Regular.ttf' },
  { family: 'Allura', file: '/assets/Allura-Regular.ttf' },
  { family: 'Dancing Script', file: '/assets/DancingScript-Regular.ttf' },
  { family: 'Amatic SC', file: '/assets/AmaticSC-Regular.ttf' },
];

// The two frame sheets are drawn by hand and dropped over the file of the same
// name, and that name is the one thing neither cache lets go of: nginx answers
// /assets/ immutable for 30 days (nginx.conf) and the service worker serves the
// path cache-first (sw.js) — both stored for the sheet that was there the day the
// visitor first loaded the app, so a sheet swapped in today arrives as yesterday's.
// The build stamp in the query is what makes the URL move with the build; the old
// entry stays in both caches, unasked for, and ages out on its own.
const ART = `?v=${import.meta.env.VITE_VERSION ?? ''}`;

// The fonts never change under a build, so they keep the plain URL.
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/${file}` });
  if (!assets) {
    const [textFont, emojiFont, wallframePng, oldFilmPng, markFonts] = await Promise.all([
      buf('/assets/Cousine-Regular.ttf'),
      buf('/assets/NotoEmoji-GPS.ttf'),
      buf(`/assets/wallframe.png${ART}`),
      buf(`/assets/old_film.png${ART}`),
      Promise.all(MARK_FACES.map(async (face) => ({ family: face.family, bytes: await buf(face.file) }))),
    ]);
    assets = {
      textFont,
      emojiFont,
      wallframe: new Uint8Array(wallframePng),
      oldFilm: new Uint8Array(oldFilmPng),
      markFonts,
    };
  }
  return { assets, gpu: probeGpu() };
}