// Downloads the fonts the screenshot template needs, subset by Google Fonts (css2 `text=`) to exactly the characters
// your copy uses, so even CJK stays small: title + body family for Latin text, plus one Noto family per non-Latin
// script found in the copy (CJK, Arabic, Hebrew, Devanagari, Thai, Cyrillic / Greek).
//   storebound shots fonts          (re-run after editing the copy)
// Out: <project>/.storebound/fonts/*.woff2 + fonts.css. All of these fonts are SIL Open Font License 1.1.
import { mkdirSync, readFileSync, writeFileSync } from 'node:fs';
import { join } from 'node:path';
import type { Ctx } from '../lib/ctx';
import { need } from '../lib/ctx';
import { done, log } from '../lib/log';
import { shotsStyle } from '../lib/config';
import { type CopyFile, copyText, scriptFont, shotFonts } from './lib';

const UA = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36';
const ASCII = Array.from({ length: 95 }, (_, i) => String.fromCharCode(32 + i)).join('') + '·';

async function fetchSubset(family: string, chars: string, variable: boolean): Promise<ArrayBuffer> {
  const fam = encodeURIComponent(family) + (variable ? ':wght@100..900' : '');
  let res = await fetch(`https://fonts.googleapis.com/css2?family=${fam}&text=${encodeURIComponent(chars)}&display=block`, { headers: { 'user-agent': UA } });
  if (!res.ok && variable) return fetchSubset(family, chars, false);
  if (!res.ok) throw new Error(`${family}: ${res.status} ${await res.text()}`);
  const src = /url\((https:[^)]+)\)/.exec(await res.text())?.[1];
  if (!src) throw new Error(`${family}: no font url`);
  res = await fetch(src, { headers: { 'user-agent': UA } });
  return res.arrayBuffer();
}

export async function run(ctx: Ctx): Promise<void> {
  const { config, root, resolve } = ctx.loaded;
  const shots = need(config.shots, 'shots');
  const copy = JSON.parse(readFileSync(resolve(shots.copy), 'utf8')) as CopyFile;
  const dir = join(root, '.storebound', 'fonts');
  mkdirSync(dir, { recursive: true });
  const { title, body, titleVariable } = shotFonts(shots, shotsStyle(config));

  const latin = new Set(ASCII);
  const scripts = new Map<string, { family: string; chars: Set<string> }>();
  for (const [lang, c] of Object.entries(copy)) {
    const text = copyText(lang, c);
    const s = scriptFont(lang, text);
    if (!s) { for (const ch of text) latin.add(ch); continue; }
    const cur = scripts.get(s.slug) ?? { family: s.family, chars: new Set(ASCII) };
    for (const ch of text) cur.chars.add(ch);
    scripts.set(s.slug, cur);
  }
  for (const ch of config.app.name) latin.add(ch);
  const latinChars = [...latin].sort().join('');

  let css = '/* Generated by storebound shots fonts (Google Fonts, SIL Open Font License 1.1), subset to the copy. */\n';
  const jobs: [string, string, string, boolean][] = [[title, 'title', latinChars, titleVariable], [body, 'body', latinChars, true],
    ...[...scripts.entries()].map(([slug, s]) => [s.family, slug, [...s.chars].sort().join(''), true] as [string, string, string, boolean])];
  for (const [family, slug, chars, variable] of jobs) {
    const bin = await fetchSubset(family, chars, variable);
    const file = `${slug}.woff2`;
    writeFileSync(join(dir, file), Buffer.from(bin));
    const face = slug === 'title' ? title : slug === 'body' ? body : `Store ${slug}`;
    css += `@font-face { font-family: '${face}'; font-weight: 100 900; src: url(${file}) format('woff2'); }\n`;
    log('shots', `${file.padEnd(18)} ${family.padEnd(22)} ${(bin.byteLength / 1024).toFixed(1)} KB, ${[...chars].length} chars`);
  }
  writeFileSync(join(dir, 'fonts.css'), css);
  done('shots', 'fonts done');
}