import { Font } from "@react-pdf/renderer";
import { FONT_MANIFEST } from "./manifest";
import { familySources } from "./stack";

export { FONT_STACK, familySources, stack, type FamilySource } from "./stack";

let registered = false;

/**
 * Registers every bundled family from the manifest. Idempotent; never call Font.reset(), the fonts
 * would not load again.
 *
 * `base` is a URL prefix in the app ("/fonts") and a directory under Node (tests). Only static TTF is
 * used: WOFF2 embeds glyphs without outlines (invisible text) and variable fonts embed only their
 * default instance.
 */
export function registerBundledFonts(base: string): void {
  if (registered) return;
  registered = true;

  for (const fam of FONT_MANIFEST.families) {
    const sources = familySources(fam).map((s) => ({
      src: `${base}/${fam.folder}/${s.file}`,
      fontWeight: s.fontWeight,
      fontStyle: s.fontStyle,
    }));
    Font.register({ family: fam.family, fonts: sources });
  }

  // The default hyphenation inserts "-" into e-mail addresses, URLs and identifiers.
  Font.registerHyphenationCallback((word) => [word]);
}

const MIN_FONT_BYTES = 10 * 1024;

function hasTrueTypeMagic(b: Uint8Array): boolean {
  if (b.length < 4) return false;
  if (b[0] === 0 && b[1] === 1 && b[2] === 0 && b[3] === 0) return true;
  return String.fromCharCode(b[0], b[1], b[2], b[3]) === "true";
}

/**
 * Fetches every bundled font and returns a list of problems (empty when all are fine). Tauri answers
 * an unknown path with index.html and HTTP 200, so the response bytes must be checked, not the status.
 */
export async function preflightFonts(
  fetchBytes: (url: string) => Promise<Uint8Array>,
  base: string,
): Promise<string[]> {
  const problems: string[] = [];
  for (const fam of FONT_MANIFEST.families) {
    for (const font of fam.fonts) {
      const url = `${base}/${fam.folder}/${font.file}`;
      try {
        const bytes = await fetchBytes(url);
        if (!hasTrueTypeMagic(bytes)) problems.push(`${url}: not a TrueType font`);
        else if (bytes.length <= MIN_FONT_BYTES) problems.push(`${url}: only ${bytes.length} bytes`);
      } catch (err) {
        problems.push(`${url}: ${err instanceof Error ? err.message : String(err)}`);
      }
    }
  }
  return problems;
}