/**
 * Erzeugt Favicon und PWA-Icons aus den SVG-Quellen unter public/brand/.
 *
 *   npm run icons
 *
 * Quelle ist immer das Vektor-Logo — die Rasterdateien sind reine Ableitungen
 * und werden bei Bedarf neu erzeugt.
 */
import { readFileSync, writeFileSync, mkdirSync } from "node:fs";
import { join } from "node:path";
import sharp from "sharp";

const ROOT = process.cwd();
const BRAND = join(ROOT, "public", "brand");
const ICONS = join(ROOT, "public", "icons");

const ICON_SVG = join(BRAND, "flimmer-icon.svg");
const MASKABLE_SVG = join(BRAND, "flimmer-icon-maskable.svg");

/** Rendert ein SVG in ein quadratisches PNG. */
async function png(svgPath: string, size: number): Promise<Buffer> {
  const svg = readFileSync(svgPath);
  return sharp(svg, { density: Math.max(72, Math.ceil((size / 128) * 96) * 4) })
    .resize(size, size, { fit: "contain", background: { r: 0, g: 0, b: 0, alpha: 0 } })
    .png({ compressionLevel: 9 })
    .toBuffer();
}

/**
 * Minimaler ICO-Container mit eingebetteten PNGs.
 * Alle Browser ab IE11 verstehen PNG-in-ICO; das spart eine Abhängigkeit.
 */
function buildIco(images: { size: number; data: Buffer }[]): Buffer {
  const header = Buffer.alloc(6);
  header.writeUInt16LE(0, 0); // reserviert
  header.writeUInt16LE(1, 2); // Typ 1 = Icon
  header.writeUInt16LE(images.length, 4);

  const entries: Buffer[] = [];
  let offset = 6 + images.length * 16;

  for (const img of images) {
    const entry = Buffer.alloc(16);
    entry.writeUInt8(img.size >= 256 ? 0 : img.size, 0); // Breite (0 = 256)
    entry.writeUInt8(img.size >= 256 ? 0 : img.size, 1); // Höhe
    entry.writeUInt8(0, 2); // Farbpalette
    entry.writeUInt8(0, 3); // reserviert
    entry.writeUInt16LE(1, 4); // Farbebenen
    entry.writeUInt16LE(32, 6); // Bits pro Pixel
    entry.writeUInt32LE(img.data.length, 8);
    entry.writeUInt32LE(offset, 12);
    entries.push(entry);
    offset += img.data.length;
  }

  return Buffer.concat([header, ...entries, ...images.map((i) => i.data)]);
}

const PWA_SIZES = [64, 96, 128, 192, 256, 384, 512];
const FAVICON_SIZES = [16, 32, 48];

async function main() {
  mkdirSync(ICONS, { recursive: true });

  // PWA-Icons (transparenter Rand, „any"-Purpose)
  for (const size of PWA_SIZES) {
    const data = await png(ICON_SVG, size);
    writeFileSync(join(ICONS, `icon-${size}.png`), data);
    console.log(`  icons/icon-${size}.png`);
  }

  // Maskable (randlose Fläche, Motiv in der Sicherheitszone)
  for (const size of [192, 512]) {
    const data = await png(MASKABLE_SVG, size);
    writeFileSync(join(ICONS, `maskable-${size}.png`), data);
    console.log(`  icons/maskable-${size}.png`);
  }

  // Apple Touch Icon — iOS mag keine Transparenz, deshalb deckend
  const apple = await sharp(readFileSync(MASKABLE_SVG), { density: 576 })
    .resize(180, 180)
    .flatten({ background: "#12101d" })
    .png({ compressionLevel: 9 })
    .toBuffer();
  writeFileSync(join(ICONS, "apple-touch-icon.png"), apple);
  console.log("  icons/apple-touch-icon.png");

  // Favicon: SVG (scharf in jeder Größe) + ICO (Fallback, Lesezeichenleisten)
  writeFileSync(join(ROOT, "public", "favicon.svg"), readFileSync(ICON_SVG));
  console.log("  favicon.svg");

  const icoImages = [];
  for (const size of FAVICON_SIZES) {
    icoImages.push({ size, data: await png(ICON_SVG, size) });
  }
  writeFileSync(join(ROOT, "public", "favicon.ico"), buildIco(icoImages));
  console.log("  favicon.ico");

  // Open-Graph-Bild für geteilte Links
  const og = await sharp({
    create: {
      width: 1200,
      height: 630,
      channels: 4,
      background: { r: 12, g: 10, b: 20, alpha: 1 },
    },
  })
    .composite([
      {
        input: await sharp(readFileSync(join(BRAND, "flimmer-logo.svg")), { density: 300 })
          .resize({ width: 760 })
          .png()
          .toBuffer(),
        gravity: "centre",
      },
    ])
    .png({ compressionLevel: 9 })
    .toBuffer();
  writeFileSync(join(ROOT, "public", "og-image.png"), og);
  console.log("  og-image.png");
}

main().then(
  () => console.log("Icons erzeugt."),
  (err) => {
    console.error(err);
    process.exit(1);
  },
);