/*!
 * Tectum
 * Copyright © 2026 Machiel Heinen.
 * Alle rechten voorbehouden. Gebruik uitsluitend met schriftelijke toestemming.
 * Zie LICENTIE.md.
 */
// ZIP zonder compressie (stored): meerdere bestanden in één download.

window.ZipWriter = (() => {
  const CRC = new Uint32Array(256);
  for (let n = 0; n < 256; n++) {
    let c = n;
    for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
    CRC[n] = c >>> 0;
  }
  function crc32(parts) {
    let c = 0xffffffff;
    parts.forEach(b => { for (let i = 0; i < b.length; i++) c = CRC[(c ^ b[i]) & 0xff] ^ (c >>> 8); });
    return (c ^ 0xffffffff) >>> 0;
  }

  // files: [{ name, data: Uint8Array | Uint8Array[] }]
  function build(files) {
    const enc = new TextEncoder();
    const out = [], central = [];
    let offset = 0;
    const d = new Date();
    const time = (d.getHours() << 11) | (d.getMinutes() << 5) | (d.getSeconds() >> 1);
    const date = ((d.getFullYear() - 1980) << 9) | ((d.getMonth() + 1) << 5) | d.getDate();
    files.forEach(f => {
      const parts = Array.isArray(f.data) ? f.data : [f.data];
      const size = parts.reduce((a, b) => a + b.length, 0);
      const name = enc.encode(f.name), crc = crc32(parts);
      const head = (sig, extra) => {
        const h = new DataView(new ArrayBuffer(extra ? 46 : 30));
        let p = 0;
        const u32 = (v) => { h.setUint32(p, v, true); p += 4; }, u16 = (v) => { h.setUint16(p, v, true); p += 2; };
        u32(sig);
        if (extra) u16(20);
        u16(20); u16(0x0800); u16(0); u16(time); u16(date); u32(crc); u32(size); u32(size); u16(name.length); u16(0);
        if (extra) { u16(0); u16(0); u16(0); u32(0); u32(offset); }
        return new Uint8Array(h.buffer);
      };
      const local = head(0x04034b50, false);
      central.push(head(0x02014b50, true), name);
      out.push(local, name, ...parts);
      offset += local.length + name.length + size;
    });
    const cdSize = central.reduce((a, b) => a + b.length, 0);
    const end = new DataView(new ArrayBuffer(22));
    end.setUint32(0, 0x06054b50, true);
    end.setUint16(8, files.length, true); end.setUint16(10, files.length, true);
    end.setUint32(12, cdSize, true); end.setUint32(16, offset, true);
    return out.concat(central, [new Uint8Array(end.buffer)]);
  }

  function save(files, filename) {
    const blob = new Blob(build(files), { type: 'application/zip' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = filename;
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
    URL.revokeObjectURL(url);
  }

  return { build, save };
})();