// The wire codec: the subset of msgpack MNP uses (maps, strings, integers,
// binary, arrays, null), and hex for the ids the transport mints.

// ── Minimal msgpack encode/decode ────────────────────────────────────────────
// Covers the subset used by MNP: maps, strings, integers, binary, arrays, null.

function msgpack_encode(obj) {
  const parts = [];
  _encodeValue(obj, parts);
  const total = parts.reduce((s, p) => s + p.length, 0);
  const result = new Uint8Array(total);
  let off = 0;
  for (const p of parts) { result.set(p, off); off += p.length; }
  return result;
}

function _encodeValue(val, parts) {
  if (val === null || val === undefined) {
    parts.push(new Uint8Array([0xc0]));
  } else if (typeof val === 'boolean') {
    parts.push(new Uint8Array([val ? 0xc3 : 0xc2]));
  } else if (typeof val === 'number') {
    if (Number.isInteger(val)) {
      if (val >= 0 && val <= 127) {
        parts.push(new Uint8Array([val]));
      } else if (val >= 0 && val <= 0xff) {
        parts.push(new Uint8Array([0xcc, val]));
      } else if (val >= 0 && val <= 0xffff) {
        const b = new Uint8Array(3); b[0] = 0xcd;
        new DataView(b.buffer).setUint16(1, val, false);
        parts.push(b);
      } else if (val >= 0 && val <= 0xffffffff) {
        const b = new Uint8Array(5); b[0] = 0xce;
        new DataView(b.buffer).setUint32(1, val, false);
        parts.push(b);
      } else if (val >= 0 && val <= Number.MAX_SAFE_INTEGER) {
        // Same split as the 0xcf decoder case above, in reverse — without
        // this, a value over 0xffffffff fell to the plain int32 branch
        // below and silently wrapped to a wrong, unrelated number instead
        // of failing loudly.
        const b = new Uint8Array(9); b[0] = 0xcf;
        const dv = new DataView(b.buffer);
        dv.setUint32(1, Math.floor(val / 4294967296), false);
        dv.setUint32(5, val % 4294967296, false);
        parts.push(b);
      } else if (val >= -32 && val < 0) {
        parts.push(new Uint8Array([val & 0xff]));
      } else if (val >= -128 && val < 0) {
        const b = new Uint8Array(2); b[0] = 0xd0; b[1] = val & 0xff;
        parts.push(b);
      } else {
        const b = new Uint8Array(5); b[0] = 0xd2;
        new DataView(b.buffer).setInt32(1, val, false);
        parts.push(b);
      }
    } else {
      const b = new Uint8Array(9); b[0] = 0xcb;
      new DataView(b.buffer).setFloat64(1, val, false);
      parts.push(b);
    }
  } else if (typeof val === 'string') {
    const encoded = new TextEncoder().encode(val);
    if (encoded.length <= 31) {
      parts.push(new Uint8Array([0xa0 | encoded.length]));
    } else if (encoded.length <= 0xff) {
      parts.push(new Uint8Array([0xd9, encoded.length]));
    } else if (encoded.length <= 0xffff) {
      const b = new Uint8Array(3); b[0] = 0xda;
      new DataView(b.buffer).setUint16(1, encoded.length, false);
      parts.push(b);
    } else {
      const b = new Uint8Array(5); b[0] = 0xdb;
      new DataView(b.buffer).setUint32(1, encoded.length, false);
      parts.push(b);
    }
    parts.push(encoded);
  } else if (val instanceof Uint8Array) {
    if (val.length <= 0xff) {
      parts.push(new Uint8Array([0xc4, val.length]));
    } else if (val.length <= 0xffff) {
      const b = new Uint8Array(3); b[0] = 0xc5;
      new DataView(b.buffer).setUint16(1, val.length, false);
      parts.push(b);
    } else {
      const b = new Uint8Array(5); b[0] = 0xc6;
      new DataView(b.buffer).setUint32(1, val.length, false);
      parts.push(b);
    }
    parts.push(val);
  } else if (Array.isArray(val)) {
    if (val.length <= 15) {
      parts.push(new Uint8Array([0x90 | val.length]));
    } else if (val.length <= 0xffff) {
      const b = new Uint8Array(3); b[0] = 0xdc;
      new DataView(b.buffer).setUint16(1, val.length, false);
      parts.push(b);
    } else {
      const b = new Uint8Array(5); b[0] = 0xdd;
      new DataView(b.buffer).setUint32(1, val.length, false);
      parts.push(b);
    }
    for (const item of val) _encodeValue(item, parts);
  } else if (typeof val === 'object') {
    const keys = Object.keys(val);
    if (keys.length <= 15) {
      parts.push(new Uint8Array([0x80 | keys.length]));
    } else if (keys.length <= 0xffff) {
      const b = new Uint8Array(3); b[0] = 0xde;
      new DataView(b.buffer).setUint16(1, keys.length, false);
      parts.push(b);
    } else {
      const b = new Uint8Array(5); b[0] = 0xdf;
      new DataView(b.buffer).setUint32(1, keys.length, false);
      parts.push(b);
    }
    for (const k of keys) {
      _encodeValue(k, parts);
      _encodeValue(val[k], parts);
    }
  }
}

function msgpack_decode(buf) {
  const view = new DataView(buf.buffer, buf.byteOffset, buf.byteLength);
  const [val] = _decodeValue(buf, view, 0);
  return val;
}

function _decodeValue(buf, view, offset) {
  const byte = buf[offset];

  if (byte <= 0x7f) return [byte, offset + 1];
  if ((byte & 0xe0) === 0xe0) return [byte - 256, offset + 1];
  if ((byte & 0xa0) === 0xa0) {
    const len = byte & 0x1f;
    return [new TextDecoder().decode(buf.slice(offset + 1, offset + 1 + len)), offset + 1 + len];
  }
  if ((byte & 0xf0) === 0x90) {
    const len = byte & 0x0f;
    return _decodeArray(buf, view, offset + 1, len);
  }
  if ((byte & 0xf0) === 0x80) {
    const len = byte & 0x0f;
    return _decodeMap(buf, view, offset + 1, len);
  }

  switch (byte) {
    case 0xc0: return [null, offset + 1];
    case 0xc2: return [false, offset + 1];
    case 0xc3: return [true, offset + 1];
    case 0xc4: { const len = buf[offset + 1]; return [buf.slice(offset + 2, offset + 2 + len), offset + 2 + len]; }
    case 0xc5: { const len = view.getUint16(offset + 1, false); return [buf.slice(offset + 3, offset + 3 + len), offset + 3 + len]; }
    case 0xc6: { const len = view.getUint32(offset + 1, false); return [buf.slice(offset + 5, offset + 5 + len), offset + 5 + len]; }
    case 0xcc: return [buf[offset + 1], offset + 2];
    case 0xcd: return [view.getUint16(offset + 1, false), offset + 3];
    case 0xce: return [view.getUint32(offset + 1, false), offset + 5];
    // uint64/int64 — never emitted by this file's own encoder (a JS number
    // above 0xffffffff falls to float64 there), but the node's real msgpack
    // library sends a plain uint64 for any Python int over ~4.3 billion, and
    // a raw byte count crosses that easily (found live: IndexProgress.
    // scanned_bytes/total_bytes in the handshake ack, indexer.py, for a
    // group whose total library size exceeds ~4 GB). Split into two 32-bit
    // halves rather than DataView's getBigUint64/getBigInt64 — a BigInt
    // would silently poison every arithmetic use of these fields elsewhere
    // (percentage math, comparisons) — and every real byte count fits in a
    // plain JS number well under Number.MAX_SAFE_INTEGER (2^53).
    case 0xcf: {
      const hi = view.getUint32(offset + 1, false);
      const lo = view.getUint32(offset + 5, false);
      return [hi * 4294967296 + lo, offset + 9];
    }
    case 0xd3: {
      const hi = view.getInt32(offset + 1, false);
      const lo = view.getUint32(offset + 5, false);
      return [hi * 4294967296 + lo, offset + 9];
    }
    case 0xcb: return [view.getFloat64(offset + 1, false), offset + 9];
    case 0xd0: return [view.getInt8(offset + 1), offset + 2];
    case 0xd1: return [view.getInt16(offset + 1, false), offset + 3];
    case 0xd2: return [view.getInt32(offset + 1, false), offset + 5];
    case 0xd9: {
      const len = buf[offset + 1];
      return [new TextDecoder().decode(buf.slice(offset + 2, offset + 2 + len)), offset + 2 + len];
    }
    case 0xda: {
      const len = view.getUint16(offset + 1, false);
      return [new TextDecoder().decode(buf.slice(offset + 3, offset + 3 + len)), offset + 3 + len];
    }
    case 0xdb: {
      const len = view.getUint32(offset + 1, false);
      return [new TextDecoder().decode(buf.slice(offset + 5, offset + 5 + len)), offset + 5 + len];
    }
    case 0xdc: { const len = view.getUint16(offset + 1, false); return _decodeArray(buf, view, offset + 3, len); }
    case 0xdd: { const len = view.getUint32(offset + 1, false); return _decodeArray(buf, view, offset + 5, len); }
    case 0xde: { const len = view.getUint16(offset + 1, false); return _decodeMap(buf, view, offset + 3, len); }
    case 0xdf: { const len = view.getUint32(offset + 1, false); return _decodeMap(buf, view, offset + 5, len); }
    default: throw new Error(`Unknown msgpack type: 0x${byte.toString(16)}`);
  }
}

function _decodeArray(buf, view, offset, count) {
  const arr = [];
  for (let i = 0; i < count; i++) {
    const [val, newOff] = _decodeValue(buf, view, offset);
    arr.push(val);
    offset = newOff;
  }
  return [arr, offset];
}

function _decodeMap(buf, view, offset, count) {
  const obj = {};
  for (let i = 0; i < count; i++) {
    const [key, off1] = _decodeValue(buf, view, offset);
    const [val, off2] = _decodeValue(buf, view, off1);
    obj[key] = val;
    offset = off2;
  }
  return [obj, offset];
}

function _hex(bytes) {
  return [...bytes].map(b => b.toString(16).padStart(2, '0')).join('');
}