// A NaCl `crypto_box_seal`, in TypeScript, byte-compatible with Go's `box.SealAnonymous`.
//
// **Why this file exists, and why it is exactly this.** novox/hq ADR 0050's refreshable-grant
// carve-out delivers the refresh token to the manager module the way the mesh delivers every other
// credential: sealed to the node's key, and unsealed by the *host* — never by the module. The host
// unseals with Go's `golang.org/x/crypto/nacl/box.OpenAnonymous` (mesh-host
// internal/identity/sealing.go), and mesh-control seals with `box.SealAnonymous`
// (mesh-control internal/secrets/seal.go). Both are NaCl `crypto_box_seal`:
//
//     sealed = ephemeralPub(32) ‖ crypto_box(msg, nonce, recipientPub, ephemeralSecret)
//     nonce  = blake2b( ephemeralPub ‖ recipientPub , 24 bytes, unkeyed )
//
// When the vendor rotates the refresh token, the manager module must store the new one back the
// same way — sealed to the manager node's own sealing key — so mesh-control keeps it without ever
// reading it and the host can later unseal it to deliver the cleartext again. That reseal happens
// here, on the manager node, in TypeScript. It therefore has to produce the *identical* byte format
// Go's `Open` accepts, or the host would refuse the delivery.
//
// **Dependency-free on purpose.** The module runtime image carries only mesh-tools' node_modules
// (novox/hq ADR 0052), so a module cannot pull `tweetnacl` at runtime. node:crypto gives X25519 but
// not XSalsa20-Poly1305 or a 24-byte BLAKE2b, so the `crypto_box` and the nonce hash are transcribed
// here from the public-domain TweetNaCl (Chestnykh/Mandiri, 2014) and blakejs (dcposch, RFC 7693).
// X25519 (ephemeral key generation and the Diffie-Hellman) is left to node:crypto, which is
// standards-conformant and interoperates with Go's curve25519 regardless of who generated a key.
//
// **How it is kept honest.** A cross-language test seals a fixture here and opens it in Go
// (mesh-control internal/secrets/sealedbox_xcheck_test.go), and this module's own test round-trips
// it against a second decrypt. A transcription slip surfaces there as a seal Go cannot open, not as
// a refresh token silently mangled in production.
//
// This module SEALS only. It never opens — opening is the host's job, with the node private key the
// module is deliberately never given.

import {
  createPublicKey,
  diffieHellman,
  generateKeyPairSync,
  type KeyObject,
} from "node:crypto";

const RAW_KEY_LEN = 32;
// "expand 32-byte k", the Salsa20 constant.
const SIGMA = new Uint8Array([
  101, 120, 112, 97, 110, 100, 32, 51, 50, 45, 98, 121, 116, 101, 32, 107,
]);

/**
 * Seal a value to a node's public sealing key, producing what Go's `box.OpenAnonymous` opens.
 *
 * @param value               the plaintext (e.g. a rotated refresh token)
 * @param recipientPublicB64  the node's raw 32-byte X25519 public key, standard base64
 * @returns                   standard-base64( ephemeralPub ‖ box )
 */
export function seal(value: Uint8Array, recipientPublicB64: string): string {
  const recipientPub = Buffer.from(recipientPublicB64, "base64");
  if (recipientPub.length !== RAW_KEY_LEN) {
    throw new Error(`a sealing public key is 32 bytes, not ${recipientPub.length}`);
  }
  const recipientKey = importRawX25519Public(recipientPub);

  // Ephemeral-static ECDH: a throwaway X25519 key pair whose public half rides in front, and the
  // raw Diffie-Hellman point shared with the recipient. node:crypto does both.
  const eph = generateKeyPairSync("x25519");
  const ephemeralPub = rawX25519Public(eph.publicKey);
  const dh = new Uint8Array(diffieHellman({ privateKey: eph.privateKey, publicKey: recipientKey }));

  // The crypto_box shared key is HSalsa20 of the DH point (crypto_box_beforenm).
  const boxKey = new Uint8Array(32);
  cryptoCoreHsalsa20(boxKey, new Uint8Array(16), dh, SIGMA);

  // nonce = blake2b(ephemeralPub ‖ recipientPub, 24), unkeyed — exactly Go's sealNonce.
  const nonce = blake2b24(concat(ephemeralPub, recipientPub));

  const boxed = cryptoBox(value, nonce, boxKey);

  return Buffer.from(concat(ephemeralPub, boxed)).toString("base64");
}

// --- X25519 via node:crypto ------------------------------------------------------------------

function importRawX25519Public(raw: Uint8Array): KeyObject {
  return createPublicKey({
    key: { kty: "OKP", crv: "X25519", x: Buffer.from(raw).toString("base64url") },
    format: "jwk",
  });
}

function rawX25519Public(key: KeyObject): Uint8Array {
  const jwk = key.export({ format: "jwk" }) as { x?: string };
  if (!jwk.x) throw new Error("a public key had no point");
  return new Uint8Array(Buffer.from(jwk.x, "base64url"));
}

// --- crypto_box / crypto_secretbox (XSalsa20-Poly1305) ---------------------------------------
//
// Transcribed from TweetNaCl (public domain). crypto_box after the DH/HSalsa20 above is exactly
// crypto_secretbox: XSalsa20 keystream XOR, then a Poly1305 tag over the ciphertext.

/** crypto_box_afternm: secretbox(msg, nonce, key), returning tag(16) ‖ ciphertext. */
function cryptoBox(msg: Uint8Array, nonce: Uint8Array, key: Uint8Array): Uint8Array {
  // secretbox operates on a 32-byte-zero-prefixed message; its output's first 16 bytes are zero,
  // and the useful box is everything from byte 16 (the Poly1305 tag, then the ciphertext).
  const m = new Uint8Array(32 + msg.length);
  m.set(msg, 32);
  const c = new Uint8Array(m.length);
  cryptoSecretbox(c, m, m.length, nonce, key);
  return c.subarray(16);
}

function cryptoSecretbox(
  c: Uint8Array,
  m: Uint8Array,
  d: number,
  n: Uint8Array,
  k: Uint8Array,
): void {
  if (d < 32) throw new Error("secretbox message underflow");
  cryptoStreamXor(c, 0, m, 0, d, n, k);
  cryptoOnetimeauth(c, 16, c, 32, d - 32, c);
  for (let i = 0; i < 16; i++) c[i] = 0;
}

function L32(x: number, c: number): number {
  return (x << c) | (x >>> (32 - c));
}

function ld32(x: Uint8Array, i: number): number {
  let u = x[i + 3] & 0xff;
  u = (u << 8) | (x[i + 2] & 0xff);
  u = (u << 8) | (x[i + 1] & 0xff);
  return (u << 8) | (x[i + 0] & 0xff);
}

function st32(x: Uint8Array, j: number, u: number): void {
  for (let i = 0; i < 4; i++) {
    x[j + i] = u & 255;
    u >>>= 8;
  }
}

function core(out: Uint8Array, inp: Uint8Array, k: Uint8Array, c: Uint8Array, h: boolean): void {
  const w = new Uint32Array(16);
  const x = new Uint32Array(16);
  const y = new Uint32Array(16);
  const t = new Uint32Array(4);

  for (let i = 0; i < 4; i++) {
    x[5 * i] = ld32(c, 4 * i);
    x[1 + i] = ld32(k, 4 * i);
    x[6 + i] = ld32(inp, 4 * i);
    x[11 + i] = ld32(k, 16 + 4 * i);
  }

  for (let i = 0; i < 16; i++) y[i] = x[i];

  for (let i = 0; i < 20; i++) {
    for (let j = 0; j < 4; j++) {
      for (let m = 0; m < 4; m++) t[m] = x[(5 * j + 4 * m) % 16];
      t[1] ^= L32((t[0] + t[3]) | 0, 7);
      t[2] ^= L32((t[1] + t[0]) | 0, 9);
      t[3] ^= L32((t[2] + t[1]) | 0, 13);
      t[0] ^= L32((t[3] + t[2]) | 0, 18);
      for (let m = 0; m < 4; m++) w[4 * j + ((j + m) % 4)] = t[m];
    }
    for (let m = 0; m < 16; m++) x[m] = w[m];
  }

  if (h) {
    for (let i = 0; i < 16; i++) x[i] = (x[i] + y[i]) | 0;
    for (let i = 0; i < 4; i++) {
      x[5 * i] = (x[5 * i] - ld32(c, 4 * i)) | 0;
      x[6 + i] = (x[6 + i] - ld32(inp, 4 * i)) | 0;
    }
    for (let i = 0; i < 4; i++) {
      st32(out, 4 * i, x[5 * i]);
      st32(out, 16 + 4 * i, x[6 + i]);
    }
  } else {
    for (let i = 0; i < 16; i++) st32(out, 4 * i, (x[i] + y[i]) | 0);
  }
}

function cryptoCoreHsalsa20(out: Uint8Array, inp: Uint8Array, k: Uint8Array, c: Uint8Array): void {
  core(out, inp, k, c, true);
}

function cryptoStreamSalsa20Xor(
  c: Uint8Array,
  cpos: number,
  m: Uint8Array,
  mpos: number,
  b: number,
  n: Uint8Array,
  k: Uint8Array,
): void {
  const z = new Uint8Array(16);
  const x = new Uint8Array(64);
  if (!b) return;
  for (let i = 0; i < 8; i++) z[i] = n[i];
  while (b >= 64) {
    coreSalsa20(x, z, k, SIGMA);
    for (let i = 0; i < 64; i++) c[cpos + i] = m[mpos + i] ^ x[i];
    let u = 1;
    for (let i = 8; i < 16; i++) {
      u = (u + (z[i] & 0xff)) | 0;
      z[i] = u & 0xff;
      u >>>= 8;
    }
    b -= 64;
    cpos += 64;
    mpos += 64;
  }
  if (b > 0) {
    coreSalsa20(x, z, k, SIGMA);
    for (let i = 0; i < b; i++) c[cpos + i] = m[mpos + i] ^ x[i];
  }
}

function coreSalsa20(out: Uint8Array, inp: Uint8Array, k: Uint8Array, c: Uint8Array): void {
  core(out, inp, k, c, false);
}

function cryptoStreamXor(
  c: Uint8Array,
  cpos: number,
  m: Uint8Array,
  mpos: number,
  d: number,
  n: Uint8Array,
  k: Uint8Array,
): void {
  const s = new Uint8Array(32);
  cryptoCoreHsalsa20(s, n, k, SIGMA);
  cryptoStreamSalsa20Xor(c, cpos, m, mpos, d, n.subarray(16), s);
}

const MINUSP = new Uint32Array([5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 252]);

function add1305(h: Uint32Array, c: Uint32Array): void {
  let u = 0;
  for (let j = 0; j < 17; j++) {
    u = (u + ((h[j] + c[j]) | 0)) | 0;
    h[j] = u & 255;
    u >>>= 8;
  }
}

function cryptoOnetimeauth(
  out: Uint8Array,
  outpos: number,
  m: Uint8Array,
  mpos: number,
  n: number,
  k: Uint8Array,
): void {
  const x = new Uint32Array(17);
  const r = new Uint32Array(17);
  const h = new Uint32Array(17);
  const c = new Uint32Array(17);
  const g = new Uint32Array(17);
  for (let j = 0; j < 16; j++) r[j] = k[j];
  r[3] &= 15;
  r[4] &= 252;
  r[7] &= 15;
  r[8] &= 252;
  r[11] &= 15;
  r[12] &= 252;
  r[15] &= 15;

  let j: number;
  while (n > 0) {
    for (j = 0; j < 17; j++) c[j] = 0;
    for (j = 0; j < 16 && j < n; ++j) c[j] = m[mpos + j];
    c[j] = 1;
    mpos += j;
    n -= j;
    add1305(h, c);
    for (let i = 0; i < 17; i++) {
      x[i] = 0;
      for (j = 0; j < 17; j++) {
        x[i] =
          (x[i] + (h[j] * (j <= i ? r[i - j] : (320 * r[i + 17 - j]) | 0)) | 0) | 0;
      }
    }
    for (let i = 0; i < 17; i++) h[i] = x[i];
    let u = 0;
    for (j = 0; j < 16; j++) {
      u = (u + h[j]) | 0;
      h[j] = u & 255;
      u >>>= 8;
    }
    u = (u + h[16]) | 0;
    h[16] = u & 3;
    u = (5 * (u >>> 2)) | 0;
    for (j = 0; j < 16; j++) {
      u = (u + h[j]) | 0;
      h[j] = u & 255;
      u >>>= 8;
    }
    u = (u + h[16]) | 0;
    h[16] = u;
  }

  for (j = 0; j < 17; j++) g[j] = h[j];
  add1305(h, MINUSP);
  const s = -(h[16] >>> 7) | 0;
  for (j = 0; j < 17; j++) h[j] ^= s & (g[j] ^ h[j]);

  for (j = 0; j < 16; j++) c[j] = k[j + 16];
  c[16] = 0;
  add1305(h, c);
  for (j = 0; j < 16; j++) out[outpos + j] = h[j];
}

// --- BLAKE2b (24-byte, unkeyed) — the sealed-box nonce hash ----------------------------------
//
// Transcribed from blakejs (RFC 7693 reference). Only the fixed path this needs: no key, no salt,
// no personalisation, a single ≤128-byte input.

const BLAKE2B_IV32 = new Uint32Array([
  0xf3bcc908, 0x6a09e667, 0x84caa73b, 0xbb67ae85, 0xfe94f82b, 0x3c6ef372, 0x5f1d36f1, 0xa54ff53a,
  0xade682d1, 0x510e527f, 0x2b3e6c1f, 0x9b05688c, 0xfb41bd6b, 0x1f83d9ab, 0x137e2179, 0x5be0cd19,
]);

const SIGMA82 = new Uint8Array(
  [
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2,
    11, 7, 5, 3, 11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4, 7, 9, 3, 1, 13, 12, 11, 14,
    2, 6, 5, 10, 4, 0, 15, 8, 9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13, 2, 12, 6, 10, 0,
    11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9, 12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11, 13,
    11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10, 6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4,
    10, 5, 10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
    11, 12, 13, 14, 15, 14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3,
  ].map((n) => n * 2),
);

interface Blake2bCtx {
  b: Uint8Array;
  h: Uint32Array;
  t: number;
  c: number;
  outlen: number;
}

function b2bGet32(arr: Uint8Array, i: number): number {
  return (arr[i] ^ (arr[i + 1] << 8) ^ (arr[i + 2] << 16) ^ (arr[i + 3] << 24)) >>> 0;
}

function add64aa(v: Uint32Array, a: number, b: number): void {
  const o0 = v[a] + v[b];
  let o1 = v[a + 1] + v[b + 1];
  if (o0 >= 0x100000000) o1++;
  v[a] = o0;
  v[a + 1] = o1;
}

function add64ac(v: Uint32Array, a: number, b0: number, b1: number): void {
  let o0 = v[a] + b0;
  if (b0 < 0) o0 += 0x100000000;
  let o1 = v[a + 1] + b1;
  if (o0 >= 0x100000000) o1++;
  v[a] = o0;
  v[a + 1] = o1;
}

function b2bG(
  v: Uint32Array,
  m: Uint32Array,
  a: number,
  b: number,
  c: number,
  d: number,
  ix: number,
  iy: number,
): void {
  const x0 = m[ix];
  const x1 = m[ix + 1];
  const y0 = m[iy];
  const y1 = m[iy + 1];

  add64aa(v, a, b);
  add64ac(v, a, x0, x1);

  let xor0 = v[d] ^ v[a];
  let xor1 = v[d + 1] ^ v[a + 1];
  v[d] = xor1;
  v[d + 1] = xor0;

  add64aa(v, c, d);

  xor0 = v[b] ^ v[c];
  xor1 = v[b + 1] ^ v[c + 1];
  v[b] = (xor0 >>> 24) ^ (xor1 << 8);
  v[b + 1] = (xor1 >>> 24) ^ (xor0 << 8);

  add64aa(v, a, b);
  add64ac(v, a, y0, y1);

  xor0 = v[d] ^ v[a];
  xor1 = v[d + 1] ^ v[a + 1];
  v[d] = (xor0 >>> 16) ^ (xor1 << 16);
  v[d + 1] = (xor1 >>> 16) ^ (xor0 << 16);

  add64aa(v, c, d);

  xor0 = v[b] ^ v[c];
  xor1 = v[b + 1] ^ v[c + 1];
  v[b] = (xor1 >>> 31) ^ (xor0 << 1);
  v[b + 1] = (xor0 >>> 31) ^ (xor1 << 1);
}

function blake2bCompress(ctx: Blake2bCtx, last: boolean): void {
  const v = new Uint32Array(32);
  const m = new Uint32Array(32);
  for (let i = 0; i < 16; i++) {
    v[i] = ctx.h[i];
    v[i + 16] = BLAKE2B_IV32[i];
  }
  v[24] = v[24] ^ ctx.t;
  v[25] = v[25] ^ (ctx.t / 0x100000000);
  if (last) {
    v[28] = ~v[28];
    v[29] = ~v[29];
  }
  for (let i = 0; i < 32; i++) m[i] = b2bGet32(ctx.b, 4 * i);
  for (let i = 0; i < 12; i++) {
    b2bG(v, m, 0, 8, 16, 24, SIGMA82[i * 16 + 0], SIGMA82[i * 16 + 1]);
    b2bG(v, m, 2, 10, 18, 26, SIGMA82[i * 16 + 2], SIGMA82[i * 16 + 3]);
    b2bG(v, m, 4, 12, 20, 28, SIGMA82[i * 16 + 4], SIGMA82[i * 16 + 5]);
    b2bG(v, m, 6, 14, 22, 30, SIGMA82[i * 16 + 6], SIGMA82[i * 16 + 7]);
    b2bG(v, m, 0, 10, 20, 30, SIGMA82[i * 16 + 8], SIGMA82[i * 16 + 9]);
    b2bG(v, m, 2, 12, 22, 24, SIGMA82[i * 16 + 10], SIGMA82[i * 16 + 11]);
    b2bG(v, m, 4, 14, 16, 26, SIGMA82[i * 16 + 12], SIGMA82[i * 16 + 13]);
    b2bG(v, m, 6, 8, 18, 28, SIGMA82[i * 16 + 14], SIGMA82[i * 16 + 15]);
  }
  for (let i = 0; i < 16; i++) ctx.h[i] = ctx.h[i] ^ v[i] ^ v[i + 16];
}

function blake2b24(input: Uint8Array): Uint8Array {
  const outlen = 24;
  const ctx: Blake2bCtx = {
    b: new Uint8Array(128),
    h: new Uint32Array(16),
    t: 0,
    c: 0,
    outlen,
  };
  // Parameter block: outlen, keylen=0, fanout=1, depth=1; the rest zero.
  const param = new Uint8Array(64);
  param[0] = outlen;
  param[2] = 1;
  param[3] = 1;
  for (let i = 0; i < 16; i++) ctx.h[i] = BLAKE2B_IV32[i] ^ b2bGet32(param, i * 4);

  for (let i = 0; i < input.length; i++) {
    if (ctx.c === 128) {
      ctx.t += ctx.c;
      blake2bCompress(ctx, false);
      ctx.c = 0;
    }
    ctx.b[ctx.c++] = input[i];
  }

  ctx.t += ctx.c;
  while (ctx.c < 128) ctx.b[ctx.c++] = 0;
  blake2bCompress(ctx, true);

  const out = new Uint8Array(outlen);
  for (let i = 0; i < outlen; i++) out[i] = ctx.h[i >> 2] >> (8 * (i & 3));
  return out;
}

// --- small helpers ---------------------------------------------------------------------------

function concat(a: Uint8Array, b: Uint8Array): Uint8Array {
  const out = new Uint8Array(a.length + b.length);
  out.set(a, 0);
  out.set(b, a.length);
  return out;
}