// SPDX-License-Identifier: Unlicense

// Minimum necessary functions extracted and made TypeScript compatible from:
// https://github.com/dchest/tweetnacl-js/blob/fecde6ecf0eb81e31d54ca0509531ab1b825f490/nacl-fast.js

function gf(init?: number[]): Float64Array {
  const r = new Float64Array(16);
  if (init) {
    for (let i = 0; i < init.length; i++) r[i] = init[i];
  }
  return r;
}

export const crypto_box_SECRETKEYBYTES = 32 as const;
export const crypto_box_PUBLICKEYBYTES = 32 as const;
export const crypto_scalarmult_BYTES = 32 as const;
export const crypto_scalarmult_SCALARBYTES = 32 as const;

const _9 = new Uint8Array(32);
_9[0] = 9;
const _121665 = gf([0xdb41, 1]);

function sel25519(p: Float64Array, q: Float64Array, b: number) {
  let t;
  const c = ~(b - 1);
  for (let i = 0; i < 16; i++) {
    t = c & (p[i] ^ q[i]);
    p[i] ^= t;
    q[i] ^= t;
  }
}

function inv25519(o: Float64Array, i: Float64Array) {
  const c = gf();
  let a;
  for (a = 0; a < 16; a++) c[a] = i[a];
  for (a = 253; a >= 0; a--) {
    S(c, c);
    if (a !== 2 && a !== 4) M(c, c, i);
  }
  for (a = 0; a < 16; a++) o[a] = c[a];
}

function car25519(o: Float64Array) {
  let v,
    c = 1;
  for (let i = 0; i < 16; i++) {
    v = o[i] + c + 65535;
    c = Math.floor(v / 65536);
    o[i] = v - c * 65536;
  }
  o[0] += c - 1 + 37 * (c - 1);
}

function unpack25519(o: Float64Array, n: Uint8Array) {
  for (let i = 0; i < 16; i++) o[i] = n[2 * i] + (n[2 * i + 1] << 8);
  o[15] &= 0x7fff;
}

function pack25519(o: Uint8Array, n: Float64Array) {
  let i: number, j: number, b: number;
  const m = gf(),
    t = gf();
  for (i = 0; i < 16; i++) t[i] = n[i];
  car25519(t);
  car25519(t);
  car25519(t);
  for (j = 0; j < 2; j++) {
    m[0] = t[0] - 0xffed;
    for (i = 1; i < 15; i++) {
      m[i] = t[i] - 0xffff - ((m[i - 1] >> 16) & 1);
      m[i - 1] &= 0xffff;
    }
    m[15] = t[15] - 0x7fff - ((m[14] >> 16) & 1);
    b = (m[15] >> 16) & 1;
    m[14] &= 0xffff;
    sel25519(t, m, 1 - b);
  }
  for (i = 0; i < 16; i++) {
    o[2 * i] = t[i] & 0xff;
    o[2 * i + 1] = t[i] >> 8;
  }
}

function A(o: Float64Array, a: Float64Array, b: Float64Array) {
  for (let i = 0; i < 16; i++) o[i] = a[i] + b[i];
}

function Z(o: Float64Array, a: Float64Array, b: Float64Array) {
  for (let i = 0; i < 16; i++) o[i] = a[i] - b[i];
}

function M(o: Float64Array, a: Float64Array, b: Float64Array) {
  let v,
    c,
    t0 = 0,
    t1 = 0,
    t2 = 0,
    t3 = 0,
    t4 = 0,
    t5 = 0,
    t6 = 0,
    t7 = 0,
    t8 = 0,
    t9 = 0,
    t10 = 0,
    t11 = 0,
    t12 = 0,
    t13 = 0,
    t14 = 0,
    t15 = 0,
    t16 = 0,
    t17 = 0,
    t18 = 0,
    t19 = 0,
    t20 = 0,
    t21 = 0,
    t22 = 0,
    t23 = 0,
    t24 = 0,
    t25 = 0,
    t26 = 0,
    t27 = 0,
    t28 = 0,
    t29 = 0,
    t30 = 0;
  const b0 = b[0],
    b1 = b[1],
    b2 = b[2],
    b3 = b[3],
    b4 = b[4],
    b5 = b[5],
    b6 = b[6],
    b7 = b[7],
    b8 = b[8],
    b9 = b[9],
    b10 = b[10],
    b11 = b[11],
    b12 = b[12],
    b13 = b[13],
    b14 = b[14],
    b15 = b[15];

  v = a[0];
  t0 += v * b0;
  t1 += v * b1;
  t2 += v * b2;
  t3 += v * b3;
  t4 += v * b4;
  t5 += v * b5;
  t6 += v * b6;
  t7 += v * b7;
  t8 += v * b8;
  t9 += v * b9;
  t10 += v * b10;
  t11 += v * b11;
  t12 += v * b12;
  t13 += v * b13;
  t14 += v * b14;
  t15 += v * b15;
  v = a[1];
  t1 += v * b0;
  t2 += v * b1;
  t3 += v * b2;
  t4 += v * b3;
  t5 += v * b4;
  t6 += v * b5;
  t7 += v * b6;
  t8 += v * b7;
  t9 += v * b8;
  t10 += v * b9;
  t11 += v * b10;
  t12 += v * b11;
  t13 += v * b12;
  t14 += v * b13;
  t15 += v * b14;
  t16 += v * b15;
  v = a[2];
  t2 += v * b0;
  t3 += v * b1;
  t4 += v * b2;
  t5 += v * b3;
  t6 += v * b4;
  t7 += v * b5;
  t8 += v * b6;
  t9 += v * b7;
  t10 += v * b8;
  t11 += v * b9;
  t12 += v * b10;
  t13 += v * b11;
  t14 += v * b12;
  t15 += v * b13;
  t16 += v * b14;
  t17 += v * b15;
  v = a[3];
  t3 += v * b0;
  t4 += v * b1;
  t5 += v * b2;
  t6 += v * b3;
  t7 += v * b4;
  t8 += v * b5;
  t9 += v * b6;
  t10 += v * b7;
  t11 += v * b8;
  t12 += v * b9;
  t13 += v * b10;
  t14 += v * b11;
  t15 += v * b12;
  t16 += v * b13;
  t17 += v * b14;
  t18 += v * b15;
  v = a[4];
  t4 += v * b0;
  t5 += v * b1;
  t6 += v * b2;
  t7 += v * b3;
  t8 += v * b4;
  t9 += v * b5;
  t10 += v * b6;
  t11 += v * b7;
  t12 += v * b8;
  t13 += v * b9;
  t14 += v * b10;
  t15 += v * b11;
  t16 += v * b12;
  t17 += v * b13;
  t18 += v * b14;
  t19 += v * b15;
  v = a[5];
  t5 += v * b0;
  t6 += v * b1;
  t7 += v * b2;
  t8 += v * b3;
  t9 += v * b4;
  t10 += v * b5;
  t11 += v * b6;
  t12 += v * b7;
  t13 += v * b8;
  t14 += v * b9;
  t15 += v * b10;
  t16 += v * b11;
  t17 += v * b12;
  t18 += v * b13;
  t19 += v * b14;
  t20 += v * b15;
  v = a[6];
  t6 += v * b0;
  t7 += v * b1;
  t8 += v * b2;
  t9 += v * b3;
  t10 += v * b4;
  t11 += v * b5;
  t12 += v * b6;
  t13 += v * b7;
  t14 += v * b8;
  t15 += v * b9;
  t16 += v * b10;
  t17 += v * b11;
  t18 += v * b12;
  t19 += v * b13;
  t20 += v * b14;
  t21 += v * b15;
  v = a[7];
  t7 += v * b0;
  t8 += v * b1;
  t9 += v * b2;
  t10 += v * b3;
  t11 += v * b4;
  t12 += v * b5;
  t13 += v * b6;
  t14 += v * b7;
  t15 += v * b8;
  t16 += v * b9;
  t17 += v * b10;
  t18 += v * b11;
  t19 += v * b12;
  t20 += v * b13;
  t21 += v * b14;
  t22 += v * b15;
  v = a[8];
  t8 += v * b0;
  t9 += v * b1;
  t10 += v * b2;
  t11 += v * b3;
  t12 += v * b4;
  t13 += v * b5;
  t14 += v * b6;
  t15 += v * b7;
  t16 += v * b8;
  t17 += v * b9;
  t18 += v * b10;
  t19 += v * b11;
  t20 += v * b12;
  t21 += v * b13;
  t22 += v * b14;
  t23 += v * b15;
  v = a[9];
  t9 += v * b0;
  t10 += v * b1;
  t11 += v * b2;
  t12 += v * b3;
  t13 += v * b4;
  t14 += v * b5;
  t15 += v * b6;
  t16 += v * b7;
  t17 += v * b8;
  t18 += v * b9;
  t19 += v * b10;
  t20 += v * b11;
  t21 += v * b12;
  t22 += v * b13;
  t23 += v * b14;
  t24 += v * b15;
  v = a[10];
  t10 += v * b0;
  t11 += v * b1;
  t12 += v * b2;
  t13 += v * b3;
  t14 += v * b4;
  t15 += v * b5;
  t16 += v * b6;
  t17 += v * b7;
  t18 += v * b8;
  t19 += v * b9;
  t20 += v * b10;
  t21 += v * b11;
  t22 += v * b12;
  t23 += v * b13;
  t24 += v * b14;
  t25 += v * b15;
  v = a[11];
  t11 += v * b0;
  t12 += v * b1;
  t13 += v * b2;
  t14 += v * b3;
  t15 += v * b4;
  t16 += v * b5;
  t17 += v * b6;
  t18 += v * b7;
  t19 += v * b8;
  t20 += v * b9;
  t21 += v * b10;
  t22 += v * b11;
  t23 += v * b12;
  t24 += v * b13;
  t25 += v * b14;
  t26 += v * b15;
  v = a[12];
  t12 += v * b0;
  t13 += v * b1;
  t14 += v * b2;
  t15 += v * b3;
  t16 += v * b4;
  t17 += v * b5;
  t18 += v * b6;
  t19 += v * b7;
  t20 += v * b8;
  t21 += v * b9;
  t22 += v * b10;
  t23 += v * b11;
  t24 += v * b12;
  t25 += v * b13;
  t26 += v * b14;
  t27 += v * b15;
  v = a[13];
  t13 += v * b0;
  t14 += v * b1;
  t15 += v * b2;
  t16 += v * b3;
  t17 += v * b4;
  t18 += v * b5;
  t19 += v * b6;
  t20 += v * b7;
  t21 += v * b8;
  t22 += v * b9;
  t23 += v * b10;
  t24 += v * b11;
  t25 += v * b12;
  t26 += v * b13;
  t27 += v * b14;
  t28 += v * b15;
  v = a[14];
  t14 += v * b0;
  t15 += v * b1;
  t16 += v * b2;
  t17 += v * b3;
  t18 += v * b4;
  t19 += v * b5;
  t20 += v * b6;
  t21 += v * b7;
  t22 += v * b8;
  t23 += v * b9;
  t24 += v * b10;
  t25 += v * b11;
  t26 += v * b12;
  t27 += v * b13;
  t28 += v * b14;
  t29 += v * b15;
  v = a[15];
  t15 += v * b0;
  t16 += v * b1;
  t17 += v * b2;
  t18 += v * b3;
  t19 += v * b4;
  t20 += v * b5;
  t21 += v * b6;
  t22 += v * b7;
  t23 += v * b8;
  t24 += v * b9;
  t25 += v * b10;
  t26 += v * b11;
  t27 += v * b12;
  t28 += v * b13;
  t29 += v * b14;
  t30 += v * b15;

  t0 += 38 * t16;
  t1 += 38 * t17;
  t2 += 38 * t18;
  t3 += 38 * t19;
  t4 += 38 * t20;
  t5 += 38 * t21;
  t6 += 38 * t22;
  t7 += 38 * t23;
  t8 += 38 * t24;
  t9 += 38 * t25;
  t10 += 38 * t26;
  t11 += 38 * t27;
  t12 += 38 * t28;
  t13 += 38 * t29;
  t14 += 38 * t30;
  // t15 left as is

  // first car
  c = 1;
  v = t0 + c + 65535;
  c = Math.floor(v / 65536);
  t0 = v - c * 65536;
  v = t1 + c + 65535;
  c = Math.floor(v / 65536);
  t1 = v - c * 65536;
  v = t2 + c + 65535;
  c = Math.floor(v / 65536);
  t2 = v - c * 65536;
  v = t3 + c + 65535;
  c = Math.floor(v / 65536);
  t3 = v - c * 65536;
  v = t4 + c + 65535;
  c = Math.floor(v / 65536);
  t4 = v - c * 65536;
  v = t5 + c + 65535;
  c = Math.floor(v / 65536);
  t5 = v - c * 65536;
  v = t6 + c + 65535;
  c = Math.floor(v / 65536);
  t6 = v - c * 65536;
  v = t7 + c + 65535;
  c = Math.floor(v / 65536);
  t7 = v - c * 65536;
  v = t8 + c + 65535;
  c = Math.floor(v / 65536);
  t8 = v - c * 65536;
  v = t9 + c + 65535;
  c = Math.floor(v / 65536);
  t9 = v - c * 65536;
  v = t10 + c + 65535;
  c = Math.floor(v / 65536);
  t10 = v - c * 65536;
  v = t11 + c + 65535;
  c = Math.floor(v / 65536);
  t11 = v - c * 65536;
  v = t12 + c + 65535;
  c = Math.floor(v / 65536);
  t12 = v - c * 65536;
  v = t13 + c + 65535;
  c = Math.floor(v / 65536);
  t13 = v - c * 65536;
  v = t14 + c + 65535;
  c = Math.floor(v / 65536);
  t14 = v - c * 65536;
  v = t15 + c + 65535;
  c = Math.floor(v / 65536);
  t15 = v - c * 65536;
  t0 += c - 1 + 37 * (c - 1);

  // second car
  c = 1;
  v = t0 + c + 65535;
  c = Math.floor(v / 65536);
  t0 = v - c * 65536;
  v = t1 + c + 65535;
  c = Math.floor(v / 65536);
  t1 = v - c * 65536;
  v = t2 + c + 65535;
  c = Math.floor(v / 65536);
  t2 = v - c * 65536;
  v = t3 + c + 65535;
  c = Math.floor(v / 65536);
  t3 = v - c * 65536;
  v = t4 + c + 65535;
  c = Math.floor(v / 65536);
  t4 = v - c * 65536;
  v = t5 + c + 65535;
  c = Math.floor(v / 65536);
  t5 = v - c * 65536;
  v = t6 + c + 65535;
  c = Math.floor(v / 65536);
  t6 = v - c * 65536;
  v = t7 + c + 65535;
  c = Math.floor(v / 65536);
  t7 = v - c * 65536;
  v = t8 + c + 65535;
  c = Math.floor(v / 65536);
  t8 = v - c * 65536;
  v = t9 + c + 65535;
  c = Math.floor(v / 65536);
  t9 = v - c * 65536;
  v = t10 + c + 65535;
  c = Math.floor(v / 65536);
  t10 = v - c * 65536;
  v = t11 + c + 65535;
  c = Math.floor(v / 65536);
  t11 = v - c * 65536;
  v = t12 + c + 65535;
  c = Math.floor(v / 65536);
  t12 = v - c * 65536;
  v = t13 + c + 65535;
  c = Math.floor(v / 65536);
  t13 = v - c * 65536;
  v = t14 + c + 65535;
  c = Math.floor(v / 65536);
  t14 = v - c * 65536;
  v = t15 + c + 65535;
  c = Math.floor(v / 65536);
  t15 = v - c * 65536;
  t0 += c - 1 + 37 * (c - 1);

  o[0] = t0;
  o[1] = t1;
  o[2] = t2;
  o[3] = t3;
  o[4] = t4;
  o[5] = t5;
  o[6] = t6;
  o[7] = t7;
  o[8] = t8;
  o[9] = t9;
  o[10] = t10;
  o[11] = t11;
  o[12] = t12;
  o[13] = t13;
  o[14] = t14;
  o[15] = t15;
}

function S(o: Float64Array, a: Float64Array) {
  M(o, a, a);
}

function crypto_scalarmult(q: Uint8Array, n: Uint8Array, p: Uint8Array) {
  const z = new Uint8Array(32);
  const x = new Float64Array(80);
  let r, i;
  const a = gf(),
    b = gf(),
    c = gf(),
    d = gf(),
    e = gf(),
    f = gf();
  for (i = 0; i < 31; i++) z[i] = n[i];
  z[31] = (n[31] & 127) | 64;
  z[0] &= 248;
  unpack25519(x, p);
  for (i = 0; i < 16; i++) {
    b[i] = x[i];
    d[i] = a[i] = c[i] = 0;
  }
  a[0] = d[0] = 1;
  for (i = 254; i >= 0; --i) {
    r = (z[i >>> 3] >>> (i & 7)) & 1;
    sel25519(a, b, r);
    sel25519(c, d, r);
    A(e, a, c);
    Z(a, a, c);
    A(c, b, d);
    Z(b, b, d);
    S(d, e);
    S(f, a);
    M(a, c, a);
    M(c, b, e);
    A(e, a, c);
    Z(a, a, c);
    S(b, a);
    Z(c, d, f);
    M(a, c, _121665);
    A(a, a, d);
    M(c, c, a);
    M(a, d, f);
    M(d, b, x);
    S(b, e);
    sel25519(a, b, r);
    sel25519(c, d, r);
  }
  for (i = 0; i < 16; i++) {
    x[i + 16] = a[i];
    x[i + 32] = c[i];
    x[i + 48] = b[i];
    x[i + 64] = d[i];
  }
  const x32 = x.subarray(32);
  const x16 = x.subarray(16);
  inv25519(x32, x32);
  M(x16, x16, x32);
  pack25519(q, x16);
  return q;
}

function crypto_scalarmult_base(q: Uint8Array, n: Uint8Array) {
  return crypto_scalarmult(q, n, _9);
}

export class MuNaclError extends Error {}

export interface BoxKeyPair {
  publicKey: Uint8Array;
  secretKey: Uint8Array;
}

export function naclScalarMult(n: Uint8Array, p: Uint8Array): Uint8Array {
  if (n.length !== crypto_scalarmult_SCALARBYTES) {
    throw new MuNaclError('bad n size');
  }
  if (p.length !== crypto_scalarmult_BYTES) {
    throw new MuNaclError('bad p size');
  }
  return crypto_scalarmult(new Uint8Array(crypto_scalarmult_BYTES), n, p);
}

export function naclScalarMultBase(n: Uint8Array): Uint8Array {
  return naclScalarMult(n, _9);
}

export function boxKeyPairFromSecretKey(secretKey: Uint8Array): BoxKeyPair {
  if (secretKey.length !== crypto_box_SECRETKEYBYTES) {
    throw new MuNaclError('bad secret key size');
  }
  return {
    publicKey: crypto_scalarmult_base(
      new Uint8Array(crypto_box_PUBLICKEYBYTES),
      secretKey,
    ),
    secretKey: new Uint8Array(secretKey),
  };
}