/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

// A pure JS implementation of a string hashing function. We do not use it for
// security or obfuscation purposes, only to create compact hashes. So we
// prioritize speed over collision avoidance. For example, we use this to hash
// the component key path used by useFormState for MPA-style submissions.
//
// In environments where built-in hashing functions are available, we prefer
// those instead. Like Node's crypto module, or Bun.hash. Unfortunately this
// does not include the web standard crypto API because those methods are all
// async. For our purposes, we need it to be sync because the cost of context
// switching is too high to be worth it.
//
// The most popular hashing algorithm that meets these requirements in the JS
// ecosystem is MurmurHash3, and almost all implementations I could find used
// some version of the implementation by Gary Court inlined below.

export function createFastHashJS(key: string): number {
  return murmurhash3_32_gc(key, 0);
}

/* eslint-disable prefer-const, no-fallthrough */

/**
 * @license
 *
 * JS Implementation of MurmurHash3 (r136) (as of May 20, 2011)
 *
 * Copyright (c) 2011 Gary Court
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

function murmurhash3_32_gc(key: string, seed: number): number {
  let remainder, bytes, h1, h1b, c1, c2, k1, i;

  remainder = key.length & 3; // key.length % 4
  bytes = key.length - remainder;
  h1 = seed;
  c1 = 0xcc9e2d51;
  c2 = 0x1b873593;
  i = 0;

  while (i < bytes) {
    k1 =
      (key.charCodeAt(i) & 0xff) |
      ((key.charCodeAt(++i) & 0xff) << 8) |
      ((key.charCodeAt(++i) & 0xff) << 16) |
      ((key.charCodeAt(++i) & 0xff) << 24);
    ++i;

    k1 =
      ((k1 & 0xffff) * c1 + ((((k1 >>> 16) * c1) & 0xffff) << 16)) & 0xffffffff;
    k1 = (k1 << 15) | (k1 >>> 17);
    k1 =
      ((k1 & 0xffff) * c2 + ((((k1 >>> 16) * c2) & 0xffff) << 16)) & 0xffffffff;

    h1 ^= k1;
    h1 = (h1 << 13) | (h1 >>> 19);
    h1b =
      ((h1 & 0xffff) * 5 + ((((h1 >>> 16) * 5) & 0xffff) << 16)) & 0xffffffff;
    h1 = (h1b & 0xffff) + 0x6b64 + ((((h1b >>> 16) + 0xe654) & 0xffff) << 16);
  }

  k1 = 0;

  switch (remainder) {
    case 3:
      k1 ^= (key.charCodeAt(i + 2) & 0xff) << 16;
    case 2:
      k1 ^= (key.charCodeAt(i + 1) & 0xff) << 8;
    case 1:
      k1 ^= key.charCodeAt(i) & 0xff;

      k1 =
        ((k1 & 0xffff) * c1 + ((((k1 >>> 16) * c1) & 0xffff) << 16)) &
        0xffffffff;
      k1 = (k1 << 15) | (k1 >>> 17);
      k1 =
        ((k1 & 0xffff) * c2 + ((((k1 >>> 16) * c2) & 0xffff) << 16)) &
        0xffffffff;
      h1 ^= k1;
  }

  h1 ^= key.length;

  h1 ^= h1 >>> 16;
  h1 =
    ((h1 & 0xffff) * 0x85ebca6b +
      ((((h1 >>> 16) * 0x85ebca6b) & 0xffff) << 16)) &
    0xffffffff;
  h1 ^= h1 >>> 13;
  h1 =
    ((h1 & 0xffff) * 0xc2b2ae35 +
      ((((h1 >>> 16) * 0xc2b2ae35) & 0xffff) << 16)) &
    0xffffffff;
  h1 ^= h1 >>> 16;

  return h1 >>> 0;
}
