/**
 * Copyright 2018-present Facebook.
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 * @format
 */

export function hash(str: string): string {
  const m = 0x5bd1e995
  const r = 24
  let h = str.length
  let length = str.length
  let currentIndex = 0

  while (length >= 4) {
    let k = UInt32(str, currentIndex)

    k = Umul32(k, m)
    k ^= k >>> r
    k = Umul32(k, m)

    h = Umul32(h, m)
    h ^= k

    currentIndex += 4
    length -= 4
  }

  switch (length) {
    case 3:
      h ^= UInt16(str, currentIndex)
      h ^= str.charCodeAt(currentIndex + 2) << 16
      h = Umul32(h, m)
      break

    case 2:
      h ^= UInt16(str, currentIndex)
      h = Umul32(h, m)
      break

    case 1:
      h ^= str.charCodeAt(currentIndex)
      h = Umul32(h, m)
      break
  }

  h ^= h >>> 13
  h = Umul32(h, m)
  h ^= h >>> 15

  return (h >>> 0).toString(36)
}

function UInt32(str: string, pos: number): number {
  return (
    str.charCodeAt(pos++) +
    (str.charCodeAt(pos++) << 8) +
    (str.charCodeAt(pos++) << 16) +
    (str.charCodeAt(pos) << 24)
  )
}

function UInt16(str: string, pos: number): number {
  return str.charCodeAt(pos++) + (str.charCodeAt(pos++) << 8)
}

function Umul32(n: number, m: number): number {
  n |= 0
  m |= 0
  const nlo = n & 0xffff
  const nhi = n >>> 16
  const res = (nlo * m + (((nhi * m) & 0xffff) << 16)) | 0
  return res
}