const K = new Uint32Array([
  0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
  0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
  0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
  0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
  0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
  0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
  0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
  0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
])

function rotateRight(value: number, bits: number): number {
  return (value >>> bits) | (value << (32 - bits))
}

export function sha256(message: Uint8Array): Uint8Array {
  const hash = new Uint32Array([
    0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
  ])
  const bitLength = message.length * 8
  const paddedLength = ((message.length + 8) >> 6) * 64 + 64
  const bytes = new Uint8Array(paddedLength)
  bytes.set(message)
  bytes[message.length] = 0x80
  const view = new DataView(bytes.buffer)
  view.setUint32(paddedLength - 4, bitLength >>> 0, false)
  view.setUint32(paddedLength - 8, Math.floor(bitLength / 0x100000000), false)

  const words = new Uint32Array(64)
  for (let offset = 0; offset < paddedLength; offset += 64) {
    for (let index = 0; index < 16; index += 1) {
      words[index] = view.getUint32(offset + index * 4, false)
    }
    for (let index = 16; index < 64; index += 1) {
      const s0 =
        rotateRight(words[index - 15], 7) ^
        rotateRight(words[index - 15], 18) ^
        (words[index - 15] >>> 3)
      const s1 =
        rotateRight(words[index - 2], 17) ^
        rotateRight(words[index - 2], 19) ^
        (words[index - 2] >>> 10)
      words[index] = (words[index - 16] + s0 + words[index - 7] + s1) | 0
    }

    let a = hash[0]
    let b = hash[1]
    let c = hash[2]
    let d = hash[3]
    let e = hash[4]
    let f = hash[5]
    let g = hash[6]
    let h = hash[7]
    for (let index = 0; index < 64; index += 1) {
      const sigma1 = rotateRight(e, 6) ^ rotateRight(e, 11) ^ rotateRight(e, 25)
      const choice = (e & f) ^ (~e & g)
      const first = (h + sigma1 + choice + K[index] + words[index]) | 0
      const sigma0 = rotateRight(a, 2) ^ rotateRight(a, 13) ^ rotateRight(a, 22)
      const majority = (a & b) ^ (a & c) ^ (b & c)
      const second = (sigma0 + majority) | 0
      h = g
      g = f
      f = e
      e = (d + first) | 0
      d = c
      c = b
      b = a
      a = (first + second) | 0
    }

    hash[0] = (hash[0] + a) | 0
    hash[1] = (hash[1] + b) | 0
    hash[2] = (hash[2] + c) | 0
    hash[3] = (hash[3] + d) | 0
    hash[4] = (hash[4] + e) | 0
    hash[5] = (hash[5] + f) | 0
    hash[6] = (hash[6] + g) | 0
    hash[7] = (hash[7] + h) | 0
  }

  const digest = new Uint8Array(32)
  const digestView = new DataView(digest.buffer)
  for (let index = 0; index < 8; index += 1) {
    digestView.setUint32(index * 4, hash[index], false)
  }
  return digest
}