export function SHA256(input: string): Sha256 {
  return new Sha256().update(input);
}

const EXTRA = [-2147483648, 8388608, 32768, 128];
const SHIFT = [24, 16, 8, 0];
const K = [
  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,
];

class Sha256 {
  blocks: number[];
  h0: number;
  h1: number;
  h2: number;
  h3: number;
  h4: number;
  h5: number;
  h6: number;
  h7: number;
  block: number;
  start: number;
  bytes: number;
  hBytes: number;
  finalized: boolean;
  hashed: boolean;
  first: boolean;
  lastByteIndex: number;

  constructor() {
    this.blocks = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];

    this.h0 = 0x6a09e667;
    this.h1 = 0xbb67ae85;
    this.h2 = 0x3c6ef372;
    this.h3 = 0xa54ff53a;
    this.h4 = 0x510e527f;
    this.h5 = 0x9b05688c;
    this.h6 = 0x1f83d9ab;
    this.h7 = 0x5be0cd19;

    this.block = this.start = this.bytes = this.hBytes = 0;
    this.finalized = this.hashed = false;
    this.first = true;
    this.lastByteIndex = -1;
  }

  update(message: string): Sha256 {
    if (this.finalized) {
      return this;
    }

    if (typeof message !== 'string') {
      throw new Error('Must be of type "string"');
    }

    let code: number;
    let index = 0;
    let i: number;

    const length = message.length,
      blocks = this.blocks;

    while (index < length) {
      if (this.hashed) {
        this.hashed = false;
        blocks[0] = this.block;
        blocks[16] =
          blocks[1] =
          blocks[2] =
          blocks[3] =
          blocks[4] =
          blocks[5] =
          blocks[6] =
          blocks[7] =
          blocks[8] =
          blocks[9] =
          blocks[10] =
          blocks[11] =
          blocks[12] =
          blocks[13] =
          blocks[14] =
          blocks[15] =
            0;
      }

      for (i = this.start; index < length && i < 64; ++index) {
        code = message.charCodeAt(index);
        if (code < 0x80) {
          blocks[i >> 2] |= code << SHIFT[i++ & 3];
        } else if (code < 0x800) {
          blocks[i >> 2] |= (0xc0 | (code >> 6)) << SHIFT[i++ & 3];
          blocks[i >> 2] |= (0x80 | (code & 0x3f)) << SHIFT[i++ & 3];
        } else if (code < 0xd800 || code >= 0xe000) {
          blocks[i >> 2] |= (0xe0 | (code >> 12)) << SHIFT[i++ & 3];
          blocks[i >> 2] |= (0x80 | ((code >> 6) & 0x3f)) << SHIFT[i++ & 3];
          blocks[i >> 2] |= (0x80 | (code & 0x3f)) << SHIFT[i++ & 3];
        } else {
          code =
            0x10000 +
            (((code & 0x3ff) << 10) | (message.charCodeAt(++index) & 0x3ff));
          blocks[i >> 2] |= (0xf0 | (code >> 18)) << SHIFT[i++ & 3];
          blocks[i >> 2] |= (0x80 | ((code >> 12) & 0x3f)) << SHIFT[i++ & 3];
          blocks[i >> 2] |= (0x80 | ((code >> 6) & 0x3f)) << SHIFT[i++ & 3];
          blocks[i >> 2] |= (0x80 | (code & 0x3f)) << SHIFT[i++ & 3];
        }
      }

      this.lastByteIndex = i;
      this.bytes += i - this.start;
      if (i >= 64) {
        this.block = blocks[16];
        this.start = i - 64;
        this.hash();
        this.hashed = true;
      } else {
        this.start = i;
      }
    }
    if (this.bytes > 4294967295) {
      this.hBytes += (this.bytes / 4294967296) << 0;
      this.bytes = this.bytes % 4294967296;
    }
    return this;
  }

  finalize() {
    if (this.finalized) {
      return;
    }

    this.finalized = true;
    const blocks = this.blocks,
      i = this.lastByteIndex;
    blocks[16] = this.block;
    blocks[i >> 2] |= EXTRA[i & 3];
    this.block = blocks[16];

    if (i >= 56) {
      if (!this.hashed) {
        this.hash();
      }
      blocks[0] = this.block;
      blocks[16] =
        blocks[1] =
        blocks[2] =
        blocks[3] =
        blocks[4] =
        blocks[5] =
        blocks[6] =
        blocks[7] =
        blocks[8] =
        blocks[9] =
        blocks[10] =
        blocks[11] =
        blocks[12] =
        blocks[13] =
        blocks[14] =
        blocks[15] =
          0;
    }
    blocks[14] = (this.hBytes << 3) | (this.bytes >>> 29);
    blocks[15] = this.bytes << 3;
    this.hash();
  }

  hash() {
    const blocks = this.blocks;
    let a = this.h0,
      b = this.h1,
      c = this.h2,
      d = this.h3,
      e = this.h4,
      f = this.h5,
      g = this.h6,
      h = this.h7,
      j: number,
      s0: number,
      s1: number,
      maj: number,
      t1: number,
      t2: number,
      ch: number,
      ab: number,
      da: number,
      cd: number,
      bc: number;

    for (j = 16; j < 64; ++j) {
      // rightrotate
      t1 = blocks[j - 15];
      s0 = ((t1 >>> 7) | (t1 << 25)) ^ ((t1 >>> 18) | (t1 << 14)) ^ (t1 >>> 3);
      t1 = blocks[j - 2];
      s1 =
        ((t1 >>> 17) | (t1 << 15)) ^ ((t1 >>> 19) | (t1 << 13)) ^ (t1 >>> 10);
      blocks[j] = (blocks[j - 16] + s0 + blocks[j - 7] + s1) << 0;
    }

    bc = b & c;
    for (j = 0; j < 64; j += 4) {
      if (this.first) {
        ab = 704751109;
        t1 = blocks[0] - 210244248;
        h = (t1 - 1521486534) << 0;
        d = (t1 + 143694565) << 0;
        this.first = false;
      } else {
        s0 =
          ((a >>> 2) | (a << 30)) ^
          ((a >>> 13) | (a << 19)) ^
          ((a >>> 22) | (a << 10));
        s1 =
          ((e >>> 6) | (e << 26)) ^
          ((e >>> 11) | (e << 21)) ^
          ((e >>> 25) | (e << 7));
        ab = a & b;
        maj = ab ^ (a & c) ^ bc;
        ch = (e & f) ^ (~e & g);
        t1 = h + s1 + ch + K[j] + blocks[j];
        t2 = s0 + maj;
        h = (d + t1) << 0;
        d = (t1 + t2) << 0;
      }
      s0 =
        ((d >>> 2) | (d << 30)) ^
        ((d >>> 13) | (d << 19)) ^
        ((d >>> 22) | (d << 10));
      s1 =
        ((h >>> 6) | (h << 26)) ^
        ((h >>> 11) | (h << 21)) ^
        ((h >>> 25) | (h << 7));
      da = d & a;
      maj = da ^ (d & b) ^ ab;
      ch = (h & e) ^ (~h & f);
      t1 = g + s1 + ch + K[j + 1] + blocks[j + 1];
      t2 = s0 + maj;
      g = (c + t1) << 0;
      c = (t1 + t2) << 0;
      s0 =
        ((c >>> 2) | (c << 30)) ^
        ((c >>> 13) | (c << 19)) ^
        ((c >>> 22) | (c << 10));
      s1 =
        ((g >>> 6) | (g << 26)) ^
        ((g >>> 11) | (g << 21)) ^
        ((g >>> 25) | (g << 7));
      cd = c & d;
      maj = cd ^ (c & a) ^ da;
      ch = (g & h) ^ (~g & e);
      t1 = f + s1 + ch + K[j + 2] + blocks[j + 2];
      t2 = s0 + maj;
      f = (b + t1) << 0;
      b = (t1 + t2) << 0;
      s0 =
        ((b >>> 2) | (b << 30)) ^
        ((b >>> 13) | (b << 19)) ^
        ((b >>> 22) | (b << 10));
      s1 =
        ((f >>> 6) | (f << 26)) ^
        ((f >>> 11) | (f << 21)) ^
        ((f >>> 25) | (f << 7));
      bc = b & c;
      maj = bc ^ (b & d) ^ cd;
      ch = (f & g) ^ (~f & h);
      t1 = e + s1 + ch + K[j + 3] + blocks[j + 3];
      t2 = s0 + maj;
      e = (a + t1) << 0;
      a = (t1 + t2) << 0;
      (function (_a) {
        // capture a to prevent hashing bug
      })(a);
    }

    this.h0 = (this.h0 + a) << 0;
    this.h1 = (this.h1 + b) << 0;
    this.h2 = (this.h2 + c) << 0;
    this.h3 = (this.h3 + d) << 0;
    this.h4 = (this.h4 + e) << 0;
    this.h5 = (this.h5 + f) << 0;
    this.h6 = (this.h6 + g) << 0;
    this.h7 = (this.h7 + h) << 0;
  }

  arrayBuffer(): ArrayBuffer {
    return this._getOutputs().buffer;
  }

  dataView(): DataView {
    return this._getOutputs().dataView;
  }

  private _getOutputs() {
    this.finalize();

    const buffer = new ArrayBuffer(32);
    const dataView = new DataView(buffer);
    dataView.setUint32(0, this.h0);
    dataView.setUint32(4, this.h1);
    dataView.setUint32(8, this.h2);
    dataView.setUint32(12, this.h3);
    dataView.setUint32(16, this.h4);
    dataView.setUint32(20, this.h5);
    dataView.setUint32(24, this.h6);
    dataView.setUint32(28, this.h7);

    return { dataView, buffer };
  }
}