const UINT8_BLOCK = 16

const Sbox = Uint8Array.from([
  0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
  0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
  0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
  0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
  0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
  0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
  0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
  0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
  0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
  0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
  0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
  0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
  0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
  0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
  0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
  0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48
])

const CK = Uint32Array.from([
  0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269,
  0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
  0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249,
  0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
  0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229,
  0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
  0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209,
  0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279
])

const FK = Uint32Array.from([
  0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc
])

const Crypt = {
  /**
   * Converts a JS string to an UTF-8 uint8array.
   *
   * @static
   * @param {String} str 16-bit unicode string.
   * @return {Uint8Array} UTF-8 Uint8Array.
   * @memberof Crypt
   */
  stringToArrayBufferInUtf8 (str) {
    // always utf-8
    const encoder = new TextEncoder()
    return encoder.encode(str)
  },

  /**
   * Converts an UTF-8 uint8array to a JS string.
   *
   * @static
   * @param {Uint8Array} strBuffer UTF-8 Uint8Array.
   * @return {String} 16-bit unicode string.
   * @memberof Crypt
   */
  utf8ArrayBufferToString (strBuffer) {
    const decoder = new TextDecoder('utf-8')
    return decoder.decode(strBuffer)
  }
}

export default class SM4 {
  /**
   * Creates an instance of SM4.
   * @param {Object} config
   * @memberof SM4
   */
  constructor (config) {
    const keyBuffer = typeof config.key === 'string' ? Crypt.stringToArrayBufferInUtf8(config.key) : Uint8Array.from(config.key)
    if (keyBuffer.length !== 16) {
      throw new Error('key should be a 16 bytes string')
    }
    /**
     * key should be 16 bytes string
     * @member {Uint8Array} key
     */
    this.key = keyBuffer
    /**
     * iv also should be 16 bytes string
     * @member {Uint8Array} iv
     */
    let ivBuffer = new Uint8Array(0)
    if (config.iv !== undefined && config.iv !== null) {
      // need iv
      ivBuffer = Crypt.stringToArrayBufferInUtf8(config.iv)
      if (ivBuffer.length !== 16) {
        throw new Error('iv should be a 16 bytes string')
      }
    }
    this.iv = ivBuffer
    /**
     * sm4's encrypt mode
     * @member {Enum} mode
     */
    this.mode = 'ecb'
    if (['cbc', 'ecb'].includes(config.mode)) {
      // set encrypt mode. default is ecb
      this.mode = config.mode
    }
    /**
     * sm4's cipher data type
     * @member {Enum} outType
     */
    this.cipherType = 'uint8array'
    if (['uint8array', 'text'].includes(config.outType)) {
      // set data type. default is uint8array
      this.cipherType = config.outType
    }
    /**
     * sm4's encrypt round key array
     * @member {Uint32Array} encryptRoundKeys
     */
    this.encryptRoundKeys = new Uint32Array(32)
    // spawn 32 round keys
    this.spawnEncryptRoundKeys()

    /**
     * sm4's decrypt round key array
     * @member {Uint32Array} encryptRoundKeys
     */
    this.decryptRoundKeys = Uint32Array.from(this.encryptRoundKeys)
    this.decryptRoundKeys.reverse()
  }

  /**
   * general sm4 encrypt/decrypt algorithm for a 16 bytes block using roundKey
   *
   * @param {Uint32Array} blockData
   * @param {Uint32Array} roundKeys
   * @return {Uint32Array} return a 16 bytes cipher block
   * @memberof SM4
   */
  doBlockCrypt (blockData, roundKeys) {
    const xBlock = new Uint32Array(36)
    xBlock.set(blockData, 0)
    // loop to process 32 rounds crypt
    for (let i = 0; i < 32; i++) {
      xBlock[i + 4] = xBlock[i] ^ this.tTransform1(xBlock[i + 1] ^ xBlock[i + 2] ^ xBlock[i + 3] ^ roundKeys[i])
    }
    const yBlock = new Uint32Array(4)
    // reverse last 4 xBlock member
    yBlock[0] = xBlock[35]
    yBlock[1] = xBlock[34]
    yBlock[2] = xBlock[33]
    yBlock[3] = xBlock[32]
    return yBlock
  }

  /**
   * spawn round key array for encrypt. reverse this key array when decrypt.
   * every round key's length is 32 bytes.
   * there are 32 round keys.
   * @return {Uint32Array}
   * @memberof SM4
   */
  spawnEncryptRoundKeys () {
    // extract mk in key
    const mk = new Uint32Array(4)
    mk[0] = this.key[0] << 24 | this.key[1] << 16 | this.key[2] << 8 | this.key[3]
    mk[1] = this.key[4] << 24 | this.key[5] << 16 | this.key[6] << 8 | this.key[7]
    mk[2] = this.key[8] << 24 | this.key[9] << 16 | this.key[10] << 8 | this.key[11]
    mk[3] = this.key[12] << 24 | this.key[13] << 16 | this.key[14] << 8 | this.key[15]
    // calculate the K array
    const k = new Uint32Array(36)
    k[0] = mk[0] ^ FK[0]
    k[1] = mk[1] ^ FK[1]
    k[2] = mk[2] ^ FK[2]
    k[3] = mk[3] ^ FK[3]
    // loop to spawn 32 round keys
    for (let i = 0; i < 32; i++) {
      k[i + 4] = k[i] ^ this.tTransform2(k[i + 1] ^ k[i + 2] ^ k[i + 3] ^ CK[i])
      this.encryptRoundKeys[i] = k[i + 4]
    }
  }

  /**
   * left rotate x by y bits
   *
   * @param {*} x
   * @param {Number} y
   * @returns
   * @memberof SM4
   */
  rotateLeft (x, y) {
    return x << y | x >>> (32 - y)
  }

  /**
   * L transform function for encrypt
   *
   * @param {Uint32Number} b
   * @returns {Uint32Number}
   * @memberof SM4
   */
  linearTransform1 (b) {
    return b ^ this.rotateLeft(b, 2) ^ this.rotateLeft(b, 10) ^ this.rotateLeft(b, 18) ^ this.rotateLeft(b, 24)
  }

  /**
   * L' transform function for key expand
   *
   * @param {Uint32Number} b
   * @returns {Uint32Number}
   * @memberof SM4
   */
  linearTransform2 (b) {
    return b ^ this.rotateLeft(b, 13) ^ this.rotateLeft(b, 23)
  }

  /**
   * τ transform function
   *
   * @param {Uint32Number} a
   * @returns {Uint32Number}
   * @memberof SM4
   */
  tauTransform (a) {
    return Sbox[a >>> 24 & 0xff] << 24 | Sbox[a >>> 16 & 0xff] << 16 | Sbox[a >>> 8 & 0xff] << 8 | Sbox[a & 0xff]
  }

  /**
   * mix replacement T transform for encrypt
   *
   * @param {Uint32Number} z
   * @returns {Uint32Number}
   * @memberof SM4
   */
  tTransform1 (z) {
    const b = this.tauTransform(z)
    const c = this.linearTransform1(b)
    return c
  }

  /**
   * mix replacement T transform for key expand
   *
   * @param {Uint32Number} z
   * @returns {Uint32Number}
   * @memberof SM4
   */
  tTransform2 (z) {
    const b = this.tauTransform(z)
    const c = this.linearTransform2(b)
    return c
  }

  /**
   * padding the array length to multiple of BLOCK
   *
   * @param {ByteArray} originalBuffer
   * @returns {ByteArray}
   * @memberof SM4
   */
  padding (originalBuffer) {
    if (originalBuffer === null) {
      return null
    }
    const paddingLength = UINT8_BLOCK - originalBuffer.length % UINT8_BLOCK
    const paddedBuffer = new Uint8Array(originalBuffer.length + paddingLength)
    paddedBuffer.set(originalBuffer, 0)
    paddedBuffer.fill(paddingLength, originalBuffer.length)
    return paddedBuffer
  }

  /**
   * depadding the byte array to its original length
   *
   * @param {ByteArray} paddedBuffer
   * @returns {ByteArray}
   * @memberof SM4
   */
  dePadding (paddedBuffer) {
    if (paddedBuffer === null) {
      return null
    }
    const paddingLength = paddedBuffer[paddedBuffer.length - 1]
    const originalBuffer = paddedBuffer.slice(0, paddedBuffer.length - paddingLength)
    return originalBuffer
  }

  /**
   * exctract uint32 array block from uint8 array
   *
   * @param {Uint8Array} uint8Array
   * @param {Number} baseIndex
   * @returns {Uint32Array}
   * @memberof SM4
   */
  uint8ToUint32Block (uint8Array, baseIndex = 0) {
    const block = new Uint32Array(4)// make Uint8Array to Uint32Array block
    block[0] = uint8Array[baseIndex] << 24 | uint8Array[baseIndex + 1] << 16 | uint8Array[baseIndex + 2] << 8 | uint8Array[baseIndex + 3]
    block[1] = uint8Array[baseIndex + 4] << 24 | uint8Array[baseIndex + 5] << 16 | uint8Array[baseIndex + 6] << 8 | uint8Array[baseIndex + 7]
    block[2] = uint8Array[baseIndex + 8] << 24 | uint8Array[baseIndex + 9] << 16 | uint8Array[baseIndex + 10] << 8 | uint8Array[baseIndex + 11]
    block[3] = uint8Array[baseIndex + 12] << 24 | uint8Array[baseIndex + 13] << 16 | uint8Array[baseIndex + 14] << 8 | uint8Array[baseIndex + 15]
    return block
  }

  /**
   * encrypt the string plaintext
   *
   * @param {String} plaintext
   * @memberof SM4
   * @return {Unit8Array|String} cipherByteArray
   */
  encrypt (plaintext) {
    const plainByteArray = Crypt.stringToArrayBufferInUtf8(plaintext)
    const padded = this.padding(plainByteArray)
    const blockTimes = padded.length / UINT8_BLOCK
    const outArray = new Uint8Array(padded.length)
    if (this.mode === 'cbc') {
      // CBC mode
      if (this.iv === null || this.iv.length !== 16) {
        throw new Error('iv error')
      }
      // init chain with iv (transform to uint32 block)
      let chainBlock = this.uint8ToUint32Block(this.iv)
      for (let i = 0; i < blockTimes; i++) {
        // extract the 16 bytes block data for this round to encrypt
        const roundIndex = i * UINT8_BLOCK
        const block = this.uint8ToUint32Block(padded, roundIndex)
        // xor the chain block
        chainBlock[0] = chainBlock[0] ^ block[0]
        chainBlock[1] = chainBlock[1] ^ block[1]
        chainBlock[2] = chainBlock[2] ^ block[2]
        chainBlock[3] = chainBlock[3] ^ block[3]
        // use chain block to crypt
        const cipherBlock = this.doBlockCrypt(chainBlock, this.encryptRoundKeys)
        // make the cipher block be part of next chain block
        chainBlock = cipherBlock
        for (let l = 0; l < UINT8_BLOCK; l++) {
          outArray[roundIndex + l] = cipherBlock[parseInt(l / 4)] >> ((3 - l) % 4 * 8) & 0xff
        }
      }
    } else {
      // this will be ECB mode
      for (let i = 0; i < blockTimes; i++) {
        // extract the 16 bytes block data for this round to encrypt
        const roundIndex = i * UINT8_BLOCK
        const block = this.uint8ToUint32Block(padded, roundIndex)
        const cipherBlock = this.doBlockCrypt(block, this.encryptRoundKeys)
        for (let l = 0; l < UINT8_BLOCK; l++) {
          outArray[roundIndex + l] = cipherBlock[parseInt(l / 4)] >> ((3 - l) % 4 * 8) & 0xff
        }
      }
    }

    if (this.cipherType === 'text') {
      return Crypt.utf8ArrayBufferToString(outArray)
    }
    return outArray
  }

  /**
   * decrypt the Unit8Array cipherByteArray
   *
   * @param {String|Unit8Array} cipherByteArray
   * @memberof SM4
   */
  decrypt (cipherObj) {
    let cipherByteArray
    if (typeof cipherObj === 'string') {
      cipherByteArray = Crypt.stringToArrayBufferInUtf8(cipherObj)
    } else {
      cipherByteArray = cipherObj
    }
    const blockTimes = cipherByteArray.length / UINT8_BLOCK
    const outArray = new Uint8Array(cipherByteArray.length)
    // decrypt the cipherByteArray by block
    if (this.mode === 'cbc') {
      // todo CBC mode
      if (this.iv === null || this.iv.length !== 16) {
        throw new Error('iv error')
      }
      // init chain with iv (transform to uint32 block)
      let chainBlock = this.uint8ToUint32Block(this.iv)
      for (let i = 0; i < blockTimes; i++) {
        // extract the 16 bytes block data for this round to encrypt
        const roundIndex = i * UINT8_BLOCK
        // make Uint8Array to Uint32Array block
        const block = this.uint8ToUint32Block(cipherByteArray, roundIndex)
        // reverse the round keys to decrypt
        const plainBlockBeforeXor = this.doBlockCrypt(block, this.decryptRoundKeys)
        // xor the chain block
        const plainBlock = new Uint32Array(4)
        plainBlock[0] = chainBlock[0] ^ plainBlockBeforeXor[0]
        plainBlock[1] = chainBlock[1] ^ plainBlockBeforeXor[1]
        plainBlock[2] = chainBlock[2] ^ plainBlockBeforeXor[2]
        plainBlock[3] = chainBlock[3] ^ plainBlockBeforeXor[3]
        // make the cipher block be part of next chain block
        chainBlock = block
        for (let l = 0; l < UINT8_BLOCK; l++) {
          outArray[roundIndex + l] = plainBlock[parseInt(l / 4)] >> ((3 - l) % 4 * 8) & 0xff
        }
      }
    } else {
      // ECB mode
      for (let i = 0; i < blockTimes; i++) {
        // extract the 16 bytes block data for this round to encrypt
        const roundIndex = i * UINT8_BLOCK
        // make Uint8Array to Uint32Array block
        const block = this.uint8ToUint32Block(cipherByteArray, roundIndex)
        // reverse the round keys to decrypt
        const plainBlock = this.doBlockCrypt(block, this.decryptRoundKeys)
        for (let l = 0; l < UINT8_BLOCK; l++) {
          outArray[roundIndex + l] = plainBlock[parseInt(l / 4)] >> ((3 - l) % 4 * 8) & 0xff
        }
      }
    }
    // depadding the decrypted data
    const depaddedPlaintext = this.dePadding(outArray)
    // transform data to utf8 string
    return Crypt.utf8ArrayBufferToString(depaddedPlaintext)
  }
}