import {
  EncryptionPayload,
  JsonRpcRequest,
  JsonRpcSuccess,
  JsonRpcFailure,
} from '@binance/w3w-types'

import {
  arrayToBuffer,
  hexToArray,
  arrayToHex,
  bufferToArray,
  concatArrays,
  utf8ToArray,
  arrayToUtf8,
  removeHexPrefix,
  convertArrayBufferToBuffer,
  convertBufferToArrayBuffer,
} from '../encoding'

import * as lib from './lib'

export function generateKey(length?: number): ArrayBuffer {
  const _length = (length || 256) / 8
  const bytes = lib.randomBytes(_length)
  const result = convertBufferToArrayBuffer(arrayToBuffer(bytes))

  return result
}

function verifyHmac(payload: EncryptionPayload, key: Uint8Array): boolean {
  const cipherText = hexToArray(payload.data)
  const iv = hexToArray(payload.iv)
  const hmac = hexToArray(payload.hmac)
  const hmacHex: string = arrayToHex(hmac, false)
  const unsigned = concatArrays(cipherText, iv)
  const chmac = lib.hmacSha256Sign(key, unsigned)
  const chmacHex: string = arrayToHex(chmac, false)

  if (removeHexPrefix(hmacHex) === removeHexPrefix(chmacHex)) {
    return true
  }

  return false
}

export function encrypt(
  data: JsonRpcRequest,
  key: ArrayBuffer,
  providedIv?: ArrayBuffer
): EncryptionPayload {
  const _key = bufferToArray(convertArrayBufferToBuffer(key))

  const ivArrayBuffer: ArrayBuffer = providedIv || generateKey(128)
  const iv = bufferToArray(convertArrayBufferToBuffer(ivArrayBuffer))
  const ivHex: string = arrayToHex(iv, false)

  const contentString: string = JSON.stringify(data)
  const content = utf8ToArray(contentString)

  const cipherText = lib.aesCbcEncrypt(iv, _key, content)
  const cipherTextHex: string = arrayToHex(cipherText, false)

  const unsigned = concatArrays(cipherText, iv)
  const hmac = lib.hmacSha256Sign(_key, unsigned)
  const hmacHex: string = arrayToHex(hmac, false)

  return {
    data: cipherTextHex,
    hmac: hmacHex,
    iv: ivHex,
  }
}

export function decrypt(
  payload: EncryptionPayload,
  key: ArrayBuffer
): JsonRpcRequest | JsonRpcSuccess | JsonRpcFailure | null {
  const _key = bufferToArray(convertArrayBufferToBuffer(key))

  if (!_key) {
    throw new Error('Missing key: required for decryption')
  }

  const verified: boolean = verifyHmac(payload, _key)
  if (!verified) {
    return null
  }

  const cipherText = hexToArray(payload.data)
  const iv = hexToArray(payload.iv)
  const buffer = lib.aesCbcDecrypt(iv, _key, cipherText)
  const utf8: string = arrayToUtf8(buffer)
  let data
  try {
    data = JSON.parse(utf8)
  } catch (error) {
    return null
  }

  return data
}