// const key = 'karakal@123Qcomyidongtiantianhaoting'
const DELTA = 2654435769n
const MIN_LENGTH = 32
// const SPECIAL_CHAR = '0'
const keyArr = [
  27303562373562475n,
  18014862372307051n,
  22799692160172081n,
  34058940340699235n,
  30962724186095721n,
  27303523720101991n,
  27303523720101998n,
  31244139033526382n,
  28992395054481524n,
]


const teaDecrypt = (data: bigint[], key: bigint[]): bigint[] => {
  const length = data.length
  const lengthBitint = BigInt(length)
  if (length >= 1) {
    // let j = data[data.length - 1];
    let j2 = data[0]
    let j3 = toLong((6n + (52n / lengthBitint)) * DELTA)
    while (true) {
      let j4 = j3
      if (j4 == 0n) break
      let j5 = toLong(3n & toLong(j4 >> 2n))
      let j6 = lengthBitint
      while (true) {
        j6--
        if (j6 > 0n) {
          let j7 = data[(j6 - 1n) as unknown as number]
          let i = j6 as unknown as number
          j2 = toLong(data[i] - (toLong(toLong(j2 ^ j4) + toLong(j7 ^ key[toLong(toLong(3n & j6) ^ j5) as unknown as number])) ^ toLong(toLong(toLong(j7 >> 5n) ^ toLong(j2 << 2n)) + toLong(toLong(j2 >> 3n) ^ toLong(j7 << 4n)))))
          data[i] = j2
        } else break
      }
      let j8 = data[lengthBitint - 1n as unknown as number]
      j2 = toLong(data[0n as unknown as number] - toLong(toLong(toLong(key[toLong(toLong(j6 & 3n) ^ j5) as unknown as number] ^ j8) + toLong(j2 ^ j4)) ^ toLong(toLong(toLong(j8 >> 5n) ^ toLong(j2 << 2n)) + toLong(toLong(j2 >> 3n) ^ toLong(j8 << 4n)))))
      data[0] = j2
      j3 = toLong(j4 - DELTA)
    }
  }
  return data
}

const longArrToString = (data: bigint[]): string => {
  const arrayList: string[] = []
  for (const j of data) arrayList.push(longToBytes(j).toString('utf16le'))
  return arrayList.join('')
}

// https://stackoverflow.com/a/29132118
const longToBytes = (l: bigint): Buffer => {
  const result = Buffer.alloc(8)
  for (let i = 0; i < 8; i++) {
    result[i] = parseInt((l & 0xFFn) as unknown as string)
    l >>= 8n
  }
  return result
}


const toBigintArray = (data: string): bigint[] => {
  const length = Math.floor(data.length / 16)
  const jArr: bigint[] = Array(length)
  for (let i = 0; i < length; i++) {
    jArr[i] = toLong(data.substring(i * 16, (i * 16) + 16))
  }
  return jArr
}

// 基于社区通用的 mrc 逐字歌词解析思路
const MAX = 9223372036854775807n
const MIN = -9223372036854775808n
const toLong = (str: string | bigint): bigint => {
  const num = typeof str == 'string' ? BigInt('0x' + str) : str
  if (num > MAX) return toLong(num - (1n << 64n))
  else if (num < MIN) return toLong(num + (1n << 64n))
  return num
}

export const decrypt = (data: string | null): string | null => {
  // console.log(data.length)
  // -3551594764563790630
  // console.log(toLongArrayFromArr(Buffer.from(key)))
  // console.log(teaDecrypt(toBigintArray(data), keyArr))
  // console.log(longArrToString(teaDecrypt(toBigintArray(data), keyArr)))
  // console.log(toByteArray(teaDecrypt(toBigintArray(data), keyArr)))
  return (data == null || data.length < MIN_LENGTH)
    ? data
    : longArrToString(teaDecrypt(toBigintArray(data), keyArr))
}

// console.log(14895149309145760986n - )
// console.log(toLong('14895149309145760986'))
// console.log(decrypt(str))
// console.log(decrypt(str))
// console.log(toByteArray([6048138644744000495n]))
// console.log(toByteArray([16325999628386395n]))
// console.log(toLong(90994076459972177136n))