export const bytes = function (value, type = -1, dot=2) {
  if (type == 1) {
    return asciiCompute(value, 1024, ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'], 1)
  } else if (type == -1) {
    return asciiCompute(value, 1024, ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'], dot)
  } else {
    return asciiCompute(value, 1024, ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'], 2)
  }
}

/*
* 一般数值格式化方法
* num: 需要格式化的值
* ascii:进制，比如数据为1024
* units：单位列表
* dot：保留的小数位，
* */
function asciiCompute (num, ascii, units, dot = 2) {
  if (isNaN(num) || num === null) {
    return num
  }
  const scientificNotationValue = formatScientificNotation(num, dot)
  if (!numberWithEConvent(scientificNotationValue)) {
    return scientificNotationValue
  }
  if (!num && num !== 0 && num !== '0') {
    return ''
  }
  num = Number(num)
  const SIGN = num > 0 ? 1 : -1
  num = Math.abs(num)
  let carry = 0
  if (num > 1) {
    const log = Math.log(num) / Math.log(ascii)
    carry = parseInt(log)
    num = num / Math.pow(ascii, carry)
  }
  if (Number.isInteger(num)) {
    return {
      value: num * SIGN,
      unit: units[carry]
    }
  } else {
    return{
      value: num.toFixed(dot) * SIGN,
      unit: units[carry]
    }
  }
}
/* 数字转换保留小数，数字很小时转为科学计数法, dot为保留几位小数 */
function formatScientificNotation (value, dot = 2) {
  if (isNaN(value) || value === null) {
    return value
  }
  let val = value ? parseFloat(Number(value).toFixed(dot)) : 0
  if (val === 0) {
    val = Number(value).toPrecision(dot + 1)
  }
  return val
}
function numberWithEConvent (num) {
  if (num) {
    if ((('' + num).indexOf('E') !== -1) || (('' + num).indexOf('e') !== -1)) {
      const regExp = /'^((\\d+.?\\d+)[Ee]{1}(\\d+))$', 'ig'/
      let result = regExp.exec(num)
      let resultValue = ''
      let power
      if (result != null) {
        resultValue = result[2]
        power = result[3]
        result = regExp.exec(num)
      }

      if (resultValue) {
        if (power) {
          const powVer = Math.pow(10, power)
          resultValue = resultValue * powVer
          return resultValue
        }
      }
    } else {
      return num
    }
  }
  if (isNaN(num) || num === null) {
    return num
  }
  return 0
}