function accAdd(num1, num2) { // 加法
  num1 = Number(num1)
  num2 = Number(num2)
  let dec1, dec2
  try { dec1 = countDecimals(num1) + 1 } catch (e) { dec1 = 0 }
  try { dec2 = countDecimals(num2) + 1 } catch (e) { dec2 = 0 }
  const times = Math.pow(10, Math.max(dec1, dec2))
  // let result = (num1 * times + num2 * times) / times
  const result = (accMul(num1, times) + accMul(num2, times)) / times
  return getCorrectResult('add', num1, num2, result)
  // return result
}

function accSub(num1, num2) { // 减法
  num1 = Number(num1)
  num2 = Number(num2)
  let dec1, dec2
  try { dec1 = countDecimals(num1) + 1 } catch (e) { dec1 = 0 }
  try { dec2 = countDecimals(num2) + 1 } catch (e) { dec2 = 0 }
  const times = Math.pow(10, Math.max(dec1, dec2))
  // let result = Number(((num1 * times - num2 * times) / times)
  const result = Number((accMul(num1, times) - accMul(num2, times)) / times)
  return getCorrectResult('sub', num1, num2, result)
  // return result
}

function accDiv(num1, num2) { // 除法
  num1 = Number(num1)
  num2 = Number(num2)
  let t1 = 0
  let t2 = 0
  try { t1 = countDecimals(num1) } catch (e) { console.log(e) }
  try { t2 = countDecimals(num2) } catch (e) { console.log(e) }
  const dec1 = convertToInt(num1)
  const dec2 = convertToInt(num2)
  const result = accMul((dec1 / dec2), Math.pow(10, t2 - t1))
  return getCorrectResult('div', num1, num2, result)
  // return result
}

function accMul(num1, num2) { // 乘法
  num1 = Number(num1)
  num2 = Number(num2)
  let times = 0
  const s1 = num1.toString()
  const s2 = num2.toString()
  try { times += countDecimals(s1) } catch (e) { console.log(e) }
  try { times += countDecimals(s2) } catch (e) { console.log(e) }
  const result = convertToInt(s1) * convertToInt(s2) / Math.pow(10, times)
  return getCorrectResult('mul', num1, num2, result)
  // return result
}

function countDecimals(num) {
  var len = 0
  try {
    num = Number(num)
    let str = num.toString().toUpperCase()
    if (str.split('E').length === 2) { // scientific notation
      let isDecimal = false
      if (str.split('.').length === 2) {
        str = str.split('.')[1]
        if (parseInt(str.split('E')[0]) !== 0) {
          isDecimal = true
        }
      }
      const x = str.split('E')
      if (isDecimal) {
        len = x[0].length
      }
      len -= parseInt(x[1])
    } else if (str.split('.').length === 2) { // decimal
      if (parseInt(str.split('.')[1]) !== 0) {
        len = str.split('.')[1].length
      }
    }
  } catch (e) {
    throw e
  } finally {
    if (isNaN(len) || len < 0) {
      len = 0
    }
    // return len
  }
  return len
}

function convertToInt(num) {
  num = Number(num)
  let newNum = num
  const times = countDecimals(num)
  const temp_num = num.toString().toUpperCase()
  if (temp_num.split('E').length === 2) {
    newNum = Math.round(num * Math.pow(10, times))
  } else {
    newNum = Number(temp_num.replace('.', ''))
  }
  return newNum
}

function getCorrectResult(type, num1, num2, result) {
  let temp_result = 0
  switch (type) {
    case 'add':
      temp_result = num1 + num2
      break
    case 'sub':
      temp_result = num1 - num2
      break
    case 'div':
      temp_result = num1 / num2
      break
    case 'mul':
      temp_result = num1 * num2
      break
  }
  if (Math.abs(result - temp_result) > 1) {
    return temp_result
  }
  return result
}

function checkWeight(input) {
  return input.replace(/[^\d]/gi, '')
}

function showWeight(input) {
  return accDiv(input, 1000).toFixed(3)
}

function checkSumWeight(input) {
  return input.replace(/[^\d.]/gi, '')
}

module.exports = {
  accAdd: accAdd,
  accSub: accSub,
  accDiv: accDiv,
  accMul: accMul,
  checkWeight: checkWeight,
  checkSumWeight: checkSumWeight,
  convertToInt: convertToInt,
  showWeight: showWeight
}