export 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
}

export 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
}

export 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
}

export 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;
}