/* eslint-disable no-restricted-properties */
type numType = number | string;
/**
 * @desc 解决浮动运算问题，避免小数点后产生多位数和计算精度损失。
 * 问题示例：2.3 + 2.4 = 4.699999999999999，1.0 - 0.9 = 0.09999999999999998
 */

/**
 * 把错误的数据转正
 * strip(0.09999999999999998)=0.1
 */
function strip(num: numType, precision = 15): number {
  return +parseFloat(Number(num).toPrecision(precision));
}

/**
 * Return digits length of a number
 * @param {*number} num Input number
 */
function digitLength(num: numType): number {
  // Get digit length of e
  const eSplit = num.toString().split(/[eE]/);
  const len = (eSplit[0].split('.')[1] || '').length - +(eSplit[1] || 0);
  return len > 0 ? len : 0;
}

/**
 * 把小数转成整数，支持科学计数法。如果是小数则放大成整数
 * @param {*number} num 输入数
 */
function float2Fixed(num: numType): number {
  if (num.toString().indexOf('e') === -1) {
    return Number(num.toString().replace('.', ''));
  }
  const dLen = digitLength(num);
  return dLen > 0 ? strip(Number(num) * Math.pow(10, dLen)) : Number(num);
}

/**
 * 迭代操作
 */
function iteratorOperation(arr: numType[], operation: (...args: numType[]) => number): number {
  const [num1, num2, ...others] = arr;
  let res = operation(num1, num2);

  others.forEach((num) => {
    res = operation(res, num);
  });

  return res;
}

/**
 * 精确乘法
 */
function times(...nums: numType[]): number {
  if (nums.length > 2) {
    return iteratorOperation(nums, times);
  }

  const [num1, num2] = nums;
  const num1Changed = float2Fixed(num1);
  const num2Changed = float2Fixed(num2);
  const baseNum = digitLength(num1) + digitLength(num2);
  const leftValue = num1Changed * num2Changed;

  checkBoundary(leftValue);

  return leftValue / Math.pow(10, baseNum);
}

/**
 * 精确加法
 */
function plus(...nums: numType[]): number {
  if (nums.length > 2) {
    return iteratorOperation(nums, plus);
  }

  const [num1, num2] = nums;
  // 取最大的小数位
  const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
  // 把小数都转为整数然后再计算
  return (times(num1, baseNum) + times(num2, baseNum)) / baseNum;
}

/**
 * 精确减法
 */
function minus(...nums: numType[]): number {
  if (nums.length > 2) {
    return iteratorOperation(nums, minus);
  }

  const [num1, num2] = nums;
  const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
  return (times(num1, baseNum) - times(num2, baseNum)) / baseNum;
}

/**
 * 精确除法
 */
function divide(...nums: numType[]): number {
  if (nums.length > 2) {
    return iteratorOperation(nums, divide);
  }

  const [num1, num2] = nums;
  const num1Changed = float2Fixed(num1);
  const num2Changed = float2Fixed(num2);
  checkBoundary(num1Changed);
  checkBoundary(num2Changed);
  // fix: 类似 10 ** -4 为 0.00009999999999999999，strip 修正
  return times(
    num1Changed / num2Changed,
    // eslint-disable-next-line no-restricted-properties
    strip(Math.pow(10, digitLength(num2) - digitLength(num1))),
  );
}

let _boundaryCheckingState = true;
/**
 * 是否进行边界检查，默认开启
 * @param flag 标记开关，true 为开启，false 为关闭，默认为 true
 */
function enableBoundaryChecking(flag = true) {
  _boundaryCheckingState = flag;
}

/**
 * 检测数字是否越界，如果越界给出提示
 * @param {*number} num 输入数
 */
function checkBoundary(num: number) {
  if (_boundaryCheckingState) {
    if (num > Number.MAX_SAFE_INTEGER || num < Number.MIN_SAFE_INTEGER) {
      console.warn(
        `${num} is beyond boundary when transfer to integer, the results may not be accurate`,
      );
    }
  }
}

export { strip, plus, minus, times, divide, digitLength, float2Fixed, enableBoundaryChecking };