'use strict';

const { camelCase } = require('camel-case');

function getter(key) {
  return function() {
    return this[key];
  };
}

function setter(key) {
  return function(value) {
    this[key] = value;
  };
}

function toCamelCase(str) {
  let prefixLength = -1;

  while (str[++prefixLength] === '_');

  if (!prefixLength) {
    return camelCase(str);
  }
  return str.substring(0, prefixLength) + camelCase(str.substring(prefixLength));
}

function camelCaseKeys(obj) {
  if (typeof obj !== 'object') throw new TypeError('obj must be an object!');

  const keys = Object.keys(obj);
  const result = {};

  for (const oldKey of keys) {
    const newKey = toCamelCase(oldKey);

    result[newKey] = obj[oldKey];

    if (newKey !== oldKey) {
      Object.defineProperty(result, oldKey, {
        get: getter(newKey),
        set: setter(newKey),
        configurable: true,
        enumerable: true
      });
    }
  }

  return result;
}

module.exports = camelCaseKeys;