/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2015 - present Instructure, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

// https://github.com/facebook/fbjs/blob/master/packages/fbjs/src/core/shallowEqual.js
const hasOwnProperty = Object.prototype.hasOwnProperty

/**
 * ---
 * category: utilities/utils
 * ---
 * Performs equality by iterating through keys on an object and returning false
 * when any key has values which are not strictly equal between the arguments.
 *
 * @module shallowEqual
 *
 * @param {Object} objA
 * @param {Object} objB
 * @returns {Boolean} Returns true when the values of all keys are strictly equal
 */
function shallowEqual(objA: Record<string, any>, objB: Record<string, any>) {
  if (is(objA, objB)) {
    return true
  }

  if (
    typeof objA !== 'object' ||
    objA === null ||
    typeof objB !== 'object' ||
    objB === null
  ) {
    return false
  }

  const keysA = Object.keys(objA)
  const keysB = Object.keys(objB)

  if (keysA.length !== keysB.length) {
    return false
  }

  // Test for A's keys different from B.
  for (let i = 0; i < keysA.length; i++) {
    if (
      !hasOwnProperty.call(objB, keysA[i]) ||
      !is(objA[keysA[i]], objB[keysA[i]])
    ) {
      return false
    }
  }

  return true
}

/*
 * inlined Object.is polyfill to avoid requiring consumers ship their own
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
 */
function is(x: unknown, y: unknown) {
  // SameValue algorithm
  if (x === y) {
    // Steps 1-5, 7-10
    // Steps 6.b-6.e: +0 != -0
    return x !== 0 || y !== 0 || 1 / x === 1 / y
  } else {
    // Step 6.a: NaN == NaN
    return x !== x && y !== y
  }
}

export default shallowEqual
export { shallowEqual }