var collectionCompare = compare;

/*
  primitives: value1 === value2
  functions: value1.toString == value2.toString
  arrays: if length, sequence and values of properties are identical
  objects: if length, names and values of properties are identical
  compare([[1, [2, 3]], [[1, [2, 3]]); // true
  compare([[1, [2, 3], 4], [[1, [2, 3]]); // false
  compare({a: 2, b: 3}, {a: 2, b: 3}); // true
  compare({a: 2, b: 3}, {b: 3, a: 2}); // true
  compare({a: 2, b: 3, c: 4}, {a: 2, b: 3}); // false
  compare({a: 2, b: 3}, {a: 2, b: 3, c: 4}); // false
  compare([[1, [2, {a: 4}], 4], [[1, [2, {a: 4}]]); // true
*/

function compare(value1, value2) {
  if (value1 === value2) {
    return true;
  }
  /* eslint-disable no-self-compare */
  // if both values are NaNs return true
  if (value1 !== value1 && value2 !== value2) {
    return true;
  }
  if ({}.toString.call(value1) != {}.toString.call(value2)) {
    return false;
  }
  if (value1 !== Object(value1)) {
    // non equal primitives
    return false;
  }
  if (!value1) {
    return false;
  }
  if (Array.isArray(value1)) {
    return compareArrays(value1, value2);
  }
  if ({}.toString.call(value1) == '[object Set]') {
    return compareArrays(Array.from(value1), Array.from(value2));
  }
  if ({}.toString.call(value1) == '[object Object]') {
    return compareObjects(value1, value2);
  } else {
    return compareNativeSubtypes(value1, value2);
  }
}

function compareNativeSubtypes(value1, value2) {
  // e.g. Function, RegExp, Date
  return value1.toString() === value2.toString();
}

function compareArrays(value1, value2) {
  var len = value1.length;
  if (len != value2.length) {
    return false;
  }
  var alike = true;
  for (var i = 0; i < len; i++) {
    if (!compare(value1[i], value2[i])) {
      alike = false;
      break;
    }
  }
  return alike;
}

function compareObjects(value1, value2) {
  var keys1 = Object.keys(value1).sort();
  var keys2 = Object.keys(value2).sort();
  var len = keys1.length;
  if (len != keys2.length) {
    return false;
  }
  for (var i = 0; i < len; i++) {
    var key1 = keys1[i];
    var key2 = keys2[i];
    if (!(key1 == key2 && compare(value1[key1], value2[key2]))) {
      return false;
    }
  }
  return true;
}

export {collectionCompare as default};