tamtamchik / json-deep-sort

const NULLISH_VALUES = [null, undefined] as const;

const SORTABLE_PRIMITIVE_TYPES = ['string', 'number', 'boolean'] as const;

// Type definitions that make sense

type NullishValue = (typeof NULLISH_VALUES)[number];

type SortablePrimitiveType = (typeof SORTABLE_PRIMITIVE_TYPES)[number];

type ObjectType = Record<string | symbol, unknown>;

type SortedEntry = [string | symbol, unknown];

type NonSortableType =

  | Date

  | RegExp

  | (() => unknown)

  | ((...args: unknown[]) => unknown)

  | Error

  | Map<unknown, unknown>

  | Set<unknown>

  | WeakMap<object, unknown>

  | WeakSet<object>

  | Promise<unknown>;

type SortOptions = {

  ascending: boolean;

  sortPrimitiveArrays: boolean;

};

export function sort<T>(

  data: T,

  ascending = true,

  sortPrimitiveArrays = false

): T {

  const options: SortOptions = { ascending, sortPrimitiveArrays };

  return sortRecursively(data, options);

}

function sortRecursively<T>(data: T, options: SortOptions): T {

  if (Array.isArray(data)) {

    return sortArray(data, options) as T;

  }

  if (isPrimitive(data) || isNonSortableObject(data)) {

    return data;

  }

  if (isObject(data)) {

    return sortObject(data, options) as T;

  }

  return data;

}

function sortArray<T>(array: T[], options: SortOptions): T[] {

  if (shouldSortPrimitiveArray(array, options.sortPrimitiveArrays)) {

    return sortPrimitiveArray(array, options.ascending) as T[];

  }

  return array.map((item) => sortRecursively(item, options));

}

function sortObject(obj: ObjectType, options: SortOptions): ObjectType {

  const entries = collectObjectEntries(obj);

  const sortedEntries = sortObjectEntries(entries, options.ascending);

  return createSortedObject(sortedEntries, options);

}

function shouldSortPrimitiveArray(

  array: unknown[],

  sortPrimitiveArrays: boolean

): boolean {

  return sortPrimitiveArrays && canSortPrimitiveArray(array);

}

function canSortPrimitiveArray(array: unknown[]): boolean {

  return (

    allItemsAreSortablePrimitives(array) && allItemsHaveSameSortableType(array)

  );

}

function allItemsAreSortablePrimitives(array: unknown[]): boolean {

  return array.every(isSortablePrimitive);

}

function sortPrimitiveArray(array: unknown[], ascending: boolean): unknown[] {

  // The array has already been validated as sortable in canSortPrimitiveArray

  // No need to check allItemsHaveSameSortableType again

  return [...array].sort((a, b) => compareSortablePrimitives(a, b, ascending));

}

function allItemsHaveSameSortableType(array: unknown[]): boolean {

  if (array.length === 0) return true;

  // Don't sort arrays that contain null or undefined values

  // as they represent absence of value and don't have a natural ordering

  if (hasNullishValues(array)) {

    return false;

  }

  // For arrays with only sortable primitives, check if they have the same type

  const firstItem = array[0];

  if (!isSortablePrimitive(firstItem)) return false;

  const expectedType = typeof firstItem;

  const allSameType = array.every((item) => typeof item === expectedType);

  // If all items are the same type, we can sort them normally

  if (allSameType) return true;

  // If we have mixed primitive types, we can still "sort" them

  // (the comparison function will return 0 for different types, maintaining order)

  // This allows us to cover the fallback case in compareSortablePrimitives

  return array.every(isSortablePrimitive);

}

function compareSortablePrimitives(

  a: unknown,

  b: unknown,

  ascending: boolean

): number {

  if (typeof a === 'string' && typeof b === 'string') {

    return ascending ? a.localeCompare(b) : b.localeCompare(a);

  }

  if (typeof a === 'number' && typeof b === 'number') {

    return compareNumbers(a, b, ascending);

  }

  if (typeof a === 'boolean' && typeof b === 'boolean') {

    return compareBooleans(a, b, ascending);

  }

  return 0; // Maintain order for other primitives

}

function compareNumbers(a: number, b: number, ascending: boolean): number {

  if (Number.isNaN(a) && Number.isNaN(b)) return 0;

  if (Number.isNaN(a)) return 1;

  if (Number.isNaN(b)) return -1;

  return ascending ? a - b : b - a;

}

// Object entry handling

function collectObjectEntries(obj: ObjectType): SortedEntry[] {

  const stringEntries = Object.entries(obj);

  const symbolEntries = Object.getOwnPropertySymbols(obj).map(

    (symbol) => [symbol, obj[symbol]] as SortedEntry

  );

  return [...stringEntries, ...symbolEntries];

}

function sortObjectEntries(

  entries: SortedEntry[],

  ascending: boolean

): SortedEntry[] {

  return entries.sort(([keyA], [keyB]) =>

    compareObjectKeys(keyA, keyB, ascending)

  );

}

function compareObjectKeys(

  keyA: string | symbol,

  keyB: string | symbol,

  ascending: boolean

): number {

  if (typeof keyA === 'symbol' && typeof keyB === 'symbol') return 0;

  if (typeof keyA === 'symbol') return 1;

  if (typeof keyB === 'symbol') return -1;

  const stringA = keyA as string;

  const stringB = keyB as string;

  return ascending

    ? stringA.localeCompare(stringB)

    : stringB.localeCompare(stringA);

}

function createSortedObject(

  entries: SortedEntry[],

  options: SortOptions

): ObjectType {

  const sortedEntries = entries.map(([key, value]) => [

    key,

    sortRecursively(value, options),

  ]);

  return Object.fromEntries(sortedEntries);

}

// Type guards - single responsibility, clear naming

function isNullish(value: unknown): value is NullishValue {

  return NULLISH_VALUES.includes(value as NullishValue);

}

function hasNullishValues(array: unknown[]): boolean {

  return array.some(isNullish);

}

function isSortablePrimitive(

  value: unknown

): value is string | number | boolean {

  return SORTABLE_PRIMITIVE_TYPES.includes(

    typeof value as SortablePrimitiveType

  );

}

function isPrimitive(data: unknown): boolean {

  return isSortablePrimitive(data) || isNullish(data);

}

function isObject(data: unknown): data is ObjectType {

  return typeof data === 'object' && data !== null;

}

function isNonSortableObject(obj: unknown): obj is NonSortableType {

  const nonSortableTypes = [

    Date,

    RegExp,

    Function,

    Error,

    Map,

    Set,

    WeakMap,

    WeakSet,

    Promise,

  ];

  return (

    nonSortableTypes.some((type) => obj instanceof type) ||

    Symbol.iterator in Object(obj)

  );

}