GCTC-NTGC / TalentCloud

 * Shortcut function that returns the id attribute of an object.

 * @param item

 */

export function getId<T extends { id: number }>(item: T): number {

  return item.id;

}

export function identity<T>(value: T): T {

  return value;

}

/**

 * Returns true if value is not null or undefined.

 * Can be used to filter nulls and undefined values out of an array.

 * @param item

 */

export function notEmpty<T>(value: T | null | undefined): value is T {

  return value !== null && value !== undefined;

}

export function stringNotEmpty(value: string | null): value is string {

  return notEmpty(value) && value.length > 0;

}

/**

 * Returns true if value id null OR undefined.

 * @param item

 */

export function empty<T>(

  value: T | null | undefined,

): value is null | undefined {

  return value === null || value === undefined;

}

/**

 * From an array of objects, return the first object with a specific id value.

 * @param objs

 * @param id

 */

export function find<T extends { id: number }>(

  objs: T[],

  id: number,

): T | null {

  const found = objs.filter((item) => item.id === id);

  return found.length > 0 ? found[0] : null;

}

/**

 * Return all objects from array with the specified key-value attribute.

 * @param objs

 * @param prop

 * @param value

 */

export function where<T, K extends keyof T>(

  objs: T[],

  prop: K,

  value: any,

): T[] {

  return objs.filter((obj) => prop in obj && obj[prop] === value);

}

/**

 * Return first object from array with the specified key-value attribute.

 * @param objs

 * @param prop

 * @param value

 */

export function whereFirst<T, K extends keyof T>(

  objs: T[],

  prop: K,

  value: any,

): T {

  return where(objs, prop, value)[0];

}

/**

 * Map each key-value attribute of an object into an array

 * @param object

 * @param mapFn

 */

export function objectMap<A, B>(

  object: {

    [key: string]: A;

  },

  mapFn: (key: string, value: A) => B,

): B[] {

  return Object.keys(object).reduce((result: B[], key: string): B[] => {

    result.push(mapFn(key, object[key]));

    return result;

  }, []);

}

/**

 * Return a copy of an object, with each value being passed through a map function.

 * Each value's key is unaffected.

 * @param object

 * @param mapFn

 */

export function mapObjectValues<A, B>(

  object: IndexedObject<A>,

  mapFn: (value: A) => B,

): IndexedObject<B> {

  return Object.entries(object).reduce(

    (result: IndexedObject<B>, [key, value]) => {

      result[key] = mapFn(value);

      return result;

    },

    {},

  );

}

type IndexedObject<T> = {

  [key: string]: T;

};

/**

 * Maps an array of items into an object, with each transformed into an attribute

 * @param items array of objects

 * @param keyFn Function that returns a unique key for each object. Typically the getId function.

 * @param valFn Function that returns a new value for each object.

 */

export function mapToObjectTrans<A, B>(

  items: A[],

  keyFn: (item: A) => string | number,

  valFn: (item: A) => B,

): IndexedObject<B> {

  return items.reduce((result: IndexedObject<B>, item: A): IndexedObject<B> => {

    const key = keyFn(item);

    result[key] = valFn(item);

    return result;

  }, {});

}

/**

 * Maps an array of items into an object, with each item set as an attribute.

 * @param items array of objects

 * @param keyFn Function that returns a unique key for each object. Typically the getId function.

 */

export function mapToObject<T>(

  items: T[],

  keyFn: (item: T) => string | number,

): IndexedObject<T> {

  return mapToObjectTrans(items, keyFn, (item): T => item);

}

/**

 * Checks if an object has an attribute with a particular key

 * @param object

 * @param key

 */

export function hasKey<T>(

  object: { [key: string]: T },

  key: string | number,

): boolean {

  return object[key] !== undefined;

}

/**

 * Returns the value at the specified key. If the key is not present, throws an error.

 * @param object

 * @param key

 * @param errorMessage

 */

export function getOrThrowError<T>(

  object: { [key: string]: T },

  key: string | number,

  errorMessage: string,

): T {

  if (!hasKey(object, key)) {

    throw new Error(errorMessage);

  }

  return object[key];

}

/** Return a copy of the object with specific property removed */

export function deleteProperty<T, K extends keyof T>(

  obj: T,

  key: K,

): Omit<T, K> {

  const { [key]: _, ...newObj } = obj;

  return newObj;

}

/**

 * Iterate through the properties of the object, checking which return true for the filterFunction.

 * Return a copy of the object, without the properties that don't pass the filter.

 */

export function filterObjectProps<T>(

  obj: IndexedObject<T>,

  filter: (value: T) => boolean,

): IndexedObject<T> {

  return Object.entries(obj).reduce(

    (newObj: IndexedObject<T>, [key, value]): IndexedObject<T> => {

      if (filter(value)) {

        newObj[key] = value;

      }

      return newObj;

    },

    {},

  );

}

/** Return a copy of the list with duplicate elements removed */

export function uniq<T>(x: T[]): T[] {

  return Array.from(new Set(x));

}

export function flatten<T>(x: T[][]): T[] {

  const concat = (ls: T[], xs: T[]): T[] => ls.concat(xs);

  return x.reduce(concat, []);

}

export function removeDuplicatesById<T extends { id: number }>(

  items: T[],

): T[] {

  interface Accumulator {

    contents: T[];

    ids: number[];

  }

  const reducer = (result: Accumulator, next: T): Accumulator => {

    if (!result.ids.includes(next.id)) {

      result.contents.push(next);

      result.ids.push(next.id);

    }

    return result;

  };

  return items.reduce(reducer, { contents: [], ids: [] }).contents;

}

/**

 * Decrement the number if it above zero, else return 0.

 * This helps to avoid some pathological edge cases where pendingCount becomes permanently bugged.

 * @param num

 */

export function decrement(num: number): number {

  return num <= 0 ? 0 : num - 1;

}