feat(@angular-ru/common): item functions type

packages/common/array/src/take-first-item.ts

@@ -1,5 +1,5 @@
-import { Nullable } from '@angular-ru/common/typings';
+import { Nullable, TupleItem } from '@angular-ru/common/typings';
 
-export function takeFirstItem<T>(array?: Nullable<T[]>): Nullable<T> {
-    return array?.[0];
+export function takeFirstItem<ArrayType extends Nullable<unknown[]>>(array: ArrayType): TupleItem<ArrayType, 0> {
+    return (Array.isArray(array) ? array[0] : undefined) as TupleItem<ArrayType, 0>;
 }

packages/common/array/src/take-last-item.ts

@@ -1,5 +1,5 @@
-import { Nullable } from '@angular-ru/common/typings';
+import { LastOfTuple, Nullable } from '@angular-ru/common/typings';
 
-export function takeLastItem<T>(array?: Nullable<T[]>): Nullable<T> {
-    return array?.[array?.length - 1];
+export function takeLastItem<ArrayType extends Nullable<unknown[]>>(array: ArrayType): LastOfTuple<ArrayType> {
+    return (Array.isArray(array) ? array[array.length - 1] : undefined) as LastOfTuple<ArrayType>;
 }

packages/common/array/src/take-second-item.ts

@@ -1,5 +1,5 @@
-import { Nullable } from '@angular-ru/common/typings';
+import { Nullable, TupleItem } from '@angular-ru/common/typings';
 
-export function takeSecondItem<T>(array?: Nullable<T[]>): Nullable<T> {
-    return array?.[1];
+export function takeSecondItem<ArrayType extends Nullable<unknown[]>>(array: ArrayType): TupleItem<ArrayType, 1> {
+    return (Array.isArray(array) ? array[1] : undefined) as TupleItem<ArrayType, 1>;
 }

packages/common/array/src/take-third-item.ts

@@ -1,6 +1,10 @@
-import { Nullable } from '@angular-ru/common/typings';
+import { Nullable, TupleItem } from '@angular-ru/common/typings';
 
-export function takeThirdItem<T>(array?: Nullable<T[]>): Nullable<T> {
-    const thirdItemIndex: number = 2;
-    return array?.[thirdItemIndex];
+type ThirdItemIndex = 2;
+const thirdItemIndex: ThirdItemIndex = 2;
+
+export function takeThirdItem<ArrayType extends Nullable<unknown[]>>(
+    array: ArrayType
+): TupleItem<ArrayType, ThirdItemIndex> {
+    return (Array.isArray(array) ? array[thirdItemIndex] : undefined) as TupleItem<ArrayType, ThirdItemIndex>;
 }

packages/common/docs/typings.md

@@ -190,3 +190,43 @@ function makeSomeOperations(form: FormGroup, descriptor: DateIntervalDescriptor)
     // ...
 }
 ```
+
+-   `Tuple`
+
+```ts
+type NumberCouple = Tuple<number, 2>; // [number, number]
+type Number4 = Tuple<number, 4>; // [number, number, number, number]
+type BracedString = Tuple<string>; // [string]
+type NumberCouple = Tuple<string, 0>; // []
+```
+
+-   `InfiniteTuple`
+
+```ts
+type CoupleAndMaybeSomeNumbers = InfiniteTuple<number, 2>; // [number, number, ...number]
+type AtLeast4Numbers = InfiniteTuple<number, 4>; // [number, number, number, number, ...number]
+type AtLeastOneLine = InfiniteTuple<string>; // [string, ...string]
+type SomeLines = InfiniteTuple<string, 0>; // string[]
+```
+
+-   `LastOfTuple`
+
+```ts
+type Number = LastOfTuple<[number]>; // number
+type MaybeString = LastOfTuple<string[]>; // string | undefined
+type Boolean = LastOfTuple<[string, boolean]>; // boolean
+type StringOrNumber = LastOfTuple<[string, ...number[]]>; // string | number
+type Nothing = LastOfTuple<[]>; // undefined
+```
+
+-   `TupleItem`
+
+```ts
+type Number = TupleItem<[number], 0>; // number
+type MaybeString = TupleItem<string[], 1>; // string | undefined
+type Boolean = TupleItem<[string, boolean], 1>; // boolean
+type String = TupleItem<[string, ...number[]], 0>; // string
+type MaybeNumber = TupleItem<[string, ...number[]], 3>; // number | undefined
+type Nothing = TupleItem<[], 0>; // undefined
+type NothingToo = TupleItem<[], 3>; // undefined
+```

packages/common/typings/src/infinite-tuple.ts

@@ -0,0 +1,3 @@
+import { Tuple } from './tuple';
+
+export type InfiniteTuple<ItemType, Length extends number = 1> = [...Tuple<ItemType, Length>, ...ItemType[]];

packages/common/typings/src/last-of-tuple.ts

@@ -0,0 +1,7 @@
+export type LastOfTuple<ArrayType> = ArrayType extends unknown[]
+    ? ArrayType extends []
+        ? undefined
+        : ArrayType extends [unknown, ...unknown[]]
+        ? ArrayType[ArrayType extends [unknown, ...infer Rest] ? Rest['length'] : number]
+        : ArrayType[number] | undefined
+    : undefined;

packages/common/typings/src/public_api.ts

@@ -13,12 +13,14 @@ export { Descriptor } from './descriptor';
 export { EmptyValue } from './empty-value';
 export { Fn } from './fn';
 export { Immutable, Mutable, PrimitiveType } from './immutability';
+export { InfiniteTuple } from './infinite-tuple';
 export { InputBoolean } from './input-boolean';
 export { Join } from './join';
 export { KeyOfList } from './key-of-list';
 export { KeyValueComparator } from './key-value-comparator';
 export { KeyboardKeys } from './keyboard';
 export { KeysOfType } from './keys-of-type';
+export { LastOfTuple } from './last-of-tuple';
 export { Leaves } from './leaves';
 export { NgCssClasses } from './ng-css-classes';
 export { Nullable } from './nullable';
@@ -30,3 +32,5 @@ export { Resolver } from './resolver';
 export { SortOrderType } from './sort-order-type';
 export { StringValuesOfEnum } from './string-values-of-enum';
 export { Timestamp } from './timestamp';
+export { Tuple } from './tuple';
+export { TupleItem } from './tuple-item';

packages/common/typings/src/tuple-item.ts

@@ -0,0 +1,7 @@
+import { InfiniteTuple } from './infinite-tuple';
+
+export type TupleItem<ArrayType, Index extends number> = ArrayType extends unknown[]
+    ? ArrayType extends [unknown, ...InfiniteTuple<unknown, Index>]
+        ? ArrayType[Index]
+        : ArrayType[Index] | undefined
+    : undefined;

packages/common/typings/src/tuple.ts

@@ -0,0 +1,3 @@
+export type Tuple<ItemType, Length extends number = 1, Base extends unknown[] = []> = Base['length'] extends Length
+    ? Base
+    : Tuple<ItemType, Length, [ItemType, ...Base]>;