type-samurai/src/slice.d.ts

Advanced utility types for Typescript

import { IsEqual } from "./equal";
import { Abs, IfPositive, IsNegative, ParseNumber } from "./number";
import { IfGreaterOrEqual, IsGreaterOrEqual } from "./greater-than";
import { Sum } from "./sum";
import { Or } from "./or";
import { Push } from "./push";
import { IsEmptyArray } from "./array";
import { And } from "./and";
import { If } from "./if";
import { IsLowerThan } from "./lower-than";
import { IsArrayIndex } from "./is-array-index";

type SliceRemovedItemValue = Record<"__type-samurai_internal__", symbol>;

type FilterRemoved<
  T extends readonly unknown[],
  Result extends unknown[] = []
> = T extends readonly [infer First, ...infer Rest extends unknown[]]
  ? FilterRemoved<
      Rest,
      First extends SliceRemovedItemValue ? Result : Push<Result, First>
    >
  : Result;

/**
 * Type version of `Array.prototype.slice()` method. Returns a shallow copy of a portion of an array into a new array object selected from `start` to `end` (`end` not included)
 * @example
 * ```ts
 * // [2, 3]
 * type T0 = Slice<[1, 2, 3, 4], 1>;
 * // [2, 3]
 * type T1 = Slice<[1, 2, 3, 4], 1, 3>;
 * ```
 */
type Slice<
  T extends readonly unknown[],
  Start extends number = 0,
  End extends number = T["length"]
> = (
  IsEmptyArray<T> extends true
    ? "self"
    : IsGreaterOrEqual<Start, T["length"]> extends true
    ? "empty"
    : IsNegative<End> extends true
    ? IsGreaterOrEqual<Abs<End>, T["length"]> extends true
      ? "empty"
      : [
          IfPositive<Start, Start, Sum<T["length"], Start>>,
          Sum<T["length"], End>
        ]
    : And<
        Or<IsEqual<Start, 0>, IsGreaterOrEqual<Abs<Start>, T["length"]>>,
        IsGreaterOrEqual<End, T["length"]>
      > extends true
    ? "self"
    : [IfPositive<Start, Start, Sum<T["length"], Start>>, End]
) extends infer Indexes
  ? Indexes extends "self"
    ? T
    : Indexes extends "empty"
    ? []
    : Indexes extends [
        infer NewStart extends number,
        infer NewEnd extends number
      ]
    ? IfGreaterOrEqual<NewStart, NewEnd> extends true
      ? []
      : FilterRemoved<{
          [K in keyof T]: IsArrayIndex<K> extends true
            ? If<
                And<
                  IsGreaterOrEqual<ParseNumber<K>, NewStart>,
                  IsLowerThan<ParseNumber<K>, NewEnd>
                >,
                T[K],
                SliceRemovedItemValue
              >
            : T[K];
        }>
    : T
  : T;