[Typescript] 104. Hard - Tuple to Enum Object

The enum is an original syntax of TypeScript (it does not exist in JavaScript). So it is converted to like the following form as a result of transpilation:

let OperatingSystem;
(function (OperatingSystem) {
    OperatingSystem[OperatingSystem["MacOS"] = 0] = "MacOS";
    OperatingSystem[OperatingSystem["Windows"] = 1] = "Windows";
    OperatingSystem[OperatingSystem["Linux"] = 2] = "Linux";
})(OperatingSystem || (OperatingSystem = {}));

In this question, the type should convert a given string tuple to an object that behaves like an enum. Moreover, the property of an enum is preferably a pascal case.

Enum<["macOS", "Windows", "Linux"]>
// -> { readonly MacOS: "macOS", readonly Windows: "Windows", readonly Linux: "Linux" }

If true is given in the second argument, the value should be a number literal.

Enum<["macOS", "Windows", "Linux"], true>
// -> { readonly MacOS: 0, readonly Windows: 1, readonly Linux: 2 }

 

/* _____________ Your Code Here _____________ */
type FindIndex<T extends readonly any[], K, ACC extends unknown[] = []> = T extends readonly [infer F, ...infer RT]
  ? K extends F
    ? ACC['length']
    : FindIndex<RT, K, [...ACC, unknown]>
  : -1;
type Enum<T extends readonly string[], N extends boolean = false> = {
  readonly [Key in T[number] as `${Capitalize<Key>}`]: N extends false ? Key : FindIndex<T, Key> 
}


/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

const OperatingSystem = ['macOS', 'Windows', 'Linux'] as const
const Command = ['echo', 'grep', 'sed', 'awk', 'cut', 'uniq', 'head', 'tail', 'xargs', 'shift'] as const

type cases = [
  Expect<Equal<Enum<[]>, {}>>,
  Expect<Equal<
  Enum<typeof OperatingSystem>,
  {
    readonly MacOS: 'macOS'
    readonly Windows: 'Windows'
    readonly Linux: 'Linux'
  }
  >>,
  Expect<Equal<
  Enum<typeof OperatingSystem, true>,
  {
    readonly MacOS: 0
    readonly Windows: 1
    readonly Linux: 2
  }
  >>,
  Expect<Equal<
  Enum<typeof Command>,
  {
    readonly Echo: 'echo'
    readonly Grep: 'grep'
    readonly Sed: 'sed'
    readonly Awk: 'awk'
    readonly Cut: 'cut'
    readonly Uniq: 'uniq'
    readonly Head: 'head'
    readonly Tail: 'tail'
    readonly Xargs: 'xargs'
    readonly Shift: 'shift'
  }
  >>,
  Expect<Equal<
  Enum<typeof Command, true>,
  {
    readonly Echo: 0
    readonly Grep: 1
    readonly Sed: 2
    readonly Awk: 3
    readonly Cut: 4
    readonly Uniq: 5
    readonly Head: 6
    readonly Tail: 7
    readonly Xargs: 8
    readonly Shift: 9
  }
  >>,
]