type UtoL = {
  'A': 'a'
  'B': 'b'
  'C': 'c'
  'D': 'd'
  'E': 'e'
  'F': 'f'
  'G': 'g'
  'H': 'h'
  'I': 'i'
  'J': 'j'
  'K': 'k'
  'L': 'l'
  'M': 'm'
  'N': 'n'
  'O': 'o'
  'P': 'p'
  'Q': 'q'
  'R': 'r'
  'S': 's'
  'T': 't'
  'U': 'u'
  'V': 'v'
  'W': 'w'
  'X': 'x'
  'Y': 'y'
  'Z': 'z'
}
type Kebab<S, Outer> =
  S extends keyof UtoL
    ? Outer extends true
      ? UtoL[S]
      : `-${UtoL[S]}`
    : S
type KebabCase<S, Outer = true> =
  S extends `${infer First}${infer Rest}`
    ? `${Kebab<First, Outer>}${KebabCase<Rest, false>}`
    : S

import type { Equal, Expect } from '@type-challenges/utils'

type cases = [
  Expect<Equal<KebabCase<'FooBarBaz'>, 'foo-bar-baz'>>,
  Expect<Equal<KebabCase<'fooBarBaz'>, 'foo-bar-baz'>>,
  Expect<Equal<KebabCase<'foo-bar'>, 'foo-bar'>>,
  Expect<Equal<KebabCase<'foo_bar'>, 'foo_bar'>>,
  Expect<Equal<KebabCase<'Foo-Bar'>, 'foo--bar'>>,
  Expect<Equal<KebabCase<'ABC'>, 'a-b-c'>>,
  Expect<Equal<KebabCase<'-'>, '-'>>,
  Expect<Equal<KebabCase<''>, ''>>,
  Expect<Equal<KebabCase<'😎'>, '😎'>>,
]