type Func = (...args: any) => any
type Format<T extends string, Res extends Func | string = string> = T extends `${infer L}%${infer F}${infer R}`
  ? F extends 's' ? Res extends Func ? Format<R, ((...args: Parameters<Res>) => (s1: string) => ReturnType<Res>)> : Format<R, (s1: string) => string>
  : F extends 'd' ? Res extends Func ? Format<R, ((...args: Parameters<Res>) => (d1: number) => ReturnType<Res>)> : Format<R, (d1: number) => string>
  : Format<R, Res>
  : Res

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

type cases = [
  Expect<Equal<Format<'abc'>, string>>,
  Expect<Equal<Format<'a%sbc'>, (s1: string) => string>>,
  Expect<Equal<Format<'a%dbc'>, (d1: number) => string>>,
  Expect<Equal<Format<'a%dbc%s'>, (d1: number) => (s1: string) => string>>,
]