9.ts

// TS playground link: https://tsplay.dev/advent-of-typescript-2023-9

// Is Santa Dyslexic?
// [it's early Saturday morning and the team has been working overtime. Santa storms into the factory floor shouting..]
//     [Santa] Don't you elves take any pride in your work?!?! Others would love to have your job for much less pay! I asked for a simple type that will reverse strings!! How hard is that?!? What do we even pay you for??
// [unfortunately, Santa is conveniently forgetting that the Reverse type was cut from the sprint (which... of course... he agreed to)]
//     [floor manager] Ok. We never got acceptance criteria for that ticket.
//     [Santa] How difficult is it to understand what Reverse does!? 'rehsaD' should be transformed into 'Dasher', 'recnaD' should be transformed into 'Dancer', 'recnarP' should be transformed into 'Prancer'.. DO I NEED TO KEEP GOING?
//     [floor manager] Well you might be surprised. For example, what should happen to multi-codepoint unicode characters?
//     [Santa] What are you on about with all that accessibility stuff again!
//     [floor manager] Accessibility is important, sir.
//     [Santa] Look, this is just an MVP. We can add accessibility later. Just get me my Reverse type! I'm having a hard time reading this stuff otherwise!

type Reverse<T extends string> = T extends `${infer FirstLetter}${infer RestLetters}` ? `${Reverse<RestLetters>}${FirstLetter}` : T