LearningTemplateLiteralTypes.ts

type RouteLeaf = string | number | bigint | boolean | null | undefined
// there's probably a tidier way to get around TS's lack of support for recursive `type`'s
type RouteBranch<SubBranch = RouteLeaf> = Record<string | number | symbol, RouteLeaf | SubBranch>
type RouteComponent = 
    | RouteLeaf
    | RouteBranch<RouteBranch>
    | RouteBranch<RouteBranch<RouteBranch>>
    | RouteBranch<RouteBranch<RouteBranch<RouteBranch>>>
    | RouteBranch<RouteBranch<RouteBranch<RouteBranch<RouteBranch>>>>
    | RouteBranch<RouteBranch<RouteBranch<RouteBranch<RouteBranch<RouteBranch>>>>>
type Route<Map extends RouteComponent> = Map extends Record<infer Key, RouteComponent>
    ? Key extends RouteLeaf
        ? `/${Key}${Route<Map[Key]>}` 
        : never
    : Map extends RouteLeaf 
        ? `/${Map}` 
        : never

type DivvyRoute = Route<{
    "wallet": number,
    "transactions": Record<number, 'summary' | 'details'>,
    "potatoes": "russet" | "yukon"
}>

function theWay(n: number) {
    const path: DivvyRoute = `/transactions/${n}/summary`
}