neat-path-example.ts

export enum KnownPaths {
  GetHelp = "/app/get-help",
  RunDetail = "/app/history/:runId"
}

/** Parses a string type into an object of route params */
type ExtractRouteParams<T extends string> = string extends T
  ? Record<string, string>
  : T extends `${infer _Start}:${infer Param}/${infer Rest}`
  ? { [K in Param | keyof ExtractRouteParams<Rest>]: string }
  : T extends `${infer _Start}:${infer Param}`
  ? { [K in Param]: string }
  : undefined;

export function getPath<
  Path extends KnownPaths,
  Params extends ExtractRouteParams<Path>
  >(pathString: Path, ...[params]: Params extends undefined ? [] : [Params]): string {
  if (params) {
    return Object
      .entries(params)
      .reduce<string>((path, [key, value]) =>
        path.replace(`:${key}`, encodeURIComponent(value)),
        pathString
      )
  }
  
  return pathString;
}