Help migrating from ts-toolbelt

[kvnwolf]

So far I have been using ts-toolbelt to create a function that receives a raw Next.js route path, and returns the appropriate prop types that route will use. So, it goes through all the route segments and:

• Transforms [mySegment] to { mySegment: string }
• Transforms [...mySegment] to { mySegment: [string, ...string[]] }
• Transforms [[...mySegment]] to { mySegment?: [string, ...string[]] }

Then, I loop through all the segments, get the props for each segment, and join all the props from the segments, using the following function (live repro: https://tsplay.dev/N5xKVw):

import type { List, Object, String, Union } from "ts-toolbelt"

type RouteParams<
  TRoutePath extends string,
  TRoutePathSegment = List.UnionOf<String.Split<TRoutePath, "/">>,
> = Union.Merge<
  TRoutePathSegment extends `[[...${infer TRouteParam}]]`
    ? { [key in TRouteParam]?: [string, ...string[]] }
    : TRoutePathSegment extends `[...${infer TRouteParam}]`
    ? { [key in TRouteParam]: [string, ...string[]] }
    : TRoutePathSegment extends `[${infer TRouteParam}]`
    ? { [key in TRouteParam]: string }
    : never
>

Having this output:

type Home = RouteParams<"/">
//   ^? type Home = {}

type Projects = RouteParams<"/projects">
//   ^? type Projects = {}

type Project = RouteParams<"/projects/[projectSlug]">
//   ^? type Project = { projectSlug: string; }

type ProjectTasks = RouteParams<"/projects/[projectSlug]/tasks">
//   ^? type ProjectTasks = { projectSlug: string; }

type ProjectTask = RouteParams<"/projects/[projectSlug]/tasks/[taskSlug]">
//   ^? type ProjectTask = { projectSlug: string; taskSlug: string; }

type ProjectDoc = RouteParams<"/projects/[projectSlug]/docs/[...docSlug]">
//   ^? type ProjectDoc = { projectSlug: string; docSlug: [string, ...string[]]; }

type ProjectFile = RouteParams<"/projects/[projectSlug]/files/[[...fileSlug]]">
//   ^? type ProjectFile = { projectSlug: string; fileSlug?: [string, ...string[]] | undefined; }

I would love to practice more functional programming, and give this library a chance, is there any recommended way to do it? So far I have tried the following (live repro: https://tsplay.dev/NDdpVN):

import type { ComposeLeft, Match, Pipe, Strings, Tuples } from "hotscript";

type RouteParams<TRoutePath extends string> = Pipe<TRoutePath, [
  Strings.Split<"/">,
  Tuples.Map<
    ComposeLeft<[
      Match<[
        Match.With<`[[...${string}]]`, { prop?: [string,...string[]] }>,
        Match.With<`[...${string}]`, { prop: [string,...string[]] }>,
        Match.With<`[${string}]`, { prop: string }>
      ]>
    ]>
  >
]>

... but I am stuck and haven't found a way to infer the param name within Match.With 😅