btrc-hub/frontend/src/lib/prefetchers.ts

import { QueryClient } from '@tanstack/react-query'
import { match } from 'path-to-regexp'

import { fetchPost, fetchPosts } from '@/lib/posts'

type Prefetcher = (qc: QueryClient, url: URL) => Promise<void>

const mPost = match<{ id: string }> ('/posts/:id')


const prefetchPostsIndex: Prefetcher = async (qc, url) => {
  const tags = url.searchParams.get ('tags') ?? ''
  const match = url.searchParams.get ('match') === 'any' ? 'any' : 'all'
  const limit = Number (url.searchParams.get ('limit') || 20)
  await qc.prefetchQuery ({
      queryKey: ['posts', 'index', { tags, match, limit }],
      queryFn:  () => fetchPosts ({ tags, match, limit }) })
}


const prefetchPostShow: Prefetcher = async (qc, url) => {
  const m = mPost (url.pathname)
  if (!(m))
    return

  const { id } = m.params
  await qc.prefetchQuery ({
      queryKey: ['posts', id],
      queryFn:  () => fetchPost (id) })
}


export const routePrefetchers: { test: (u: URL) => boolean; run: Prefetcher }[] = [
    { test: u => u.pathname === '/' || u.pathname === '/posts', run: prefetchPostsIndex },
    { test: u => Boolean (mPost (u.pathname)), run: prefetchPostShow }]


export const prefetchForURL = async (qc: QueryClient, urlLike: string): Promise<void> => {
  const u = new URL (urlLike, location.origin)
  const jobs = routePrefetchers.filter (r => r.test (u)).map (r => r.run (qc, u))
  if (jobs.length === 0)
    return

  await Promise.all (jobs)
}