example.ts

import {clientImport} from '../main.ts'

const e = await clientImport(import.meta.url, "../examples/web_components/content_warning.ts")

console.log(e)

main.ts

import * as path from "https://deno.land/std@0.163.0/path/mod.ts";
import { encode } from "https://deno.land/std@0.99.0/encoding/base64.ts";
const genImport = (code: string) => new URL(`data:application/typescript;base64,${encode(code)}`)

const template = (asUsed: string, resolved: string) => `
"${asUsed}": _clientImport(
  "${resolved}",
  () => import("${resolved}")
),
`

const wrapper = (inner: string) => `
export function _clientImport <G>(
  path: string,
  code: () => Promise<G>
) {
  return { path, code }
}

export const library = {
  ${inner}
}
`

const { library } = await import('../import_library.ts').catch(() => ({ library: undefined }))

export async function clientImport <K extends keyof NonNullable<typeof library>>(metaUrl: string, p: K): Promise<NonNullable<typeof library>[K]> {
  const lib = library ? library : {} as NonNullable<typeof library>;
  const pInternal: string = p as string
  const resolve = (v: string) => {
    return path.resolve(path.dirname(metaUrl.replace('file://', '')), v)
  }
  const resolveHere = (v: string) => {
    return path.resolve(path.dirname(import.meta.url.replace('file://', '')), v)
  }
  if (p in lib) {
    return lib[p]
  }

  await Deno.create(resolveHere('../import_library.json'));
  const data = await Deno.readTextFile(resolveHere('../import_library.json'))
  const value = data === '' ? {} : JSON.parse(data)
  const importMap: { clientImport: {asUsed: string, resolved: string }[] } = { ...value, clientImport: []}
  const { clientImport } = importMap
  clientImport.push({asUsed: pInternal, resolved: resolve(pInternal)})

  const inner = clientImport.map(v => template(v.asUsed, v.resolved)).join('\n')
  const content = wrapper(inner)
  
  await Deno.writeTextFile(resolveHere('../import_library.json'), JSON.stringify({...importMap, clientImport}, null, 2))
  await Deno.writeTextFile(resolveHere('../import_library.ts'), content)
  const contentUrl = genImport(content)

  const file = await import(contentUrl.href)
  
  const { library: library2 } = file
  
  if (p in library2) {
    return library2[p]
  }

  throw new Error(`can not find import ${pInternal}`)
}