import Path from 'path'
import File from 'fs/promises'

const DIR = '.cache'

/**
 * @param {string} id
 * @returns {Promise<ArrayBuffer | undefined>}
 */
const get = async id => {
  if (!await File.exists(DIR)) {
    await File.mkdir(DIR)
  }

  const p = Path.join(DIR, id)
  return (await File.exists(p)) ? (await File.readFile(p)).buffer : undefined
}

/**
 * @param {string} id
 * @param {() => Promise<ArrayBuffer>} onMiss
 * @returns {Promise<ArrayBuffer>}
 */
const tryGet = async (id, onMiss) => {
  if (!await File.exists(DIR)) {
    await File.mkdir(DIR)
  }

  const p = Path.join(DIR, id)

  if (!await File.exists(p)) {
    const buf = await onMiss()
    await File.writeFile(p, buf)
    return buf
  } else {
    return (await File.readFile(p)).buffer
  }
}

/**
 * @template T
 * @param {string} id
 * @param {() => Promise<T>} onMiss
 * @returns {Promise<T>}
 */
const tryGetJson = async (id, onMiss) => {
  const buf = await tryGet(id + '.json', async () => Buffer.from(JSON.stringify(await onMiss())))
  return JSON.parse(Buffer.from(buf).toString('utf8'))
}

export { get, tryGet, tryGetJson }