Execute a callback once for the lifetime of the process.

initializeOnce.ts

import {
  existsSync,
  mkdirSync,
  readFileSync,
  writeFileSync,
  unlinkSync,
} from 'node:fs'
import { resolve } from 'node:path'
import { homedir } from 'node:os'

const cacheDirectory = resolve(homedir(), '.config', 'mdxts')
const cacheFilePath = resolve(cacheDirectory, 'updated.txt')
let callbackCleanup: (() => void) | undefined

if (!existsSync(cacheDirectory)) {
  mkdirSync(cacheDirectory, { recursive: true })
}

/**
 * Execute a callback once for the lifetime of the process that calls this function.
 * If the process is stale for more than an hour, the callback will be called again.
 */
export async function initializeOnce(callback: () => Promise<() => void>) {
  const now = Date.now()

  if (existsSync(cacheFilePath)) {
    const lastRunTimestamp = parseInt(readFileSync(cacheFilePath, 'utf-8'), 10)
    const difference = now - lastRunTimestamp
    const oneHour = 60 * 60 * 1000
    if (difference < oneHour) {
      return
    } else {
      callbackCleanup?.()
    }
  }

  let cleanupCalled = false
  callbackCleanup = await callback()
  const cleanup = () => {
    if (cleanupCalled) {
      return
    }
    cleanupCalled = true

    callbackCleanup?.()

    if (existsSync(cacheFilePath)) {
      unlinkSync(cacheFilePath)
    }
  }

  writeFileSync(cacheFilePath, now.toString())

  process.on('exit', cleanup)
  process.on('SIGINT', cleanup)
}