Node app safe configuration

node-environment-setup.ts

import { parseArgs } from 'node:util'
import { env } from 'node:process'
import { Input, Issue, Output, boolean, custom, object, safeParse, string, transform } from 'valibot'

// @infra/environment/environment-error.ts
export class EnvironmentError extends Error {
  constructor(public readonly issues: Issue[]) {
    super('Environment Error')
  }
}

// @infra/environment/schema.ts
// could be adapted to zod, joy or your favorite schema validation lib.
const schema = object({
  port: transform(string([
    custom(
      val => Number.isInteger(Number(val)),
      'port must be a numeric strig',
    ),
  ]), Number),
  debug: boolean(),
})

export type EnvironmentInput = Input<typeof schema>
export type EnvironmentConfig = Output<typeof schema>

// @infra/environment/configure.ts
// the env config setup is here
function getArguments(): Partial<EnvironmentInput> {
  const args = parseArgs({
    options: {
      port: { type: 'string' },
      debug: { type: 'boolean' },
    },
  })

  return args.values
}

function getEnvironmentVariables(): Partial<EnvironmentInput> {
  const variables = {
    port: env.PORT,
    debug: env.DEBUG === 'true',
  }

  return { ...variables }
}

const result = safeParse(schema, {
  ...getEnvironmentVariables(),
  ...getArguments(),
})

if (result.success === false) {
  throw new EnvironmentError(result.issues)
}

export const config: EnvironmentConfig = result.output

/**
 * @infra/environment/index.ts
 * 
 * export { config } from './configure'
 * export { EnvironmentConfig } from './schema'
 */

/**
 * Usage example
 * @/main.ts
 * import { exit } from 'node:process'
 * import { server } from '@infra/server'
 * import { config } from '@infra/environment'
 * 
 * async function main() {
 *   server.listen(config.port)
 * }
 *
 * function onError(error: unknown) {
 *   console.error(error)
 * exit(1)
 * }
 * 
 * main().catch(onError)
 */

/**
 * CLI
 * 
 * dev
 * npx tsx --env-file=.env src/main.ts --port 9090 --debug
 * 
 * prod
 * PORT=3000 node build/main.js
 */