next.js/bin/next

#!/usr/bin/env node

import { join } from 'path'
import { spawn } from 'cross-spawn'
import { watchFile } from 'fs'

const defaultCommand = 'dev'
const commands = new Set([
  'init',
  'build',
  'start',
  defaultCommand
])

let cmd = process.argv[2]
let args

if (new Set(['--help', '-h']).has(cmd)) {
  console.log(`
    Usage
      $ next <command>

    Available commands
      ${Array.from(commands).join(', ')}

    For more information run a command with the --help flag
      $ next init --help
  `)
  process.exit(0)
}

if (commands.has(cmd)) {
  args = process.argv.slice(3)
} else {
  cmd = defaultCommand
  args = process.argv.slice(2)
}

const bin = join(__dirname, 'next-' + cmd)

const startProcess = () => {
  const proc = spawn(bin, args, { stdio: 'inherit', customFds: [0, 1, 2] })
  proc.on('close', (code) => process.exit(code))
  proc.on('error', (err) => {
    console.error(err)
    process.exit(1)
  })
  return proc
}

let proc = startProcess()

if (cmd === 'dev') {
  watchFile(join(process.cwd(), 'next.config.js'), (cur, prev) => {
    if (cur.size > 0 || prev.size > 0) {
      console.log('\n> Found a change in next.config.js, restarting the server...')
      // Don't listen to 'close' now since otherwise parent gets killed by listener
      proc.removeAllListeners('close')
      proc.kill()
      proc = startProcess()
    }
  })
}