// Boots a built Nuxt server (`<outputDir>/server/index.mjs`) on 127.0.0.1
// against a given Journal API base and waits until it answers HTTP.
// Plain .mjs with JSDoc types so it runs from node_modules unchanged.

import { spawn } from 'node:child_process'
import { createServer } from 'node:net'
import { existsSync } from 'node:fs'
import { join, resolve } from 'node:path'

/** @returns {Promise<number>} */
function freePort() {
  return new Promise((done, fail) => {
    const srv = createServer()
    srv.once('error', fail)
    srv.listen(0, '127.0.0.1', () => {
      const { port } = /** @type {import('node:net').AddressInfo} */ (srv.address())
      srv.close(() => done(port))
    })
  })
}

/**
 * @param {{ outputDir: string, apiBase: string, port?: number, env?: Record<string, string>, timeoutMs?: number }} opts
 * @returns {Promise<{ url: string, close: () => Promise<void> }>}
 */
export async function startNuxtServer({ outputDir, apiBase, port = 0, env = {}, timeoutMs = 30000 }) {
  const entry = join(resolve(outputDir), 'server', 'index.mjs')
  if (!existsSync(entry)) throw new Error(`nuxt-server: ${entry} does not exist; build first`)
  const listenPort = port || (await freePort())
  const url = `http://127.0.0.1:${listenPort}`

  const child = spawn(process.execPath, [entry], {
    env: {
      ...process.env,
      NODE_ENV: 'production',
      NITRO_HOST: '127.0.0.1',
      NITRO_PORT: String(listenPort),
      NUXT_JOURNAL_API_BASE: apiBase,
      ...env,
    },
    stdio: ['ignore', 'pipe', 'pipe'],
  })
  let log = ''
  child.stdout.on('data', (b) => (log += b))
  child.stderr.on('data', (b) => (log += b))
  let exited = false
  child.once('exit', () => (exited = true))

  const close = () =>
    new Promise((/** @type {(v?: void) => void} */ done) => {
      if (exited) return done()
      child.once('exit', () => done())
      child.kill('SIGTERM')
      setTimeout(() => {
        if (!exited) child.kill('SIGKILL')
      }, 5000).unref()
    })

  const deadline = Date.now() + timeoutMs
  while (Date.now() < deadline) {
    if (exited) throw new Error(`nuxt-server: server exited before answering\n${log}`)
    try {
      await fetch(url + '/', { redirect: 'manual', signal: AbortSignal.timeout(2000) })
      return { url, close }
    } catch {
      await new Promise((r) => setTimeout(r, 200))
    }
  }
  await close()
  throw new Error(`nuxt-server: no answer on ${url} within ${timeoutMs} ms\n${log}`)
}