const { fork } = require('node:child_process')
const { createHash } = require('node:crypto')
const { createWriteStream } = require('node:fs')
const { readFile } = require('node:fs/promises')
const { EOL } = require('node:os')
const { join } = require('node:path')

require('../../lib/environment-helper')
const db = require('../../lib/db')

const { EXIT } = require('./consts')
const CLI = require('./cli')

const help_message = "Create and insert fake machines into the DB."

const cli = CLI({
  grammar: [
    [["--help"], "Show this help message"],
    [["--machine", "PATH"], "Path to the machine's source code root"],
    [["--device_ids_path", "PATH"], "Where to save the list of device IDs"],
    [["-n", "NUMBER"], "Number of fake machines to create"],
    [["--replace_existing"], "Remove machines of previous runs"],
  ],
})

const help = (exit_code) => {
  console.log("Usage: lamassu-server-stress-testing machines ARGS...")
  console.log(help_message)
  cli.help()
  return exit_code
}

const close_stream = (stream) => (
  new Promise((resolve, reject) => (
    stream.close((err) => err ? reject(err) : resolve())
  ))
)

const compute_machine_id = cert => {
    cert = cert.split('\r\n')
    const raw = Buffer.from(cert.slice(1, cert.length-2).join(''), 'base64')
    return createHash('sha256').update(raw).digest('hex')
}

const create_fake_machine = async (device_ids_file, self_sign, i) => {
  console.log("creating machine", i)
  const { cert } = await self_sign.generateCertificate()
  const device_id = compute_machine_id(cert)
  await db.none(
    `INSERT INTO devices (device_id, cassette1, cassette2, paired, display, created, name, last_online, location)
     VALUES ($1, 0, 0, 't', 't', now(), $2, now(), '{}'::json)`,
    [device_id, `machine_${i}`]
  )
  device_ids_file.write(device_id + EOL)
  console.log("created machine", i, "with device ID", device_id)
}

const create_fake_machines = async ({ machine, device_ids_path, n, replace_existing }) => {
  n = parseInt(n)
  if (Number.isNaN(n) || n <= 0) {
    console.error("Expected n to be a positive number, got", n)
    return help(EXIT.BADARGS)
  }

  const device_ids_file = createWriteStream(device_ids_path, {
    flags: replace_existing ? "w" : "a",
    mode: 0o640,
    flush: true,
  })
  if (replace_existing) await db.none("DELETE FROM devices")

  const self_sign = require(join(process.cwd(), machine, "lib", "self_sign"))
  for (let i = 0; i < n; i++)
    await create_fake_machine(device_ids_file, self_sign, i)

  await close_stream(device_ids_file)

  return EXIT.OK
}

const run = async (args) => {
  const [err, options, positional] = cli.parse(args)
  if (err) {
    console.error(err)
    return help(EXIT.BADARGS)
  }

  if (options.help)
    return help(EXIT.OK)

  const missing_options = ["n", "machine", "device_ids_path"].filter((opt) => !options[opt])
  if (missing_options.length > 0) {
    console.error("The following options are required:", missing_options.join(", "))
    return help(EXIT.BADARGS)
  }

  return await create_fake_machines(options)
}

module.exports = {
  help_message,
  run,
}