import { serverLogger } from '@/observability/logging.js'
import { appFactory as metricsAppFactory } from '@/observability/metricsApp.js'
import { getMetricsHost, getMetricsPort } from '@/utils/env.js'
import http from 'http'
import { isNaN, isString, toNumber } from 'lodash-es'

export const startServer = (params?: { serveOnRandomPort?: boolean }) => {
  // we place the metrics on a separate port as we wish to expose it to external monitoring tools, but do not wish to expose other routes (for now)
  const inputMetricsPort = params?.serveOnRandomPort
    ? 0
    : normalizePort(getMetricsPort())
  const metricsApp = metricsAppFactory()
  metricsApp.set('port', inputMetricsPort)

  /**
   * Create HTTP server.
   */
  const metricsServer = http.createServer(metricsApp)

  const metricsHost = getMetricsHost()
  metricsServer.on('error', onErrorFactory(inputMetricsPort))
  metricsServer.on('listening', () => {
    serverLogger.info('📊 Started Database monitor server')
    onListening(metricsServer)
  })
  metricsServer.listen(inputMetricsPort, metricsHost)

  return { metricsServer }
}

export const stopServer = (params: { server: http.Server }) => {
  const { server } = params
  server.close()
}

/**
 * Normalize a port into a number, string, or false.
 */
function normalizePort(val: string | number) {
  const port = toNumber(val)
  if (!isNaN(port) && port >= 0) return port

  throw new Error('Invalid port; port must be a positive integer.')
}

/**
 * Event listener for HTTP server "error" event.
 */

const onErrorFactory = (port: string | number | false) => (error: Error) => {
  if ('syscall' in error && error.syscall !== 'listen') {
    throw error
  }

  const bind = isString(port) ? 'Pipe ' + port : 'Port ' + port

  if (!('code' in error)) throw error

  // handle specific listen errors with friendly messages
  switch (error.code) {
    case 'EACCES':
      serverLogger.error(error, bind + ' requires elevated privileges')
      process.exit(1)
    case 'EADDRINUSE':
      serverLogger.error(error, bind + ' is already in use')
      process.exit(1)
    default:
      throw error
  }
}

/**
 * Event listener for HTTP server "listening" event.
 */

function onListening(referenceServer: http.Server) {
  const addr = referenceServer.address()
  if (!addr) throw new Error('Server address is not defined')

  switch (typeof addr) {
    case 'string':
      serverLogger.info(`Listening on pipe ${addr}`)
      return addr
    default:
      serverLogger.info(`Listening on port ${addr.port}`)
      return addr.port
  }
}