import http from 'node:http'
import net from 'node:net'

const upstreamHost = 'qualification-ingress'
const upstreamPort = 80

const server = http.createServer((request, response) => {
  const headers = upstreamHeaders(request.headers)
  const upstream = http.request(
    {
      host: upstreamHost,
      port: upstreamPort,
      method: request.method,
      path: request.url,
      headers,
    },
    (upstreamResponse) => {
      response.writeHead(
        upstreamResponse.statusCode ?? 502,
        upstreamResponse.headers,
      )
      upstreamResponse.pipe(response)
    },
  )
  upstream.on('error', () => {
    response.writeHead(502)
    response.end()
  })
  request.pipe(upstream)
})

server.on('upgrade', (request, socket, head) => {
  const upstream = net.connect(upstreamPort, upstreamHost, () => {
    const headers = Object.entries(upstreamHeaders(request.headers))
      .filter(([name]) => name.toLowerCase() !== 'host')
      .map(([name, value]) => `${name}: ${String(value)}`)
      .join('\r\n')
    upstream.write(
      `${request.method} ${request.url} HTTP/${request.httpVersion}\r\nHost: ${upstreamHost}\r\n${headers}\r\n\r\n`,
    )
    if (head.length > 0) upstream.write(head)
    socket.pipe(upstream).pipe(socket)
  })
  upstream.on('error', () => socket.destroy())
  socket.on('error', () => upstream.destroy())
})

function upstreamHeaders(incoming) {
  const headers = { ...incoming, host: upstreamHost }
  const session = qualificationSession(headers.cookie)
  if (typeof session === 'string' && /^[A-Za-z0-9_-]{43}$/.test(session))
    headers.cookie = `__Host-remora-session=${session}`
  else delete headers.cookie
  return headers
}

function qualificationSession(cookieHeader) {
  if (typeof cookieHeader !== 'string') return null
  for (const cookie of cookieHeader.split(';')) {
    const [name, value] = cookie.trim().split('=', 2)
    if (name === 'remora-qualification-session') return value
  }
  return null
}

server.listen(4174, '127.0.0.1')