docker-compose/src/map-ports.ts

const mapPorts = (
  ports: string
): Array<{
  mapped?: { address: string; port: number }
  exposed: { port: number; protocol: string }
}> => {
  if (!ports) {
    return []
  }

  return ports.split(',').map((untypedPort) => {
    const exposedFragments = untypedPort.trim().split('->')

    const [port, protocol] =
      exposedFragments.length === 1
        ? exposedFragments[0].split('/')
        : exposedFragments[1].split('/')

    const mapped = exposedFragments[0]
    const lastDoubleColon = mapped.lastIndexOf(':')

    if (lastDoubleColon === -1) {
      return {
        exposed: { port: Number(port), protocol }
      }
    }

    const address = mapped.substr(0, lastDoubleColon)
    const mappedPort = mapped.substr(lastDoubleColon + 1)

    return {
      exposed: { port: Number(port), protocol },
      mapped: { port: Number(mappedPort), address }
    }
  })
}

export default mapPorts