/*
Copyright © 2020 The Pragmatic Programmers, LLC
Copyrights apply to this source code.
Check LICENSE for details.

*/
// Package scan provides types and functions to perform TCP port
// scans on a list of hosts
package scan

import (
  "fmt"
  "net"
  "time"
)

// PortState represents the state of a single TCP port
type PortState struct {
  Port int
  Open state
}

type state bool

// String converts the boolean value of state to a human readable string
func (s state) String() string {
  if s {
    return "open"
  }

  return "closed"
}

// scanPort performs a port scan on a single TCP port
func scanPort(host string, port int) PortState {
  p := PortState{
    Port: port,
  }

  address := net.JoinHostPort(host, fmt.Sprintf("%d", port))
  scanConn, err := net.DialTimeout("tcp", address, 1*time.Second)

  if err != nil {
    return p
  }

  scanConn.Close()
  p.Open = true
  return p
}

// Results represents the scan results for a single host
type Results struct {
  Host       string
  NotFound   bool
  PortStates []PortState
}

// Run performs a port scan on the hosts list
func Run(hl *HostsList, ports []int) []Results {
  res := make([]Results, 0, len(hl.Hosts))
  for _, h := range hl.Hosts {
    r := Results{
      Host: h,
    }

    if _, err := net.LookupHost(h); err != nil {
      r.NotFound = true
      res = append(res, r)
      continue
    }

    for _, p := range ports {
      r.PortStates = append(r.PortStates, scanPort(h, p))
    }

    res = append(res, r)
  }

  return res
}