package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"time"

	"github.com/miekg/dns"
	"github.com/sparrc/go-ping"

	"git.nemunai.re/lectures/adlin/libadlin"
)

// ICMP

func check_ping(ip string, cb func(pkt *ping.Packet)) (err error) {
	var pinger *ping.Pinger
	pinger, err = ping.NewPinger(ip)
	if err != nil {
		return
	}

	pinger.Timeout = time.Second * 5
	pinger.Count = 1
	pinger.OnRecv = cb
	pinger.SetPrivileged(true)
	pinger.Run()

	return
}

// PORT 53

func check_dns(domain, ip string) (err error) {
	client := dns.Client{Timeout: time.Second * 5}

	m := new(dns.Msg)
	m.SetQuestion(domain, dns.TypeSOA)

	_, _, err = client.Exchange(m, fmt.Sprintf("[%s]:53", ip))
	return
}

// PORT 80

func check_http(ip string) (err error) {
	var resp *http.Response
	resp, err = http.Get(fmt.Sprintf("http://[%s]/", ip))
	if err != nil {
		return
	}
	defer resp.Body.Close()
	_, err = ioutil.ReadAll(resp.Body)
	return
}

// PORT 443

func check_https(domain, ip string) (err error) {
	var resp *http.Response
	resp, err = http.Get(fmt.Sprintf("https://%s/", domain))
	if err != nil {
		return
	}
	defer resp.Body.Close()
	_, err = ioutil.ReadAll(resp.Body)
	return
}

// Main

func studentsChecker() {
	students, err := adlin.GetStudents()
	if err != nil {
		log.Println("Unable to check students:", err)
		return
	}

	for _, s := range students {
		time.Sleep(250 * time.Millisecond)
		// Check ping
		std := s
		stdIP := adlin.StudentIP(std.Id).String() + "1"
		go check_ping(stdIP, func(pkt *ping.Packet) {
			std.OnPong(true)

			// Check HTTP
			if err := check_http(stdIP); err == nil {
				if _, err := std.UnlockNewChallenge(100, ""); err != nil {
					if _, err := std.UpdateUnlockedChallenge(100, ""); err != nil {
						log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
					}
				}
			}

			// Check HTTPs
			if err := check_https(std.MyAssociatedDomain(), stdIP); err == nil {
				if _, err := std.UnlockNewChallenge(101, ""); err != nil {
					if _, err := std.UpdateUnlockedChallenge(101, ""); err != nil {
						log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
					}
				}
			}

			// Check DNS
			if err := check_dns(std.MyDelegatedDomain(), stdIP); err == nil {
				if _, err := std.UnlockNewChallenge(102, ""); err != nil {
					if _, err := std.UpdateUnlockedChallenge(102, ""); err != nil {
						log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
					}
				}
			}

			return
		})
	}
}