package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/julienschmidt/httprouter"
	"github.com/miekg/dns"

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

type checkGLUE struct {
	Domain string `json:"domain"`
	IP     string `json:"ip"`
}

func init() {
	router.POST("/api/check/GLUE", apiAuthHandler(func(student *adlin.Student, ps httprouter.Params, body []byte) (interface{}, error) {
		var uc checkGLUE
		if err := json.Unmarshal(body, &uc); err != nil {
			return nil, err
		}
		return true, check_GLUE_respond(student, uc.Domain, uc.IP)
	}))
}
func check_GLUE_respond(student *adlin.Student, domain string, ip string) (err error) {
	if !strings.HasPrefix(ip, adlin.StudentIP(student.Id, 0).String()) {
		return fmt.Errorf("%q is not your IP range", ip)
	}

	client := dns.Client{Net: "tcp", Timeout: time.Second * 5}

	m := new(dns.Msg)
	m.SetQuestion(domain, dns.TypeAAAA)
	m.RecursionDesired = false
	m.SetEdns0(4096, true)

	var r *dns.Msg
	r, _, err = client.Exchange(m, fmt.Sprintf("[%s]:53", ip))
	if err != nil {
		return
	}

	if r == nil {
		return errors.New("Response from name server is nil")
	}
	if r.Rcode != dns.RcodeSuccess {
		return fmt.Errorf("Name server returns %s", dns.RcodeToString[r.Rcode])
	}

	if len(r.Answer) == 0 {
		return errors.New("Empty response for this NS record")
	}

	found := false

	for _, answer := range r.Answer {
		if t, ok := answer.(*dns.AAAA); ok {
			found = found || t.AAAA.String() == ip
		}
	}

	if !found {
		return fmt.Errorf("%q not found in records", ip)
	}

	return
}