package main

import (
	"crypto/sha512"
	"encoding/base64"
	"encoding/binary"
	"io"
	"log"
	"net/http"
	"os"
	"os/exec"
	"time"

	"gopkg.in/gomail.v2"
)

func (l LDAPConn) genToken(dn string, previous bool) string {
	hour := time.Now()
	// Generate the previous token?
	if previous {
		hour.Add(time.Hour * -1)
	}

	b := make([]byte, binary.MaxVarintLen64)
	binary.PutVarint(b, hour.Round(time.Hour).Unix())

	// Search the email address and current password
	entries, err := l.GetEntry(dn)
	if err != nil {
		log.Println("Unable to generate token:", err)
		return "#err"
	}

	email := ""
	curpasswd := ""
	for _, e := range entries {
		if e.Name == "mail" {
			email += e.Values[0]
		} else if e.Name == "userPassword" {
			curpasswd += e.Values[0]
		}
	}

	// Hash that
	hash := sha512.New()
	hash.Write(b)
	hash.Write([]byte(dn))
	hash.Write([]byte(email))
	hash.Write([]byte(curpasswd))

	return base64.StdEncoding.EncodeToString(hash.Sum(nil)[:])
}

func lostPassword(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		displayTmpl(w, "lost.html", map[string]interface{}{})
		return
	}

	// Connect to the LDAP server
	conn, err := myLDAP.Connect()
	if err != nil || conn == nil {
		log.Println(err)
		displayTmplError(w, http.StatusInternalServerError, "lost.html", map[string]interface{}{"error": err.Error()})
		return
	}

	// Bind as service to perform the search
	err = conn.ServiceBind()
	if err != nil {
		log.Println(err)
		displayTmplError(w, http.StatusInternalServerError, "lost.html", map[string]interface{}{"error": err.Error()})
		return
	}

	// Search the dn of the given user
	dn, err := conn.SearchDN(r.PostFormValue("login"), true)
	if err != nil {
		log.Println(err)
		displayTmplError(w, http.StatusInternalServerError, "lost.html", map[string]interface{}{"error": err.Error()})
		return
	}

	// Generate the token
	token := conn.genToken(dn, false)

	// Search the email address
	entries, err := conn.GetEntry(dn)
	if err != nil {
		log.Println(err)
		displayTmplError(w, http.StatusInternalServerError, "lost.html", map[string]interface{}{"error": err.Error()})
		return
	}

	email := ""
	cn := ""
	for _, e := range entries {
		if e.Name == "mail" {
			email = e.Values[0]
		}
		if e.Name == "cn" {
			cn = e.Values[0]
		}
	}

	if email == "" {
		log.Println("Unable to find a valid adress for user " + dn)
		displayTmplError(w, http.StatusBadRequest, "lost.html", map[string]interface{}{"error": "We were unable to find a valid email address associated with your account. Please contact an administrator."})
		return
	}

	// Send the email
	m := gomail.NewMessage()
	m.SetHeader("From", "noreply@nemunai.re")
	m.SetHeader("To", email)
	m.SetHeader("Subject", "SSO nemunai.re: password recovery")
	m.SetBody("text/plain", "Hello "+cn+"!\n\nSomeone, and we hope it's you, requested to reset your account password. \nIn order to continue, go to:\nhttps://ldap.nemunai.re/reset?l="+r.PostFormValue("login")+"&t="+token+"\n\nBest regards,\n-- \nnemunai.re SSO")

	var s gomail.Sender
	if myLDAP.MailHost != "" {
		d := gomail.NewDialer(myLDAP.MailHost, myLDAP.MailPort, myLDAP.MailUser, myLDAP.MailPassword)
		s, err = d.Dial()
		if err != nil {
			log.Println("Unable to connect to email server: " + err.Error())
			displayTmplError(w, http.StatusInternalServerError, "lost.html", map[string]interface{}{"error": "Unable to connect to email server: " + err.Error()})
			return
		}
	} else {
		// Using local sendmail: delegate to the local admin sys the responsability to transport the mail
		s = gomail.SendFunc(func(from string, to []string, msg io.WriterTo) error {
			cmd := exec.Command("sendmail", "-t")
			cmd.Stdout = os.Stdout
			cmd.Stderr = os.Stderr

			pw, err := cmd.StdinPipe()
			if err != nil {
				return err
			}

			err = cmd.Start()
			if err != nil {
				return err
			}

			var errs [3]error
			_, errs[0] = m.WriteTo(pw)
			errs[1] = pw.Close()
			errs[2] = cmd.Wait()
			for _, err = range errs {
				if err != nil {
					return err
				}
			}
			return nil
		})
	}

	if err := gomail.Send(s, m); err != nil {
		log.Println("Unable to send email: " + err.Error())
		displayTmplError(w, http.StatusInternalServerError, "lost.html", map[string]interface{}{"error": "Unable to send email: " + err.Error()})
		return
	}

	displayMsg(w, "Password recovery email sent, check your inbox.", http.StatusOK)
}