package main

import (
	"fmt"
	"log"
	"os"
	"os/signal"
	"syscall"
	"strings"
	"encoding/json"
	"encoding/base64"
	"math/rand"

	consul "github.com/hashicorp/consul/api"
	ldap "github.com/vjeantet/ldapserver"
	message "github.com/vjeantet/goldap/message"
)

func dnToConsul(dn string) string {
	rdns := strings.Split(dn, ",")

	// Reverse rdns
	for i, j := 0, len(rdns)-1; i < j; i, j = i+1, j-1 {
		rdns[i], rdns[j] = rdns[j], rdns[i]
	}

	return strings.Join(rdns, "/")
}

type DNComponent struct {
	Type string
	Value string
}

func parseDN(dn string) ([]DNComponent, error) {
	rdns := strings.Split(dn, ",")

	ret := []DNComponent{}

	for _, rdn := range rdns {
		splits := strings.Split(rdn, "=")
		if len(splits) != 2 {
			return nil, fmt.Errorf("Wrong DN component: %s (expected type=value)", rdn)
		}
		ret = append(ret, DNComponent{
			Type: splits[0],
			Value: splits[1],
		})
	}
	return ret, nil
}

type Config struct {
	Suffix string
}

type Server struct {
	config Config
	kv *consul.KV
}

type Attributes map[string]interface{}

func main() {
	//ldap logger
	ldap.Logger = log.New(os.Stdout, "[server] ", log.LstdFlags)

	// Connect to Consul
	client, err := consul.NewClient(consul.DefaultConfig())
	if err != nil {
		panic(err)
	}
	kv := client.KV()

	// TODO read config from somewhere
	config := Config {
		Suffix: "dc=gobottin,dc=eu",
	}

	gobottin := Server{config: config, kv: kv}
	err = gobottin.init()
	if err != nil {
		panic(err)
	}

	//Create a new LDAP Server
	ldapserver := ldap.NewServer()

	routes := ldap.NewRouteMux()
	routes.Bind(gobottin.handleBind)
	ldapserver.Handle(routes)

	// listen on 10389
	go ldapserver.ListenAndServe("127.0.0.1:10389")

	// When CTRL+C, SIGINT and SIGTERM signal occurs
	// Then stop server gracefully
	ch := make(chan os.Signal)
	signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM)
	<-ch
	close(ch)

	ldapserver.Stop()
}

func (server *Server) init() error {
	pair, _, err := server.kv.Get(dnToConsul(server.config.Suffix) + "/attribute=objectClass", nil)
	if err != nil {
		return err
	}

	if pair != nil {
		return nil
	}

	base_attributes := Attributes{
		"objectClass": []string{"top", "dcObject", "organization"},
		"structuralObjectClass": "Organization",
	}
	suffix_dn, err := parseDN(server.config.Suffix)
	if err != nil {
		return err
	}
	base_attributes[suffix_dn[0].Type] = suffix_dn[0].Value

	err = server.addElements(server.config.Suffix, base_attributes)
	if err != nil {
		return err
	}

	admin_pass := make([]byte, 8)
	rand.Read(admin_pass)
	admin_pass_str := base64.RawURLEncoding.EncodeToString(admin_pass)
	admin_pass_hash := SSHAEncode([]byte(admin_pass_str))

	admin_dn := "cn=admin," + server.config.Suffix
	admin_attributes := Attributes{
		"objectClass": []string{"simpleSecurityObject", "organizationalRole"},
		"description": "LDAP administrator",
		"cn": "admin",
		"userpassword": admin_pass_hash,
		"structuralObjectClass": "organizationalRole",
		"permissions": []string{"read", "write"},
	}

	err = server.addElements(admin_dn, admin_attributes)
	if err != nil {
		return err
	}

	log.Printf(
		"It seems to be a new installation, we created a default user for you:\n\n    dn:          %s\n    password:    %s\n\nWe didn't use true random, you should replace it as soon as possible.",
		admin_dn,
		admin_pass_str,
	)

	return nil
}

func (server *Server) addElements(dn string, attrs Attributes) error {
	prefix := dnToConsul(dn)
	for k, v := range attrs {
		json, err := json.Marshal(v)
		if err != nil {
			return err
		}
		pair := &consul.KVPair{Key: prefix + "/attribute=" + k, Value: json}
		_, err = server.kv.Put(pair, nil)
		if err != nil {
			return err
		}
	}
	return nil
}

func (server *Server) handleBind(w ldap.ResponseWriter, m *ldap.Message) {
	r := m.GetBindRequest()

	result_code, err := server.handleBindInternal(w, r)

	res := ldap.NewBindResponse(result_code)
	if err != nil {
		res.SetDiagnosticMessage(err.Error())
		log.Printf("Failed bind for %s: %s", string(r.Name()), err.Error())
	}
	w.Write(res)
}

func (server *Server) handleBindInternal(w ldap.ResponseWriter, r message.BindRequest) (int, error) {

	pair, _, err := server.kv.Get(dnToConsul(string(r.Name())) + "/attribute=userpassword", nil)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	if pair == nil {
		return ldap.LDAPResultNoSuchObject, nil
	}

	hash := ""
	err = json.Unmarshal(pair.Value, &hash)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	valid := SSHAMatches(hash, []byte(r.AuthenticationSimple()))
	if valid {
		return ldap.LDAPResultSuccess, nil
	} else {
		return ldap.LDAPResultInvalidCredentials, nil
	}
}