package main

// @FIXME: Implement a real permission system: limit read/write scope/attributes, possibly based on group membership
// @FIXME: Implement missing search filters (in applyFilter)
// @FIXME: Add an initial prefix to the consul key value

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

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

func dnToConsul(dn string) (string, error) {
	if strings.Contains(dn, "/") {
		return "", fmt.Errorf("DN %s contains a /", dn)
	}

	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, "/"), nil
}

func consulToDN(key string) (string, string) {
	path := strings.Split(key, "/")
	dn := ""
	for _, cpath := range path {
		if cpath == "" {
			continue
		}
		kv := strings.Split(cpath, "=")
		if len(kv) == 2 && kv[0] == "attribute" {
			return dn, kv[1]
		}
		if dn != "" {
			dn = "," + dn
		}
		dn = cpath + dn
	}
	panic("Consul key " + key + " does not end with attribute=something")
}

func parseValue(value []byte) ([]string, error) {
	val := []string{}
	err := json.Unmarshal(value, &val)
	if err == nil {
		return val, nil
	}

	val2 := ""
	err = json.Unmarshal(value, &val2)
	if err == nil {
		return []string{val2}, nil
	}

	return nil, fmt.Errorf("Not a string or list of strings: %s", value)
}

func parseConsulResult(data []*consul.KVPair) (map[string]Entry, error) {
	aggregator := map[string]Entry{}

	for _, kv := range data {
		log.Printf("(parseConsulResult) %s %s", kv.Key, string(kv.Value))
		dn, attr := consulToDN(kv.Key)
		if _, exists := aggregator[dn]; !exists {
			aggregator[dn] = Entry{}
		}
		value, err := parseValue(kv.Value)
		if err != nil {
			return nil, err
		}
		aggregator[dn][attr] = value
	}

	return aggregator, nil
}

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 State struct {
	bindDn string
}

type Entry map[string][]string

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()
	ldapserver.NewUserState = func() ldap.UserState {
		return &State{}
	}

	routes := ldap.NewRouteMux()
	routes.Bind(gobottin.handleBind)
	routes.Search(gobottin.handleSearch)
	routes.Add(gobottin.handleAdd)
	routes.Compare(gobottin.handleCompare)
	routes.Delete(gobottin.handleDelete)
	routes.Modify(gobottin.handleModify)
	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 {
	path, err := dnToConsul(server.config.Suffix)
	if err != nil {
		return err
	}

	pair, _, err := server.kv.Get(path+"/attribute=objectClass", nil)
	if err != nil {
		return err
	}

	if pair != nil {
		return nil
	}

	base_attributes := Entry{
		"objectClass":           []string{"top", "dcObject", "organization"},
		"structuralObjectClass": []string{"Organization"},
	}
	suffix_dn, err := parseDN(server.config.Suffix)
	if err != nil {
		return err
	}
	base_attributes[suffix_dn[0].Type] = []string{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 := Entry{
		"objectClass":           []string{"simpleSecurityObject", "organizationalRole"},
		"description":           []string{"LDAP administrator"},
		"cn":                    []string{"admin"},
		"userpassword":          []string{admin_pass_hash},
		"structuralObjectClass": []string{"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 Entry) error {
	prefix, err := dnToConsul(dn)
	if err != nil {
		return err
	}

	for k, v := range attrs {
		path := prefix + "/attribute=" + k
		if len(v) == 0 {
			// If we have zero values, delete associated k/v pair
			_, err := server.kv.Delete(path, nil)
			if err != nil {
				return err
			}
		} else {
			json, err := json.Marshal(v)
			if err != nil {
				return err
			}
			pair := &consul.KVPair{Key: path, Value: json}
			_, err = server.kv.Put(pair, nil)
			if err != nil {
				return err
			}
		}
	}
	return nil
}

func (server *Server) getAttribute(dn string, attr string) ([]string, error) {
	path, err := dnToConsul(dn)
	if err != nil {
		return nil, err
	}

	pair, _, err := server.kv.Get(path+"/attribute="+attr, nil)
	if err != nil {
		return nil, err
	}

	if pair == nil {
		return nil, nil
	}

	return parseValue(pair.Value)
}

func (server *Server) objectExists(dn string) (bool, error) {
	prefix, err := dnToConsul(dn)
	if err != nil {
		return false, err
	}

	data, _, err := server.kv.List(prefix+"/", nil)
	if err != nil {
		return false, err
	}
	return len(data) > 0, nil
}

func (server *Server) checkSuffix(dn string, allow_extend bool) (string, error) {
	suffix := server.config.Suffix
	if len(dn) < len(suffix) {
		if dn != suffix[-len(dn):] || !allow_extend {
			return suffix, fmt.Errorf(
				"Only handling stuff under DN %s", suffix)
		}
		return suffix, nil
	} else {
		if dn[len(dn)-len(suffix):] != suffix {
			return suffix, fmt.Errorf(
				"Only handling stuff under DN %s", suffix)
		}
		return dn, nil
	}
}

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

	result_code, err := server.handleBindInternal(state, &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(state *State, r *message.BindRequest) (int, error) {
	passwd, err := server.getAttribute(string(r.Name()), "userpassword")
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

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

	for _, hash := range passwd {
		valid := SSHAMatches(hash, []byte(r.AuthenticationSimple()))
		if valid {
			state.bindDn = string(r.Name())
			return ldap.LDAPResultSuccess, nil
		}
	}
	return ldap.LDAPResultInvalidCredentials, nil
}

func (server *Server) handleSearch(s ldap.UserState, w ldap.ResponseWriter, m *ldap.Message) {
	state := s.(*State)
	r := m.GetSearchRequest()

	code, err := server.handleSearchInternal(state, w, &r)

	res := ldap.NewResponse(code)
	if err != nil {
		res.SetDiagnosticMessage(err.Error())
	}
	w.Write(message.SearchResultDone(res))
}

func (server *Server) handleSearchInternal(state *State, w ldap.ResponseWriter, r *message.SearchRequest) (int, error) {
	log.Printf("-- SEARCH REQUEST: --")
	log.Printf("Request BaseDn=%s", r.BaseObject())
	log.Printf("Request Filter=%s", r.Filter())
	log.Printf("Request FilterString=%s", r.FilterString())
	log.Printf("Request Attributes=%s", r.Attributes())
	log.Printf("Request TimeLimit=%d", r.TimeLimit().Int())

	// TODO check authorizations

	baseObject, err := server.checkSuffix(string(r.BaseObject()), true)
	if err != nil {
		return ldap.LDAPResultInvalidDNSyntax, err
	}
	basePath, err := dnToConsul(baseObject)
	if err != nil {
		return ldap.LDAPResultInvalidDNSyntax, err
	}

	data, _, err := server.kv.List(basePath+"/", nil)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	entries, err := parseConsulResult(data)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}
	log.Printf("in %s: %#v", basePath+"/", data)
	log.Printf("%#v", entries)

	for dn, entry := range entries {
		// TODO filter out if no permission to read this
		matched, err := applyFilter(entry, r.Filter())
		if err != nil {
			return ldap.LDAPResultUnwillingToPerform, err
		}
		if !matched {
			continue
		}

		e := ldap.NewSearchResultEntry(dn)
		for attr, val := range entry {
			// If attribute is not in request, exclude it from returned entry
			if len(r.Attributes()) > 0 {
				found := false
				for _, requested := range r.Attributes() {
					if strings.EqualFold(string(requested), attr) {
						found = true
						break
					}
				}
				if !found {
					continue
				}
			}
			// Send result
			for _, v := range val {
				e.AddAttribute(message.AttributeDescription(attr),
					message.AttributeValue(v))
			}
		}
		w.Write(e)
	}

	return ldap.LDAPResultSuccess, nil
}

func applyFilter(entry Entry, filter message.Filter) (bool, error) {
	if fAnd, ok := filter.(message.FilterAnd); ok {
		for _, cond := range fAnd {
			res, err := applyFilter(entry, cond)
			if err != nil {
				return false, err
			}
			if !res {
				return false, nil
			}
		}
		return true, nil
	} else if fOr, ok := filter.(message.FilterOr); ok {
		for _, cond := range fOr {
			res, err := applyFilter(entry, cond)
			if err != nil {
				return false, err
			}
			if res {
				return true, nil
			}
		}
		return false, nil
	} else if fNot, ok := filter.(message.FilterNot); ok {
		res, err := applyFilter(entry, fNot.Filter)
		if err != nil {
			return false, err
		}
		return !res, nil
	} else if fPresent, ok := filter.(message.FilterPresent); ok {
		what := string(fPresent)
		// Case insensitive search
		for desc, values := range entry {
			if strings.EqualFold(what, desc) {
				return len(values) > 0, nil
			}
		}
		return false, nil
	} else if fEquality, ok := filter.(message.FilterEqualityMatch); ok {
		desc := string(fEquality.AttributeDesc())
		target := string(fEquality.AssertionValue())
		// Case insensitive attribute search
		for entry_desc, value := range entry {
			if strings.EqualFold(entry_desc, desc) {
				for _, val := range value {
					if val == target {
						return true, nil
					}
				}
				return false, nil
			}
		}
		return false, nil
	} else {
		return false, fmt.Errorf("Unsupported filter: %#v %T", filter, filter)
	}
}

func (server *Server) handleAdd(s ldap.UserState, w ldap.ResponseWriter, m *ldap.Message) {
	state := s.(*State)
	r := m.GetAddRequest()

	code, err := server.handleAddInternal(state, &r)

	res := ldap.NewResponse(code)
	if err != nil {
		res.SetDiagnosticMessage(err.Error())
	}
	w.Write(message.AddResponse(res))
}

func (server *Server) handleAddInternal(state *State, r *message.AddRequest) (int, error) {
	dn := string(r.Entry())

	_, err := server.checkSuffix(dn, false)
	if err != nil {
		return ldap.LDAPResultInvalidDNSyntax, err
	}

	exists, err := server.objectExists(dn)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}
	if exists {
		return ldap.LDAPResultEntryAlreadyExists, nil
	}

	// TODO check permissions

	var members []string = nil

	entry := Entry{}
	for _, attribute := range r.Attributes() {
		key := string(attribute.Type_())
		vals_str := []string{}
		for _, val := range attribute.Vals() {
			vals_str = append(vals_str, string(val))
		}

		// Fail if they are trying to write memberOf, we manage this ourselves
		if strings.EqualFold(key, "memberOf") {
			return ldap.LDAPResultObjectClassViolation, fmt.Errorf(
				"memberOf cannot be defined directly, membership must be specified in the group itself")
		}
		// If they are writing a member key, we have to check they are adding valid members
		if strings.EqualFold(key, "member") {
			members = vals_str
			for _, member := range members {
				_, err := server.checkSuffix(member, false)
				if err != nil {
					return ldap.LDAPResultInvalidDNSyntax, err
				}
				exists, err = server.objectExists(member)
				if err != nil {
					return ldap.LDAPResultOperationsError, err
				}
				if !exists {
					return ldap.LDAPResultNoSuchObject, fmt.Errorf(
						"Cannot add %s to members, it does not exist!",
						member)
				}
			}
		}
		entry[key] = vals_str
	}

	err = server.addElements(dn, entry)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	if members != nil {
		for _, member := range members {
			memberGroups, err := server.getAttribute(member, "memberOf")
			if err != nil {
				return ldap.LDAPResultOperationsError, err
			}
			if memberGroups == nil {
				memberGroups = []string{}
			}

			alreadyMember := false
			for _, mb := range memberGroups {
				if mb == dn {
					alreadyMember = true
					log.Printf("Warning: inconsistency detected, %s was memberOf %s at a time when it didn't exist!",
						member, dn)
					break
				}
			}

			if !alreadyMember {
				memberGroups = append(memberGroups, dn)
				err = server.addElements(member, Entry{
					"memberOf": memberGroups,
				})
				if err != nil {
					return ldap.LDAPResultOperationsError, err
				}
			}
		}
	}

	return ldap.LDAPResultSuccess, nil
}

func (server *Server) handleCompare(s ldap.UserState, w ldap.ResponseWriter, m *ldap.Message) {
	state := s.(*State)
	r := m.GetCompareRequest()

	code, err := server.handleCompareInternal(state, &r)

	res := ldap.NewResponse(code)
	if err != nil {
		res.SetDiagnosticMessage(err.Error())
	}
	w.Write(message.CompareResponse(res))
}

func (server *Server) handleCompareInternal(state *State, r *message.CompareRequest) (int, error) {
	dn := string(r.Entry())
	attr := string(r.Ava().AttributeDesc())
	expected := string(r.Ava().AssertionValue())

	_, err := server.checkSuffix(dn, false)
	if err != nil {
		return ldap.LDAPResultInvalidDNSyntax, err
	}

	// TODO check user for permissions to read dn

	exists, err := server.objectExists(dn)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}
	if !exists {
		return ldap.LDAPResultNoSuchObject, fmt.Errorf("Not found: %s", dn)
	}

	values, err := server.getAttribute(dn, attr)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	for _, v := range values {
		if v == expected {
			return ldap.LDAPResultCompareTrue, nil
		}
	}

	return ldap.LDAPResultCompareFalse, nil
}

func (server *Server) handleDelete(s ldap.UserState, w ldap.ResponseWriter, m *ldap.Message) {
	state := s.(*State)
	r := m.GetDeleteRequest()

	code, err := server.handleDeleteInternal(state, &r)

	res := ldap.NewResponse(code)
	if err != nil {
		res.SetDiagnosticMessage(err.Error())
	}
	w.Write(message.DelResponse(res))
}

func (server *Server) handleDeleteInternal(state *State, r *message.DelRequest) (int, error) {
	dn := string(*r)

	_, err := server.checkSuffix(dn, false)
	if err != nil {
		return ldap.LDAPResultInvalidDNSyntax, err
	}

	// TODO check user for permissions to write dn

	// Check that this LDAP entry exists and has no children
	path, err := dnToConsul(dn)
	if err != nil {
		return ldap.LDAPResultInvalidDNSyntax, err
	}

	items, _, err := server.kv.List(path+"/", nil)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	if len(items) == 0 {
		return ldap.LDAPResultNoSuchObject, fmt.Errorf("Not found: %s", dn)
	}
	for _, item := range items {
		itemDN, _ := consulToDN(item.Key)
		if itemDN != dn {
			return ldap.LDAPResultNotAllowedOnNonLeaf, fmt.Errorf(
				"Cannot delete %d as it has children", dn)
		}
	}

	// Retrieve group membership before we delete everything
	memberOf, err := server.getAttribute(dn, "memberOf")
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	// Delete the LDAP entry
	_, err = server.kv.DeleteTree(path+"/", nil)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	// Delete it from the member list of all the groups it was a member of
	if memberOf != nil {
		for _, group := range memberOf {
			groupMembers, err := server.getAttribute(dn, "member")
			if err != nil {
				return ldap.LDAPResultOperationsError, err
			}

			newMembers := []string{}
			for _, memb := range groupMembers {
				if memb != dn {
					newMembers = append(newMembers, memb)
				}
			}

			err = server.addElements(group, Entry{
				"member": newMembers,
			})
			if err != nil {
				return ldap.LDAPResultOperationsError, err
			}
		}
	}

	return ldap.LDAPResultSuccess, nil
}

func (server *Server) handleModify(s ldap.UserState, w ldap.ResponseWriter, m *ldap.Message) {
	state := s.(*State)
	r := m.GetModifyRequest()

	code, err := server.handleModifyInternal(state, &r)

	res := ldap.NewResponse(code)
	if err != nil {
		res.SetDiagnosticMessage(err.Error())
	}
	w.Write(message.ModifyResponse(res))
}

func (server *Server) handleModifyInternal(state *State, r *message.ModifyRequest) (int, error) {
	dn := string(r.Object())

	_, err := server.checkSuffix(dn, false)
	if err != nil {
		return ldap.LDAPResultInvalidDNSyntax, err
	}

	// TODO check user for permissions to write dn

	// Retrieve previous values (by the way, check object exists)
	path, err := dnToConsul(dn)
	if err != nil {
		return ldap.LDAPResultInvalidDNSyntax, err
	}

	items, _, err := server.kv.List(path+"/attribute=", nil)
	if err != nil {
		return ldap.LDAPResultOperationsError, err
	}

	if len(items) == 0 {
		return ldap.LDAPResultNoSuchObject, fmt.Errorf("Not found: %s", dn)
	}

	prevEntry := Entry{}
	for _, item := range items {
		itemDN, attr := consulToDN(item.Key)
		if itemDN != dn {
			panic("itemDN != dn in handleModifyInternal")
		}
		vals, err := parseValue(item.Value)
		if err != nil {
			return ldap.LDAPResultOperationsError, err
		}
		prevEntry[attr] = vals
	}

	// Keep track of group members added/deleted
	addMembers, delMembers := []string{}, []string{}

	// Produce new entry values to be saved
	newEntry := Entry{}
	for _, change := range r.Changes() {
		attr := string(change.Modification().Type_())
		values := change.Modification().Vals()

		if change.Operation() == ldap.ModifyRequestChangeOperationAdd {
			newEntry[attr] = prevEntry[attr]
			for _, val := range values {
				present := false
				for _, prevVal := range newEntry[attr] {
					if prevVal == string(val) {
						present = true
						break
					}
				}
				if !present {
					newEntry[attr] = append(newEntry[attr], string(val))
					if strings.EqualFold(attr, "member") {
						addMembers = append(addMembers, string(val))
					}
				}
			}
		} else if change.Operation() == ldap.ModifyRequestChangeOperationDelete {
			if len(values) == 0 {
				// Delete everything
				newEntry[attr] = []string{}
				if strings.EqualFold(attr, "member") {
					delMembers = append(delMembers, prevEntry[attr]...)
				}
			} else {
				// Delete only those specified
				newEntry[attr] = []string{}
				for _, prevVal := range prevEntry[attr] {
					keep := true
					for _, delVal := range values {
						if string(delVal) == prevVal {
							keep = false
							break
						}
					}
					if keep {
						newEntry[attr] = append(newEntry[attr], prevVal)
					} else {
						if strings.EqualFold(attr, "member") {
							delMembers = append(delMembers, prevVal)
						}
					}
				}
			}
		} else if change.Operation() == ldap.ModifyRequestChangeOperationReplace {
			newEntry[attr] = []string{}
			for _, newVal := range values {
				newEntry[attr] = append(newEntry[attr], string(newVal))
			}
			if strings.EqualFold(attr, "member") {
				for _, newMem := range newEntry[attr] {
					mustAdd := true
					for _, prevMem := range prevEntry[attr] {
						if prevMem == newMem {
							mustAdd = false
							break
						}
					}
					if mustAdd {
						addMembers = append(addMembers, newMem)
					}
				}
				for _, prevMem := range prevEntry[attr] {
					mustDel := true
					for _, newMem := range newEntry[attr] {
						if newMem == prevMem {
							mustDel = false
							break
						}
					}
					if mustDel {
						delMembers = append(delMembers, prevMem)
					}
				}
			}
		}
	}

	// Check that added members actually exist
	for _, addMem := range addMembers {
		exists, err := server.objectExists(addMem)
		if err != nil {
			return ldap.LDAPResultOperationsError, err
		}
		if !exists {
			return ldap.LDAPResultNoSuchObject, fmt.Errorf(
				"Cannot add member %s, it does not exist", addMem)
		}
	}

	// Save the edited values
	server.addElements(dn, newEntry)

	// Update memberOf for added members and deleted members
	for _, addMem := range addMembers {
		memberOf, err := server.getAttribute(addMem, "memberOf")
		if err != nil {
			return ldap.LDAPResultOperationsError, err
		}
		if memberOf == nil {
			memberOf = []string{}
		}
		memberOf = append(memberOf, dn)
		err = server.addElements(addMem, Entry{"memberOf": memberOf})
		if err != nil {
			return ldap.LDAPResultOperationsError, err
		}
	}

	for _, delMem := range delMembers {
		memberOf, err := server.getAttribute(delMem, "memberOf")
		if err != nil {
			return ldap.LDAPResultOperationsError, err
		}
		if memberOf == nil {
			memberOf = []string{}
		}
		newMemberOf := []string{}
		for _, g := range memberOf {
			if g != dn {
				newMemberOf = append(newMemberOf, g)
			}
		}

		err = server.addElements(delMem, Entry{"memberOf": newMemberOf})
		if err != nil {
			return ldap.LDAPResultOperationsError, err
		}
	}

	return ldap.LDAPResultSuccess, nil
}