package ldapSync

import (
	"encoding/json"
	"fmt"
	"git.stuve.uni-ulm.de/stuve-it/stuve-it-backend/logger"
	"github.com/go-ldap/ldap/v3"
	"github.com/google/uuid"
	"github.com/pocketbase/dbx"
	"github.com/pocketbase/pocketbase"
	"github.com/pocketbase/pocketbase/forms"
	"github.com/pocketbase/pocketbase/models"
	"os"
	"time"
)

type SyncResult struct {
	Found   int
	Synced  int
	Removed int
	Errors  []error
}

// getObjectGUID This function gets the objectGUID from an ldap entry
//
// since the objectGUID is a binary value, it is returned as a string (uuid)
func getObjectGUID(entry *ldap.Entry) (string, error) {
	// get the objectGUID
	var bytes = entry.GetRawAttributeValue("objectGUID")

	// convert to uuid
	u, err := uuid.FromBytes(bytes)
	if err != nil {
		return "", err
	}
	return u.String()[:15], nil // only use the first 15 characters of the uuid
}

// upsertLDAPGroup This function creates / updates a record in the ldap groups table
//
// this function expects that the table ldapGroups already exists
//
// old groups are removed from the database. a group is considered old if it has not been synced for 1 day
func syncLdapGroups(app *pocketbase.PocketBase, ldapClient *ldap.Conn) SyncResult {
	var syncedCount int
	var errors []error

	// Create a search request for groups
	groupsSearchRequest := ldap.NewSearchRequest(
		os.Getenv("LDAP_GROUP_BASE_DN"), // The base dn to search
		ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 30, false,
		os.Getenv("LDAP_GROUP_FILTER"), // The filter to apply
		[]string{"description", "dn", "cn", "msSFU30NisDomain", "memberOf", "objectGUID"},
		nil,
	)

	groupsFoundInLdap, err := ldapClient.Search(groupsSearchRequest)
	if err != nil {
		return SyncResult{
			Errors: []error{fmt.Errorf("unable to search in ldap for groups - %s", err)},
		}
	}

	for _, entry := range groupsFoundInLdap.Entries {

		var id, e = getObjectGUID(entry)

		if e != nil {
			errors = append(errors, fmt.Errorf("unable to get objectGUID for group with dn: %s - %s", entry.DN, e))
		}

		err := upsertLDAPGroup(app, &LDAPGroup{
			id:               id,
			description:      entry.GetAttributeValue("description"),
			dn:               entry.DN,
			cn:               entry.GetAttributeValue("cn"),
			msSFU30NisDomain: entry.GetAttributeValue("msSFU30NisDomain"),
			memberOf:         entry.GetAttributeValues("memberOf"),
		})
		if err != nil {
			errors = append(errors, err)
		} else {
			syncedCount++
		}
	}

	var removedCount int

	// remove old groups
	// step1: get a timeStamp one day ago
	timeStamp := time.Now().AddDate(0, 0, -1)

	// step2: get all groups that have not been synced since that timeStamp
	records, err := app.Dao().FindRecordsByFilter(
		ldapGroupsTableName,
		"updated < {:timeStamp}", "", 0, 0,
		dbx.Params{"timeStamp": timeStamp},
	)

	if err != nil {
		errors = append(errors, fmt.Errorf("unable to get old ldap groups from db - %s", err))
		return SyncResult{
			Found:  len(groupsFoundInLdap.Entries),
			Synced: syncedCount,
			Errors: errors,
		}
	}

	// step3: delete all groups that have not been synced since that timeStamp
	for _, record := range records {
		err := app.Dao().DeleteRecord(record)
		if err != nil {
			errors = append(errors, fmt.Errorf("unable to remove old group with dn: %s - %s", record.Get("dn"), err))
		} else {
			removedCount++
		}
	}

	return SyncResult{
		Found:   len(groupsFoundInLdap.Entries),
		Synced:  syncedCount,
		Removed: removedCount,
		Errors:  errors,
	}
}

// syncLdapUsers This function syncs the ldap users with the database
//
// this function expects that the tables ldapUsers and ldapGroups already exist
//
// old users are removed from the database. a user is considered old if it has not been synced for 1 day
func syncLdapUsers(app *pocketbase.PocketBase, ldapClient *ldap.Conn) SyncResult {
	var syncedCount int
	var errors []error

	// Create a search request for users
	userSearchRequest := ldap.NewSearchRequest(
		os.Getenv("LDAP_BASE_DN"), // The base dn to search
		ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 30, false,
		os.Getenv("LDAP_USER_FILTER"), // The filter to apply
		[]string{"givenName", "sn", "accountExpires", "mail", "dn", "cn", "msSFU30NisDomain", "memberOf", "objectGUID"},
		nil,
	)

	usersFoundInLdap, err := ldapClient.Search(userSearchRequest)
	if err != nil {
		return SyncResult{
			Errors: []error{fmt.Errorf("unable to search in ldap for users - %s", err)},
		}
	}

	for _, entry := range usersFoundInLdap.Entries {

		var id, e = getObjectGUID(entry)

		if e != nil {
			errors = append(errors, fmt.Errorf("unable to get objectGUID for user with dn: %s - %s", entry.DN, e))
		}

		err := upsertLDAPUser(app, &LDAPUser{
			givenName:        entry.GetAttributeValue("givenName"),
			sn:               entry.GetAttributeValue("sn"),
			accountExpires:   entry.GetAttributeValue("accountExpires"),
			id:               id,
			mail:             entry.GetAttributeValue("mail"),
			dn:               entry.DN,
			cn:               entry.GetAttributeValue("cn"),
			msSFU30NisDomain: entry.GetAttributeValue("msSFU30NisDomain"),
			memberOf:         entry.GetAttributeValues("memberOf"),
		})
		if err != nil {
			errors = append(errors, err)
		} else {
			syncedCount++
		}
	}

	var removedCount int

	// remove old users
	// step1: get a timeStamp one day ago
	timeStamp := time.Now().AddDate(0, 0, -1)

	// step2: get all users that have not been synced since that timeStamp
	records, err := app.Dao().FindRecordsByFilter(
		ldapUsersTableName,
		"updated < {:timeStamp}", "", 0, 0,
		dbx.Params{"timeStamp": timeStamp},
	)

	if err != nil {
		return SyncResult{
			Found:  len(usersFoundInLdap.Entries),
			Synced: syncedCount,
			Errors: []error{fmt.Errorf("unable to get old ldap users from db - %s", err)},
		}
	}

	// step3: delete all users that have not been synced since that timeStamp
	for _, record := range records {
		err := app.Dao().DeleteRecord(record)
		if err != nil {
			errors = append(errors, fmt.Errorf("unable to remove old user with dn: %s - %s", record.Get("dn"), err))
		} else {
			removedCount++
		}
	}

	return SyncResult{
		Found:   len(usersFoundInLdap.Entries),
		Synced:  syncedCount,
		Removed: removedCount,
		Errors:  errors,
	}
}

// syncLdap This function syncs the ldap groups and users with the database
func syncLdap(app *pocketbase.PocketBase) {

	// Connect to the LDAP server
	conn, err := ldap.DialURL(os.Getenv("LDAP_URL"))
	if err != nil {
		logger.LogErrorF("unable to connect to ldap server - %s", err)
		return
	}
	defer conn.Close()

	// Bind to the server
	err = conn.Bind(os.Getenv("LDAP_BIND_DN"), os.Getenv("LDAP_BIND_PASSWORD"))
	if err != nil {
		logger.LogErrorF("unable to bind to ldap server - %s", err)
		return
	}

	// sync groups
	groupSyncResult := syncLdapGroups(app, conn)

	// sync users
	userSyncResult := syncLdapUsers(app, conn)

	// store sync log in database
	collection, err := app.Dao().FindCollectionByNameOrId(ldapSyncLogsTableName)
	if err != nil {
		logger.LogErrorF("unable to find % table: %s", ldapSyncLogsTableName, err)
		return
	}
	record := models.NewRecord(collection)
	form := forms.NewRecordUpsert(app, record)
	form.LoadData(map[string]any{
		"usersFound":      userSyncResult.Found,
		"usersSynced":     userSyncResult.Synced,
		"usersRemoved":    userSyncResult.Removed,
		"userSyncErrors":  errorsToJSON(userSyncResult.Errors),
		"groupsFound":     groupSyncResult.Found,
		"groupsSynced":    groupSyncResult.Synced,
		"groupsRemoved":   groupSyncResult.Removed,
		"groupSyncErrors": errorsToJSON(groupSyncResult.Errors),
	})
	if err := form.Submit(); err != nil {
		logger.LogErrorF("unable to store ldap sync log: %s", err)
		return
	}
}

// errorsToJSON converts an array of errors to a json string
func errorsToJSON(errors []error) string {
	var jsonErrors []string
	for _, err := range errors {
		jsonErrors = append(jsonErrors, err.Error())
	}
	jsonString, _ := json.Marshal(jsonErrors)
	s := string(jsonString)
	return s
}