outposts/ldap: optimise backend Search API requests

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

internal/outpost/ldap/instance_search_user.go

@@ -0,0 +1,38 @@
+package ldap
+
+import (
+	ber "github.com/nmcclain/asn1-ber"
+	"github.com/nmcclain/ldap"
+	"goauthentik.io/api"
+)
+
+func parseFilterForUser(req api.ApiCoreUsersListRequest, filter string) api.ApiCoreUsersListRequest {
+	f, err := ldap.CompileFilter(filter)
+	if err != nil {
+		return req
+	}
+	switch f.Tag {
+	case ldap.FilterEqualityMatch:
+		return parseFilterForUserSingle(req, f)
+	case ldap.FilterAnd:
+		for _, child := range f.Children {
+			req = parseFilterForUserSingle(req, child)
+		}
+		return req
+	}
+	return req
+}
+
+func parseFilterForUserSingle(req api.ApiCoreUsersListRequest, f *ber.Packet) api.ApiCoreUsersListRequest {
+	v := f.Children[1].Value.(string)
+	switch f.Children[0].Value.(string) {
+	case "cn":
+		return req.Username(v)
+	case "name":
+	case "displayName":
+		return req.Name(v)
+	case "mail":
+		return req.Email(v)
+	}
+	return req
+}