Refactor DB configuration

config/cli.go

@@ -45,7 +45,7 @@ func (o *Options) declareFlags() {
 	flag.StringVar(&o.ExternalURL, "externalurl", o.ExternalURL, "Begining of the URL, before the base, that should be used eg. in mails")
 	flag.StringVar(&o.BaseURL, "baseurl", o.BaseURL, "URL prepended to each URL")
 	flag.StringVar(&o.DefaultNameServer, "default-ns", o.DefaultNameServer, "Adress to the default name server")
-	flag.StringVar(&o.StorageEngine, "storage-engine", "leveldb", fmt.Sprintf("Select the storage engine between %v", storage.GetStorageEngines()))
+	flag.Var(&o.StorageEngine, "storage-engine", fmt.Sprintf("Select the storage engine between %v", storage.GetStorageEngines()))
 
 	// Others flags are declared in some other files likes sources, storages, ... when they need specials configurations
 }

config/config.go

@@ -38,6 +38,8 @@ import (
 	"os"
 	"path"
 	"strings"
+
+	"git.happydns.org/happydns/storage"
 )
 
 type Options struct {
@@ -47,7 +49,7 @@ type Options struct {
 	BaseURL           string
 	DevProxy          string
 	DefaultNameServer string
-	StorageEngine     string
+	StorageEngine     storage.StorageEngine
 }
 
 func (o *Options) BuildURL(url string) string {
@@ -67,7 +69,7 @@ func ConsolidateConfig() (opts *Options, err error) {
 		ExternalURL:       "http://localhost:8081",
 		BaseURL:           "/",
 		DefaultNameServer: "127.0.0.1:53",
-		StorageEngine:     "leveldb",
+		StorageEngine:     storage.StorageEngine("leveldb"),
 	}
 
 	opts.declareFlags()

storage/config.go

@@ -1,36 +0,0 @@
-// Copyright or © or Copr. happyDNS (2020)
-//
-// contact@happydns.org
-//
-// This software is a computer program whose purpose is to provide a modern
-// interface to interact with DNS systems.
-//
-// This software is governed by the CeCILL license under French law and abiding
-// by the rules of distribution of free software.  You can use, modify and/or
-// redistribute the software under the terms of the CeCILL license as
-// circulated by CEA, CNRS and INRIA at the following URL
-// "http://www.cecill.info".
-//
-// As a counterpart to the access to the source code and rights to copy, modify
-// and redistribute granted by the license, users are provided only with a
-// limited warranty and the software's author, the holder of the economic
-// rights, and the successive licensors have only limited liability.
-//
-// In this respect, the user's attention is drawn to the risks associated with
-// loading, using, modifying and/or developing or reproducing the software by
-// the user in light of its specific status of free software, that may mean
-// that it is complicated to manipulate, and that also therefore means that it
-// is reserved for developers and experienced professionals having in-depth
-// computer knowledge. Users are therefore encouraged to load and test the
-// software's suitability as regards their requirements in conditions enabling
-// the security of their systems and/or data to be ensured and, more generally,
-// to use and operate it in the same conditions as regards security.
-//
-// The fact that you are presently reading this means that you have had
-// knowledge of the CeCILL license and that you accept its terms.
-
-package storage
-
-import ()
-
-type DBConfig interface{}

storage/singleton.go

@@ -31,15 +31,42 @@
 
 package storage
 
+import (
+	"fmt"
+)
+
+// StorageEngine defines an interface that handle configuration throught custom
+// flag.
+type StorageEngine string
+
+func (i *StorageEngine) String() string {
+	return string(*i)
+}
+
+func (i *StorageEngine) Set(value string) (err error) {
+	se := StorageEngine(value)
+	if _, ok := StorageEngines[se]; !ok {
+		return fmt.Errorf("Unexistant storage engine: please select one between: %v", GetStorageEngines())
+	}
+	*i = se
+	return nil
+}
+
+// MainStore is the singleton holding the database connection.
 var MainStore Storage
 
+// StorageInstanciation is a function that a Storage implementation
+// has to expose in order to be usable in configuration.
 type StorageInstanciation func() (Storage, error)
 
-var StorageEngines = map[string]StorageInstanciation{}
+// StorageEngines lists all Storage implementations declared, with a
+// way to instanciate automatically each.
+var StorageEngines = map[StorageEngine]StorageInstanciation{}
 
+// GetStorageEngines returns all declared Storage implementation.
 func GetStorageEngines() (se []string) {
 	for k := range StorageEngines {
-		se = append(se, k)
+		se = append(se, string(k))
 	}
 
 	return