Make storage backend configurable via -storage.url

Same mechanism as for configuring the auth backend.

cmd/tokidoki/main.go

@@ -18,13 +18,14 @@ func main() {
 	var (
 		addr       string
 		authURL    string
+		storageURL string
 	)
 	flag.StringVar(&addr, "addr", ":8080", "listening address")
-	// TODO: make flag mandatory instead of default value
-	flag.StringVar(&authURL, "auth.url", "imaps://imap.migadu.com:993", "auth backend URL")
+	flag.StringVar(&authURL, "auth.url", "", "auth backend URL (required)")
+	flag.StringVar(&storageURL, "storage.url", "", "storage backend URL (required)")
 	flag.Parse()
 
-	if len(flag.Args()) != 0 {
+	if len(flag.Args()) != 0 || authURL == "" || storageURL == "" {
 		flag.Usage()
 		os.Exit(1)
 	}
@@ -41,8 +42,7 @@ func main() {
 	}
 	mux.Use(authProvider.Middleware())
 
-	//backend := storage.NewPostgreSQL()
-	backend, err := storage.NewFilesystem("./teststorage")
+	backend, err := storage.NewFromURL(storageURL)
 	if err != nil {
 		log.Fatalf("failed to load storage backend: %s", err.Error())
 	}

storage/url.go

@@ -0,0 +1,24 @@
+package storage
+
+import (
+	"fmt"
+	"net/url"
+
+	"github.com/emersion/go-webdav/carddav"
+)
+
+func NewFromURL(storageURL string) (carddav.Backend, error) {
+	u, err := url.Parse(storageURL)
+	if err != nil {
+		return nil, fmt.Errorf("error parsing storage URL: %s", err.Error())
+	}
+
+	switch u.Scheme {
+	case "file":
+		return NewFilesystem(u.Path)
+	case "postgresql":
+		return NewPostgreSQL(), nil
+	default:
+		return nil, fmt.Errorf("no storage provider found for %s:// URL", u.Scheme)
+	}
+}