multi player / per user playing and translation

private/playlists.rkt

@@ -11,7 +11,9 @@
          open-playlist-store
          close-playlist-store!
          load-user-playlists
-         save-user-playlists!)
+         save-user-playlists!
+         load-user-language
+         save-user-language!)
 
 (struct persisted-tab (id name tracks) #:transparent)
 (struct playlist-store (keystore lock) #:transparent)
@@ -19,6 +21,11 @@
 (define (user-playlists-key username)
   (format "playlists-for-~a" username))
 
+(define (user-language-key username)
+  (format "language-for-~a" username))
+
+(define supported-language-names '("en" "nl" "de" "fr" "es"))
+
 (define (track->datum item)
   (hasheq 'file (path->string (track-file item))
           'title (track-title item)
@@ -116,6 +123,45 @@
         (ks-set! ks index-key ids))
        (void)))))
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+; goal   : Load one user's persisted interface language.
+; pre    : Store is #f or an open playlist store; username is normalized.
+; post   : Store contents remain unchanged.
+; result : A supported ISO language name, or #f when none was saved.
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+(define (load-user-language store username)
+  (and store
+       (call-with-semaphore
+        (playlist-store-lock store)
+        (λ ()
+          (define value
+            (ks-get (playlist-store-keystore store)
+                    (user-language-key username)
+                    #f))
+          (and (member value supported-language-names) value)))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+; goal   : Persist one user's interface language.
+; pre    : Store is #f or open, username is normalized, and language is one of
+;          en, nl, de, fr, or es.
+; post   : The user's language key contains language when a store exists.
+; result : Void.
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+(define (save-user-language! store username language)
+  (unless (member language supported-language-names)
+    (raise-argument-error
+     'save-user-language!
+     "one of en, nl, de, fr, or es"
+     language))
+  (when store
+    (call-with-semaphore
+     (playlist-store-lock store)
+     (λ ()
+       (ks-set! (playlist-store-keystore store)
+                (user-language-key username)
+                language))))
+  (void))
+
 (module+ test
   (require rackunit
            uuid/random)
@@ -166,6 +212,11 @@
       (check-equal?
        (map persisted-tab-name (load-user-playlists store "local" libraries))
        '("Local"))
+      (check-false (load-user-language store "hans"))
+      (save-user-language! store "hans" "fr")
+      (check-equal? (load-user-language store "hans") "fr")
+      (check-exn exn:fail:contract?
+                 (λ () (save-user-language! store "hans" "it")))
 
       ;; Rewriting the user's GUID index durably removes the omitted playlist.
       (save-user-playlists!